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A study of production and ergonomic factors in grapple yarding operations using an electronic data logger… de Souza, Amaury Paulo 1983

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A STUDY OF PRODUCTION AND ERGONOMIC FACTORS IN GRAPPLE YARDING OPERATIONS USING AN ELECTRONIC DATA LOGGER SYSTEM By AMAURY PAULO DE SOUZA For. Eng., Federal U n i v e r s i t y of Vicosa, B r a z i l M. Sc., The U n i v e r s i t y of Washington, U.S.A. A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (Department of Forestry) We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December 1983 ®Amaury Paulo de Souza, 1983 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s t h e s i s for s c h o l a r l y purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or publi c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Forestry.  The University of B r i t i s h Columbia 1956 Main Ma l l Vancouver, Canada V6T 1Y3 Date December ly , 1.983 ABSTRACT This thesis reports a study of production and ergonomic factors i n a grapple yarding operation, observed during 1982 at MacMillan Bloedel Ltd's Shawnigan Logging D i v i s i o n , near Duncan, B r i t i s h Columbia. Optimizing safety, health and performance requires d e t a i l e d evaluation of factors a f f e c t i n g man-machine re l a t i o n s h i p s during actual i n d u s t r i a l operations. In the case of grapple yarding, these factors were divided into two groups: (1) Production factors: yarding distance; mainline speed and tension; load volume, weight and number of logs; and c l i m a t i c , ground and stand conditions; (2) Ergonomic f a c t o r s : oper-ator's heart rate; cab noise l e v e l , temperature and humidity; and t r i -a x i a l v i b r a t i o n at the operator's seat. The research objectives were to: develop and evaluate an e l e c t r o n i c Data Logger system for man-machine studies; automatically determine work-cycle, work-element and delay times; test hypothesized r e l a t i o n s h i p s among production and ergonomic variables; analyze trends i n the duration of work-element times over the working s h i f t ; and compare measured ergonomic conditions with recommended standards. Data were simultaneously sampled and recorded using the Data Logger, a microprocessor-controlled, multi-channel, d i g i t a l s i g n a l -recording instrument, newly developed for t h i s s p e c i f i c research. Reliable f i e l d performance confirmed the a b i l i t y of the Data Logger to function as a p r a c t i c a l research t o o l i n forest harvesting operations. - i i i -Development of pattern-recognition computer programs allowed automated and consistent i n t e r p r e t a t i o n of recorded signals into machine work cycles, work elements and cer t a i n delays. Time measurement accu-racy of 0.001 min together with automated data recording allowed i d e n t i -f i c a t i o n of fast grapple yarding a c t i v i t i e s not previously i d e n t i f i e d . Correlation and regression analyses examined i n t e r - r e l a t i o n s h i p s among measured factors i n the complex grapple yarding system. Yarding distance was the most important variable a f f e c t i n g grapple t r a v e l time, but was not s i g n i f i c a n t l y associated with hookup time. Work-element times were not s i g n i f i c a n t l y related to cumulative working time over the s h i f t . Weak associations were found between most pairs of production and ergonomic vari a b l e s . The grapple yarder operator's work load, based on measured heart rate, was judged "very low". This also indicated a r e l a t i v e l y low l e v e l of emotional or mental stress placed on the experienced operator during grapple yarding a c t i v i t y . Ergonomic factors associated with the grapple yarder man-machine system were, i n general, acceptable; however, they could be improved. For instance, v i b r a t i o n acceleration l e v e l s exceeded the International Organization for Standardization (ISO) l i m i t s for "fatigue-decreased p r o f i c i e n c y " and "reduced comfort". Noise l e v e l (Leq) was below the recommended Workers' Compensation Board of B r i t i s h Columbia (WCB) hear-ing r i s k l i m i t , but high enough to cause concern to many ergonomic s p e c i a l i s t s . Cab cl i m a t i c conditions were not completely s a t i s f a c t o r y . - i v -To improve workplace conditions to meet the ergonomic standards, measures should be taken to reduce noise and v i b r a t i o n l e v e l s , and to maintain optimum c l i m a t i c conditions inside the operator's cab. Future studies could u s e f u l l y investigate: long-term health e f f e c t s ; oper-ator's v i s i b i l i t y of the working area; ergonomic and production charac-t e r i s t i c s of other forest machines and t h e i r crews under d i f f e r e n t s i t e , stand and c l i m a t i c conditions. These studies should e n l i s t the oper-ators i n explaining extraordinary observations, as well as t h e i r opinions on machine workplace conditions. Suggested improvements of the e l e c t r o n i c Data Logger include: on-site, signal-monitoring controls and displays; a f a s t e r data record-ing system; and, a method for r e g i s t e r i n g causes of delays, i n the f i e l d . - v -TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS v LIST OF TABLES x LIST OF FIGURES x i i i ACKNOWLEDGEMENTS x v i 1. INTRODUCTION 1 1.1 The General Problem: Understanding Man-Machine System. 1 1.1.1 Ergonomic Factors Problems 4 1.1.1.1 Noise 4 1.1.1.2 V i b r a t i o n 7 1.1.1.3 Working P o s i t i o n R e l a t i v e to Seat, Controls and Pedals 9 1.1.1.4 V i s i b i l i t y . 10 1.1.1.5 Cab Environment 11 1.1.1.6 St r e s s , S t r a i n and Fatigue.. 13 1.1.2 P r o d u c t i v i t y Problems 15 1.2 Some Technical Problems i n Evaluating Production and Ergonomic Factors 16 2. SCOPE, OBJECTIVE AND HYPOTHESES 20 2.1 Scope of the Study 20 2.2 Study Objectives and Hypotheses 21 3 . STUDY AREA AND MATERIALS USED IN DATA COLLECTION 23 3.1 Study Area D e s c r i p t i o n 23 3.2 Logging Equipment and Operating Crew 24 - v i -3.3 Data C o l l e c t i o n Equipment 28 3.3.1 The E l e c t r o n i c B.C. Forest Harvesting Data Logger and Peripherals 28 3.3.1.1 Yarding Distance 32 3.3.1.2 Number of Logs 35 3.3.1.3 Mainline Tension 35 3.3.1.4 Heart Rate 36 3.3.1.5 Noise Level 38 3.3.1.6 V i b r a t i o n A c c e l e r a t i o n 40 3.3.1.7 Temperature and Humidity 42 4. METHODS USED FOR COLLECTING, PROCESSING AND ANALYZING DATA 44 4.1 Data C o l l e c t i o n Methods 44 4.1.1 Yarding Distance.... 44 4.1.2 Number of Logs 46 4.1.3 Mainline Tension 46 4.1.4 Heart Rate 48 4.1.5 Noise Level 50 4.1.6 V i b r a t i o n A c c e l e r a t i o n 52 4.1.7 Temperature and Humidity 54 4.2 Data Processing Methods 54 4.2.1 Data Handling Computer Programs 54 4.2.1.1 Hexadecimal T r a n s c r i p t i o n 55 4.2.1.2 Hexadecimal Conversion.... 55 4.2.1.3 Channel Sorting 57 - v i i -Page 4.2.1.4 Data P l o t t i n g 57 4.2.1.5 Data Preparation 58 4.2.1.6 Data Conversion 59 4.2.2 Work-Cycle I n t e r p r e t a t i o n 59 4.2.2.1 Data F i l t e r i n g 61 4.2.2.2 Data I n t e r p r e t a t i o n 65 4.2.2.3 Elapsed Time for Work-Element and Delays 68 4.3 Data Analysis Methods 68 4.3.1 Comparison with the Standards 69 4.3.1.1 Noise Level 69 4.3.1.2 V i b r a t i o n A c c e l e r a t i o n 69 4.3.1.3 E f f e c t i v e Temperature 70 4.3.1.4 Heart Rate 70 4.3.1.5 Mainline Tension 71 4.3.2 S t a t i s t i c a l Analyses 71 4.3.2.1 Work-cycle S t a t i s t i c s 71 4.3.2.2 Other S t a t i s t i c a l A nalysis 74 5. RESULTS 75 5.1 Des c r i p t i v e S t a t i s t i c s For a l l Variables over the Study Period 76 5.2 Computer-Interpreted Work-Shift and Work-Cycles 79 5.2.1 Detailed Time I n t e r p r e t a t i o n 82 5.2.2 Grapple Travel Time Relationships 94 5.2.3 Hooking Time and Yarding Distance Relationship 96 - v i i i -Page 5.2.4 Execution Time of Work-Cycle Elements During the S h i f t 99 5.2.5 Production and Ergonomic Factors Within Work-Cycles 99 5.2.6 Production and Ergonomic Factors Within Work-Elements 104 5.2.6.1 Heart Rate 104 5.2.6.2 Noise Level 110 5.2.6.3 V i b r a t i o n A c c e l e r a t i o n 110 5.2.6.4 Mainline Tension 112 5.3 Comparison with the Standards. 114 5.3.1 Heart Rate 114 5.3.2 Noise Level 118 5.3.3 V i b r a t i o n A c c e l e r a t i o n 122 5.3.4 E f f e c t i v e Temperature...... 130 5.3.5 Mainline Tension 130 5.4 Ergonomic and Production Factors Relationships 134 5.4.1 Relationship Between Variable Values Within Work-Cycles 134 5.4.2 Relationship Between Variable Values Within Inhaul and Out haul Elements 143 5.4.3 Relationship Between Values Recorded Over the S h i f t s 148 6. DISCUSSION 150 6.1 Computer-Interpreted Work-Cycle, Work-Elements and Element-Delays 150 6.1.1 Grapple Travel Time Relationships and Yarding Distance 152 - ix -6.1.2 Hooking Time and Yarding Distance Relationships 152 6.1.3 Execution Time of Work-Elements During the Shift 153 6.1.4 Production and Ergonomic Factors Within Work-Elements 154 6.2 Comparison with the Standards 155 6.2.1 Heart Rate 155 6.2.2 Noise Level 156 6.2.3 Vibration Acceleration. 158 6.2.4 Effective Temperature 160 6.2.5 Mainline Tension 161 6.3 Production and Ergonomic Factor Relationships 161 7 . SUMMARY AND CONCLUSIONS 164 8. RECOMMENDATIONS 169 9. GLOSSARY 172 10. LITERATURE CITED 175 1 1 . APPENDICES 183 1. General Specifications for the Madil l 044 Grapple Yarder 184 2. Data Conversion Procedures 185 3. Flow Chart of "TURNIN" Computer Programs and i ts Subroutines 194 4. Computation Methods for Comparing Noise and Vibration Levels with the Recommended Standards 205 - X ~ LIST OF TABLES Table Page 1 Des c r i p t i v e s t a t i s t i c s for noise l e v e l , heart rate, mainline tension, yarding distance and number of logs, over the study period 77 2 Descriptive s t a t i s t i c s for v i b r a t i o n a c c e l e r a t i o n and temperature, over the study period 78 3 Summary of work-cycle time for the grapple yarder operation ( s h i f t 1) 84 4 Summary of work-cycle time for the grapple yarder operation ( s h i f t 2) 85 5 Summary of work-cycle time for the grapple yarder operation ( s h i f t 3) 86 6 Summary of work-cycle time f o r the grapple yarder operation ( s h i f t 4) 87 7 Summary of work-cycle element and delay time f o r the grapple yarder operation, over the f o u r - s h i f t study 89 8 Summary of work-cycle elements ( i n c l u d i n g delay time) f o r the grapple yarder operation, over the f o u r - s h i f t study 90 9 Summary of delay a n a l y s i s 92 10 Regression equations f o r grapple yarder outhaul and inhaul time, f o r each s h i f t studied 95 11 C o e f f i c i e n t of l i n e a r c o r r e l a t i o n (r) between turn number (time sequence) and work-element time, over the study period 100 12 D e s c r i p t i v e s t a t i s t i c s of a l l v a r i a b l e s measured for each machine work-cycle i n the study period 101 13 Average heart rate for each work-element and delay 109 14 Average noise l e v e l for each work-element and delay..... I l l - x i -Table Page 15 Average mainline tension for each work-element and delay 113 16 Comparison of noise l e v e l r e s u l t s with WCB recommended standard f o r three grapple yarder operating s h i f t s 120 17 Percentage of t o t a l measured exposure time v i b r a t i o n l e v e l s exceeded the recommended ISO l i m i t s for health or safety, fatigue and comfort c r i t e r i a . . . . . 127 18 Calculated equivalent exposure times for the three ISO c r i t e r i a : exposure l i m i t , fatigue-decreased p r o f i c i e n c y and reduced comfort during four grapple yarding s h i f t s 129 19 Machine cab and atmospheric environment during the study period 131 20 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) and regression equations for ergonomic and production v a r i a b l e s , s h i f t 1. 135 21 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) and regression equations for ergonomic and production v a r i a b l e s , s h i f t 2 136 22 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) and regression equations for ergonomic and production v a r i a b l e s , s h i f t 3 137 23 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) and regression equations for ergonomic and production v a r i a b l e s , s h i f t 4 138 24 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) f o r yarding distance and mainline speed against heart rate, noise l e v e l and mainline tension 144 25 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) between noise l e v e l and mainline tension for each work-element and delay ( s h i f t 1) 145 - x i i -Table Page 26 C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) between operator's heart rate and noise l e v e l for each work-element and delay 146 27 Calculated r e l a t i o n s h i p s between average values during inhaul and outhaul elements f o r : heart rate, noise l e v e l and mainline tension 149 - x l i i -LIST OF FIGURES Figure Page 1 Grapple yarding man-task system 19 2, 3 Madil l 044 grapple yarder (2) and Caterpi l lar D8H backspar (3) 25 4, 5 Madi l l 044 operator's cab (4) and machine grapple (5) 26 6 Schematic of grapple yarding system 27 7 Process chart of the grapple yarding o p e r a t i o n . . . . . . . . 29 8, 9 Electronic Data Logger system components: f i e l d recording unit (8) and laboratory data interpreting unit (9) 31 10 Schematic of the electronic Data Logger system 33 11 Yarding distance measuring device (metal target and magnetic switches) . . . . 34 12 Log count device (d ig i ta l display and push button switch) 34 13 Ectron amplifier 37 14 Tensiometer showing the load c e l l , the crank mechanism and the main sheave 37 15 Heart rate monitor (monitor cabinet, electrodes and belt) 39 16 Bruel & Kjaer sound level meter (type 2225) 39 17 Vibration analyzer 41 18 Kyowa accelerometer 41 19 Temperature measuring device (wet-bulb and dry-bulb thermometers) 43 20 Instal lat ion of the distance measuring device on the mainline drum of the Madil l 044 grapple yarder 45 - x i v -Figure Page 21, 22 I n s t a l l a t i o n of log count switch (21) and log count display (22) i n operator's cab 47 23 I n s t a l l a t i o n of tensiometer on the grapple tower 49 24 Placement of the heart rate monitoring electrodes on the operator's chest 49 25, 26 I n s t a l l a t i o n of the sound l e v e l meter on machine cab (25) and placement of the meter microphone at the operator's l e f t ear (26) 51 27, 28 False seat used to hold the accelerometer (27) and i t s i n s t a l l a t i o n on the operator's seat (28) 52 29 Data flow used i n t h i s research 56 30 Schematic of grapple yarder work-cycles showing possible delay patterns 60 31 Flow chart of subroutine "FILTER" used to compress distance data during work-cycle i n t e r p r e t a t i o n 63 32 Distance data sample p l o t s showing d i f f e r e n t patterns of grapple movement encountered during work-cycle i n t e r p r e t a t i o n 64 33 Yarding distance versus s h i f t time ( s h i f t 1 and 2).... 80 34 Yarding distance versus s h i f t time ( s h i f t 3 and 4).... 81 35 Computer-interpreted grapple yarder work-cycles 83 36 Relationship between grapple t r a v e l time and distance t r a v e l l e d f o r outhaul and inhaul work-elements .............*. 93 37 Scatter plots of t o t a l hookup time and yarding distance ( s h i f t 1 and 2) 97 38 Scatter p l o t s of t o t a l hookup time and yarding distance ( s h i f t 3 and 4) 98 39 T y p i c a l pattern of yarding distance, noise l e v e l , mainline tension, v i b r a t i o n a c c e l e r a t i o n and number of logs simultaneously recorded ( s h i f t 1) 105 - XV -Figure Page 40 T y p i c a l pattern of yarding distance, mainline tension, v i b r a t i o n a c c e l e r a t i o n and number of logs simultaneously recorded ( s h i f t 2) 106 41 T y p i c a l pattern of yarding distance, noise l e v e l , heart rate, v i b r a t i o n a c c e l e r a t i o n and number of logs simultaneously recorded ( s h i f t 3) 107 42 T y p i c a l pattern of yarding distance, noise l e v e l , heart r a t e , v i b r a t i o n a c c e l e r a t i o n and number of logs simultaneously recorded ( s h i f t 4) 108 43 Heart rate measurements of the grapple yarder operator over the s h i f t ( s h i f t 3 and 4 ) . . . 115 44 Histogram and cumulative d i s t r i b u t i o n f u n c t i o n f o r the grapple yarder operator's heart rate data ( s h i f t 3 and 4) 116 45 Noise l e v e l measurements at l e f t ear of the grapple yarder operator over the s h i f t ( s h i f t 1, 3 and 4) 119 46 Histogram and cumulative d i s t r i b u t i o n f u n c t i o n of the grapple yarder noise l e v e l data ( s h i f t 1, 3 and 4) 121 47 Horizontal (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the grapple yarder over the s h i f t ( s h i f t 1) 123 48 Horizontal (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the grapple yarder over the s h i f t ( s h i f t 2) 124 49 Horizontal (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the grapple yarder over the s h i f t ( s h i f t 3) 125 50 Horizontal (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the grapple yarder over the s h i f t ( s h i f t 4) - 126 51 Mainline tension through the s h i f t 1 and 2 f o r the M a d i l l 044 grapple yarder 132 52 Histogram and cumulative d i s t r i b u t i o n function for the grapple yarder mainline tension data ( s h i f t 1 and 2) . 133 - x v i -ACKNOWLEDGEMENTS I wish to express my sincere gratitude and deep appreciation to my research supervisor, Dr. P. L. C o t t e l l , Adjunct Professor (Forestry) and D i r e c t o r of MacMillan Bloedel's Wood Harvesting Research D i v i s i o n f o r h i s s p e c i a l e f f o r t , f i r m guidance, constant encouragement and con-s t r u c t i v e c r i t i c i s m throughout the course of t h i s study. Sincere appreciation i s extended to my academic supervisor Dr. A. Kozak, Professor and Associate Dean of the Faculty of Forestry, f o r h i s advice, support and recommendations concerning the s t a t i s t i c a l a n a l y s i s used i n t h i s research. I also express s p e c i a l acknowledgements to my committee members: Mr. G. G. Young, Associate Professor ( F o r e s t r y ) , f o r his advice, a s s i s t a n c e , and c o n t r i b u t i o n to the cable tensiometer design and con-s t r u c t i o n , and his p a r t i c u l a r a t t e n t i o n i n the s o l u t i o n of computer r e l a t e d problems; Dr. P. D. Lawrence, Associate Professor ( E l e c t r i c a l Engineering), f o r h i s advice, suggestions and supervision during the development of the e l e c t r o n i c Data Logger equipment; and Mr. L. Adamovich, Professor ( F o r e s t r y ) , for his i n i t i a l p a r t i c i p a t i o n i n the graduate committee work. Special thanks are extended to the e l e c t r o n i c engineers that p a r t i c i p a t e d i n the development of the e l e c t r o n i c Data Logger system: C. K. Huscroft, J . Clark, and A. Kindsvater. I also thank Mr. R. Mason, B. S.F. f o r his co n t r i b u t i o n to the design and construction of the cable tensiometer. - x v i i -I am i n debt to Mr. B. Sauder, M.F., f o r permitting me to modify and use his "TRANSF" and "CONVRT" computer programs. I also thank MacMillan Bloedel Ltd. for providing a l l f i e l d f a c i l i t i e s i n the course of equipment te s t and data c o l l e c t i o n . I am g r a t e f u l to the employees of Shawnigan D i v i s i o n , e s p e c i a l l y Mr. T. Kimoto, M. Pickard and S. Gorle for t h e i r help. Acknowledgement i s extended to Dr. V. Butora f o r h i s constructive comments and suggestions. Thanks are due to the Canadian I n t e r n a t i o n a l Development Agency (CIDA) and the Federal U n i v e r s i t y of Vicosa (UFV) for f i n a n c i a l sup-port. I thank the coordinators of CIDA/UFV agreement Dr. V. J . Nordin (Canada), Dr. A. Brune ( B r a z i l ) and Mr. A. F. Shirran (Canada) f or t h e i r help. The f i n a n c i a l support of the U n i v e r s i t y of B r i t i s h Columbia, the Natural Sciences and Engineering Research Council and the Science Council of B r i t i s h Columbia for the i n i t i a l design, construction and te s t of the Data Logger system i s g r a t e f u l l y acknowledged. F i n a l l y I would l i k e to thank my wife Graca for her encourage-ment, understanding and patience during t h i s study. Amaury Paulo de Souza - 1 -1. INTRODUCTION 1.1 The General Problem: Understanding Man-Machine Systems In recent years grapple yarding* has become an important cable logging system i n Western North America. The f o r e s t industry has being p r i m a r i l y i n t e r e s t e d i n the economic benefits of these machines. However, to optimize safety or health and performance, a better under-standing of the f a c t o r s a f f e c t i n g the man-machine r e l a t i o n s h i p s during a c t u a l grapple yarding operations i s required. Ergonomics i s a m u l t i - d i s c i p l i n a r y subject where the objective i s to achieve an optimum man-machine system, i n which a proper balance can be maintained between human and machine fa c t o r s (Zander 1979). It i s concerned with f i t t i n g the work conditions to the p h y s i c a l and psycho-l o g i c a l nature of human beings (Grandjean 1981). That i s , the goal of ergonomics i s to optimize the r e l a t i o n s h i p s between man and his work, economically employing the human labour force, and optimally f i t t i n g the working conditions to man's p h y s i c a l and mental properties (Eisenhauer 1979). The above d e f i n i t i o n s suggest that ergonomics research can be The grapple yarding system uses a grapple to seize and transport logs from the stump area to the haul road. The man-machine system i s us u a l l y composed of a mobile track or rubber-mounted yarder (crane) with swing c a p a b i l i t y , a mobile backspar and a 3-man crew. - 2 -used to: reduce stress by f i t t i n g the demand of work to the e f f i c i e n c y of man; ensure correct body posture by working out proportions and conditions of the workplace; and adapt noise, v i b r a t i o n , l i g h t i n g , and environment to s u i t man's phys i c a l and mental requirements by Improving machine design. The expected r e s u l t s would be an increase i n the opera-tor's general s a t i s f a c t i o n and well-being at the workplace, a decrease i n accident rate, and an increase i n p r o d u c t i v i t y . There i s very l i t t l e a v a i l a b l e information describing the ergono-mic and production status of grapple yarding operations i n B r i t i s h Columbia. However, i t i s generally accepted that the ergonomic goal i s often not achieved. Factor recognition i s the f i r s t step involved i n the process of des c r i b i n g the ergonomic and production status of these machines. Grapple yarding operations are composed of numerous f a c t o r s , many of which have a s i g n i f i c a n t influence on work p r o d u c t i v i t y and on human safety or health. Some of these factors can be c l a s s i f i e d as follows: A. Ergonomic f a c t o r s a. Human f a c t o r s : age, motivation, s k i l l , p h y s i c a l capacity, body weight, and body dimensions. b. Machine f a c t o r s : noise, v i b r a t i o n , cab environment ( a i r v e l o c i t y , temperature, humidity and exhaust fumes), v i s i b i l i t y ( l i g h t i n g and co l o u r ) , and design character-i s t i c s (seat, displays and c o n t r o l s ) . B. Production f a c t o r s a. Environmental f a c t o r s - 3 -1. Ground conditions: roughness, slope and s o i l c h a r a c t e r i s t i c s . 2. Stand c h a r a c t e r i s t i c s : tree branchiness, timber volume per hectare, log weight and volume. 3. C l i m a t i c conditions: temperature, humidity, a i r v e l o c i t y , and p r e c i p i t a t i o n . b. Operating f a c t o r s : machine power, type, s i z e , l i n e tension and speed c a p a c i t i e s , yarding distance, load volume, weight and number of logs. c. Work organization f a c t o r s : wage system, labour t r a i n i n g , and work planning. The machine operator's performance, safety and health are func-t i o n s of the ergonomic and production f a c t o r s . For instance, the design of the grapple yarder cab establishes the operator's seating p o s i t i o n r e l a t i v e to c o n t r o l s , pedals and instruments. Deviations from recommen-ded standards for c o n t r o l placement, co n t r o l actuating forces, and type can cause fatigue to the operator which may lead to losses i n produc-t i v i t y , and to safety or health r i s k s . A well-designed cab, besides providing comfortable working conditions, and access to c o n t r o l s , provides v i s i b i l i t y of the working area and o f f e r s the operator protec-t i o n against external causes of accidents. The seat also plays an important role i n determining the degree of comfort; for example, i n the amount of v i b r a t i o n that reaches the man. A w e l l - p o s i t i o n e d seat also determines the correct operator's posture with respect to machine controls and instruments. - 4 -In North America, the f o r e s t machines have been b a s i c a l l y b u i l t as extremely rugged machines, each of which performs a p a r t i c u l a r job i n a prescribed manner. Attempts at making these machines ergonomically optimum for the operator have been a secondary consideration (Myles 1981). This may have contributed to occupational health problems ( i . e . , those associated with noise, v i b r a t i o n , working posture, v i s i b i l i t y , and cab c l i m a t e ) , f a t i g u e , accidents, and reduced performance ( i . e . , loss i n p r o d u c t i v i t y due to f a t i g u e , and mechanical and non-mechanical delays). In view of these general problems t h i s t h e s i s i s concerned with the measurement and evaluation of production and ergonomic f a c t o r s that could contribute to improve work conditions, safety and health, job s a t i s f a c t i o n , and p r o d u c t i v i t y of grapple yarding operations. 1.1.1 Ergonomic Factors Problems The most common, and therefore important, problems which could i n f l u e n c e workers' safety or health and p r o d u c t i v i t y are associated with the ergonomic f a c t o r s discussed i n t h i s s e c t i o n . 1.1.1.1 Noise A number of studies have reported the e f f e c t s of noise on hearing l o s s and on work performance (Berrien 1946, Broadbent 1957, Teicher e_t a l . 1963, Kryter 1970, Eschenbrenner 1971, Benwell and Repacholi 1979). These studies have y i e l d e d c o n f l i c t i n g r e s u l t s , due to the large - 5 -number of variables to be c o n t r o l l e d , such as: noise l e v e l , frequency; duration; task v a r i a b l e s ; and v a r i a t i o n s i n i n d i v i d u a l response (Benwell and Repacholi 1979). I t i s d i f f i c u l t to demonstrate c l e a r l y that noise a f f e c t s performance. However, under some circumstances, some i n d i -v i d u a l s may become i r r i t a t e d by c e r t a i n types of noise and t h i s i n turn may have an e f f e c t on t h e i r work (Murrell 1979). Hearing l o s s r e s u l t i n g from high noise l e v e l at the workplace can be temporary or permanent (Benwell and Repacholi 1979). The hearing l o s s i s temporary i f hearing returns a f t e r a r e s t period. Temporary hearing loss may l a s t from a few minutes to a few days, depending upon the i n d i v i d u a l and the s e v e r i t y and length of exposure. Permanent hear-ing loss occurs as a r e s u l t of the aging process, disease, i n j u r y , or exposure to loud noise over a long period of time. Temporary hearing loss occurs from nerve or h a i r c e l l (sensor c e l l ) d estruction of the inner ear. The theory of hearing l o s s i s well documented i n the ergo-nomic l i t e r a t u r e (ANSI 1954, McCormick 1976, I r v i n and Graf 1979, Grandjean 1981). Other noise re l a t e d problems include: p h y s i o l o g i c a l and psycho-l o g i c a l e f f e c t s ; speech i n t e r f e r e n c e ; and increase i n heart rate and blood pressure (Grandjean 1981). The human ear has great s e n s i t i v i t y , as well as a great dynamic range over which i t normally functions ( I r v i n and Graf 1979). According to I r v i n and Graf (1979) the threshold of hearing varies from 0.00002 "•"Superscript (+) i n d i c a t e s word or term defined i n the glossary. - 6 -N/m or 0 dB (a young adult can j u s t perceive a 1000 Hz tone at t h i s pressure) to about 135 to 140 dB (threshold of p a i n ) . The threshold of hearing i s a function of frequency; the human ear i s most s e n s i t i v e i n the frequency range of 2000 to 5000 Hz ( I r v i n and Graf 1979). Hearing l o s s i s u s u a l l y measured i n terms of changes i n the threshold of hearing (Benwell and Repacholi 1979). Results from a l l these studies have contributed to the e s t a b l i s h -ment of standards for safety and health. In B r i t i s h Columbia, indus-t r i a l noise l e v e l s are governed by the Workers' Compensation Board I n d u s t r i a l Health and Safety Regulations (WCB 1980). These regulations (Section 13.21) o u t l i n e how sound l e v e l s should be measured, give t o l e r a b l e l e v e l s and durations of steady state and impact noise, and s p e c i f y requirements f o r t e s t i n g of hearing, and hearing p r o t e c t i o n . The Workers' Compensation Board's recommended l i m i t s f o r steady-state n o i s e + permit a maximum, unprotected exposure of machine operators to noise of 90 dBA + during an eight hour day. Exposure to noise l e v e l s greater than t h i s i s permitted by halving the exposure time per each a d d i t i o n a l 3 dBA increase, up to the maximum permissible noise l e v e l of 105 dBA (15 min). Some i n v e s t i g a t o r s (Benwell and Repacholi 1979) reported that the 90 dBA l i m i t f o r eight hours of exposure r e s u l t s i n an a d d i t i o n a l 20% of the workers s u f f e r i n g hearing impairment i n terms of verbal communica-t i o n , a f t e r 30 years, exposure to noisy workplaces, compared with a normal population of the same age group. Grandjean (1981) showed that the r i s k of damage to hearing, as a presumptive percentage of the work - 7 -f o r c e , as a function of noise l e v e l i n dBA and length of exposure i n years. In Sweden, the noise l e v e l i n s i d e logging machine cabs has been subject to continuous reduction, aimed at a lower l e v e l of 70-75 dBA (Axelsson 1981). The demand f o r quieter cabs for Swedish machines has demonstrated that the continuous noise, i n a confined workplace, can be very i r r i t a t i n g . Noise can cause a higher incidence of errors and accidents, which are reasons f o r taking steps to reduce the l e v e l s , or to provide personal p r o t e c t i o n ( M u r r e l l 1979). Even when noise i s not i n j u r i o u s , i t can be d i s t u r b i n g , and may lower p r o d u c t i v i t y , and cause communications d i f f i c u l t i e s (Hansson and Pettersson 1980). Results of noise studies i n Canadian logging operations (Myles e£ a l . 1971, Reif and Howell 1973, Howell 1974, Boivin et a l . 1977) have shown that machine operators work i n an environment with noise l e v e l s s u f f i c i e n t to cause hearing l o s s . 1.1.1.2 V i b r a t i o n The e f f e c t of whole-body vibration"*" (WBV) on humans has been the subject of many studies (Diekmann 1958, Goldman and von Gierke 1960, von Gierke 1965, Miwa 1967, Grether 1971, Guignard 1974, Hansson 1981). The influ e n c e of WBV on humans depends on v i b r a t i o n frequency ( s i n u s o i d a l , combination of various frequencies, or random); v i b r a t i o n i n t e n s i t y (amplitude, v e l o c i t y and a c c e l e r a t i o n ) ; direction" 1" of v i b r a t i o n with - 8 -respect to the body's anatomic co-ordinate system (X, Y and Z axis ); duration of exposure; body posture; and body surface i n contact with the source of v i b r a t i o n ( S j o f l o t 1971, McCormick 1976, Hansson 1981). Humans respond to v i b r a t i o n both p h y s i o l o g i c a l l y and subjec-t i v e l y . Gunderson and Wilson (1981) and Grim et a l . (undated) i n v e s t i -gating t r a c t o r v i b r a t i o n , reported studies c a r r i e d out i n Canada and i n Germany showing p o s i t i v e c o r r e l a t i o n between prolonged exposure to terrain-induced v i b r a t i o n and p h y s i o l o g i c a l d e t e r i o r a t i o n of the s p i n a l system. Goldman and von Gierke (1960) have observed changes also i n r e s p i r a t i o n , heart a c t i v i t y , and p e r i p h e r a l c i r c u l a t i o n , as immediate and t r a n s i e n t responses to moderate v i b r a t i o n . According to M u r r e l l (1979), humans who t r a v e l i n vehicles such as t r a c t o r s , frequently complain of traces of blood i n the urine, or of lumbar or abdominal pain. Subjective responses to v i b r a t i o n include f e e l i n g s of discomfort, apprehension and pain (Goldman and von Gierke 1960). Whole-body v i b r a t i o n i s f a t i g u i n g to operators of f o r e s t r y machinery; thus, i t a f f e c t s work performance (Hansson 1981). McCormick (1976), on the basis of Grether's (1971) study, l i s t e d the following g e n e r a l i z a t i o n s concerning the e f f e c t s of v i b r a t i o n on human perfo r -mance: impairment of v i s u a l a c u i t y , impairment of human tra c k i n g a b i l i t y , and decrement on tasks that require steadiness or p r e c i s i o n of muscular c o n t r o l . Howat (1978) included the following i n a l i s t of f a c tors i n f l u e n c i n g WBV: the s i z e and design of the machine; the operator's handling of the machine, i n c l u d i n g pace of work; t i r e condition; ground surface condition; and, load s i z e . - 9 -The accumulated knowledge from v i b r a t i o n research has resu l t e d i n t e c h n i c a l methods f o r determining the e f f e c t s of v i b r a t i o n on humans. The "Guide for the Evaluation of Human Exposure to Whole-Body V i b r a t i o n " (ISO + Guide No. 2631) was adopted i n 1974 and published i n 1978 (ISO 1978). This standard deals with v i b r a t i o n i n the frequency range of 1 to 80 Hz, and provides a c c e l e r a t i o n tolerance l e v e l s ( i n X, Y and Z d i r e c t i o n ) f o r d i f f e r e n t exposure times, f o r the three recognizable c r i t e r i a of preserving comfort, working e f f i c i e n c y , and safety or health. In Sweden, several studies of v i b r a t i o n i n logging machines have been c a r r i e d out according to the ISO guide (Axelsson 1981). The r e s u l t s showed that, f o r most modern machines, the v i b r a t i o n l e v e l l a y we l l below the standard exposure l i m i t s for "safety and health". The "fatigue-decreased p r o f i c i e n c y boundary", however, was generally exceeded f o r most machines. Furthermore, there have been no major improvements i n the v i b r a t i o n c h a r a c t e r i s t i c s of fo r e s t machines i n the past 5 to 10 years (Hansson 1981). In Canada, v i b r a t i o n studies of logging machines are scarce. However, the a v a i l a b l e l i t e r a t u r e (Brammer 1978, Howat 1978, Webb and Hope 1983) in d i c a t e d that v i b r a t i o n could contribute to health r i s k s among wood workers. 1.1.1.3 Working Position Relative to Seat, Controls and Pedals I d e a l l y , equipment design should s t a r t with the operator, who should have h i s equipment l a i d out around him i n po s i t i o n s which w i l l - 10 -ensure that h i s posture i s adequate, that he can see what he has to do, and so that he can operate h i s controls i n the most e f f i c i e n t manner (Mu r r e l l 1979). Unfortunately, these requirements are not always met. As i n d i c a t e d by Axelsson (1981) i n Sweden, the f o r e s t machine cab i s generally too small, the seat cannot be rotated without h i t t i n g the operator's knees, the controls are often i n c o r r e c t l y located, and cannot be a l t e r e d to s u i t the i n d i v i d u a l operator. In B r i t i s h Columbia, s i m i l a r r e s u l t s have been found for grapple yarders (Sauder 1980b, Souza 1980a), i n c l u d i n g i n s u f f i c i e n t seat adjust-ment and i n s u f f i c i e n t space for seat r o t a t i o n . Poor design of machine cabs r e s u l t s i n uncomfortable working postures which may lead to back, neck and shoulder pain and fatigue (Axelsson 1981). 1.1.1.4 V i s i b i l i t y The most common v i s i b i l i t y problems encountered i n grapple yard-ing operations can be placed i n two groups: those associated with the machine cab design (cab l o c a t i o n , window size and p r o t e c t i o n devices); and, those associated with the environmental (ground, stand and c l i m a t i c conditions) and operating (yarding distance and log size) f a c t o r s . Logging machine operators often must work i n uncomfortable p o s i -tions to overcome d e f i c i e n c i e s i n machine design, with respect to v i s i b i l i t y . For instance, when working on steep slopes i n B r i t i s h Columbia, grapple yarder operators must lean forward to see the working area (Sauder 1980b). This i s due to the cab's maximum v e r t i c a l v i s i -b i l i t y of 32° above the operators' eye l e v e l . - 11 -Window protection ( c r i s s - c r o s s s t e e l bars) has also contributed to obstructing operator's v i s i o n . To overcome t h i s problem, some modern Swedish machines are being equipped with impact-resistent safety glass (Axelsson 1981). Grapple yarding machines present a s p e c i a l type of v i s i b i l i t y problem. To e f f i c i e n t l y grapple or "hook" logs, the operators must p r e c i s e l y locate logs at varying distances along the e n t i r e yarding ' road. When logs are hidden from view, or yarding distances are greater than 90 m, a spotter (man equipped with a radio transmitter) to a s s i s t i n the log hooking operation i s required. The use of spott e r s , although e s s e n t i a l , tends to increase cycle time. The consequence i s the tendency to adopt smaller yarding distances than 180 to 210 m, as recommended by Conway (1978); as yarding distance decreases, road b u i l d -ing requirements increase. In a d d i t i o n , Sauder (1980b) observed that concave s i d e h i l l s f a c i n g the operator allowed for improved v i s i b i l i t y , but decreased depth perception at longer distances, and prevented e f f e c t i v e grappling unless the operator had the assistance of a spotter. L i g h t and weather conditions are other f a c t o r s that probably a f f e c t logging operators' working area v i s i b i l i t y . These v i s i b i l i t y problems reduce p r o d u c t i v i t y , and may increase fatigue and accident r i s k . 1.1.1.5 Cab Environment The environmental conditions i n s i d e a machine cab are a r e s u l t of \ - 12 -the combined a c t i o n of several f a c t o r s such as a i r temperature, humidity, and a i r v e l o c i t y . For convenience, the information provided by temperature and humidity measures has been reduced to s o - c a l l e d s t r e s s i n d i c e s (FAO 1974). Some of the more well-known are new e f f e c -t i v e temperature"1" (ETx), correct e f f e c t i v e temperature"*" (CET), and wet-bulb globe temperature"1" (WBGT). The FERIC + guide to ergonomic evalua-t i o n (Zerbe 1979) recommends, for logging operations, the use of the ETx. Each ETx value represents those combinations of dry-bulb tempera-ture and r e l a t i v e humidity that produce the same l e v e l of skin "wetness" as caused by regular sweating (McCormick 1976, Zerbe 1979). Men working i n unfavourable c l i m a t i c conditions do not perform as w e l l as those working where the environment i s optimum (Zander 1979). Heat st r e s s a f f e c t s body temperature. A r i s e i n body temperature can induce other corresponding p h y s i o l o g i c a l changes which, i f continued, can cause hyperthermia and dehydration. Increase i n heart rate i s another consequence of r i s e i n body temperature (Murrel 1979). Reduc-t i o n i n body temperature, due to co l d , can cause f r o s t - b i t e and, i n the extreme, death (McCormick 1976). Swedish studies have shown that temperature i n the machine cab i s often at a high l e v e l (35 to 40°C), and that operator comfort and work capacity are negatively a f f e c t e d (Axelsson 1981). The optimum l e v e l of temperature i n logging machine cabs recommended i n the Swedish ergonomic c h e c k l i s t (Aminoff et a l . 1974, Hansson and Pettersson 1981) i s 18 to 22°C. The FERIC ergonomic guideline (Zerbe 1979) recommends 19°C (ETx) f o r medium l e v e l of a c t i v i t y and l i g h t c l o t h i n g . - 13 -1.1.1.6 S t r e s s , S t r a i n and Fatigue The terms fa t i g u e , stress and s t r a i n are commonly used with d i f f e r e n t meanings. M u r r e l l (1979) defined fatigue as "the detrimental e f f e c t s of work upon continued work, which may manifest i t s e l f as a decrement i n performance". Fatigue can be c l a s s i f i e d as muscular or general. Grandjean (1981) made the following d i s t i n c t i o n between these fatigue categories: muscular fatigue i s "an acutely p a i n f u l phenomenon which a r i s e s i n the overstressed muscle, and i s l o c a l i s e d there"; general fatigue i s "a d i f f u s e d sensation, which i s accompanied by f e e l i n g s of indolence and d i s i n c l i n a t i o n for any kind of a c t i v i t y " . McCormick (1976) used the term " s t r e s s " to r e f e r to "any aspect of human a c t i v i t y or environmental a c t i o n upon the i n d i v i d u a l which r e s u l t s i n some undesirable cost to, or r e a c t i o n upon, the i n d i v i d u a l " . The cost or consequence on the i n d i v i d u a l he c a l l e d " s t r a i n " . H e r t i g (1979), based on Grandjean's (1970) work, considered the most important f a c t o r s that produce general fatigue to be: monotony; environmental f a c t o r s such as i l l u m i n a t i o n , climate, noise and v i b r a -t i o n ; manual or mental work i n t e n s i t y ; psychological f a c t o r s such as r e s p o n s i b i l i t y , worry, and c o n f l i c t ; and other f a c t o r s such as i l l n e s s , pain, and eating h a b i t s . H e r t i g (1979) concluded that, i n everyday work, fatigue i s an accumulation of the e f f e c t s of these sources. The common symptoms of fatigue are: decrease of a t t e n t i o n ; slowed and impaired perception; impairment of thinking; decrease of motivation; decrease of performance speed; decrease of accuracy and - 14 -increase of e r r o r s ; and, i n general, decrease of performance c a p a b i l i t y for p h y s i c a l and mental a c t i v i t i e s (Grandjean 1981). The ergonomic l i t e r a t u r e describes a number of methods f o r measuring fatigue (Grandjean and K o j i 1971, McCormick 1976, M u r r e l l 1979, F i b i g e r 1980, Ager 1981, Grandjean 1981). Some of these methods are: a. Electrocardiogram (ECG) or heart rate b. Electroencephalogram (EEG) c. Oxygen consumption d. F l i c k e r - f u s i o n frequency e. Electromyogram (EMG) f . Psychological and subjective t e s t s g. Blood content t e s t s (adrenaline or noradrenaline) h. Performance or mental t e s t s . Oxygen consumption and heart rate are methods frequently used to assess fatigue i n f o r e s t r y workers. These methods present several l i m i t a t i o n s which are r e l a t e d to i n d i v i d u a l f a c t o r s such as body c o n s t i t u t i o n , p h y s i c a l condition and sex (McCormick 1979). Several authors have used heart rate as a measure of p h y s i o l o g i c a l demands i n f o r e s t r y workers (Eide 1971, S j o f l o t 1971, van Loon 1971, Vik 1971, Wencl and Wenter 1971, Rohmert 1973, Smith et a l . 1982). P o s s i b l e explanations f o r heart rate preference among researchers could include the f a c t that heart rate i s r e l a t i v e l y simple to measure under f i e l d conditions, and that heart rate can i n d i c a t e psychophysiological stress during s t a t i c or dynamic work. - 15 -1.1 .2 Productivity Problems Numerous factors a f f e c t p r o d u c t i v i t y (output/unit of time) i n logging operations. The discussion of a l l p r o d u c t i v i t y r e l a t e d v a r i -ables i s not the object of t h i s research, since the e f f e c t s of environ-mental and operating f a c t o r s on p r o d u c t i v i t y have been the subject of many studies over the past 20 years. Studies on the e f f e c t s of ergo-nomic f a c t o r s are r e l a t i v e l y scarce. Several authors were concerned about low p r o d u c t i v i t y i n Canadian logging operations (Jegr and Thompson 1975, C o t t e l l and Lawrence 1980, C o t t e l l et a l . 1980). C o t t e l l et a l . (1980) reported that r e l a t i v e l y low p r o d u c t i v i t y , combined with high labour cost per hour, has resu l t e d i n high cost per unit of production i n Canadian logging operations. The preferred way to improve p r o d u c t i v i t y and reduce logging costs has been the mechanization of logging operations. However, new a l t e r n a t i v e s have to be considered i n the process of searching f o r more productive methods i n modern logging. The previous ergonomic factors d i s c u s s i o n has in d i c a t e d that ergonomic research can provide new a l t e r -natives to improve p r o d u c t i v i t y by properly balancing task and machine requirements against man's anatomical, p h y s i o l o g i c a l , perceptual and information processing c a p a b i l i t i e s (Smith and S i r o i s 1982). For instance, operational and mechanical delays are recognized causes of loss i n p r o d u c t i v i t y . However, i t i s possible that an important part of - 16 -the l o s s In productive time i s associated with design f a u l t s (e.g., poor layout of controls and di s p l a y s , uncomfortable seat) i n the man-machine system ( C o t t e l l et_ a l . 1980). These f a u l t s may lead the operator to boredom and fatigue which can cause loss i n productive time through e r r o r s , unnecessary or prolonged r e s t s , absenteeism, and l a t e s t a r t or early quit of scheduled work. 1 .2 Some Technical Problems In Evaluating Production and Ergonomic  Factors The reason f o r evaluating production and ergonomic factors i s to determine the changes needed i n equipment design or working method to achieve the ergonomic goal. Several authors ( C o t t e l l e_t a l . 1980, Axelsson 1981, Lawrence et_ a l . 1982) have recognized the necessity of adopting a "systems approach" i n man-machine studies. A systems approach attempts to consider the e n t i r e working environment of logging operations. Ergonomic studies i n logging have taken i n t o account a l i m i t e d set of fa c t o r s (Myles ejt a l . 1971, S j o f l o t 1971, Boiv i n et^ a l . 1977, Brammer 1978, Howat 1978, Smith et a l . 1982, Webb and Hope 1983); i n some instances, the researcher i s Interested i n a s p e c i f i c f a c t o r . However, lack of appropriate equipment, or d i f f i c u l t i e s i n applying t r a d i t i o n a l work study techniques, have prevented the design of e x p e r i -ments to explore man-machine systems. S j o f l o t (1971) and Myles et a l . (1971) have discussed d i f f i c u l -- 17 -t i e s and e f f o r t required to carry out such s tud ie s . Lawrence ^t_ a l . (1982) l i s t e d a number of problems that a r i se i f work study methods ( i n c l u d i n g the use of movie cameras) are used to inves t iga te the e f fect of machine changes ( e . g . , better v i s i b i l i t y , controls and seating) on system performance. These problems are : Personnel and equipment costs escalate with the number of man-machine functions observed. - Simultaneous time r e g i s t r a t i o n of events among observers and cameras becomes d i f f i c u l t . - Data must be t rans la ted to computer compatible forms. - A d d i t i o n a l var iab les taped or chart-recorded d i v e r s i f y the data base modes and increase the data processing problems. In forest harvest ing the major i ty of the ergonomic research pro jec t s have been conducted without taking i n t o account the production f a c t o r s . Studies attempting simultaneous measurement of ergonomic and product ion factors are even rarer (van Loon and Spoelstra 1971, Vik 1971, S j o f l o t 1971, Smith et a l . 1982). In these s tud ie s , the recording of the elapsed time for the d i f f e r e n t work a c t i v i t i e s usua l ly required researcher i n t e r v e n t i o n . The researcher e i t h e r pressed a button on a t imer-recorder device to i n d i -cate the end point or s t a r t of the work a c t i v i t i e s (Wencl 1973) or he used the t r a d i t i o n a l time study techniques such as the stopwatch (van Loon and Spoels tra 1971, Smith et_ a l . 1982). Review of the l i t e r a t u r e indica ted that no study has been under-taken using e l e c t r o n i c floating-aperture" 1 " data compression techniques to simultaneously record production and ergonomic f ac tor s , automat ica l ly - 18 -analyze the recorded data, and automatically determine work-cycle time i n logging, e s p e c i a l l y i n grapple yarding operations. This t h e s i s examines the grapple yarding task i n terms of the man-machine system (Figure 1) u t i l i z i n g simultaneous measurements of a number of important f a c t o r s ( l i s t e d i n Section 2.1) and the time consumed for the d i f f e r e n t a c t i v i t i e s . The primary data gathering t o o l i s a r e l a t i v e l y inexpensive e l e c t r o n i c Data Logger, newly developed for t h i s s p e c i f i c research. A d e t a i l e d analysis of these f a c t o r s requires a d i v i s i o n of the operating s h i f t (day) i n t o work-cycles ( t u r n s ) , and a further d i v i s i o n of the work-cycles i n t o work-elements (outhaul, hookup, inhaul and unhook) and delay elements. The recorded data allow the researcher to automatically (by computer) i n t e r p r e t man-machine a c t i v i t i e s , and determine the elapsed time f o r each work-cycle, work-element and delay. FIGURE 1 . G r a p p l e y a r d i n g m a n - t a s k s y s t e m . - 20 -2. SCOPE, OBJECTIVES AND HYPOTHESES 2.1 Scope of the Study Factors a f f e c t i n g the man-machine system were examined i n the introductory s e c t i o n of t h i s t h e s i s . However t h i s research was l i m i t e d to an evaluation of i n t e r - r e l a t i o n s h i p s among the following f a c t o r s c h a r a c t e r i z i n g the system: A. Ergonomic f a c t o r s a. Human f a c t o r 1. Heart rate b. Machine f a c t o r s 1. Noise l e v e l 2. V i b r a t i o n a c c e l e r a t i o n (X, Y, and Z d i r e c t i o n ) 3. Cab environment (temperature and humidity) B. Production f a c t o r s a. Environmental f a c t o r s 1. Ground conditions (roughness and slope) 2. Stand c h a r a c t e r i s t i c s (stand and log volume) 3. C l i m a t i c conditions (temperature and p r e c i p i t a t i o n ) b. Operating f a c t o r s 1. Yarding distance 2. Mainline speed 3. Mainline tension 4. Number of logs per turn (production) 5. Load volume and weight c. Operating time The study was also l i m i t e d to a s i n g l e grapple yarder machine and i t s operator working i n a c o a s t a l B r i t i s h Columbia f o r e s t , under summer cond i t i o n s . - 2 1 -2.2 Study Objectives and Hypotheses The objectives of t h i s study were to use the U n i v e r s i t y of B r i t i s h Columbia e l e c t r o n i c Data Logger system to: a. Develop and t e s t an automated method f o r c o l l e c t i n g and analysing production and ergonomic data i n logging operations. b. Determine the elapsed time f o r the Madill-044 grapple yarder work-cycles (turns) and work-elements from the automatically recorded data. c. Analyze production and ergonomic f a c t o r s w i t h i n machine work-cycles and respective elements. d. Determine the r e l a t i o n s h i p s among work-element times and yarding distance, mainline tenBion and mainline speed. e. Analyze the duration of execution time of work-elements over the s h i f t . f . Compare act u a l measured values of noise l e v e l , v i b r a t i o n a c c e l e r a t i o n , e f f e c t i v e temperature, heart r a t e , and mainline tension with recommended standards for safety, health and fatigue-decreased p r o f i c i e n c y . g. Determine r e l a t i o n s h i p s among values of production and ergonomic f a c t o r s measured during the grapple yarding opera-t i o n . In the study of production and ergonomic f a c t o r s many hypotheses can be formulated. However, i n an attempt to provide a better under-standing of what i s known about the grapple yarder man-machine system, - 22 -both through the r e l a t i v e l y scarce l i t e r a t u r e and through observations of t h i s sytem, the following hypotheses were posed: a. There i s no d i f f e r e n c e i n the average value of noise l e v e l , heart rate or mainline tension from element to element of the work c y c l e . b. Yarding distance explains 70% ( r e l a t i v e high value f o r a s i n g l e grapple yarding v a r i a b l e ) or more of the v a r i a t i o n i n inhaul or outhaul time. c. Owing to fatigue e f f e c t , execution time of work-elements increases during the s h i f t . d. Hookup time increases as yarding distance increases. e. Operator's heart r a t e , noise l e v e l , v i b r a t i o n a c c e l e r a t i o n , mainline tension exceed the recommended standard l i m i t s f o r safety or health and fatigue-decreased p r o f i c i e n c y . f . There i s no l i n e a r c o r r e l a t i o n (r » 0) between the average work-cycle values f o r v a r i a b l e p a i r s within each of the fol l o w i n g sets: Set A V i b r a t i o n a c c e l e r a t i o n Mainline tension Yarding distance Mainline speed Noise l e v e l Set B Heart rate Noise l e v e l V i b r a t i o n a c c e l e r a t i o n Yarding distance Mainline speed - 23 -3. STUDY AREA AND MATERIALS USED IN DATA COLLECTION 3.1 Study Area D e s c r i p t i o n Grapple yarding operations of MacMillan Bloedel Ltd.'s Shawnigan D i v i s i o n , located approximately 35 km west of Duncan, B r i t i s h Columbia, were chosen f o r t h i s study. The harvesting area was located i n the "Coastal Western Hemlock Biogeoclimatic Zone" (Courtin and K l i n k a 1983), with a l t i t u d e (above sea l e v e l ) varying from 600 to 800 m. The area contained an old-growth c o n i f e r stand c o n s i s t i n g of approximately 45% Western Hemlock (Tsuga heterophylla (Raf.) Sarg.); 20% P a c i f i c S i l v e r F i r (Abies amabilis (Doug.) Forbes); 20% D o u g l a s - f i r (Pseudotsuga menziesii (Mirb.) Franco); 8% Western Red Cedar (Thuja  p l i c a t a (Donn)); and 7% Yellow Cedar (Chamaecyparis nootkatensis (D. Don) Spach). The stand had the following average c h a r a c t e r i s t i c s : age, 225 years; t o t a l net volume, 780 m3/ha; volume per tre e , 2.92 m3; number of tr e e s , 267/ha; height, 28.8 m; and diameter at breast height (DBH), 0.60 m. A l l trees with diameter (at stump height of 0.30 m) greater than or equal to 0.23 m were c l e a r cut. The bucking procedure attempted to optimize stem u t i l i z a t i o n up to 0.15 m top diameter. Log length varied from 9.7 m to 12.4 m; the smallest recoverable log was 3 m i n length. The study was conducted during four 8-hr s h i f t s : s h i f t 1 ( J u l y 07), s h i f t 2 (July 08), s h i f t 3 (July 22), and s h i f t 4 (July 29, 1982); - 24 -which corresponded to four d i f f e r e n t harvesting areas. Ground condition within the harvesting area varied with the d i f f e r e n t s h i f t s studied. Based on the "Terrain C l a s s i f i c a t i o n f o r Canadian Forestry" (Mellgran 1980) ground roughness ranged from rough to very rough. On s h i f t 2 and 4, there was heavier brush than on s h i f t 1 and 3. On s h i f t 1 and 3 the machine yarded logs located on paths, or yarding roads, that crossed a deep ravine. T e r r a i n slope on these paths varied from 30% to more than 90%. Slope was moderate (Mellgran 1980) c l o s e r to the roadside (machine) and very steep on both sides of the ravine. On s h i f t s 2 and 4 the logs were located on more uniform yarding roads. T e r r a i n slope was under 50% on s h i f t 2, and under 30% on s h i f t 4. Yarding was u p h i l l on a l l s h i f t s studied. 3.2 Logging Equipment and Operating Crew The logging equipment consisted of a three-year-old Madill-044 grapple yarder ( s p e c i f i c a t i o n s are presented i n Appendix 1) and a r e b u i l t C a t e r p i l l a r D8H mobile backspar (Figures 2, 3, 4, and 5). The yarder was equipped with three main cables: a mainline to p u l l the grapple and load (log) i n to the haul road; a haulback to take the grapple out to the stump area; and a t a g l i n e to open the grapple. The grapple carriage r i d e s on the haulback l i n e by means of a p u l l e y , or sheave (Figure 6). FIGURES 2, 3. M a d i l l 044 g r a p D l e yarder (2) and C a t e r p i l l a r D8H backspar (3). FIGURES 4, 5. M a d i l l 044 o p e r a t o r ' s cab (4) and machine grapple ( 5 ) . GRAPPLE YARDER CRAWLER TRACTOR (BACKSPAR) FIGURE 6. Schematic of grapple yarding system (adapted from Sauder (1980b)). - 28 -A yarder operator, a spotter and a mobile-backspar operator usually compose the yarding crew. The machine operator was a healthy, 30-year-old man with more than f i v e years, experience on grapple yarding operations. The yarder works from a logging road and the backspar from t r a i l s normally p r e - b u i l t along the boundary of the s e t t i n g area or occa-s i o n a l l y from another logging road. Once the yarder and backspar have been set up the yarding operation s t a r t s (Figure 7). The yarder operator sends the grapple out (outhaul), seizes one or more logs (hookup), brings the loaded grapple to the landing or roadside ( i n h a u l ) , and releases the log(s) i n a log deck near the machine (unhook). Delays may occur during execution of any of these work-elements. The work-cycle i s repeated u n t i l a l l logs, from a given yarding road, are yarded to the roadside (or landing) to be loaded on trucks and transported to the m i l l s . At t h i s point, the grapple yarder or the backspar moves to another l o c a t i o n and a new yarding road i s s t a r t e d . This moving a c t i v i t y i s c a l l e d "yarding road change". 3.3 Data Collection Equipment 3.3.1 The Electronic Forest Harvesting Data Logger and Peripherals The f o r e s t harvesting Data Logger System, as i l l u s t r a t e d by C o t t e l l et a l . (1980) and Sauder (1982), was used to simultaneously c o l l e c t data on operating and ergonomic f a c t o r s during grapple yarding - 2 9 -F I G U R E 7. P r o c e s s c h a r t o f t h e g r a p p l e y a r d i n g o p e r a t i o n . - 30 -operations. The e l e c t r o n i c Data Logger system i s b a s i c a l l y composed of a f i e l d recording unit and a laboratory data i n t e r p r e t i n g unit (Figures 8, 9). The f i e l d u n i t , i n s t a l l e d i n the machine cab, consists of: an RCA COSMAC microprocessor-based module which provides up to 16 analog and up to 16 d i g i t a l input channels; and an incremental d i g i t a l cassette recording module, which records data events composed of the channel i d e n t i f i c a t i o n , the data value and i t s time of occurrence. The o f f i c e u n i t comprises a Datel LPR-16 cassette reader and a Hewlett-Packard 9845B computer. Programs e s p e c i a l l y developed f o r the Data Logger's microproces-sor c o n t r o l the sampling of the operating data input channels. The present sampling rate i s set at 60 ms (millisecond) per 32 channels, which can be considered a simultaneous scan of a l l channels i n a given ergonomic study. Under program c o n t r o l , the microprocessor writes data only when a s i g n a l changes by a pre-determined quantum. The cassette unit can record a maximum of 2.5 data events per second. At t h i s recording rate, the cassette tape storage capacity i s s u f f i c i e n t f o r more than eight hours of continuous recording. This i s po s s i b l e due to the f l o a t i n g - a p e r t u r e data compression algorithm explained by Lawrence et a l . (1982) which determines whether data from a channel should be recorded at a p a r t i c u l a r sample time. That i s , data are only recorded when changes on a channel exceed a preset tolerance. At the present, the tolerance i s set to 5/51 V (Volt) (5 counts) f o r a l l analog channels. Continuous (analog) data values recorded are FIGURES 8, 9. E l e c t r o n i c Data Logger system components: f i e l d r e c o r d i n g u n i t ( m i c r o p r o c e s s o r ( t o p ) , c a s s e t t e r e c o r d e r and v i b r a t i o n a n a l y z e r ( 8 ) ) ; and l a b o -r a t o r y data i n t e r p r e t i n g u n i t ( c a s s e t t e reader ( l e f t ) , HP 9845B, p l o t t e r and d i s k d r i v e ( 9 ) ) . - 32 -represented by numbers (counts) between 0 and 255; d i g i t a l channel data values are represented by 0 or 1. The e l e c t r o n i c Data Logger system i s considered superior to the t r a d i t i o n a l stopwatch methods used i n work study due to i t s automatic capacity of simultaneous sampling and recording of a number of v a r i a b l e s at the accuracy of 1/1000 min. The present configuration of the Data Logger system (Figure 10) comprises the following measuring devices: a. Yarding distance b. Log count c. Noise l e v e l d. V i b r a t i o n a c c e l e r a t i o n e. Heart rate f . Cable tension g. Wet and dry bulb temperature. 3.3.1.1 Yarding Distance Yarding distance was measured to i n v e s t i g a t e r e l a t i o n s h i p s among va r i a b l e s and to enable automatic i n t e r p r e t a t i o n of the grapple yarder work-cycle, work-elements and delays. The yarding distance measuring device (Clark 1980a), consists b a s i c a l l y of two magnetic proximity switches or sensors (Honeywell/Micro Switch No. FYCB16A1-2) and one or more metal targets (Figure 11). The metal targets are mounted on the machine cable drum and the magnetic switches on the machine frame. When - 33 -m HOOUUTOB 4 FM TRANSCEIVER W V . TOUBCIIVER 1 m DOOOULATOt ) MICROPHONE - _ - CABLE TENSION TEN3IUMIEILU LOAd ECTRON C E L L PREANP . TEMPERATURE TEHF. A SENSOR *• • PREAM^— TAROING 01STANCE TARGET PLATE ON MACHINE ORUM • MAGNETIC • M, SWITCHES i J X DIRECTION OECOOER 1—1 O I G I T A L UP/OOUI COUNTER tttt 0/A CONVERTER MICRO • PROCESSOR UNIT F I E L D LABORATORY' S P E C I A L I/O CONNECTION PORTABLE TERMINAL SERIAL KEYBOARD INTERFACE TAPE CASSETTE DATA RECORDER PRINTER INTERFACE THERMAL PRINTER SWITCHES 4.0G COUNTER ., —»INHAUL • /""""fcriUTHAUL fTC. D I G I T A L LOG COUNTER O I S P U Y DATEL SSET HP-9845 B DESK-TOP COMPUTER b L 3E CRT SCREEN o USC COMPUTER NETWORK GRAPHICS PLOTTER FIGURE 1 0 . Schematic of the e l e c t r o n i c Data Logger system (adapted from Souza et a l . ( 1 9 8 1 ) ) . - 34 -FIGURE 12. Log count d e v i c e ( d i g i t a l d i s p l a y and push but t o n s w i t c h ) . The d e v i c e d i s p l a y s a s i g n (+) to i n d i c a t e o c c u r r e n c e of data r e c o r d i n g o v e r f l o w . - 35 -the drum ro t a t e s , the magnetic switches detect the passage of the target(s) and generate output signals which are used to count the number of corresponding r e v o l u t i o n s , as w e l l as determine the d i r e c t i o n of drum r o t a t i o n . Depending on the d i r e c t i o n of the movement, the cumulative sum of revolutions i s incremented or decremented by one count each r o t a -t i o n . The count s i g n a l i s converted from d i g i t a l to analog (conversion r e s o l u t i o n of 1 part i n 2 ) and recorded by the Data Logger. With one target the system i s accurate to within two revolutions (two counts). The sources of error are: target reverses d i r e c t i o n before reaching the second sensor: target o s c i l l a t e s about one sensor; and target makes incomplete r e v o l u t i o n ( q u a n t i z a t i o n ) . 3.3.1.2 Number of Logs Number of logs yarded per work-cycle was measured to estimate grapple yarder p r o d u c t i v i t y . The device used to t a l l y the number of logs yarded per turn c o n s i s t s of a normally open, push-button switch and a d i g i t a l d i s p l a y (Figure 12). The operator presses the button a number of times corres-ponding to the number of logs yarded per turn. The accumulated number of logs produced i n a s h i f t appears i n the displa y , and the number of logs per work-cycle i s recorded on the Data Logger cassette tape. 3.3.1.3 Mainline Tension Mainline tension was measured to i n v e s t i g a t e r e l a t i o n s h i p s among - 36 -v a r i a b l e s and to evaluate the forces involved during the log yarding operation. Mason (1982) described the mainline tension measuring device used, which consists of a tensiometer and an a m p l i f i e r (Figures 13 and 14). The a m p l i f i e r i s an Ectron model 687, operated by a 12 V battery and provided with a front panel gain switch. Selectable gain steps are 10, 20, 50, 100, 200, 500, and 1000 u n i t s . The Ectron d e l i v e r s e x c i t a t i o n of 7 V to the s t r a i n gauge bridge of the load c e l l . The tensiometer i s made up of a load c e l l , a crank mechanism, and a set of three sheaves. The load c e l l i s a BLH type U3G1 with 10000 l b (4536 kg) capacity or 15000 l b (6804 kg) of safe working load. I t s output i s 3 mV ( m i l l i v o l t ) per V o l t input, with accuracy of 0.3%. The load c e l l output varies from 0 to 21 mV, due to the a m p l i f i e r e x c i t a t i o n voltage (7 V i n p u t ) . In operation, the mainline cable i s wound through the sheaves. The d e f l e c t i o n forces generated by the main l i n e during log yarding are t r a n s f e r r e d to the load c e l l by the crank mechanism. The load c e l l produces an e l e c t r i c a l s i g n a l which i s amplified by the Ectron a m p l i f i e r and sent to the Data Logger. The tensiometer was c a l i b r a t e d using a Baldwin Tate-Emery t e s t i n g machine (Mason 1982). 3.3.1.4 Heart Rate An i n d i c a t i o n of the operator's p h y s i o l o g i c a l work i n t e n s i t y was - 37 -FIGURE 13. Ect r o n a m p l i f i e r . FIGURE 14. Tensiometer showing the load c e l l , the crank mechanism and the main sheave ( r i g h t side view). - 38 -obtained by measuring the heart rate using the electrocardiograph instrument (ECG) described by Clark (1980b). The instrument employs three electrodes and a heart rate monitor unit (Figure 15). The system generates an analog s i g n a l which corresponds d i r e c t l y to heart r a t e , s t a r t i n g from 40 beats per minute (bpm). The output s i g n a l can be d i r e c t l y or i n d i r e c t l y transmitted to the Data Logger. I n d i r e c t transmission requires a frequency modulated radio system. The accuracy of the system i s ± 1 bpm i n the range of 40 to 90 bpm. Over 90 bpm the accuracy gradually decreases (e.g., ± 2 bpm at 120 bpm and ± 3.3 bpm at 200 bpm). The monitor was c a l i b r a t e d using a standard s i g n a l delivered by an E l e c t r o n i c Signal Generator. 3.3.1.5 Noise Level Noise l e v e l measurement was c a r r i e d out to i n v e s t i g a t e the r e l a t i o n s h i p of t h i s f a c t o r to other measured conditions, and f o r comparison with WCB recommended standards (WCB 1980). Data were recorded using a Bruel and Kjaer Integrating Sound Level Meter, type 2225 (Bruel & Kjaer undated-b). The instrument consists of a detachable microphone and a sound i n t e g r a t o r unit (Figure 16). The main features of type 2225 are: b u i l t - i n A-weighting network"1"; b u i l t i n equivalent sound level"*" (Leq) measurement for 60-second time i n t e r v a l ; "fast"*"" and "slow"1"" time constants; and "peak h o l d + " mode. FIGURE 16. B r i i e l & K j a e r sound l e v e l meter ( type 2225) . - 40 -The meter measurement range varies from 25 to 140 dBA. Noise l e v e l s are read d i r e c t l y from a display , or recorded. The display mode gives a 40 dBA dynamic range with 0.5 dBA r e s o l u t i o n . The output mode gives 60 dBA range (20 dBA over the upper value of the di s p l a y range) with 0.25 dBA r e s o l u t i o n . The meter was c a l i b r a t e d using the Briiel & Kjaer Noise Level C a l i b r a t o r , type 4230. ^ 3.3.1.6 V i b r a t i o n A c c e l e r a t i o n V i b r a t i o n a c c e l e r a t i o n was measured to in v e s t i g a t e r e l a t i o n s h i p s between v i b r a t i o n and other v a r i a b l e s , and to evaluate a c c e l e r a t i o n l e v e l s with respect to the ISO recommended standard (ISO 1978). The equipment used i n v i b r a t i o n measurements consists of a v i b r a t i o n analy-zer and a Kyowa accelerometer (Figures 17 and 18). A complete d e s c r i p -t i o n of these instruments i s given by Kindsvater (1982). The accel e r o -meter generates e l e c t r i c a l s i g n a l s corresponding to ac c e l e r a t i o n s experienced i n the X, Y and Z axes over the range of 1 to 80 Hz. These signals are transmitted to the v i b r a t i o n analyzer and weighted according to the ISO standards (ISO 1978). The instrument allows f o r frequency a n a l y s i s by means of s i x one-octave +, band-pass f i l t e r s based on the following center frequen-c i e s : 1, 2, 4, 8, 16 and 32 Hz. The weighted and f i l t e r e d signals are converted to root-mean-square + (rms) values over a 10-second time i n t e r v a l . The Data Logger samples and records these rms values. FIGURE 17. V i b r a t i o n a n a l y z e r . FIGURE 18. Kyowa a c c e l e r o m e t e r . - 42 -3.3.1.7 Temperature and Humidity Measures of the machine cab environmental conditions were obtained by measuring wet-bulb and dry-bulb temperature. Thermistors"*" were used In the temperature measuring devices used i n t h i s study (Figure 19). Thermistors, when e x t e r n a l l y heated, convert changes i n ambient or contact temperatures d i r e c t l y to corresponding changes i n resistance which can be converted to a voltage or current (Anonymous 1970). The main disadvantage of these "thermal r e s i s t o r s " i s that changes i n voltage are not d i r e c t l y p roportional to changes i n temperature. There-f o r e , during the c a l i b r a t i o n process, regression equations to convert voltage to temperature were developed (Appendix 2). Two temperature measuring devices were b u i l t using the same type of thermistors and e l e c t r i c a l c i r c u i t designs: a dry-bulb thermometer that measures the ambient a i r temperature, and a wet-bulb thermometer that measures the temperature decrease due to evaporation from a wet surface. A wetted wick connected to a r e s e r v o i r of d i s t i l l e d water placed around the thermistor provided the wet surface of the wet-bulb thermometer. A small fan provided adequate a i r c i r c u l a t i o n around the wet-bulb thermometer. Re l a t i v e humidity i n s i d e the machine cab was obtained using the recorded wet-bulb and dry-bulb temperature values and the equations given by Black (undated), shown i n Appendix 2. FIGURE 19. T e m p e r a t u r e m e a s u r i n g d e v i c e ( w e t -b u l b and d r y - b u l b t h e r m o m e t e r s ) . - 44 -4. METHODS USED FOR COLLECTING, PROCESSING AND ANALYZING DATA 4.1 Data C o l l e c t i o n Methods Data c o l l e c t i o n was c a r r i e d out from January to July of 1982. The f i r s t months were scheduled to continue adjusting or c a l i b r a t i n g the e l e c t r o n i c Data Logger components to properly measure a l l variables of t h i s study. When s a t i s f a c t o r y f unctioning of the system was reached the f i n a l data c o l l e c t i o n s t a r t e d . Figure 8 i l l u s t r a t e s the i n s t a l l a t i o n of the Data Logger i n the machine cab. 4.1.1 Yarding Distance Yarding distance was obtained by i n s t a l l i n g the measuring device on the mainline drum (Figure 20). Two metal targets were mounted on the drum for greater measurement accuracy (0.5 r e v o l u t i o n ) . Distance measurement started with the grapple close to the yarder to have t h i s p o s i t i o n as the zero reference point. The accuracy of distance measurement depends on the number of targets i n s t a l l e d on the drum, the number of wire rope wraps on the drum, and on the count i n t e r v a l set on the Data Logger ( i n t h i s study equals to 5). When 2 targets were used the following re s o l u t i o n s were given: FIGURE 2 0 . I n s t a l l a t i o n o f t h e d i s t a n c e m e a s u r i n g d e v i c e on t h e m a c h i n e drum of t h e M a d i l l 044 g r a p p l e y a r d e r . - 46 -Wrap No. Sampling Recording (from f u l l Resolution Resolution drum) (m) (m) 1 ± 1.17 ± 5.85 2 ± 1.09 ± 5.45 3 ± 1.01 ± 5.05 4 ± 0.93 ± 4.65 5 ± 0.85 ± 4.25 The device's accuracy was checked using both a range f i n d e r and a measuring tape. 4.1.2 Number of Logs The number of logs was reg i s t e r e d for each turn or work-cycle. The operator used the log-count devices which had been i n s t a l l e d i n the machine cab (Figures 21 and 22). The consistent recording during the unhook phase of number of logs produced information f o r the machine work-cycle i n t e r p r e t a t i o n . 4.1.3 Mainline Tension The tensiometer was i n s t a l l e d on the grapple yarder boom (tower), - 47 -FIGURE 2 1 , 2 2 . I n s t a l l a t i o n of l o g count s w i t c h ( 2 1 ) and l o g count d i s p l a y ( 2 2 ) in o p e r a t o r s ' s cab. - 48 -and the mainline cable was positioned between the three tensiometer sheaves (Figure 23). Placing the tensiometer at the tower upper h a l f , where cable v i b r a t i o n was minimum, provided a safe and secure i n s t a l l a -t i o n . In a d d i t i o n , the tensiometer was allowed to move i n place to minimize i n t e r f e r e n c e with a c t u a l l i n e tension measurements. The r e s o l u t i o n of the system depends on the selected Ectron gain ("spacing") of the main sheave (Appendix 2, Figure A2) the higher the gain the higher i s the r e s o l u t i o n . However, considerably more data are recorded when a higher gain unit i s s e l e c t e d . Preliminary t e s t s i n d i c a -ted that e i t h e r gain 50 or 100 were adequate. The adjustments of the tensiometer system provided the following r e s o l u t i o n s : and on the tensiometer adjustments. For a c e r t a i n adjustment Gain Sampling Resolution Recording Resolution (kg) (kg) 50 ± 454 ± 2270 100 ± 227 ± 1135 4.1.4 Heart Rate The heart monitor was i n s t a l l e d on the back-rest of yarder seat and three electrodes (NDM No. 01-1015) were placed on the operator's - 49 -FIGURE 24. P l a c e m e n t o f t h e h e a r t r a t e m o n i t o r i n g e l e c t r o d e s on t h e o p e r a t o r ' s c h e s t . - 50 -chest (Figure 24) as recommended by Thakor (1978). A wide e l a s t i c belt placed around the operator's body f i x e d the electrodes more securely. The monitor sampling r e s o l u t i o n was set to ± 1.17 bpm, which gave a recording r e s o l u t i o n of ± 5.88 bpm. The heart rate s i g n a l was de l i v e r e d to the Data Logger v i a a coax i a l cable. The operator therefore had to disconnect the equipment i f he had occasion to leave the machine cab. 4.1.5 Noise Level The noise l e v e l measuring instrument was i n s t a l l e d i n the machine cab (Figures 25 and 26). An extension cord connected the microphone, placed at the operator's l e f t ear, to the meter attached to the cab w a l l . A p i l o t test i n d i c a t e d that the noise l e v e l at the operator's l e f t ear i s usu a l l y higher than at the ri g h t ear, i f the l e f t or both windows are opened. This was p r i m a r i l y due to the noise from the drums located on the l e f t side of the cab. Preliminary t e s t s i n d i c a t e d that the meter range of 50 to 110 dBA was the most appropriate f o r t h i s study. The noise meter was set to the "slow" response mode and sound l e v e l s were continuously sampled over the operating day. The "slow" mode, besides being recommended by WCB standards, was the meter record-ing mode most compatible with the Data Logger and with the objectives of the study. Data Logger recording data capacity prevented use of the more accurate " f a s t " mode. FIGURES 25, 26. I n s t a l l a t i o n of sound l e v e l meter on machine cab (25) and placement of the meter micro-phone at the o p e r a t o r ' s l e f t ear ( 2 6 ) . - 52 -Noise was sampled at ± 0.39 dBA r e s o l u t i o n and recorded at ± 1.96 dBA r e s o l u t i o n . 4.1.6 Vibration Acceleration V i b r a t i o n data were obtained through measurement of the v i b r a t i o n a c c e l e r a t i o n (according to ISO g u i d e l i n e s ) at the machine operator's seat, which i s the main point of v i b r a t i o n transmission to the human body. A c c e l e r a t i o n values were converted to root-mean-square (rms) and 2 2 expressed i n m/s or i n g u n i t s (1 g = 9.81 m/s ). The accelerometer was i n s t a l l e d on a f a l s e seat, s i m i l a r to that used by Howat (1978). I t consisted of plywood cut to the seat surface s i z e and containing a hole i n i t s center. A piece of aluminum plate was attached to the center of the plywood allowing secure i n s t a l l a t i o n of the accelerometer (Figure 27). A six-centimeter thick cushion was used to cover the f a l s e plywood seat (Figure 28). A c c e l e r a t i o n was simultaneously measured i n the three l i n e a r d i r e c t i o n s (X, Y and Z) f o r the e n t i r e operating s h i f t . V i b r a t i o n values were sampled and recorded by the Data Logger at the following r e s o l u t i o n s : V i b r a t i o n D i r e c t i o n Sampling Resolution Recording Resolution (axis) (g) (g) X ± 0.001076 ± 0.005380 Y ± 0.001019 ± 0.005095 Z ± 0.001034 ± 0.005170 FIGURE 27, 28. F a l s e seat used to h o l d the a c c e l e r o m e t e r (27) and i t s i n s t a l l a t i o n on o p e r a t o r ' s seat (28 ) . - 54 -4.1.7 Temperature and Humidity Temperature sensors were attached to the wall of the machine cab. Dry-bulb and wet-bulb temperatures were recorded f o r the e n t i r e working s h i f t . The temperature measuring devices were c a l i b r a t e d to record data i n the range of 5 to 40°C. Temperature signals were sampled at ± 0.0196 V and recorded at ± 0.0980 V r e s o l u t i o n . In degrees C e l s i u s temperature recording r e s o l u t i o n varied approximately from ± 1.17°C at 5°C to ± 0.22°C at 40°C. Voltage was r e l a t e d to temperature by means of regression equa-t i o n s developed during the c a l i b r a t i o n process (Appendix 2). R e l a t i v e humidity was computed using the equations given by Black (undated) a l s o shown i n Appendix 2. 4.2 Data Processing Methods Data were processed using the U n i v e r s i t y of B r i t i s h Columbia Forest Harvesting computer system. I t consisted of a Hewlett-Packard (HP) 9845B desktop computer, a 9872A p l o t t e r , a 9885M disk drive and a LPR-16 Datel cassette reader (Figures 9, 10). 4.2.1 Data Handling Computer Programs Computer programs have been written to i n t e r p r e t and analyze data - 55 -from a highlead logging operation (Sauder 1979, Sauder 1980). Although some of these programs can be applied to the grapple yarder operation, mod i f i c a t i o n s and new programs were needed. M o d i f i c a t i o n s included new reading and w r i t i n g techniques f o r the "TRANSF" and "CONVRT" programs described by Sauder (1978). New programs included those f o r data i n t e r -p r e t a t i o n , data p l o t t i n g and data a n a l y s i s . Programs were written i n enhanced "BASIC" f o r the 9845B computer (Hewlett-Packard 1981). The following sections describe the data handling (Figure 29). 4.2.1.1 Hexadecimal T r a n s c r i p t i o n The t r a n s c r i p t i o n of hexadecimal data from the Data Logger cassette tape to the HP 9845B cassette tape was c o n t r o l l e d by the' "TRANSF" computer program (Sauder 1979). The o r i g i n a l program was s l i g h t l y modified to handle large amounts of data (Souza 1983). 4.2.1.2 Hexadecimal Conversion Conversion of data from hexadecimal to decimal numbering system was c a r r i e d out by the "CONVRT" computer program (Souza 1983). The major l i m i t a t i o n of the o r i g i n a l program (Sauder 1979) was lack of a tape management se c t i o n to c o n t r o l tape use. The new version improvements were: tape management subroutine which searches f o r the f i r s t to the l a s t tape containing hexadecimal data; disk management section which enables storage of converted data (decimal) on one or more disks as needed; and channel frequency count. - 56 -HEXADECIMAL DATA (OATA LOGGER CASSETTE) I 1 . TRANSF i I J HEXAOECIHAL DATA (HP CASSETTE) 1" CONVRT "! I I OECIMAl DATA (HP CASSETTE/DISK) — — « SELECT I DATA SORTED BY CHANNELS PRPARE ' | 1 j^ PLOTER J RAW OATA PLOTS (CHECK FOR M1SP.ECOROEO OATA) OATA ACCEPTEO DATA REJECTED OATA EDITED ANO CONVERTED TO PROPER UNITS LOG COUNT MAINLINE TENSION HEART RATE YARDING DISTANCE l 1—DJiJ'SLj NOISE LEVEL BASIC STATISTICS PCQRREL M , I CORRELATION ANALYSIS OMPARISON WITH 4 PRPARE I I _ _ J FILTERED OISTANCE DATA VIBRATION X IERGAVE i — -r 1  -« TURNIN j TIME FOR CYCLE ELEMENTS ANO OELAYS OEFTNEO I 1 E P. GAVE WEIGHTED AVERAGE WITHIN ELEMENTS PETEPHIWEO VIBRATION VIBRATION I UET-BULB TEMP. I 1 I HISTOG ! WEIGHTED AVERAGE WITHIN ELEMENTS DETERMINED -^TURNCA j DISTANCE, NO. LOGS AND TIME FOR ELEMENTS ANO OELAYS DETERMINED REGRESSION ANALYSIS 0RY-8UL8 TEMP. RELATIVE HUMIDITY COMPARISON WITH STANOAROS EFFECTIVE TEMPERATURE | T — « PCORREL _j CORRELATION AND/OR REGRESSION ANALYSIS BASIC STATISTICS FIGURE 29. Data flow used i n t h i s r e s e a r c h . Dashed boxes show computer programs i n v o l v e d i n data p r o c e s s i n g (program names were r e s t r i c t e d to s i x c h a r a c t e r s ) . - 57 -Other features of "CONVRT" include: decoding of d i g i t a l switch information ( i . e . , log count) i n t o data events; and detecting occurrence of Data Logger memory overflow. 4.2.1.3 Channel Sorting The "SELECT" computer program (Souza 1983) sorts data events stored by the "CONVRT" program in t o the d i f f e r e n t channels recorded. Options a v a i l a b l e are: sort 1 to 8 s p e c i f i e d channels; sort a l l channels; store s p e c i f i e d channels on s p e c i f i e d tape or on two tapes simultaneously as d i c t a t e d by storage requirements; and p r i n t data on computer screen or paper. 4.2.1.4 Data Plotting The "PLOTER" program (Souza 1983) provided a v i s u a l picture of the data c o l l e c t e d . Graphs were produced showing any v a r i a b l e studied (Y-axis) against observed time (X-axis). The graphs were important i n checking f o r misrecorded information as well as i n aiding data analysis and work-cycle i n t e r p r e t a t i o n . Program options include: a. Choice of p l o t t i n g i n t e r v a l time. A small time i n t e r v a l (e.g., 5 min) allows f o r d e t a i l e d a n a l y s i s , while a large time i n t e r v a l (e.g., 480 min or standard working s h i f t ) allows for a global a n a l y s i s of the - 58 -behavior of a c e r t a i n v a r i a b l e during the working day. b. Choice of one or two Y - v a r i a b l e s . When more d e t a i l e d information was required for a c e r t a i n v a r i a b l e , s i n g l e v a r i a b l e p l o t s were used. For example, graphs of yarding distance versus operating time produced an important v i s u a l aid for work-cycle i n t e r p r e t a t i o n . P l o t s of two v a r i a b l e s against observed time served as an aid i n the process of i d e n t i f y i n g r e l a t i o n s h i p s between f a c t o r s studied. c. Choice of work-element end-time overlay. The end-time of work-elements were p l o t t e d over the graphs of any v a r i a b l e . This p l o t t i n g procedure could be used to search f o r misinterpreted work-elements on graphs of yarding distance versus time, or to show the behaviour of a v a r i a b l e within the work-cycle. 4.2.1.5 Data Preparation The data were edited and converted for fur t h e r a n a l y s i s using the "PRPARE" computer program (Souza 1983)). The f i r s t step i n data preparation was to check f o r the presence of erroneous or unwanted data events. Erroneous data events usually occurred at the beginning or at the end of a recorded tape. Unwanted events were those recorded during lunch or coffee time. These events were deleted from the data set using the e d i t section of the "PRPARE" program. - 59 -Yarding distance data u s u a l l y required more computer processing than other v a r i a b l e s . This was p r i m a r i l y due to lack of an automatic i n i t i a l i z a t i o n procedure i n the distance measuring device. The "PRPARE" program also was used to f i l t e r " i r r e l e v a n t " events from the yarding distance data (method described i n 4.2.2.1). 4.2.1.6 Data Conversion Conversion of recorded Data Logger counts to the appropriate u n i t of measurement f o r each v a r i a b l e was c a r r i e d out by the "PRPARE" computer program as describe i n Appendix 2. 4.2.2. Work-Cycle I n t e r p r e t a t i o n A work-cycle (turn) i s composed of a s e r i e s of events (elements) occurring during the t r i p the grapple makes from the roadside (landing) to the stump area and returning to the landing with the load. Delays may occur during execution of the work-cycle. For instance, the f i r s t work-cycle shown i n Figure 30 i s defined by the following l e t t e r s typed at the end-point of each work-element: B-P-Q-A-B-C. The purpose of work-cycle i n t e r p r e t a t i o n i s to i d e n t i f y the work-elements and delays f o r the grapple yarding operation. The "TURNIN" computer program (Souza 1983) allows the user to determine elapsed time f o r the elements and delays using the recorded yarding distance and time data. - 60 -UJ 0 1 )—• i i i i —r—•— —' • • i—• • >'l'i 0 1 2 3 4 5 6 7 9 9 18 TIME (min) DESCRIPTION DESCRIPTION S T W O L STMT ENO smut START F N O UNHOOK UNHOOK K I M M M O CHARGE OUTHAUL OUTHAUL SCGHMt HO. 1 OUTHAUL OUTHAUL SEGMENT NO. 1 OUTHAUL DELAY NO. 1 OUTHAUL SEGMENT NO. 2 OUTHAUL OELAY HO. 2 OUIHAUL SEGMENT H O . } OUTHAUL DELAY HO. 3 (MOT SHOW) OUTMAUl SEGMENT HO. 4 INHAUL UNHOOK UNHOOK DELAY ROAO CHANGE OUTHAUL SEGMENT M . 1 OUTHAUL DELAY NO . 1 OUTHAUL SEGMENT HO. 2 OUTHAUL DELAY NO. 2 OUTHAUL SEGMENT NO. 1 OUTHAUL DELAY HO. ] J K L N N 0 P 0 « INHAUL DELAY HO. 1 INHAUL SEGMENT MO. 2 INHAUL DELAY NO . 2 INHAUL SEGMENT NO. ] INHAUL DELAY N O . 1 INHAUL SEGMENT NO. 4 HOOKUP INHAUL INHAUL SEGMENT NO. 1 HOOKUP DELAY INHAUL INHAUL SEGHEHT NO. 1 INHAUL SEGMENT MO. 1 INHAUL DELAY NO . 1 INHAUL SEGMENT NO. 2 INHAUL DELAY NO . 2 ' lltHAUL SEGMENT MO. 1 INHAUL DELAY NO . ] OUTHAUL OUTHAUL SEGMENT NO. 2 . ) OR 4 HUOKUP HOOKUP DELAY • T I M E E I C E E O C O S E N S I T I V I T Y L I M I T FIGURE 30. Schematic of g r a p p l e y a r d e r work-cycles showing p o s s i b l e d e l a y p a t t e r n s . L e t t e r s typed on the graph i n d i c a t e how the s t a r t and en d - p o i n t s of each work element or del a y were d e f i n e d by the "TURNIN" computer program d u r i n g work-cycle i n t e r p r e t a t i o n . - 61 -The following work elements and delays were i d e n t i f i e d : a. Outhaul b. Hookup c. Inhaul d. Unhook e. Yarding road change f. Outhaul delays g- Hookup delays h. Inhaul delays i . Unhook delays The possible occurrence of these elements and delays, together with t h e i r s t a r t and end points, i s i l l u s t r a t e d i n Figure 30. 4.2.2.1. Data F i l t e r i n g Yarding distance data were composed of numerous pairs of observa-t i o n s (time and di s t a n c e ) . The data were recorded with an accuracy varying from 4.25 to 5.85 m depending on the amount of wire rope on the mainline drum. For instance, approximately 24 observations of distance and time were recorded i n a r r i v i n g at an outhaul distance of 125 m (without d e l a y s ) . Since the outhaul t r a j e c t o r y , i n t h i s case, i s described by the f i r s t and l a s t observations, a l l the intermediate observations are "redundant" (although recording was necessary to meet accuracy r e q u i r e -ments). Thus, f o r i n t e r p r e t a t i o n purposes, these intermediate observa-- 62 -t i o n s were eliminated from the data set without a f f e c t i n g the distance or elapsed time for a p a r t i c u l a r work-element. This f i l t e r i n g process was the f i r s t step of the i n t e r p r e t a t i o n task. The "FILTER" routine (Figure 31), incorporated i n the PRPARE program, prepared the yarding distance data f o r work-cycle i n t e r p r e t a -t i o n . I n i t i a l l y , the routine determined the s t a r t i n g time of the f i r s t outhaul. When the program detected three successive events with increasing distance values, within the landing area, the s t a r t of the f i r s t outhaul was I d e n t i f i e d . Three events were s u f f i c i e n t to i n d i c a t e that the grapple was moving toward the stump area for a number of s h i f t s studied. The user could v e r i f y i f the f i r s t outhaul was properly i d e n t i f i e d by examining yarding distance versus time graphs. A f t e r i d e n t i f y i n g the f i r s t outhaul, the program compared subse-quent distance and time events and gave a code for each outcome of the comparison. The possible codes (Figure 32) were: Code De s c r i p t i o n 1 Increasing distance. 2 Decreasing distance. 3 Increasing distance and between observations i s " s e n s i t i v i t y " value. time d i f f e r e n c e greater than a 4 Decreasing distance and between observations i s " s e n s i t i v i t y " value. time d i f f e r e n c e greater than a - 63 -SUB. FILTER DECLARE VARIABLES I DETERMINE START TIME OF FIRST OUTHAUL. DELETE ALL PREVIOUS DATA. DISTANCE AND TIME EVENTS. CODIFY THE OUTCOME OF THE COMPARISON. 1 COMPARE CODES. SAVE OR DELETE EVENTS UPON RESULT OF COMPARISON l INCREMENT COUNTER FIGURE 31. Flow c h a r t of s u b r o u t i n e "FILTER" used to compress y a r d i n g d i s t a n c e data d u r i n g work-cycle i n t e r p r e t a t i o n . - 64 -BEFORE FILTERING AFTER FILTERING BEFORE FILTERING AFTER FILTERING 3 \ f\ A ^ 3Vn y A V A A A A A u \j 1V V A u 1 f^}^\3 1 / \ 3 A IA 3/ 1 A 7 A FIGURE 32. D i s t a n c e data sample p l o t s showing d i f f e r e n t p a t t e r n s of g r a p p l e movement encountered d u r i n g work-cycle i n t e r p r e t a t i o n . Dots r e p r e s e n t c o o r d i n a t e s of recorded time and d i s t a n c e , and numbers r e p r e s e n t codes used by the "FILTER" s u b r o u t i n e to d e s c r i b e the movement. - 65 -The " s e n s i t i v i t y " value i s a time constant set by the computer operator to detect stops (delays) during the outhaul or inhaul, or to detect slow motion of the grapple when i t approaches or leaves the hook-ing or unhooking areas. A " s e n s i t i v i t y " l i m i t equal to 0.1 min was s u f f i c i e n t f o r t h i s study, since at the average grapple t r a v e l l i n g speed the yarding distance data were recorded at approximately 0.017 min i n t e r v a l . Deviations from t h i s time recording pattern were e a s i l y detected on yarding distance versus time graphs. The a p p l i c a t i o n of t h i s " s e n s i t i v i t y " l i m i t was checked by overlaying the graphs obtained before and a f t e r f i l t e r i n g the data. F i n a l l y , the "FILTER" routine successively compared coded events, s t o r i n g or d e l e t i n g p a i r s of observations depending upon the r e s u l t of the comparison. 4.2.2.2. Data Interpretation The "TURNIN" program (Souza 1983) used the data stored by the "FILTER" routine to automatically i n t e r p r e t the work elements and delays. A l l the steps involved i n data i n t e r p r e t a t i o n are explained i n flow charts of the "TURNIN" program presented i n Appendix 3. Work-cycle i n t e r p r e t a t i o n required several assumptions: a. Delay " S e n s i t i v i t y L i m i t " f o r Unhook and Hookup The delay " s e n s i t i v i t y l i m i t " i d e n t i f i e d unhook or hookup delays when the grapple remained i n a c t i v e at the landing or stump area for a period equal to or greater than 0.8 min. - 66 -Thus, when the d i f f e r e n c e i n time between the s t a r t and end of unhook or hookup exceeded 0.8 min, unhook or hookup time was assumed to equal 0.8 min. The remaining time was considered delay time. b. Delay " S e n s i t i v i t y L i m i t " f o r Outhaul and Inhaul The delay " s e n s i t i v i t y l i m i t " determined outhaul or inha u l delay when these delays were not i d e n t i f i e d by abnormal change (e.g., reverse change during outhaul) i n grapple t r a v e l d i r e c t i o n . This l i m i t was set to vary with distance. To determine the s e n s i t i v i t y l i m i t equal to 0.02 min/m a very low l i n e speed of 50 m/min was chosen. A delay was detected when the r a t i o of actual time over distance exceeded the 0.02 min/m l i m i t . I f the l i m i t was exceeded the time corresponding to the inhaul or outhaul distance was r e c a l c u l a t e d to match the assumed l i n e speed. The remaining portion of time was considered as delay. The low l i n e speed chosen to determine the " s e n s i t i v i t y l i m i t " assured that the assumption was used only i n extreme cases. c. Number of Delays The program assumed an occurrence of a maximum of three outhaul or inhaul delays f o r a given work-cycle (e.g., three "hangups" occurring at d i f f e r e n t distances during i n h a u l ) . Only one hookup delay and/or one unhook delay were provided for per work-cycle. - 67 -d. Distance L i m i t Between Outhaul or Inhaul Delays The purpose of t h i s l i m i t was to separate delays (up to a maximum of three) occurring during outhaul or inhaul. I f the yarding distance between events c h a r a c t e r i z i n g delays exceeded 10 m, the delays were assumed to be separate. e. Landing Area Limit The "landing l i m i t " established the end of unhook and the s t a r t of the outhaul. This l i m i t varied with the p o s i -t i o n , r e l a t i v e to the yarder, at which the grapple dropped the logs onto the ground during unhook. The l i m i t was deter-mined by f i n d i n g the c l o s e s t distance from the yarder (zero point) to the grapple for each c y c l e . This distance was c a l l e d "Dmin". When an a r b i t r a r y value equal to 6.85 m (accuracy of distance measurement) was added to "Dmin", the "landing l i m i t " was found. For instance, i f the grapple dropped the load 6.85 m from the yarder the "landing l i m i t " was set to 13.7 m; and the outhaul started at the time the grapple t r a v e l l i n g to the stump area passed the 13.7 m l i m i t . f . Hooking Area L i m i t The "hooking l i m i t " was used to determine the end of outhaul or the s t a r t of hookup based on the maximum distance the grapple t r a v e l l e d per work cy c l e . The l i m i t was found by subtracting 6.85 m from maximum distances smaller than 40 m and by subtracting 20 m from maximum distances greater than or equal to 40 m. This implied that shorter - 68 -yarding distances required smaller hooking l i m i t , since the shorter the yarding distance the better i s the operator's view of the logs, r e s u l t i n g i n more e f f e c t i v e log grappling. On the other hand, at longer yarding distance the grapple could move, f o r example, 15 m toward the landing without the operator r e a l i z i n g that he had grappled an unmerchantable l o g . The program tested the yarding distances recorded against the "hooking l i m i t " to decide whether the grapple had reached or l e f t the hooking area, g. Yarding Road Change When the grapple reached the top of the machine boom, a zero yarding distance was recorded i n d i c a t i n g to the work cycle i n t e r p r e t a t i o n computer program that a yarding road change has occurred. 4.2.2.3. Elapsed Time f o r Work-Elements and Delays The elapsed time for each work element and delay was c a l c u l a t e d from the time data produced by the "TURNIN" computer progrm. The c a l c u -l a t i o n s were performed by the "TURNCA" computer program (Souza 1983). This program also determined the number of logs yarded per work c y c l e . 4.3. Data A n a l y s i s Methods Data a n a l y s i s consisted of comparison of observations with the - 69 -recomended WCB and ISO standards, and s t a t i s t i c a l a n a l y s i s . 4.3.1. Comparison With The Standards The variables r e q u i r i n g comparison with standards were: noise, v i b r a t i o n , e f f e c t i v e temperature, and mainline tension. 4.3.1.1. Hoise L e v e l The f o l l o w i n g measures of sound l e v e l were evaluated using the "HISTOG" computer program (Souza 1983): a. Equivalent continuous sound l e v e l (Leq). b. Percentage of time spent i n a given noise l e v e l class i n t e r v a l . c. Percentage of time noise l e v e l exceeded a given cla s s i n t e r v a l (cumulative percentage of time). d. Noise dose i n percentage. Appendix 4 shows a l l the equations used to c a l c u l a t e the noise l e v e l measures c i t e d above. 4.3.1.2. V i b r a t i o n A c c e l e r a t i o n V i b r a t i o n data for X, Y, and Z d i r e c t i o n s were evaluated according to ISO standards (ISO 1978) for whole-body v i b r a t i o n and compared with the three main human c r i t e r i a f o r : - 70 -a. the preservation of working e f f i c i e n c y ("fatigue-decreased p r o f i c i e n c y boundary"); b. the preservation of health or safety ("exposure l i m i t " ) ; and c. the preservation of comfort ("reduced comfort boundary"). The measured v i b r a t i o n a c c e l e r a t i o n values were compared with the ISO l i m i t s using the "Equivalent T o t a l Exposure Method" shown i n Appendix 4. 4.3.1.3. E f f e c t i v e Temperature Data from dry-bulb temperature and r e l a t i v e humidity were con-verted i n t o new e f f e c t i v e temperature (ETx) using graphs presented by McCormick (1976) and Zerbe (1979). The ETx was then compared with the comfort guidelines f or medium l e v e l of c l o t h i n g and medium l e v e l of work a c t i v i t y (Zerbe 1979). 4.3.1.4. Heart Rate The average value of the operator's heart rate calculated f o r each s h i f t was compared with the recommended l i m i t s f o r continuous performance (Grandjean 1981). This l i m i t was found by adding 35 bpm to the operator's r e s t i n g pulse rate. The r e s t i n g pulse was determined before the work started by pa l p a t i n g the operator's r a d i a l a r t e r y and taking the time f o r 10 beats and c a l c u l a t i n g the heart rate accordingly (Andersen 1971). - 71 -4.3.1.5. Mainline Tension Mainline tension values were compared with the safe working load of the mainline cable. The mainline cable used during the study was an "improved plow s t e e l " ( c l a s s 6x19 with 26 wires) 2.54-cm (1-in) diam-eter " p l a s t i c f i l l e d v a l l e y (PFV) wire rope" with a manufacturer's (Anonymous undated) s p e c i f i e d breaking strength of 46.4 ton (approxi-mately 42,000 kg or 92,800 l b ) , and i n good working condition. On the basis of the rated breaking strength and a safety f a c t o r of 3 (Binkley and Sessions 1978), a safe working load of 14,000 kg was obtained. 4.3.2. S t a t i s t i c a l Analyses S t a t i s t i c a l analyses were divided i n t o work-cycle s t a t i s t i c s , and c o r r e l a t i o n and regression analyses. 4.3.2.1. Work-Cycle St a t i s t i c s A d e s c r i p t i v e a n a l y s i s , i n c l u d i n g c a l c u l a t i o n of minimum, maximum, average, and standard d e v i a t i o n , was obtained f o r each work element and delay. A weighted average technique was used to determine the l e v e l , f o r each v a r i a b l e studied, which corresponded to the d i f f e r e n t work c y c l e s , work elements and delays. The weighted average i s given by the follow-ing expressions: - 72 -a. For noise l e v e l data (Magrab 1975, I r v i n and Graf 1979): W^  = 10 x Log^n - N (L /10) S 10 1 x Dt i = l N S Dt i = l j b. For other data (Bendat and P i e r s o l 1971): W d * N £ L x Dt 1=1 1 1 N £ Dt i = l 1 where: Wd = Weighted average. Wn = Noise l e v e l weighted average (dBA). Dt^ = Elapsed time between consecutive samples (min). N = Number of time i n t e r v a l s ( D t ^ within the work-element (number of observations). = Observed value for the i n t e r v a l D t ^ e . g . , dBA, bpm) kogio = Base 10 logarithm. - 73 -The "ERGAVE" computer program (Souza 1983) allows the user to determine the weighted average within work elements f o r any given v a r i -able. The main features of t h i s program were: a. Test f o r computer memory capacity for large data f i l e s . b. Automated search of s t a r t averaging time. This was important when the va r i a b l e s had d i f f e r e n t recorded s t a r t time. c. Data i n t e r p o l a t i o n . I n t e r p o l a t i o n was needed i n cases where there was no corresponding data sampled f o r the s t a r t or f o r the end of a work-element or delay. The i n t e r p o l a t i o n method searched f o r the values of the v a r i a b l e being averaged that l a y between the s t a r t and end times of an element. Often, there were no v a r i a b l e values sampled at the same time as the s t a r t or end of the element time. This could happen when, for example, noise l e v e l did not change by i t s recording threshold amount (see 4.1.5) during a p a r t i c u l a r work-element. In t h i s case, the program assigned the value of the v a r i a b l e sampled previously to the element time, to correspond to the s t a r t , or the end, of the averaging process. This was the most correct value, since the Data Logger had not detected any s i g n i f i c a n t change i n the v a r i a b l e between the previously recorded event and the s t a r t or end time of the work-element. The process was repeated f o r every element and delay. - 74 -4.3.2.2. Other S t a t i s t i c a l Analyses The regression and c o r r e l a t i o n analyses were accomplished u t i l i z i n g the MIDAS s t a t i s t i c a l package (Fox and Guire 1976) a v a i l a b l e on the U n i v e r s i t y of B r i t i s h Columbia computer system. Computer programs were written to tes t the e q u a l i t y of means (when the variances are heterogeneous) using the Games and Howell method (Sokal and Rohlf 1969). Other programs adjusted the work-element times (when they were influenced by operating f a c t o r s , f o r example, yarding distance) using covariance techniques. For example, adjustment was needed to remove the e f f e c t of yarding distance on grapple t r a v e l time, so the e f f e c t of the cumulative time worked during the s h i f t on the element time could be determined. A computer program ("PCORREL") was written to prepare the data for c o r r e l a t i o n a n a l y s i s (Souza 1983). As the Data Logger sampled a l l channels during a 60-ms i n t e r v a l , the sampling was considered simulta-neous and the data f o r c o r r e l a t i o n a n a l y s i s were i d e n t i f i e d . For instance, when the f i r s t noise observation occurred, i t s time of occur-rence was r e g i s t e r e d and a mainline tension value corresponding to t h i s time was searched. If no value of tension was encountered i t meant that the next previous value was s t i l l the current value, and i t was taken to form the pa i r of observations f o r the c o r r e l a t i o n a n a l y s i s . I f no previous value was found, the program searched for the f i r s t tension datum, and i t s time of occurrence. This search process was repeated for the e n t i r e data set. 5. RESULTS The grapple yarder operation was monitored for nine days ( s h i f t s ) during the month of July 1982. From t h i s period four complete s h i f t s of recorded data were selected f o r the a n a l y s i s . These s h i f t s were t y p i c a l of a v a r i e t y of s i t u a t i o n s that might occur during the operation of a grapple yarder (e.g., occasional yarding across and along r a v i n e s ) . However, the sample i s not representative of the f u l l range of condi-tions that might be encountered over a longer period. The in t e r m i t t e n t nature of logging operations during 1982 did not permit further sampling a c t i v i t y . The data were nonetheless s u f f i c i e n t f o r developing computer programs and t e s t i n g hypotheses to meet the objectives of the study. An evaluation of the grapple yarder studied with respect to the Canadian (Zerbe 1979) and Swedish (Aminoff et a l . 1980a) ergonomic check l i s t s i n d i c a t e d that: a. F a c i l i t i e s f o r g e t t i n g i n and out of the cab were regarded as being s a t i s f a c t o r y , except that the f i r s t step was too high f o r easy use. Cab size was adequate. b. Operator's seat was standard i n s i z e , secure and with height e a s i l y adjustable. However, i t was too close to the l a t e r a l controls support so that the operator often h i t his legs when entering or e x i t i n g from the cab. The seat did not s u f f i -c i e n t l y attenuate the v i b r a t i o n l e v e l s for an adequate degree of comfort. Also l a t e r a l arm supports lacked adjustment and were not s u f f i c i e n t l y comfortable. - 76 -c. With respect to design, l o c a t i o n and operation, frequently used controls were considered s a t i s f a c t o r y . d. V i s i b i l i t y from the cab was s a t i s f a c t o r y . Forward v i s i b i l i t y was l i m i t e d to 35° h o r i z o n t a l and to 32° v e r t i c a l view. The ri g h t side of the machine was c l e a r while the l e f t side was obstructed by g a n t r i e s . 5.1 Descriptive Statistics for all Variables Over the Study Period Tables 1 and 2 present d e s c r i p t i v e s t a t i s t i c s f o r noise l e v e l , heart rate, mainline tension, number of logs, v i b r a t i o n a c c e l e r a t i o n (X, Y and Z d i r e c t i o n ) and temperature (wet and dry-bulb). Due to d i f f e r e n t ground conditions and d i f f e r e n t v a r i a b l e s studied on the four s h i f t s , data analyses were c a r r i e d out separately for each s h i f t . Data Logger recording capacity prevented c o l l e c t i n g data for operator's heart rate and mainline tension on the same s h i f t . The number of observations l i s t e d on Table 1 and 2 shows that, although each v a r i a b l e was sampled at the 60 ms rate the Data Logger f l o a t i n g - a p e r t u r e algorithm as defined by Lawrence ejt a l . (1982), e f f i c i e n t l y compressed the data recorded for a l l analog v a r i a b l e s . I f no data compression had been used and the data recorded at the uniform time i n t e r v a l of 0.06 s, 1000 observations per min would have been recorded on tape for each v a r i a b l e . The noise l e v e l v a r i a b l e exhibited the maximum recording r a t e , with an average of approximately 50 data events per min. The noise - 77 -Table 1 - De s c r i p t i v e s t a t i s t i c s f o r noise l e v e l , heart rate, mainline tension, yarding distance and number of logs, over the study period. No. of Standard Variable S h i f t Observations Minimum Maximum Mean DeviatJ Noise l e v e l 1 5,762 50.0 99.0 80.6 6.0 (dBA) 3 21,010 51.6 100.2 83.1 6.0 4 16,696 50.0 98.6 80.7 6.3 Heart rate 3 4,314 40.0 184.7 74.7 10.8 (bpm) 4 2,844 40.0 180.0 62.5 12.0 Mainline 1 14,668 0 27,451 3,192 2,372 tension 2 3,827 0 17,696 4,368 2,709 (kg) Yarding 1 6,788 0 141.0 51.1 28.3 distance 2 2,423 0 112.1 39.2 22.3 (m) 3 7,636 0 162.0 54.2 34.6 4 6,266 0 128.9 44.7 24.0 Number of 1 249 1 3 1.1 0.4 logs per 2 156 1 4 1.1 0.4 turn 3 306 1 2 1.1 0.3 4 321 1 3 1.1 0.4 - 78 -Table 2 - D e s c r i p t i v e s t a t i s t i c s f o r v i b r a t i o n , a c c e l e r a t i o n and temperature, over the study period. No. of Standard V a r i a b l e S h i f t Observations Minimum Maximum Mean Deviation X-accel. 1 517 0 0.132 0.026 0.017 [g(rms)] 2 997 0 0.129 0.037 0.020 3 1,331 0 0.138 0.032 0.017 4 1,003 0 0.120 0.031 0.017 Y-accel. 1 476 0 0.067 0.020 0.009 [g(rras)] 2 640 0 0.053 0.023 0.009 3 895 0 0.082 0.024 0.011 4 657 0 0.102 0.023 0.011 Z-accel. 1 571 0 0.128 0.027 0.016 [g(rms)] 2 900 0 0.115 0.029 0.014 3 1,206 0 0.137 0.033 0.015 4 919 0 0.139 0.032 0.016 Wet-bulb 1 8 12 15 14 1.0 temperature 2 7 12 16 14 1.0 3 9 14 16 15 0.6 4 7 17 18 13 0.7 Dry-bulb 1 8 19 24 20 1.8 temperature 2 7 17 24 22 2.4 3 9 20 24 21 1.4 4 7 21 27 24 2.0 - 79 -l e v e l threshold was set at 1.96 dBA; thus, whenever noise l e v e l changed by 1.96 dBA, a new data event was recorded on tape. I f the threshold was set to a higher value a decrease i n the number of data recorded was achieved. A smaller number of observations would have decreased both the data storage requirement and the processing time during data analy-s i s . However, the higher the threshold the lower the accuracy. 5.2 Computer-Interpreted Work-Shift and Work-Cycles Figures 33 and 34 show graphs of the yarding distance data. These graphs present a summary of the grapple work during each s h i f t ; at any s p e c i f i c time, the current p o s i t i o n of the grapple i s given r e l a t i v e to the machine p o s i t i o n at the roadside. The t y p i c a l graph of grapple a c t i v i t y over a number of work-cycles forms a f i g u r e resembling a r i g h t t r i a n g l e . The hypotenuse i s produced by successive increases i n the grapple t r a v e l distance from the machine as the logs r e s t i n g i n the cable path (yarding road) are c o l l e c -ted. The shorter side along the X-axis i n d i c a t e s the time necessary to transport a l l the logs from a p a r t i c u l a r yarding road to the landing. The machine moves a short distance along the truck road a f t e r a l l the logs are transported, and another yarding road i s s t a r t e d . During the machine movement, the grapple i s u s u a l l y pulled i n as far as possible (to the top of the boom, or zero distance reference point on the graphs) making the i n t e r p r e t a t i o n of the yarding road change time p o s s i b l e . - 80 -YHRDING DISTANCE VERSUS SHIFT TIME ( S h i f t 1.) GRAPPLE YARDER 168 • TIrC <«tnJ YARDING D I S T R N C E V E R S U S S H I F T T I M E ( S h i f t 2) 12a • TIME (atn) FIGURE 33. Ya r d i n g d i s t a n c e v e r s u s s h i f t time ( s h i f t 1 and 2). The graph shows the t y p i c a l p a t t e r n of g r a p p l e movement d u r i n g the s h i f t . Lunch i n t e r v a l and major d e l a y s are r e p r e s e n t e d by a h o r i z o n t a l l i n e . Y a r d ing road changes are r e p r e s e n t e d by an i n t e r -r u p t i o n of the g r a p p l e movement at the x - a x i s accompanied by s u c c e s s i v e i n c r e a s e s i n y a r d i n g d i s t a n c e u n t i l the next y a r d i n g road change. - 81 -YARDING DISTANCE VERSUS SHIFT TIME C S h i f t 3) OTHPPLE YRRDER 180 TIMC Cain) YARDING DISTANCE VERSUS SHIFT TIME ( S h i f t 4) GRBPPLE YRRDER 140 • Tine (ami FIGURE 34. Yarding d i s t a n c e versus s h i f t time ( s h i f t 3 and 4). The graph shows the t y p i c a l p a t t e r n of g r a p p l e movement d u r i n g a s h i f t . - 82 -Major delays or lunch breaks are shown by an abnormal time d i f f e r e n c e between t r i a n g l e s . A h o r i z o n t a l l i n e on the graph denotes the p o s i t i o n of the grapple and the time the delay occurred. 5.2.1 D e t a i l e d Time I n t e r p r e t a t i o n A more d e t a i l e d study of the yarding distance data and respective graphs (Figures 33 and 34) permitted the a n a l y s i s of p a r t i c u l a r machine work-cycles and t h e i r elements. The r e s u l t s of the work-cycle i n t e r -p r e t a t i o n computer program ("TURNIN" (Souza 1983)) can be presented g r a p h i c a l l y or numerically. Figure 35 shows the computer-interpreted distance and elapsed time for an i n d i v i d u a l work-cycle and elements: outhaul (0), hookup (H), inhaul ( I ) , and unhook (U). The end-times f o r the elements were superimposed over the expanded yarding distance graph (Figure 35) to provide a v i s u a l p i c t u r e of the time consumed by the grapple i n i t s d i f f e r e n t a c t i v i t i e s over the work-cycle, and to detect possible occurrence of errors during work-cycle i n t e r p r e t a t i o n . Despite i r r e g u l a r grapple movements, the "TURNIN" computer program produced s a t i s f a c t o r y r e s u l t s . Tables 3 to 8 present the numerical r e s u l t s from the work-cycle (turn) i n t e r p r e t a t i o n computer program. The number of work-cycles i d e n t i f i e d per s h i f t (Tables 3 to 6) varied from 163 to 312 depending p r i m a r i l y on the occurrence of mechanical or non-mechanical delays. Thus, considering the t o t a l recorded time per s h i f t (excluding lunch YARDING DISTRNCE VERSUS OPERRTING TIME GRHPPLE YARDER 1 1 4 1 1 4 ( 1 4 11 4 f » 4 1 1 4 I I 4 TIME (min) F I G U R E 3 5 . C o m p u t e r - i n t e r p r e t e d g r a p p l e y a r d e r w o r k - c y c l e s . The g r a p h shows t h e y a r d i n g d i s t a n c e a n d e l a p s e d t i m e f o r e a c h w o r k e l e m e n t : o u t h a u l ( 0 ) , h o o k u p ( H ) , i n h a u l ( I ) a n d u n h o o k ( U ) . P r o g r a m a l l o w s g r a p h t o be p l o t t e d t o a n y s c a l e t o a l l o w d e t a i l e d e x a m i n a t i o n o f e a c h w o r k - c y c l e . Table 3 - Summary of work-cycle time for the grapple yarder operation (shift 1). Time per Turn (min) Percent Percent of 1 of Total Category No. of Work-Cycle Elements Total Time Time Time Turns Standard Range and Delays (min) (X) <*) (Observ.) Average Deviation Minimum Maximum Elements Outhaul 48.232 13.7 22.8 247 0.195 0.090 0.013 0.468 Hookup 45.421 12.9 21.4 247 0.184 0.132 0.019 0.683 Inhaul 60.924 17.3 28.8 247 0.247 0.128 0.019 1.046 Unhook 57.098 16.3 27.0 247 0.231 0.196 0.018 0.800 Sub-Total: Elements 211.675 60.2 100.0 •. 247 0.857 0.338 0.282 1.946 2 Delays . Outhaul 8.272 2.3 10.0 247(27) 0.033 NA- 0.018 1.582 Hookup 34.853 9.9 42.3 247(83) 0.141 NA 0.035 1.326 Inhaul 12.436 3.6 15.1 247(24) 0.051 NA 0.025 2.365 l Unhook 9.347 2.7 11.3 247(24) 0.038 NA 0.018 2.228 oo Unhook (other) 17.550 5.0 21.3 247(2) 0.071 NA 8.320 9.230 1 Sub-Total: Delays 82.458 23.5 100.0 247 0.334 NA 0.018 9.544 Yarding Road Change 57.331 16.3 NA 247(11) 0.232 NA 0.272 37.717 Sub-Total: Delays 139.789 39.8 RA 247 0.566 NA NA NA TOTAL 351.464 100.0 NA 247 1.423 2.713 0.285 39.528 Data were sampled and recorded to the nearest 0.001 min. 2Delay time was pro-rated over the number of turns per shift. Number of turns in parentheses represent the actual delay frequency for the element during the shift. Other delays are those with time exceeding 5 min and did not belong to the element. Warding road change includes i t s corresponding delays. **NA « not applicable since average delays were pro-rated over the total number of turns. Table 4 - Summary of work-cycle time for the grapple yarder operation (shift 2). Time per Turn (min) Percent Percent of of Total Category Ho. of Work-Cycle Elements Total Time Time Time Turns Standard Range and Delays (min) (X) (X) (Observ.) Average Deviation Minimum Maximum Elements Outhaul 21.792 7.8 16.4 163 0.134 0.062 0.019 0.327 Hookup 44.899 16.0 33.8 163 0.275 0.193 0.027 0.800 Inhaul 27.540 9.8 20.8 163 0.169 0.082 0.029 0.415 Unhook 38.449 13.7 29.0 163 0.236 0.199 0.020 0.800 Sub-Total: Elements 132.680 47.3 100.0 163 0.814 0.331 0.274 2.018 Delays Outhaul 6.154 2.2 5.1 163 (19) 0.038 HA" 0.017 1.148 Hookup 27.895 9.9 23.1 163 (50) 0.171 NA 0.036 1.922 Inhaul 7.524 2.7 6.2 163 (18) 0.046 HA 0.031 1.287 Inhaul (other) 15.240 5.5 12.6 163 (1) 0.093 NA NA 15.240 Unhook 8.474 3.0 7.1 163 (16) 0.070 HA 0.120 3.444 Unhook (other) 55.293 19.7 45.9 163 (3) 0.321 NA 5.669 26.370 Sub-Total: Delays 120.580 43.0 100.0 163 0.740 HA 0.017 26.370 Yarding Road Change 27.218 9.7 NA 163 (7) 0.167 NA 1.485 8.673 Sub-Total 147.798 52.7 HA 163 0.907 HA NA NA TOTAL 280.478 100.0 HA 163 1.721 3.294 0.274 27.752 Data were sampled and recorded to the nearest 0.001 min. !Delay time was pro-rated over the number of turns per shift. Number of turns in parenthesis represent the actual delay frequency for the element during the shift. Other delays are those with time exceeding 5 min and did not belong to the element. 'larding road change includes i t s corresponding delays. NA " not applicable. Table 5 - Summary of work-cycle time for the grapple yarder operation ( s h i f t 3). Time per Turn (min) Work-Cycle Elements and Delays Total Time 1 (min) Percent of Total Time (X) Percent of Category Time (X) No. of Turns (Observ.) Average Standard Deviation Range Minimum Maximum Elements Outhaul Hookup Inhaul Unhook 58.373 61.199 73.865 59.614 14.1 14.8 17.8 14.4 23.1 24.2 29.2 23.5 309 309 309 309 0.189 0.198 0.239 0.193 0.120 0.168 0.161 0.170 0.014 0.025 0.020 0.021 0.621 0.800 0.877 0.800 Sub-Total: Element! j 253.051 61.1 100.0 309 0.819 0.400 0.150 2.199 Delays 2 Outhaul Hookup Inhaul Unhook 23.485 37.701 32.955 13.348 5.6 9.1 8.0 3.2 21.8 35.1 30.7 12.4 309 (45) 309 (85) 309 (43) 309 (29) 0.076 0.122 0.107 0.043 NA* NA NA NA 0.021 0.060 0.008 0.008 3.205 2.039 4.604 2.460 Sub-Total: Delays 107.489 25.9 100.0 309 0.348 NA 0.021 5.899 Yarding Road Change3 53.887 13.0 NA 309 (15) 0.174 NA 0.113 13.833 Sub-Total 161.376 38.9 NA 309 0.522 NA NA NA TOTAL 414.427 100.0 NA 309 1.341 1.511 0.150 14.941 Data were sampled and recorded to the nearest 0.001 min. > Delay time was pro-rated over the number of turns per s h i f t . Number of turns In parenthesis represent the actual delay frequency for the element during the s h i f t . Other delays are those with time exceeding 5 min and did not belong to the element. 'Yarding road change Includes Its corresponding delays. if NA = not applicable. Table 6 - Summary of work-cycle time for the grapple yarder operation ( s h i f t 4). Time per Turn (min) Percent Percent of of Total Category No. of Work-Cycle Elements Total Time 1 Time Time Turns Standard Range and Delays (min) ( X ) ( I ) (Observ . ) Average Deviation Minimum Maximum Elements Outhaul 47.919 15.2 22.7 312 0.154 0.088 0.014 0.728 Hookup 48.777 15.5 23.1 312 0.156 0.132 0.020 0.800 Inhaul 51.831 16.4 24.5 312 0.166 0.103 0.015 0.800 Unhook 62.677 19.9 29.7 312 0.201 0.189 0.023 0.800 Sub-Total: Elements 211.204 67.0 100.0 312 0.677 0.338 0.200 2.111 Delays Outhaul 10.546 3.4 15.7 312 (23) 0.034 NA 0.017 2.713 Hookup 19.626 6.2 29.3 312 (63) 0.063 NA 0.059 0.973 Inhaul 9.438 3.0 14.1 312 (24) 0.030 NA 0.038 2.183 Unhook 27.407 8.7 40.9 312 (32) 0.088 NA 0.084 4.350 Sub-Total: Delays 67.017 21.3 100.0 312 0.215 NA 0.032 4.350 Yarding Road Change3 36.789 11.7 NA 312 (11) 0.117 NA 0.700 9.063 Sub-Total 103.806 33.0 NA 312 V0.332 NA NA NA TOTAL 315.010 100.0 NA 312 1.009 1.086 0.225 10.040 'Data were sampled and recorded to the nearest 0.001 min. 2 Delay time was pro-rated over the number of turns per s h i f t . Number of turns In parenthesis represent the actual delay frequency for the element during the s h i f t . Other delays are those with time exceeding 5 min and did not belong to the element. 'Yarding road change Includes Its corresponding delays. *NA = not applicable. - 88 -breaks) an average t o t a l time per work-cycle varied from 1.090 min to 1.721 min. Actual working time (outhaul, hookup, inhaul and unhook) accoun-ted f o r 47.3% to 67.0% of the t o t a l work-cycle time. The remaining time was d i s t r i b u t e d among delays with 21.3% to 43.0%, and yarding road change with 9.7% to 16.3% of the t o t a l work-cycle time. No work-cycle element was c o n s i s t e n t l y most-time consuming over the study period. This d i s t r i b u t i o n of time shows that grapple yarding p r o d u c t i v i t y might be increased by: diminishing delay time through work planning and organization; introducing equipment to improve operator's v i s i b i l i t y of the working area (e.g., video system); and diminishing the proportion of yarding road change time by i n c r e a s i n g yarding distance. The time element and delay s t a t i s t i c s f o r the combined four s h i f t s of grapple yarder operation are presented i n Table 7. The number of turns i n t e r p r e t e d over the study period t o t a l l e d 1031. The average t o t a l time per turn was 1.320 minutes. Work-element time accounted f o r 59.4% of t o t a l time per turn; the remaining 40.6% was delay with 27.8% and yarding road change with 12.8%. Unhook was the most time consuming work element (26.9%) and outhaul the least (21.8%) time-consuming. Hookup delay was the most time-consuming with 31.8% of the t o t a l delay time. The l e a s t time-consuming was outhaul delay with 12.9%. The 44 yarding road changes accounted for 12.8% of t o t a l time (average of almost 4 min per road change). Note that road change would be longer i n Table 7 - Summary of work-cycle element and delay time for the grapple yarder operation, over the f o u r - s h i f t study. Time per Turn (min) Percent Percent of of Total Category No. of Work-Cycle Elements Total Time 1 Time Time Turns Standard Range and Delays (min) (X) (X) (Observ .) Average Deviation Minimum Maximum Elements Outhaul 176.316 12.9 21.8 1031 0.171 0.099 0.013 0.728 Hookup 200.296 14.7 24.7 1031 0.194 0.159 0.019 0.800 Inhaul 214.160 15.8 26.6 1031 v0.208 0.132 0.015 1.046 Unhook 217.838 16.0 26.9 1031 0.211 0.187 0.018 0.800 Sub-Total: Elements 808.610 59.4 100.0 1031 0.784 0.363 0.150 2.199 2 Delays Outhaul 48.457 3.6 12.9 1031 (114) 0.047 NA1* 0.017 3.205 Hookup 120.075 8.8 31.8 1031 (281) 0.116 NA 0.035 2.039 Inhaul 62.353 4.6 16.5 1031 (109) 0.060 NA 0.008 4.604 Inhaul (other) 15.240 l . l 4.0 1031 (1) 0.015 NA NA 15.240 Unhook 58.576 4.3 15.5 1031 (102) 0.057 NA 0.005 4.350 Unhook (other) 72.843 5.4 19.3 1031 (4) 0.071 NA NA 26.370 Sub-Total: Delays 377.544 27.8 100.0 1031 0.366 NA 0.017 26.370 Yarding Road Change 175.225 12.8 NA 1031 (44) 0.170 NA 0.113 37.717 Sub-Total 552.769 40.6 NA 1031 0.536 NA NA NA TOTAL 1,361.379 100.0 NA 1031 1.320 2.135 0.150 39.528 Data were sampled and recorded to the nearest 0.001 min. !Delay time was pro-rated over the number of turns per s h i f t . Number of turns in parenthesis represent the actual delay frequency for the element during the s h i f t . Other delays are those with time exceeding 5 min and did not belong to the element. 'Yarding road change Includes Its corresponding delays. NA » not applicable. Table 8 - Summary of work-elements (including delay time) for the grapple yarder operation, over the four-shift study. Time per Turn (min) Work-Cycle Elements Percent of Including Total Time 1 Total Time No. of Standard Range Shift Delays (min) (%) Turns Average Deviation Minimum Maximum Outhaul 56.504 16.1 247 0.229 0.194 0.013 1.908 hookup 80.274 22.8 247 0.325 0.312 0.025 1.956 1 Inhaul 73.360 20.9 247 0.297 0.287 0.019 2.533 Unhook 66.445 18.9 247 0.269 0.294 0.018 3.028 Unhook (other) 17.550 5.0 247 (2) 0.071 NA 8.320 9.230 Yarding Road Change 57.331 16.3 247 (11) 0.232 NA 0.272 37.717 Total 351.464 100.0 247 1.423 2.715 0.285 39.528 Outhaul 27.946 10.0 163 0.171 0.167 0.019 1.475 Hookup 72.794 26.0 163 0.477 0.487 0.027 2.681 Inhaul 35.064 12.5 163 0.215 0.218 0.009 1.581 2 Inhaul (other) 15.240 5.4 163 0.094 NA NA 15.535 Unhook 46.923 16.7 163 0.288 0.414 0.073 4.244 Unhook (other) 55.293 19.7 163 (3) 0.339 NA 5.661 26.370 Yarding Road Change 27.218 9.7 163 (7) 0.167 NA 1.485 8.673 Total 280.478 100.0 163 1.721 3.294 0.274 27.752 Outhaul 81.858 19.8 309 0.265 0.337 0.014 3.724 Hookup 98.900 23.9 309 0.320 0.360 0.029 2.352 3 Inhaul 106.820 25.8 309 0.346 0.562 0.020 4.721 Unhook 72.962 17.5 309 0.236 0.320 0.021 3.260 Yarding Road Change 53.887 13.0 309 (15) 0.174 NA 0.113 13.833 Total 414.427 100.0 309 1.341 1.511 0.150 14.941 Outhaul 58.465 18.6 312 0.187 0.255 0.014 2.947 Hookup 68.403 21.7 312 0.219 0.232 0.020 1.773 4 Inhaul 61.269 19.5 312 0.196 0.204 0.015 2.485 Unhook 90.084 28.5 312 0.289 0.529 0.028 5.150 Yarding Road Change 36.789 11.7 312 (11) 0.118 NA 0.700 9.063 Total 315.010 100.0 312 1.009 1.086 0.225 10.040 TOTAL 1361.379 NA 1031 1.320 2.135 0.150 39.528 Data were sampled and recorded to the nearest 0.001 min. Number of turns in parenthesis represent the actual frequencyfor the a c t i v i t y . 30ther delays are those with time exceeding 5 min and did not belong to the element, if NA = not applicable. - 91 -operations using rigged stumps for t a i l h o l d , rather than mobile back-spar. Table 8 shows, for the four s h i f t s , the time f or the work-cycle elements in c l u d i n g delays occurring during t h e i r execution. The most time consuming elements were hookup ( s h i f t 1 and 2), inhaul ( s h i f t 3) and unhook ( s h i f t 4). This d i s t r i b u t i o n was influenced by yarding distance and delay time recorded for each element. The average time per turn ( i n c l u d i n g delays) for each work-cycle element during the study period was: Element min Outhaul 0.218 Hookup 0.310 Inhaul 0.268 Unhook 0.268 Other delays 0.085 Road change 0.171 T o t a l 1.320 Table 9 summarizes the frequency r e s u l t s f o r delays. Hookup delays were the most frequently occurring delays during the work-cycle, for a l l s h i f t s analyzed. - 92 -Table 9 - Summary of delay a n a l y s i s . Percent Percent Percent No. of of T o t a l of T o t a l of T o t a l Delay- Turns No. of No. of No. of S h i f t S h i f t Element (Observ.) Delays Delays (%) Turns (%) Time (%) Outhaul 27 16.5 10.9 2.3 1 Hookup 247 83 50.6 33.6 9.9 Inhaul 28 17.1 11.4 3.6 Unhook 26 15.8 10.5 2.7 T o t a l 164 100.0 66.4 18.5 Outhaul 19 17.4 11.7 2.2 2 Hookup 163 50 45.9 30.7 9.9 Inhaul 21 19.3 12.8 2.7 Unhook 19 17.4 11.7 3.0 T o t a l 109 100.0 66.9 17.8 Outhaul 46 21.8 14.9 5.6 3 Hookup 309 85 40.3 27.5 9.1 Inhaul 51 24.2 16.5 8.0 Unhook 29 13.7 9.4 3.2 T o t a l 211 100.0 68.3 25.9 Outhaul 23 15.6 7.4 3.4 4 Hookup 312 63 42.9 20.2 6.2 Inhaul 29 19.7 9.3 3.0 Unhook 32 21.8 10.3 8.7 T o t a l 1031 147 100.0 47.2 21.3 Outhaul 115 18.2 11.1 3.6 1-4 Hookup 1031 281 44.5 27.3 8.8 (com- Inhaul 129 20.4 12.5 4.6 bined) Unhook 106 16.9 10.3 4.3 T o t a l 1031 631 100.0 61.2 21.3 - 93 -OUTHWJL T I M E V E R S U S D I S T A N C E a. ?9 FIGURE 36. Relationship between grapple travel time and distance tr a v e l l e d for outhaul and inhaul work-elements. The graph shows 4 curves (4 s h i f t s ) and their respective regression equations. The equations for each element are S t a t i s t i c a l l y p a r a l l e l but do not have a common intercept. Hence they cannot be replaced by a single equation (at the 0.05 probability l e v e l ) . Note: N • number of observations; S.E.y * standard error of estimate; and R* • c o e f f i c i e n t of determination. - 94 -5.2.2 Grapple Travel Time Relationships Figure 36 shows the scat t e r p l o t s of time versus distance f o r outhaul and inhaul ( a l l turns except those with occurrence of delays) over the study period. The fi g u r e also presents the computed regression equation (highly s i g n i f i c a n t at the 0.05 p r o b a b i l i t y l e v e l ) f or each s h i f t together with the respective p l o t t e d curves. The c o e f f i c i e n t s of determination f o r a l l equations show that the t r a v e l distance explained 75% to 80% of the v a r i a t i o n i n t r a v e l time. Results from a " p a r a l l e l i s m and coincidence" test f or regressions (Kozak 1970) shows that while the equations for each of the element are s t a t i s -t i c a l l y p a r a l l e l they do not have a common i n t e r c e p t . Hence they cannot be replaced by a si n g l e equation. In an attempt to examine v a r i a t i o n s i n t r a v e l time due to mainline tension new regression equations were computed. Table 10 shows the r e s u l t i n g regression equations f o r outhaul and inhaul time ( a l l turns i n c l u d i n g those with occurrence of delays). The inhaul time equations are not s t a t i s t i c a l l y " p a r a l l e l " ; and the outhaul time equations are p a r a l l e l but not "coincident" (at the 0.05 p r o b a b i l i t y l e v e l ) ; therefore, they cannot be replaced by combined regression equations. On s h i f t 1, inhaul distance" 1", and mainline tension accounted f o r 65% of the v a r i a t i o n i n inhaul time. Distance was the most important va r i a b l e with 60%, followed by mainline tension with the remaining 5% of explained v a r i a t i o n . However, the equation for outhaul time included only outhaul distance"*" which explained 73% of the v a r i a t i o n i n outhaul Table 10 - Regression equations for grapple yarder outhaul and Inhaul time, for each shift studied. 1 Shift o Equation N S.E.y. F * R 2 Variable Not Significant 1 IT = -0.03641 + 0.2213E-4(TI) + 0.00317(ID) 247 0.076 227 .65 -OT - 0.01937 + 0.00274 (OD) 247 0.047 660 .73 TO 2 IT - 0.01250 + 0.5802E-5(TI) + 0.00321(ID) 163 0.041 249 .76 -OT -0.03753 + 0.00239(OD) 163 0.039 246 .60 TO 3 IT - 0.03659 + 0.00371(ID) 309 0.074 1157 .79 -OT - 0.03738 + 0.00279 (OD) 309 0.055 1176 .79 -4 IT - 0.01318 + 0.00326(10) 312 0.055 764 .71 -OT » 0.02078 + 0.00287(OD) 312 0.046 857 .73 - " •Statistically significant at the 0.05 probability level *The inhaul time equations are not statistically "parallel^ and the outhaul time equations are "parallel" but not "coincident" (at the 0.05 probability level); therefore, they cannot be replaced by combined regression equations. 2 Variable description and statistical symbols: Outhaul Inhaul Time (min) OT IT N — number of observations Yarding distance (m) 0D ID S.E.y - Standard error of estimate Mainline tention (kg) TO TI F F-test R • Coefficient of determination - 96 -time. The r e l a t i v e l y constant and low values f o r mainline tension during outhaul account for i t s exclusion from the outhaul equation. On s h i f t 2 outhaul and inhaul time included the same va r i a b l e s selected for the s h i f t 1 equations. Inhaul distance (75%) and mainline tension (1%) accounted f o r 76% of the v a r i a t i o n s i n inhaul time. Distance accounted f o r 60% of the v a r i a t i o n i n outhaul time. On s h i f t 3 and 4 mainline tension was not recorded. However, the r e s u l t s discussed above in d i c a t e d that mainline tension i s weakly asso-c i a t e d with grapple t r a v e l time. Travel distance explained from 71% to 79% of the v a r i a t i o n s i n t r a v e l time. 5.2.3 Hooking Tlae and Yarding Distance Relationship The t o t a l hookup time ( i n c l u d i n g delays) versus distance s c a t t e r p l o t s f o r a l l s h i f t s studied are presented i n Figure 37 and 38. The pl o t s show no v i s i b l e r e l a t i o n s h i p between the v a r i a b l e s . The computed c o e f f i c i e n t of l i n e a r c o r r e l a t i o n between hookup time and distance show a weakly p o s i t i v e but n o n s i g n i f i c a n t l i n e a r r e l a t i o n s h i p between the two v a r i a b l e s as follows: Hookup time S h i f t No. of observations C o e f f i c i e n t of l i n e a r c o r r e l a t i o n (r) Yarding Distance 1 2 3 4 247 163 309 312 0.11 0.08 0.10 0.11 C o e f f i c i e n t s were not s i g n i f i c a n t at the 0.05 p r o b a b i l i t y l e v e l . - 9 7 -TOTAL HOOKUP TIME VERSUS DISTANCE 2.00 1.80 1.50 1.40 h 1.20 1.00 -0.80 -0 .60 0 .40 0 .20 0 .00 2.73 2.50 2.23 2.00 1 .73 1.S0 1.23 1.00 0.73 0.S0 -0.23 0 .00 S h i f t 1 *< • i i i Bi i i i i eg <a — (M s a s -YRROING DISTRNCE Cm) TOTAL HOOKUP TIME VERSUS DISTANCE S h i f t 2 5 S" a. * 03 in YRROING DISTRNCE Cm) FIGURE 37. S c a t t e r p l o t s of t o t a l hookup time and y a r d i n g d i s t a n c e ( s h i f t 1 and 2 ) . The p l o t s show no v i s i b l e r e l a t i o n s h i p between the v a r i a b l e s . - 98 -TOTHL HOOKUP TIME VERSUS DISTANCE a.se 2 . 1 0 2 . 2 0 2 . 0 0 1.80 1.60 1.40 1.20 1.00 0 . B 0 0 . 6 0 0 . 4 0 . 0 . 2 0 0 . 0 0 S h i f t 3 M " 9 m MM * M 2 » JC T« W< K * * S S — ni YRRDING DISTRNCE (») TOTBL HOOKUP TIME VERSUS DISTANCE 1.80 1.60 1.40 1.20 -1.00 0 . 8 0 0 . 6 0 0 . 4 0 0 . 2 0 • 0 . 0 0 S h i f t 4 X « * » X I * • * • • • i i i e i SJ i i — S 9 — ni s s s — YRRDINC DISTRNCE (»> FIGURE 38. S c a t t e r p l o t s of t o t a l hookup time and y a r d i n g d i s t a n c e ( s h i f t 3 and 4 ) . The p l o t s show no v i s i b l e r e l a t i o p n s h i p between the v a r i a b l e s . - 99 -5 . 2 . 4 Execution Time of Work-Elements During the S h i f t Table 11 shows the c o e f f i c i e n t of l i n e a r c o r r e l a t i o n between work-element time and turn number (time order), a f t e r adjusting the data for other f a c t o r s a f f e c t i n g time such as distance, mainline tension and speed. The ana l y s i s revealed that, f o r the conditions of t h i s study, there i s no s t a t i s t i c a l l y s i g n i f i c a n t (at 0.05 p r o b a b i l i t y l e v e l ) c o r r e l a t i o n between the two v a r i a b l e s . A nalysis of scatte r p l o t s of these v a r i a b l e s also revealed no other r e l a t i o n s h i p s . 5 . 2 . 5 Production and Ergonomic Factors Within Work-Cycles Table 12 presents the d e s c r i p t i v e s t a t i s t i c s within the work-cycle f o r a l l v a r i a b l e s measured during the study period. The following i s a summary of these r e s u l t s for each v a r i a b l e : a. Yarding Distance The average yarding distance per turn varied from 41 to 65 m, while the maximum recorded was 148 m. These figures show that the machine operated at r e l a t i v e l y short yarding distance compared with the average of 101 to 130 m as reported by Sauder (1980b) f o r s i m i l a r machines. Conway (1978) suggested that the best maximum yarding d i s t a n -ces are between 180 and 210 m. Short yarding distance usually increases Table 11 - Coefficients of linear correlation (r) between turn number (time sequence) and work-element time, over the study period. Time Sequence Variable Shift No. of Turns (observ.) Outhaul Work-Element Time1 (min) Hookup Inhaul Unhook Turn Number (Time Order) 1 2 3 4 247 163 309 312 0.09 0.11 -0.11 0.10 -0.06 0.15 -0.02 0.01 0.03 -0.08 -0.05 0.07 0.01 0.14 0.07 -0.04 If needed, element time was adjusted for yarding distance, mainline tension and mainline speed. No significant correlation was found between turn number and time element (at the 0.05 probability level). Table 12 - Descriptive statistics of all variables measured for each machine work-cycle, over the study period. Shift 1 Shift 2 Shift ) S h i f t 4 No. of Turns' Average per Turn S.O.2 Rang Min. e Max. No. of Turns Average per Turn S.D. Range Hln. Max. No. of Turns Average per Turn S.D. Range Min. Max. No. of Turns AveraRe per Turn S.O. Ra Min. nge Max. Yarding Distance (m) 247 65 29 6 132 163 41 21 6 103 309 54 38 6 148 312 47 27 6 121 No. of logs (pro-rated) 247 1 NA 1 3 163 1 NA 1 4 309 1 NA 1 2 312 1 NA 1 Outhat|l Speed (ra/s) 247 5.7 1.4 0.8 12.2 163 5.2 1.6 0.8 10.5 309 4.7 1.6 0.8 13.1 312 5.1 1.4 0.8 8.6 Inhaul Speed (m/s) 247 4.6 1.3 0.8 12.3 163 4.1 1.1 0.8 6.8 309 3.8 1.2 0.8 6.6 312 4.9 1.4 0.8 10.6 Load Volume3 (m3) NA' 1.2 NA NA NA NA 1.2 NA NA NA NA 1.2 NA NA NA NA 1.2 NA NA NA Load Weight4 (kg) NA 836 NA NA NA NA 836 NA NA NA NA 836 NA NA NA NA 836 NA NA NA Noise Level (dBA) 64 85.2 . 3.1 78.4 90.3 NA NA NA NA NA 301 86.6 3.2 79.1 94.2 311 84.1 4.0 74.1 93.6 1 X-Acceleratlon Ig(rms)] 122 0.024 0.007 0.004 0.043 162 0.037 0.012 0.006 0.066 260 0.030 0.012 0.001 0.077 260 0.028 0.01 1 0.001 0.072 1—• o Y-Acceleratlon |g(rms)l 134 0.018 0.005 0.002 0.033 159 0.022 0.005 0.005 0.033 260 0.021 0.006 0.001 0.057 268 0.020 0.006 0.001 0.04 3 (—' Z-Acceleratlon (g(rraa)l •33 0.021 0.008 0.002 0.076 162 0.029 0.006 0.009 0.053 258 0.031 0.008 0.001 0.058 258 0.030 0.007 0.004 0.053 1 .Heart Rate (bpm) NA NA NA NA NA NA NA NA NA NA 301 74.7 3.3 63.5 87. 1 312 62.0 4.9 40.0 77.1 I I Variable may not have been recorded for all turns. ;S.0. - Standard deviation. 'Load volume was calculated using the computed average number of logs and the average log volume obtained from company records (I.2m'). 'Load weight was estimated using the load volume and the estimated green density of 697 kg/m' (green density given by Doble and Wright 1979). 'NA - not applicable. - 102 -the haul road network density requirements, thereby i n c r e a s i n g road development cost per unit area and shrinking the productive land area. However, shorter distances decrease the outhaul and inhaul time, increase the operator's f i e l d of v i s i o n , improve c o n t r o l of grapple movement, may increase cable d e f l e c t i o n , and f a c i l i t a t e the work where obstacles are present such as rocks, ravines or convex t e r r a i n . b. Number, Volume and Weight of Logs The pro-rated average number of logs per turn was 1. The maximum recorded was 4 logs per turn and the most frequent observation was 1 log per turn. The operator usually made no attempt to hook more than one l o g , to avoid i n c r e a s i n g hookup time. Therefore, the f i r s t log (or logs) the grapple encountered was immediately seized f o r transport to the roadside. The fo r e s t density (number of stems/hectare) and f e l l i n g technique were possible factors a f f e c t i n g the number of logs per turn. The average log size was obtained from company records. Logs yarded on s h i f t s 1 to 4 averaged 1.2 m . The average number of logs per turn (1) m u l t i p l i e d by the average log siz e (1.2 m ) determined the average load volume estimate, which was 1.2 m 3/turn. Since the yarding operations started s h o r t l y a f t e r the trees were cut down the average green-density of logs was estimated to be 697 kg/m (Dobie and Wright 1979). Therefore the estimated average load weight was 836 kg. - 103 -c. Grapple Yarder P r o d u c t i v i t y Based on an average t o t a l time per turn ( i n c l u d i n g delays) of 1.320 min and an average load volume of 1.2 m /turn, the grapple yarder p r o d u c t i v i t y was 55 m /hour. d. Mainline or Grapple Speed Mainline speed was calculated separately for outhaul and inha u l . Outhaul speed ranged from 4.7 to 5.7 m/s and inhaul speed ranged from 3.8 to 4.9 m/s. Factors possibly a f f e c t i n g mainline speed include: log size and weight; yarding distance; ground conditions; and, p o s i t i o n of the grapple attached to the logs (center attachment usually slows down the inhaul element because the log "leads" less w e l l ) . The average mainline speed during inhaul was s i g n i f i c a n t l y l e s s than during outhaul. This l i n e speed d i f f e r e n c e for the f i r s t three s h i f t s was approximately 23%, and for the l a s t s h i f t , with poor cable d e f l e c t i o n , about 5%. The maximum s p e c i f i e d mainline speed for the Madill-044 grapple yarder i s approximately 15 m/s ( f u l l drum). Hence the machine's speed capacity i s not a l i m i t i n g f a c t o r (Appendix 1). e. Noise L e v e l Average noise l e v e l varied from 84.1 to 86.6 dBA during the study period. f. V i b r a t i o n A c c e l e r a t i o n The average a c c e l e r a t i o n per turn ranged from 0.024 to 0.037 g (rms) f o r X; 0.018 to 0.022 g (rms) for Y; and 0.023 to 0.031 g (rms) for the Z d i r e c t i o n . - 104 -Y-a c c e l e r a t i o n within the work-cycle was s i g n i f i c a n t l y smaller than X and Z for a l l s h i f t s studied. This d i f f e r e n c e was p r i m a r i l y due to higher forces required to p u l l the logs occurring i n the X - d i r e c t i o n (yarding d i r e c t i o n ) which r e l a t i v e l y increased X and Z a c c e l e r a t i o n . g. Heart Rate The operator's average heart rate per turn was 74.7 and 62.0 bpm for s h i f t 3 and 4, r e s p e c t i v e l y . The r e s t i n g heart rate was 60 and 52 bpm for those s h i f t s . 5.2.6 Production and Ergonomic Factors Within Work—Elements T y p i c a l patterns of ergonomic factors within work elements are shown i n Figures 39 to 42. These f i g u r e s show s i m i l a r i t i e s i n recording pattern for a p a r t i c u l a r v a r i a b l e over the four s h i f t study. Tables 13, 14 and 15 show the computed average within work element and delay f o r heart rate, noise l e v e l and mainline tension r e s p e c t i v e l y . 5.2.6.1 Heart Rate Results from the heart rate a n a l y s i s for each work element are presented i n Table 13. On s h i f t 3, the highest average heart rate was 75.4 bpm for the inhaul element and the lowest was 73.4 bpm for the inhaul delay. On s h i f t 4 the average heart rate varied from 58.7 bpm during yarding road change to 63.2 bpm during outhaul delay. During the delays - 105 -O H I U O H I U O H IU O H I U OH I U O H I U O H I U O H I U O FIGURE 39. T y p i c a l p a t t e r n of y a r d i n g d i s t a n c e , n o i s e l e v e l , m a i n l i n e t e n s i o n , v i b r a t i o n a c c e l e r a t i o n and number of l o g s s i m u l t a n e o u s l y r e c o r d e d ( s h i f t 1). The graph shows a 10-min p o r t i o n of the s h i f t w i t h seven complete work c y c l e s and t h e i r elements: o u t h a u l ( 0 ) , hookup (H), i n h a u l (I) and unhook (U) shown a t top of c h a r t . - 106 -0 H I U O H I U OHIUOHI-U O H I UOH I UOH.l UOH.IUO H . I U O H . I U O H J U 'i 3 i U m 1 u 1 sa I -13« FIGURE 40. T y p i c a l p a t t e r n of y a r d i n g d i s t a n c e , m a i n l i n e t e n s i o n , v i b r a t i o n a c c e l e r a t i o n and number of l o g s s i m u l t a n e o u s l y recorded ( s h i f t 2 ) . The graph shows a 10-min p o r t i o n of the s h i f t w i t h 11 complete work c y c l e s and t h e i r elements: outhaul ( 0 ) , hookup (H), i n h a u l (U) and unhook (U) shown at top of c h a r t . - 107 -* 1 3 u I N A m 8 ^ B • * 4 a 6 * > a n 8 m I ; c m • « u 8 H U H U H H H H 0 I OIUOH I O l U 0 H IUO H I UO IUO III 0 H IUOH I U OH I UOIUO H mm i 2 a 181 128 183 184 129 121 TIrC (Bin) 127 128 129 138) FIGURE 41. Typical pattern of yarding distance, noise l e v e l , heart rate, vibration acceleration and number of logs simultaneously recorded ( s h i f t 3). The graph shows a 10-min portion of the s h i f t with 12 complete work-cycles and their elements: outhaul (0), hookup (H), inhaul (I) and unhook (U) shown at top of chart. - 108 -I H H H H H H H H J . H . uo H lyoH IUO IUOH i UOHIU o .Miup i yo IUO IUOIUOH IUOIUO IUO lae • so-sa 79 88 5» 4 0 119 • P4! 7 * 13 i l 111 3 9 1 38* 3 9 1 3 9 4 3 9 9 3 9 8 T I H C (Bin! 3 9 7 3 9 8 399 FIGURE 42. Typical pattern of yarding distance, noise l e v e l , heart rate, vibration acceleration and number of logs simultaneously recorded ( s h i f t 4). The graph shows a 10-min portion of the s h i f t with 13 complete work cycles and their elements: outhaul ( 0 ) , hookup (H), inhaul (I) and unhook (U) shown at top of chart. Table 13 - Average heart rate for each work-element and delay. Heart Ra t e n bpm) Shift 3 Shift 4 Work-Cycle No. of Average Range Turns per S.D.3 (Observ.) Turn Min. Max. No. of Average Range Turns per S.D. (Observ.) Turn Min. Max. Elements Outhaul 300 75.2 4.4 58.9 88.5 Hookup 300 74.0 4.7 60.8 87.5 Inhaul 300 75.4 4.1 63.5 87.9 Unhook 300 75.2 4.9 57.7 97.0 312 62.4 4.8 52.2 80.2 312 62.2 5.0 47.0 80.9 312 62.7 4.8 52.9 84.2 312 62.4 5.1 40.0 83.3 Delays Outhaul 42 73.8 4.4 62.3 83.6 Hookup 85 73.7 4.3 65.2 83.6 Inhaul 43 73.4 4.3 64.8 82.1 Unhook 29 73.9 4.8 64.0 85.9 23 63.2 5.4 53.8 76.1 63 62.0 5.6 52.8 76.9 24 62.0 7.3 55.4 90.6 32 59.9 4.6 51.2 74.9 Yarding Road Change 15 74.5 4.0 68.6 80.2 11 58.7 5.2 54.1 72.5 Arithmetic average calculated from time-weighted average obtained for each element. Operator's resting pulses were 60 and 52 bpm for shifts 3 and 4 respectively. No explanation of this difference is available; however, i t i s within the range of normal dally variation. 's.D. » standard deviation. - 110 -the heart rate average tended to be lower than during the work-elements, e s p e c i a l l y for s h i f t 3. This d i f f e r e n c e could be due to the lower operator a c t i v i t y (or lack of a c t i v i t y ) during delay time (e. g., wait-ing while spotter checks yarding road for missed l o g s ) . Within work elements, the higher heart rate average occurred during inhaul a c t i v i t y . Figures 41 and 42 show samples of the t y p i c a l pattern of heart rate f l u c t u a t i o n s f o r the work-cycles and t h e i r elements. 5.2.6.2 Noise L e v e l Average noise l e v e l for each element of the work cycle over the study period i s shown i n Table 14. Noise l e v e l within the work elements varied from 83.0 to 87.9 dBA. The averages for the elements were: 86.4, 84.4, 85.0, and 84.6 dBA r e s p e c t i v e l y f o r outhaul, hookup, inhaul and unhook over the study period. Probably as a r e s u l t of higher mainline speed and engine noise, the highest average noise l e v e l s were found during the outhaul element. The lowest noise l e v e l s were found among the delays. Figures 39, 41 and 42 show t y p i c a l patterns of noise l e v e l recorded over a 10-min portion of the s h i f t . The higher noise l e v e l during outhaul i s c l e a r l y shown i n the l a s t two of these f i g u r e s . 5.2.6.3 V i b r a t i o n A c c e l e r a t i o n Numerical averages f o r a c c e l e r a t i o n values occurring during Table 14 - Average noise level for each work-element and delay. Noise Level (dBA) Shift 1 Shift 3 Shift 4 Work-Cycle No. of dBA No. of dBA No. of dBA Turns Average S.D.2 Range Turns Average S.D. Range Turns Average S.D. Range (Observ.) Hln. Max. (Observ.] Min. Max. (observ. ) Min. Max. Elements Outhaul 64 86.8 5.1 77.4 96.8 300 87.9 4.7 77.2 97.8 311 85.0 5.7 75.7 95.3 Hookup 64 83.2 3.2 74.7 90.8 300 85.2 3.3 76.9 96.8 311 83.8 2.7 75.5 95.4 Inhaul 64 85.1 4.3 75.5 92.8 300 86.0 4.2 76.7 96.7 311 84.0 4.7 75.9 92.4 Unhook 64 84.9 4.1 75.6 93.2 300 85.9 3.9 76.6 96.2 311 83.0 4.2 73.4 91.9 Delays Outhaul 9 83.7 5.9 76.1 93.4 42 83.9 3.5 76.2 91.6 23 83.2 5.0 69.2 93.8 Hookup 20 82.1 3.7 71.6 86.7 85 84.5 2.7 76.4 90.5 63 83.9 3.0 79.4 95.0 Inhaul 6 84.9 2.8 82.5 90.2 43 84.9 3.2 74.8 93.0 24 82.0 3.0 76.6 87.2 Unhook 10 82.5 3.8 75.9 89.2 29 85.2 5.0 76.7 98.2 32 80.9 3.2 74.3 87.1 Yarding Road Change 3 82.5 2.4 81.0 85.2 15 83.0 2.9 77.9 89.5 11 79.0 2.6 74.8 82.7 Arithmetic average calculated from time-weighted average obtained for each element. !S.D. - Standard deviation. - 112 -execution of s p e c i f i c work-elements were not c a l c u l a t e d . This i s p r i m a r i l y due to the 10-s designed time the v i b r a t i o n analyser takes to process the v i b r a t i o n s i g n a l and d e l i v e r the rms output to the Data Logger microprocessor. This processing time was i n many instances higher than the elapsed time of a work element. A v i b r a t i o n measuring instrument that could c a l c u l a t e the rms value over a shorter time than 10 s should be used to c o l l e c t data f o r s i m i l a r a n a l y s i s . V i s u a l a n a l y s i s of the v i b r a t i o n graphs appears to show higher v i b r a t i o n values during i n h a u l . X-acceleration e x h i b i t s the highest values followed by Z and Y. Figures 39 to 42 present t y p i c a l samples of the recorded v i b r a -t i o n s i g n a l for the work-elements over the study period. 5.2.6.4 Mainline Tension Table 15 shows the d i s t r i b u t i o n of mainline tension over the work-elements and delays. The highest average mainline tension occurred during inhaul (3403 kg and 3993 kg for the data recorded on s h i f t s 1 and 2, r e s p e c t i v e l y ) . The maximum s p e c i f i e d mainline drum p u l l for the machine studied (bare drum condition) varies from 21,410 kg to 42,071 kg for high and low gear, r e s p e c t i v e l y . Figures 39 and 40 i l l u s t r a t e the t y p i c a l pattern of mainline tension occurring within the grapple yarder work cycle and elements. Table 15 - Average mainline tension for each work-element and delay. Mainline Tension 1 (kg) Shift 1 Shift 2 Work-Cycle No. of Turns (Observ. Average per Turn ) S.D.2 Min. Range Max. No. of Turns (Observ. Average per Turn ) S.D. Range Min. Max. Elements Outhaul Hookup Inhaul Unhook 246 246 246 246 1,354 1,547 3,403 1,279 639 899 1,277 695 81 139 1,064 154 4,991 5,991 10,867 5,301 161 160 162 163 2,095 2,449 3,993 1,877 814 1,059 1,215 691 356 314 1,019 228 3,864 5,596 7,481 4,537 Delays Outhaul Hookup Inhaul Unhook 27 82 24 26 1,469 1,647 2,136 1,235 920 1,387 1,543 560 82 129 562 57 3,907 8,181 7,071 2,935 19 50 19 19 1,615 2,810 3,227 1,592 529 1,581 1,635 659 454 524 544 454 2,464 7,691 6,726 2,760 Yarding Road Change 11 1,205 436 528 1,714 7 1,749 683 907 2,729 Arithmetic average calculated from time-weighted average obtained for each element. i S.D. = Standard deviation. - 114 -5.3 Comparison With the Standards The v a r i a b l e s compared with standards were: heart rate; noise l e v e l ; v i b r a t i o n a c c e l e r a t i o n ; e f f e c t i v e temperature; and, mainline tension. 5.3.1 Heart Rate Figures 43 and 44 summarize the r e s u l t s of heart rate measure-ments over the study period. According to Grandjean (1981) the l i m i t of continuous performance for workers (men) i s reached when the average working pulse i s 35 bpm above the r e s t i n g pulse. The measured operator's r e s t i n g pulse rates (seated p o s i t i o n ) were 60 bpm and 52 bpm for s h i f t 3 and 4 r e s p e c t i v e l y (no explanation was apparent for t h i s d i f f e r e n c e ) . Based on these r e s t i n g pulse values the l i m i t s f o r continuous performance of 95 bpm ( s h i f t 3) and 87 bpm ( s h i f t 4) were found. The average heart rate values for those two s h i f t s were r e s p e c t i v e l y 74.4 bpm and 61.7 bpm. Therefore the increases i n average working pulse during grapple yarding operation were r e s p e c t i v e l y 14.4 bpm and 9.7 bpm for s h i f t s 3 and 4. Figure 43 shows the t y p i c a l response of heart rate to the comparatively l i g h t grapple yarding work. The heart rate increased to the required l e v e l s of e f f o r t (74.4 or 61.7 bpm) and then o s c i l l a t e d approximately 8 bpm around these l e v e l s for the duration of the work. Heart rate (beat-to-beat) peaks of up to 180 bpm were recorded on both - 115 -HERRT RRTE VERSUS SHIFT TIME GRRPPLE YRRDER OPERATOR S h i f t 3 — • • Limit -for continuous performance — — — — Working pulse ( a v e r a g e ) — — < — Resting pulse 340 TIME (min) 300 3S0 430 490 FIGURE 43. Heart r a t e measurements of the g r a p p l e yarder o p e r a t o r over the s h i f t ( s h i f t 3 and 4) . The graph shows the o p e r a t o r ' s r e s t i n g p u l s e , working p u l s e and the recommended working p u l s e l i m i t f o r c o n t i n u o u s performance. Percentage of time heart ra te in bpm exceeded c l a s s l eve l I u cr ~o 3 o a 3 €* f l "1 o -»> (I es 9B 95 IBB IBS I IB I IS u a I2S I3B I3S M B 145 ISB 155 IEB l £ S I7B 175 IBB IBS CL I PT 15 ->. M 14 8. 21 r* r+ a. it -» O 8.83 in 8.81 cr T a oa c (U a.at r* 3 I . H O Ol a. a) 3 3 a. a) a a.>2 -h a. »2 C 3 cu 8.81 n 3 8.88 C 8.81 — 8.81 O Bl 8.81 3 8.81 < 8.81 f l 8.88 i n tr Percentage of time spent in c l a s s i n t e r v a l Percentage of time hear t ra te in bpm exceeded c l a s s l eve l 48 « SB SS GB ES 7B 7S aa as 98 as IBB IBS 118 I IS I2B I2S iaa I3S K B H 5 ISB IS5 tea IES I7B 175 tea IBS •*> O I y i . s t C C 8.18 3 3 IA 8.81 O C c* a. 82 r* — a 8.87 - 01 IQ O r* i a.e* 3 - i» a.as < 3 . 8.82 (1 8. i t 01 8.81 a 3 Q_ 8.81 IA 8.82 t* 8.82 8.82 —• 8.81 cr c 8.82 •+ 8.81 — Ul 8.82 o V 8.81 3 M • 8.84 rti rt 8.81 8.88 *• — tu uj CD CS CD <B Percentage of t i me spen t i n c l a s s i n t e r v a l - 117 -working days. The occasional occurrence of two beats i n a very short period of time (0.33 s) produced these high heart-rate values. The d i s t r i b u t i o n within the work elements and delays of number of heart-rate observations (peaks) exceeding the a r b i t r a r y value of 100 bpm i s as follows: No. of Percentage Work-cycle Observations exceeding 100 bpm Elements: Outhaul 5 5 Hookup 8 7 Inhaul 14 12 Unhook 29 26 Delays: Outhaul 9 8 Hookup 0 0 Inhaul 15 13 Unhook 4 4 Yarding Road Change: 28 25 T o t a l 112 100 This d i s t r i b u t i o n shows that 51% of the t o t a l number of peaks (greater than 100 bpm) occurred during unhook and yarding road change a c t i v i t i e s . Inhaul and corresponding delays accounted for approximately 26% of the t o t a l number of peaks. The remaining peaks were d i s t r i b u t e d among the other work elements and delays. A p o s s i b l e explanation for t h i s p a r t i c u l a r d i s t r i b u t i o n of peaks i s psychological reactions of the operator to problems encountered during execution of these tasks. Figure 43 appears to show a s l i g h t increase i n heart rate a f t e r the lunch break, then a steady decline as time passed. Recorded temperature showed that those periods of increased heart rate did not correspond with periods of increased workplace temperature. - 118 -5.3.2 Noise L e v e l The noise l e v e l s to which the grapple yarder operator was exposed during the period of t h i s study are i l l u s t r a t e d i n Figure 45. Recom-mended standard l i m i t s and numerical r e s u l t s for the three s h i f t s are shown i n Table 16. The c a l c u l a t e d Leq values were r e s p e c t i v e l y 84.5, 87.2 and 84.9 dBA for s h i f t s 1, 3 and 4. The higher noise l e v e l s obtained on s h i f t 3 were l i k e l y due to the fa c t that both cab windows were frequently open to control cab temperature. On s h i f t 3, noise l e v e l s exceeded 75, 85 and 90 dBA for approxi-mately 92%, 38% and 19% of the t o t a l exposure time r e s p e c t i v e l y (Figure 46). These percentages show that despite the fac t that the ca l c u l a t e d average noise l e v e l was below the standard l i m i t , the act u a l noise observations exceeded the 90 dBA l i m i t for a considerable proportion of time. The number of observations ( s h i f t s 1, 2 and 3 combined) exceeding 90 dBA (WCB hearing r i s k l i m i t ) was d i s t r i b u t e d within the work cy c l e as follows: - 119 -i ia -j 100 90 NOISE LEVEL VERSUS- SHIFT TIME GRAPPLE YRRDER S h i f t 1 i i E x p o s u r e l i m i t A c t u a l L s q 420 490 420 490 129 • 28 S h i f t 4 i i i S B 120 tea 24a aaa TIME (min) 360 420 460 FIGURE 45. Noise l e v e l measurements at the l e f t ear of the gra p p l e y a r d e r o p e r a t o r over the s h i f t ( s h i f t 1, 3 and 4 ) . The graph shows the c a l c u l a t e d Leq and and the WCB recommended maximum 8-hr exposure l i m i t (without h e a r i n g p r o t e c t i o n ) . Table 16 - Comparison of noise l e v e l r e s u l t s with the WCB recommended standard for three grapple yarder operating s h i f t s . WCB Standard Limit Leq* S.D. Ps Pe Et D S h i f t (dBA) (dBA) (dBA) % % (hr) % 1 90 84.5 6.6 2 90 87.2 6.7 3 90 84.9 7.6 4.0 8.4 > 8 28.2 7.7 18.6 > 8 52.5 4.8 10.4 > 8 30.9 *Leq = Equivalent sound l e v e l (dBA) S.D. = Standard deviation Ps = Percentage of time spent in the 90 dBA class ( l i m i t s : 89 - 91 dBA). Pe = Percentage of t o t a l exposure time noise l e v e l exceeded the 90 dBA c l a s s . Et = Maximum allowed exposure time ( h r ) . D = Percentage of permitted noise dose for 8-hr period (%). — ft. 35 » O f 1 in u i r t r t O m a-ji a a >n a t» >o g *»i — 01 S i • T J 3 •a a i—1 i t n s i » c ao> It r t < 3 It O ••a Ul M* It 10 r t i— n i t < tr <t c a o Bl 3 r t PJ ra C — 3 in n V r t ra o r t 3 P e r c e n t a g e o f t i m e n o i s e l e v e l I n d B R e x c e e d e d c l a s s l e v e l P e r c e n t a g e o f t i m e n o i s e l e v e l i n d B H e x c e e d e d c l a s s l e v e l P e r c e n t a g e o f t i m e n o i s e l e v e l I n d B H e x c e e d e d c l a s s l e v e l P e r c e n t a g e o f t i m e s p e n t I n c l a s s I n t e r v a l P e r c e n t a g e o f t i m e s p e n t I n c l a s s I n t e r v a l P e r c e n t a g e o f t i m e s p e n t I n c l a s s I n t e r v a l I i — • r o i—• I - 122 -Work-cycle No. of Observations Percentage exceeding 90 dBA Elements: Outhaul Hookup Inhaul Unhook 1032 351 716 731 28 9 19 20 Delays: Outhaul Hookup Inhaul Unhook 107 187 263 123 3 5 7 3 Yarding Road Change: 221 6 T o t a l 3731 100 This d i s t r i b u t i o n shows that the majority of the observations exceeding the l i m i t occurred during the outhaul (28%), unhook (20%) and inhaul a c t i v i t i e s (19%). 5 . 3 . 3 Vibration Acceleration Figures 47 to 50 show the a c c e l e r a t i o n l e v e l s i n the X, Y and Z d i r e c t i o n f o r each of the four sample s h i f t s , with the ISO recommended l i m i t s and averages superimposed on the graphs. Examination of the graphs shows that the a c c e l e r a t i o n l e v e l s p e r i o d i c a l l y , frequently and very frequently exceeded the "exposure l i m i t " , the "fatigue-decreased p r o f i c i e n c y boundary" and "reduced comfort boundary", r e s p e c t i v e l y . Table 17 shows for each s h i f t the percentage of time the v i b r a -t i o n l i m i t s were exceeded. The percentage of time that the "exposure - 123 -VIBRATION ACCELERATION S h i f t » a. is e 2 a. 10 i ' a . as 0 . 0 0 e 2 a. ia 0.89 a. SB ISO « * M l 4*r4 (t hp. I l a l t a i i — — f j i p m r a L l M t t F « « l g t M B H P t m r i P r a t 1 a 1 a m y B a u n d a r y — — ffadueaa* Caarfar* 8oun4«f>y E 1 • • 4 Average 1.1 II1 . 1 ,T 1 III. 3 a so aa 120 i s a laa 2 i o 24a 27a 3aa 3 3 a 3sa 39a <aa 4sa 4ea ™ a.is • a. ia i a . as a. aa 30 SO 30 120 130 190 210 240 270 300 330 360 390 420 430 480 9 30 SO 30 120 ISO 180 210 240 270 300 330 3S0 390 420 430 480 T i m C m t n l FIGURE 47. H o r i z o n t a l (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the g r a p p l e yarder over the s h i f t ( s h i f t 1). The graph shows average a c c e l e r a t i o n g(rms), and the ISO recommended l i m i t s . - 124 -V I B R A T I O N A C C E L E R A T I O N S h i f t 2 ~ a. is I a. ia a. a s ~ a. is 2 a . i a a.aa • w B a. ta a.aa ISO • tana'ard <8 H r . I t a t t a J i — Cicpoam'a LI a l t Faa lgua Daor.»..a P r a f f o l a n a y Sawndary — — — rraduead C a a * a r * Boundary I Average aa sa sa u « isa laa 2ia 2 4 8 27a 3ea 33a 3sa 39a <aa 43a <aa ft 3a sa aa 12a isa isa 2 i a 24a 27a 3ea 33a 3sa 33a 42a 43a 4sa FIGURE 48. H o r i z o n t a l (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the g r a p p l e y a r d e r over the s h i f t ( s h i f t 2 ) . The graph shows average a c c e l e r a t i o n g(rms), and the ISO recommended l i m i t s . - 125 -VIBRBTION SCCELERRTION S h i f t 3 m a. is • • • 2 a.ia a ' a. as ~ a. is • e 2 a. ia a.aa - a. is b a " w e o ~ a. ia m u u c x a.os I a.aa ISO a tanaara (• hp. I i a l t a l i CM»—•urm L l a t t F a t l f i M D w n m < P V « * l e l a i w y Baundary — — WadMaad C W o r t Boundary IAverage I sa sa sa iaa isa iaa zia a«e 27a sea 33a 3sa 39a «2e 43a <ae 3a sa sa 12a isa iaa aia a«e 27a saa 33a sea 39a 12a «sa «aa a 3a sa sa 12a isa iaa 21a 2«a 27a 3aa 33a 3sa 39a 4 2 a 45a -iaa T i m Cfnl o ] FIGURE 49. H o r i z o n t a l (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the gr a p p l e yarder over the s h i f t ( s h i f t 3 ). The graph shows average a c c e l e r a t i o n g(rms), and the ISO recommended l i m i t s . - 126 -VIBRATION ACCELERATION S h i f t 4 ~ a. is 2 a. ia ' a. aa a.aa r. a. is a • e 2 a. ia a.aa Z a. is a • a. ia a.aa ISO . t a n d a r a <• hp . I l a i t a l i - Caaaaura L t a t t F a t l ava Daapaaaa* P r o f l o l a n a y Baundapf Haaaaaa* Coadopt Beurrdapy IRvorsgo aa sa sa isa isa isa aia 24a 278 sea 33a 3sa 3 9 a 42a 43a 4aa 3a sa 9a 12a 13a taa 21a 24a 27a 3ea 33a 3sa 33a 42a 43a 4sa a 3a sa sa 12a isa isa 21a 24a 27a 3aa 33a 3sa 39a 42a 45a 43a TIraa CiatnJ FIGURE 50. H o r i z o n t a l (X and Y) and v e r t i c a l (Z) seat a c c e l e r a t i o n f o r the g r a p p l e yarder over the s h i f t ( s h i f t 4 ) . The graph shows average a c c e l e r a t i o n g(rms), and the ISO recommended l i m i t s . Table 17 - Percentage of t o t a l measured exposure time v i b r a t i o n l e v e l s exceeded the recommended ISO l i m i t s for health or safety, fatigue and comfort c r i t e r i a . ISO D i r e c t i o n of S h i f t 1 S h i f t 2 S h i f t 3 S h i f t 4 C r i t e r i a V i b r a t i o n (%) (%) (%) (%) Exposure Limit X 2.5 13.7 7.9 8.3 Y 0.3 0.4 1.1 1.1 Z 1.1 1.4 1.9 1.7 Fatigue-Decreased X 13.4 74.0 64.6 61.9 Prof i c i e n c y Y 8.7 23.0 23.0 20.4 Z 9.4 23.0 33.1 29.6 Reduced Comfort X 98.8 98.4 99.3 98.7 Y 99.4 98.7 98.8 99.8 Z 95.3 93.6 98.2 94.9 - 128 -l i m i t " was exceeded varied with the s h i f t s from 2.5% to 13.7%; from 0.3% to 1.1%; from 1.1% to 1.9% for X, Y and Z a c c e l e r a t i o n , r e s p e c t i v e l y . The "fatigue-decreased p r o f i c i e n c y boundary" was exceeded f o r the following percentages of the t o t a l exposure time: from 13.4% to 74.0% f o r X; from 8.7% to 23% for Y; and, from 9.4% to 33.1% for Z. The "reduced comfort boundary" was exceeded for more than 93% of the t o t a l exposure time (Table 17). These data c l e a r l y show that a l l the l i m i t s were temporarily exceeded. However, to assess the e f f e c t i v e d a i l y exposure to v i b r a t i o n the equivalent exposure time method (ISO 1978) was used. Table 18 shows the c a l c u l a t e d equivalent exposure time for the preservation of health or safety was w e l l below the 8-hr (480 min) l i m i t f o r a l l v i b r a t i o n d i r e c t i o n s (X, Y and Z). The highest equivalent times were 54%, 37%, and 38% below the 480-min l i m i t f o r X, Y and Z, r e s p e c t i v e l y . X-accele-r a t i o n exceeded Y and Z by at l e a s t 22 min and 19 min of equivalent time r e s p e c t i v e l y . On s h i f t s 2, 3 and 4, the l i m i t f o r "fatigue-decreased p r o f i -ciency boundary" for X-acceleration was exceeded by approximately 151 min, 107 min and 14 min r e s p e c t i v e l y . Values of equivalent exposure time f o r "reduced comfort boundary" were a l l above the 8—hr l i m i t . The l i m i t was exceeded by a f a c t o r varying from 3 to 10, with X the most c r i t i c a l d i r e c t i o n f o r reduced comfort. Table 18 - Calculated equivalent exposure times for the three ISO c r i t e r i a : "exposure l i m i t " , "fatigue-decreased p r o f i c i e n c y " and "reduced comfort" during four grapple yarding s h i f t s . Equivalent Exposure Time (min) ISO D i r e c t i o n C r i t e r i a of V i b r a t i o n S h i f t 1 S h i f t 2 S h i f t 3 S h i f t 4 Exposure Limit X 188 260 242 222 Y 166 173 179 175 Z 168 173 185 179 Fatigue-Decreased X 384 631* 587* 494 Prof i c i e n c y Y 276 304 341 315 Z 268 299 382 347 Reduced Comfort X 2,294* 4,770* 4,465* 3,785* Y 1,520* 1,628* 2,093* 1,862* Z 1,465* 1,566* 2,200* 1,812* Dail y l i m i t = 480 min *Limit exceeded - 130 -5.3.4 E f f e c t i v e Temperature Machine cab and atmospheric environment during the study period are summarized i n Table 19. Inside the cab, a i r temperature varied from 20°C to 24°C, r e l a t i v e humidity from 43% to 53% and the new e f f e c t i v e temperature varied from 20°C to 24°C. During the work the operator wore l i g h t to medium c l o t h i n g and the l e v e l of a c t i v i t y of the operation was considered very low, as shown by the heart rate r e s u l t s . Outside cab temperature ranged from approximately 13°C to 23°C and r e l a t i v e humidity ranged from 59% to 73%. The new e f f e c t i v e temperature outside the cab ranged from 13°C to 23°C. The d i f f e r e n c e between i n s i d e and outside cab e f f e c t i v e tempera-ture varied from approximately 1°C to 9°C. This shows the e f f e c t of the cab i n keeping the temperature c l o s e r to the comfort g u i d e l i n e s . 5.3.5 Mainline Tension Figures 51 and 52 summarize the r e s u l t s f o r mainline tension recorded during the study period. The graphs show that maximum tension values ranged from approximately 15,000 kg to 27,000 kg. The number of observations (peaks) exceeding an a r b i t r a r y value of 8,000 kg was d i s t r i b u t e d within the work-cycle as follows: Table 19 - Machine cab and atmospheric environment during the study period. Cab Environment1 Atmospheric Environment Dry-bulb Relative New Effective Air Relative New Effective Temperature Humidity Temperature Temperature Humidity Precipitation Temperature Shift (°C) (%) CC) (°C) (%) (mm) (°C) 1 20 49 20 13 73 0.0 13 2 22 43 22 13 72 0.0 13 3 21 53 21 15 72 1.5 15 4 24 52 24 23 59 0.0 23 Recommended new effective temperature (McCormick 1976): Clothing Level of Activity Low Medium Light 27°C 19°C Medium 24°C 16°C Energy expenditure: Low * 2.5 - 5.0 Kcal/min; medium = 5.0 kcal/min. Heart rate : Low =75-100 bpm; Medium - 100-125 bpm. - 132 -MRINLINE TENSION VERSUS SHIFT TIME GRAPPLE YARDER S h i f t 1 I I I > S A F E W O R K I N G L O A D a sa 128 isa 248 3ea 36a 42a 488 TIME (min) MAINLINE TENSION VERSUS SHIFT TIME GRAPPLE YARDER S h i f t 2 24a TIME (min) FIGURE 5 1 . M a i n l i n e t e n s i o n t h r o u g h s h i f t 1 and 2 f o r M a d i l l 044 g r a p p l e y a r d e r . - 133 -M a i n l i n e t e n s i o n in kg (center of the c l a s s ) FIGURE 52. Histogram and cumulative d i s t r i b u t i o n function for the mainline tension data ( s h i f t 1 and 2)-. - 134 -No. of Percentage Work-cycle Observations exceeding 8,000 kg Elements: Outhaul 9 1 Hookup 117 13 Inhaul 348 40 Unhook 12 1 Delays: Outhaul 10 1 Hookup 191 22 Inhaul 123 14 Unhook 6 1 Yarding Road Change: 59 7 T o t a l 875 100 This d i s t r i b u t i o n shows that the majority of observations exceed-in g the l i m i t occurred during the inhaul element. Figure 52 shows that for approximately 98% of the time mainline tension was below 8,000 kg. Mainline tension exceeded the safe work l e v e l of the cable approximately 0.04% of the t o t a l time. 5.4 Ergonoalc and Production Factor Relationships 5.4.1 Re l a t i o n s h i p Between V a r i a b l e Values Within the Work-Cycle The i n i t i a l hypotheses of no c o r r e l a t i o n between the work-cy c l e averages f o r the ergonomic and production v a r i a b l e s were tested using l i n e a r c o r r e l a t i o n a n a l y s i s . The c o e f f i c i e n t s of l i n e a r c o r r e l a -t i o n (r) among a l l v a r i a b l e s studied are shown i n Tables 20 to 23. Table 20 - Coefficients of linear correlation (r) and regression equations for ergonomic and production variables, shift 1.' N-55 Variable Variable 3 MT NL XA YA' ZA Dl OS IS Mainline Tension (MT) 1.000 Noise Level (NL) -0.139 1.000 X-acceleratlon (XA) 0.393** 0.098 I.000 Y-acceleratlon (YA) 0.103 0.360** 0.674** 1.000 Z-acceleratlon (ZA) 0.199 0.291* 0.750** 0.797** 1.000 Yarding Distance (Dl) 0.099 -0.305* -0.188 -0.507** -0.484** 1.000 Mainline Speed, -0.003 0.071 -0.030 -0.127 -0.005 0.140 1.000 Outhaul (OS) Mainline Speed, -0.070 0.239 -0.199 -0.110 -0.093 0.358** 0.325** 1.000 Inhaul (IS) Calculated Relationships '* Equation N S.E.y F * R 2 Variables Not Significant MT - 2083.4000 + 8.3243(D1) - 2.5686(IS) 246 707.1 19.8 .14 OS NL » 80.7990 + 155.6O0O(YA) + 0.01I6(IS) - 0.0341(D1) 55 2.6 6.4 .27 MT, XA, ZA, OS XA - 0.1389E-4 + 0.6167(ZA) + 0.4345E-5(MT) 122 0.0062 53.4 .47 YA, Dl, OS, IS YA - 0.0040 + 0.5875(ZA) 122 0.0029 256.5 .68 MT, XA, Dl, OS, IS ZA - 0.0046 + 0.9083(YA) + 0.2106(XA) - 0.3049E-4(D1) 122 0.0038 109.1 .73 MT, OS, IS XA - 0.0061 + 0.6908(ZA) 122 0.0069 65.8 .35 YA YA - 0.0040 + 0.5875(ZA) 122 0.0029 256.5 .68 XA ZA - 0.0015 + 0.992KYA) + 0.1995(XA) 122 0.0039 153.6 .72 Data were prepared using a weighted average technique (see 4.3.2) to determine the value, for each variable, corresponding to each work-cycle recorded during the s h i f t . The exceptions were: yarding distance, which used maximum distance recorded for each work-cycle; and mainline speed for outhaul and Inhaul elements, obtained by dividing yarding distance by their respective elapsed times. Statistically significant at 0.05 (*) and at 0.01 (**) probability level. 3Unlta: Noise level, dBA; mainline tension, kg; acceleration, g(rms); mainline speed, m/min; and yarding distance, m. N - Number of observations; S.E.y » Standard error of estimate; F - F-test; and R = coefficient of determination. Table 21 - Coefficients of linear correlation (r) and regression equations for ergonomic and N=159 production variables. s h i f t 2.1 Variable 2 V a r i a b l e 3 MT XA YA ZA Di OS IS Mainline Tension (MT) 1.000 X-acceleration (XA) 0.663** 1.000 Y-acceleratlon (YA) 0.498** 0.641** 1.000 Z-acceleration (ZA) 0.449** 0.838** 0.653** 1.000 Yarding Distance (DI) 0.303** 0.174* -0.033 0.014 1.000 Mainline Speed, Outhaul (OS) 0.176* 0.119 0.110 0.092 0.353** 1.000 Mainline Speed, Inhaul (IS) 0.088 0.262** 0.051 0.233** 0.370** 0.246** 1.000 If Calculated Relationships Equation N S.E.y F* R 2 Variables Not Si g n i f i c a n t MT - 1978.4000 + 11.7260 Dl 163 801.1 15.7 .09 OS, IS XA - -0.0149 + 1.2080 ZA + 0.5429E-5(MT) + 0.1406E-4(IS) 159 0.0055 220.8 .81 YA, 01, OS YA ca 0.0063 + 0.4186 (AZ) + 0.2030E-5(MT) - 0.3413E-4(D1) 159 0.0039 50.6 .49 XA, OS, IS ZA - 0.0103 + 0.4568(XA) + 0.2773(YA) - 0.1789B-5(MT) 159 0.0034 156.0 .75 Dl, OS, IS XA - -0.0099 + 1.3428(ZA) + 0.3703(YA) 159 0.0067 198.0 .71 -YA - -0.0078 + 0.3155(ZA) + 0.1383(XA) 159 0.0041 65.4 .45 -ZA - 0.0092 + 0.3876(XA) + 0.24373(YA) 159 0.0036 205.7 .72 -Data were prepared using a weighted average technique (see 4.3.2) to determine the value, for each variable, corresponding to each work-cycle recorded during the s h i f t . The exceptions were: yarding distance, which used maximum distance recorded for each work-cycle; and mainline speed for outhaul and Inhaul elements, obtained by dividing yarding distance by their respective elapsed times. S t a t i s t i c a l l y s i g n i f i c a n t at 0.05 (*) and at 0.01 (**) probability l e v e l . 3Unlts: Mainline tension, kg; acceleration, g(nns); mainline speed, m/mln; and yarding distance, m. ii N = Number of observations; S.E.y ° Standard error of estimate; F » F-test; and R » coe f f i c i e n t of determination. Table 22 - Coefficients of linear correlation (r) and regression equations for ergonomic and production variables, shift 3.' N-254 Variable Variable 3 HR NL XA YA ZA Dl OS IS Heart Rate (HR) 1.000 Noise Level (NL) 0.181** 1.000 X-acceleratlon (XA) 0.195** 0.138* 1.000 Y-acceleratlon (YA) 0.125* 0.009 0.620** 1.000 Z-acceleratlon (ZA) 0.161* 0.038 0.536** 0.538** 1.000 Yarding Distance (Dl) 0.036 0.187** -0.139* -0.173** -0.328** 1.000 Mainline Speed, Outhaul (OS) 0.166** 0.272** 0.059 -0.012 0.042 0.407** 1.000 Mainline Speed, Inhaul (IS) 0.207** 0.357** 0.026 -O.006 0.010 0.394** 0.500** 1.000 Calculated Relationships Equation N S.E.y F* R2 Variables Not Significant HR - 70.9410 + 0.9278 (IS) + 61.1340 (XA) 254 3.32 10.7 .08 NL, YA, ZA, D1.0S NL - 81.8180 + 0.0153 (IS) + 39.4370 (XA) 254 3.02 21.1 .14 YA, ZA, Dl, OS XA - 0.8025E-3 + 0.8550 (YA) + 0.3655 (ZA) 256 0.0080 99.9 .44 Dl, OS, IS YA - 0.0064 + 0.2620 (XA) + 0.2035 (ZA) 256 0.0044 100.2 .44 01, OS, IS ZA - 0.0159 + 0.4093 (YA) + 0.2242 (XA) 256 0.0062 45.2 .42 IS 0.6339E-4 (01) + 0.1228E-4 (OS) XA - 0.8025E-3 + 0.8550 (YA) + 0.3655 (ZA) 256 0.0080 99.9 .44 YA - 0.0064 + 0.2620 (XA) + 0.2035 (ZA) 256 0.0044 100.2 .44 ZA - 0.0147 + 0.4503 (YA) + 0.2479 (XA) 256 0.0066 66.9 .34 'Data were prepared using a weighted average technique (see 4.3.2) to determine the value, for each variable, corresponding to each work-cycle recorded during the shift. The exceptions were: yarding distance, which used max!mum distance recorded for each work-cycle; and mainline speed for outhaul and Inhaul elements, obtained by dividing yarding distance by their respective elapsed times. Statistically significant at 0.05 (*) and at 0.01 (**) probability level. *Unlts: Heart rate, bpm; noise level, dBA; acceleration, g(rms); mainline speed, ra/rain; and yarding distance, m. N = Number of observations; S.E.y •> Standard error of estimate; F « F-test; and R v=» coefficient of determination. Table 23 - Coeffi c i e n t s of linear c o r r e l a t i o n (r) and regression equations for ergonomic and production variables, s h i f t 4.' N-247 V a r i a b l e 3 HR NL XA YA ZA Dl OS IS Heart Rate (HR) 1.000 Noise Level (NL) 0.574** 1.000 X-acceleratlon (XA) 0.540** 0.349** 1.000 Y-acceleratlon (YA) 0.349** 0.217** 0.615** 1.000 Z-acceleratlon (ZA) 0.171" 0.300** 0.574** 0.574** 1.000 Yarding Distance (Dl) -0.029 0.020 0.017 -0.112 -0.151* 1.000 Mainline Speed, Outhaul (OS) -0.035 0.018 0.114 0.071 0.215** 0.2B2** 1.000 Mainline Speed, Inhaul (IS) 0.001 0.052 -0.108 -0.047 -0.002 0.183** 0.292** I.000 Calculated Relationships Equation N S.E.y F* R 2 Variables Not Si g n i f i c a n t HR - 15.5070 + 0.4981 (NL) + 176.2200 (XA) 247 3.44 104.1 .46 Di, OS, IS, YA, OS NL - 78.4830 + 105.5400 (XA) + 85.9570 (ZA) 247 3.84 19.4 .14 YA, Dl, OS, IS XA - -0.6829E-3 + 0.7738 (YA) + 0.5022 (ZA) + 0.5153E-4 (Dl) - 0.1474E-4 (IS) 248 0.0075 55.9 .48 OS YA - 0.0059 + 0.2321 (XA) + 0.2596 (ZA) 248 0.0042 102.4 .45 Dl , OS, IS ZA 0.0113 + 0.4176 (YA) + 0.2512 (XA) + 0.1829E-4 (OS) - 0.4591E-4 (Dl) 248 0.0053 52.2 .46 IS XA - 0.0017 + 0.7789 (YA) + 0.4722 (ZA) 248 0.0076 102.0 .45 -YA - 0.0060 + 0.2321 (YA) + 0.2596 (ZA) 248 0.0042 102.4 .45 -ZA - 0.0139 + 0.4610 (YA) + 0.2499 (XA) 248 0.0055 86.4 .41 -Data were prepared using a weighted average technique (see 4.3.2) to determine the value, for each variable, corresponding to each work-cycle recorded during the s h i f t . The exceptions were: yarding distance, which used maximum distance recorded for each work-cycle; and mainline speed for outhaul and Inhaul elements, obtained by div i d i n g yarding distance by the i r respective elapsed times. Statistically s i g n i f i c a n t at 0.05 (*) and at 0.01 (**) pro b a b i l i t y l e v e l . 3Unlts: Heart rate, bpm; noise level, dBA; acceleration, g(rms); mainline speed, m/roln; and yardIng distance, ra. Number of observations; S.E.y - Standard error of estimate; F » F-test; and R 2 * Coefficient of determination. - 139 -Heart rate was s i g n i f i c a n t l y and p o s i t i v e l y c o r r e l a t e d (Tables 22 and 23) with noise l e v e l and v i b r a t i o n a c c e l e r a t i o n (X, Y and Z d i r e c -t i o n s ) . Line speed was s i g n i f i c a n t l y c o r r e l a t e d with heart rate on s h i f t 3 (Table 22). Noise l e v e l per turn was s i g n i f i c a n t l y and p o s i t i v e l y c o r r e l a t e d with Y and Z-acceleration ( s h i f t 1); X - a c c e l e r a t i o n , yarding distance"*", d i s t a n c e , l i n e speed and heart rate ( s h i f t 2); a c c e l e r a t i o n (X, Y, and Z) and heart rate ( s h i f t 4). A p o s i t i v e s i g n i f i c a n t c o r r e l a t i o n was found among the three d i r e c t i o n s for v i b r a t i o n a c c e l e r a t i o n . The c o e f f i c i e n t varied from 0.57 to 0.84. The r e l a t i v e l y large number of negative c o e f f i c i e n t s of l i n e a r c o r r e l a t i o n obtained f o r v i b r a t i o n a c c e l e r a t i o n and yarding distance suggested that, at l e a s t for the conditions of t h i s study, the greater the yarding distance the lower the v i b r a t i o n a c c e l e r a t i o n l e v e l s . This was p o s s i b l y due to the r e l a t i v e l y high frequency of l o g dragging at shorter distances because of t e r r a i n conditions. Regression analyses were performed i n an e f f o r t to determine the r e l a t i v e importance of the independent v a r i a b l e s i n terms of explaining v a r i a t i o n s i n the dependent v a r i a b l e . This was accomplished using the stepwise (forward) l i n e a r regression technique (Fox and Guire 1976). The i n i t i a l regression models were developed u t i l i z i n g indepen-dent v a r i a b l e s that could have l o g i c a l l y influenced each of the depen-dent v a r i a b l e s . The independent v a r i a b l e s included i n the r e s u l t i n g regression equations (Tables 20 to 23) were wr i t t e n from l e f t to r i g h t - 140 -i n order of t h e i r importance i n terms of i n f l u e n c i n g the dependent v a r i a b l e . The v i b r a t i o n a c c e l e r a t i o n d i r e c t i o n s were the only v a r i a b l e s strongly associated with each other for a l l s h i f t s studied. The follow-ing dependent va r i a b l e s were analyzed: A. Heart Rate On s h i f t 3, 8% of the v a r i a t i o n i n the average heat rate per turn was associated with inhaul speed and X-acce l e r a t i o n . Noise l e v e l , yard-ing distance, outhaul speed and a c c e l e r a t i o n (Y and Z d i r e c t i o n ) made no s i g n i f i c a n t c o n t r i b u t i o n to explaining the heart rate v a r i a t i o n s . Noise l e v e l and X-a c c e l e r a t i o n were associated with 46% of the heart rate v a r i a t i o n observed on s h i f t 4. Yarding distance, l i n e speed and a c c e l e r a t i o n (Y and Z) were not s i g n i f i c a n t l y c o r r e l a t e d with heart rate. These weak r e l a t i o n s h i p s , e s p e c i a l l y on s h i f t 3, may have been due to the f a c t that the operator's heart rate was r e l a t i v e l y low and stable during grapple yarding opera-t i o n s . The l i m i t e d range of the independent v a r i a b l e s studied may also have weakened the expected r e l a t i o n s h i p s . The v a r i a t i o n s i n operator's heart rate were better explained on s h i f t 4 ( r e s t i n g pulse 52 bpm) than on s h i f t 3 ( r e s t i n g pulse 60 bpm). However, the reason for t h i s r e s u l t i s unknown. B. Noise L e v e l The noise l e v e l equations included d i f f e r e n t v a r i a b l e s f o r the d i f f e r e n t s h i f t s studied. On s h i f t 1 the variables Y - a c c e l e r a t i o n , inhaul speed, and yarding distance accounted f or 27% of the v a r i a t i o n i n - 141 -noise l e v e l per turn. The equation showed that as yarding distance increased the noise l e v e l decreased. Mainline tension, a c c e l e r a t i o n (X and Z) and outhaul speed were not s i g n i f i c a n t l y r e l a t e d to noise l e v e l . On s h i f t 3, inhaul speed and X-acceleration were the only v a r i a b l e s s i g n i f i c a n t l y r e l a t e d to noise l e v e l ; they explained 14% of the noise l e v e l v a r i a t i o n . On s h i f t 4 v i b r a t i o n a c c e l e r a t i o n represented by X and Z accounted for 14% of the v a r i a t i o n i n noise l e v e l . Yarding distance, Z-accelera-t i o n and l i n e speed were not s i g n i f i c a n t l y associated with noise l e v e l . C. V i b r a t i o n A c c e l e r a t i o n The v a r i a b l e s tested f o r r e l a t i o n s h i p with v i b r a t i o n a c c e l e r a t i o n were: a c c e l e r a t i o n (X, Y or Z); yarding distance; mainline speed (outhaul and inh a u l ) ; and mainline tension. The r e s u l t s f o r each v i b r a -t i o n d i r e c t i o n are as follows: a. X - a c c e l e r a t i o n . Z-acceleration was r e l a t e d to X-acceleration i n a l l s h i f t s studied. Mainline tension was another r e l a t i v e l y import-ant v a r i a b l e i n terms of i n f l u e n c i n g X - a c c e l e r a t i o n . Inhaul speed was d i r e c t l y associated with X-acceleration on s h i f t 2 but i n v e r s e l y asso-ci a t e d with i t on s h i f t 4. Differences i n ground conditions between the two s h i f t s are possible explanations for t h i s anomaly. b. Y - a c c e l e r a t i o n . Apart from the influence of the other v i b r a -t i o n d i r e c t i o n the only other v a r i a b l e s s i g n i f i c a n t l y r e l a t e d to Y-a c c e l e r a t i o n were mainline tension and yarding distance on s h i f t 2. Yarding distance was i n v e r s e l y r e l a t e d to Y-acce l e r a t i o n i n d i c a t i n g a - 142 -lower magnitude of l a t e r a l yarder movement at longer distances f o r that s p e c i f i c operating s h i f t . c. Z-acceleration. Apart from the other two a c c e l e r a t i o n d i r e c -tions the most important v a r i a b l e s a f f e c t i n g the Z-acceleration were yarding distance, mainline tension and outhaul speed. Yarding distance was i n v e r s e l y r e l a t e d to Z-acceleration i n a l l equations. This could be due to better log l i f t at greater distance, e s p e c i a l l y f o r the s p e c i f i c conditions of s h i f t s 1 and 3. The l a s t three equations presented i n Tables 20 to 23 were developed e x c l u s i v e l y to examine the three v i b r a t i o n d i r e c t i o n s . The r e s u l t s showed that these variables are i n t e r c o r r e l a t e d . The c o e f f i -cients of determination when two d i r e c t i o n s (independent v a r i a b l e s ) were r e l a t e d to the t h i r d (dependent v a r i a b l e ) varied from .34 to .72. D. Mainline Tension The v a r i a b l e s included i n the ana l y s i s of mainline tension were: yarding distance; mainline speed during inhaul; and mainline speed during outhaul. Simultaneous measurement of log weight (which i s assumed to be an important v a r i a b l e associated with tension) was not po s s i b l e , without e i t h e r further instrumentation or d i s r u p t i o n of the operation. External yarding distance" 1", which may also a f f e c t mainline tension was not measured. However, i n most cases i t corresponded to the maximum yarding distance the grapple t r a v e l l e d per yarding road. Yarding distance was the most important v a r i a b l e associated with mainline tension. Distance explained 7% and 9% of the v a r i a t i o n i n - 143 -tension for s h i f t 1 and 2 r e s p e c t i v e l y . As distance increased, the average mainline tension per turn increased at a rate varying from approximately 8 kg to 12 kg per meter. On s h i f t 1 inhaul speed was i n v e r s e l y r e l a t e d to mainline tension. A l i g h t load could produce lower tension than a large one and could be transported from the stump area to the roadside at a f a s t e r speed. 5.4.2 R e l a t i o n s h i p Between V a r i a b l e Values Within Inhaul and Outhaul Elements The c o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) between v a r i a b l e s measured within the work-elements are shown i n Tables 24 to 26. A. Heart Rate S i g n i f i c a n t c o r r e l a t i o n was found between heart rate and: main-l i n e speed during inhaul; mainline speed during outhaul (Table 24); noise l e v e l during outhaul; and noise l e v e l during inhaul (Table 26). The r e l a t i o n s h i p shows that as l i n e speed and noise l e v e l increased the operator's heart rate also increased. B. Noise Level Noise l e v e l and outhaul distance per turn were negatively corre-l a t e d (Table 26, s h i f t 1). At the s t a r t of the outhaul the machine t h r o t t l e was u s u a l l y f u l l y opened i n an attempt to place the grapple at the required t r a v e l l i n g speed as fast as p o s s i b l e . Hence, the tendency f o r shorter distances to be associated with higher outhaul noise l e v e l i s p o ssibly explained. This becomes more evident when sequential out-- 144 -Table 24 - C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) f o r yarding distance and mainline speed against heart rate, noise l e v e l and mainline t e n s i o n . 1 V a r i a b l e measured during outhaul or inhaul no. of Turns Heart Noise Mainline Mainline V a r i a b l e S h i f t (observ.) Rate Level Tension Speed Outhaul: 1 64 NA 2 -0.308* 0.296* 0.173 Maximum 2 163 NA NA 0.370** 0.357** Distance per 3 300 0.076 0.107 NA 0.414** Turn 4 311 0.056 -0.049 NA 0.308** Inhaul: 1 64 NA -0.193 0.253* 0.365** Maximum 2 163 NA NA 0.344** 0.359** Distance per 3 300 0.086 0.283** NA 0.377** Turn 4 311 0.040 0.098 NA 0.233** Outhaul: 1 64 NA 0.269* -0.017 I Mainline 2 163 NA NA 0.171* 1 Speed 3 300 0.227** 0.269** NA 1 4 311 0.065 0.006 NA 1 Inhaul: 1 64 NA 0.183 -0.024 I Mainline 2 163 NA NA 0.039 1 Speed 3 300 0.213** 0.267** NA 1 4 311 -0.058 0.156** NA 1 S u p e r s c r i p t a s t e r i s k s i n d i c a t e c o e f f i c i e n t s i g n i f i c a n t at 0.05 (*) or 0.01 (**) p r o b a b i l i t y l e v e l . NA = not a p p l i c a b l e . - 145 -Table 25 - C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) between noise l e v e l and mainline tension for each work-element and delay ( s h i f t l ) . 1 Mainline Tension Within Work-Elements and Delays Noise Level Within Work-elements and Delays No. of Turns (observ.) C o e f f i c i e n t of Linear C o r r e l a t i o n (r) Elements: Outhaul Hookup Inhaul Unhook 64 64 64 64 -0.292* 0.372** -0.356** -0.153 Delays Outhaul 9 -0.815** Hookup 21 0.189 Inhaul 6 0.593 Unhook 10 0.155 Yarding Road 3 0.244 Change ^Superscript a s t e r i s k s i n d i c a t e c o e f f i c i e n t s i g n i f i c a n t 0.05 (*) or 0.01 (**) p r o b a b i l i t y l e v e l . - 146 -Table 26 - C o e f f i c i e n t s of l i n e a r c o r r e l a t i o n (r) between operator's heart rate and noise l e v e l for each work-element and delay. Heart Rate Within Work-elements and Delays Noise Level Within Work-elements and Delays S h i f t 3 S h i f t 4 No. of Turns (Observ.) C o e f f i c i e n t of Linear C o r r e l a t i o n (r) No. of Turns (Observ.) C o e f f i c i e n t Linear C o r r e l a t i o n of (r) Elements: Outhaul 300 0.114* 311 0.363** Hookup 300 -0.024 311 0.242** Inhaul 300 0.081 311 0.383** Unhook 300 0.041 311 0.501** Delays: Outhaul 42 0.086 23 0.591** Hookup 85 -0.052 63 0.093 Inhaul 43 0.199 24 0.007 Unhook 29 0.380 32 0.268 Yarding Road Change 15 0.344 11 0.339 Superscript a s t e r i s k s i n d i c a t e c o e f f i c i e n t s i g n i f i c a n t at 0.05 (*) or 0.01 (**) p r o b a b i l i t y l e v e l . - 147 -haul distances are cor r e l a t e d with sequential outhaul noise l e v e l s ; negative c o e f f i c i e n t s of l i n e a r c o r r e l a t i o n were obtained for a l l s h i f t s studied (see 5.4.3). Noise l e v e l was higher at higher l i n e speed, due to the higher drum and engine noise. C. Mainline Speed Mainline speed was r e l a t e d to outhaul and inhaul distance. These r e l a t i o n s h i p s occurred i n a l l s h i f t s except for s h i f t 1 where outhaul distance and mainline speed were not s i g n i f i c a n t l y c o r r e l a t e d (Table 24). The grapple usually reached higher speed at longer d i s t a n -ces than at smaller ones. Factors c o n t r i b u t i n g to t h i s r e l a t i o n s h i p could include the mainline a c c e l e r a t i o n capacity and the fac t that the operator could be attempting to l e v e l his performance by running f a s t e r at longer distances, so he can keep time per turn approximately constant. However, further i n v e s t i g a t i o n would be needed to test t h i s hypothesis. D. Mainline Tension When inhaul distance increased mainline tension also increased. P o s s i b l e explanations could include: the operator's attempt to achieve higher log l i f t ; and operator's poor v i s i b i l i t y from the cab at l a r g e r distances. An explanation f o r the p o s i t i v e c o r r e l a t i o n between tension and outhaul speed could be that tension increased to suspend the grapple free of obstacles and consequently a higher speed was reached. However, during the inhaul higher tension was r e l a t e d to lower speed ( s h i f t 1), perhaps i n d i c a t i v e of a l a r g e r load. - 148 -Calculated regression equations between average values of heart r a t e , noise l e v e l and mainline tension during inhaul and outhaul e l e -ments are shown i n Table 27. The order of independent v a r i a b l e s i n the equations i n d i c a t e s t h e i r degree of i n f l u e n c e , i n terms of explaining v a r i a t i o n i n the respective dependent v a r i a b l e s . The low c o e f f i c i e n t of determination obtained for a l l equations ind i c a t e d the weak r e l a t i o n -ships e x i s t i n g among the v a r i a b l e s examined within outhaul and i n h a u l . 5.4.3 R e l a t i o n s h i p s Between V a r i a b l e Values Recorded Over the S h i f t The purpose of examining r e l a t i o n s h i p s between v a r i a b l e values recorded over the s h i f t was to determine i f c o e f f i c i e n t s of l i n e a r c o r r e l a t i o n could be improved by examining the v a r i a b l e s s e q u e n t i a l l y i n time or as they were recorded, instead of examining them within the work-cycle as i n sections 5.4.1 and 5.4.2. The r e s u l t s i n d i c a t e d approximately the same tendencies and low values of c o e f f i c i e n t s of l i n e a r c o r r e l a t i o n were found for the work-cycle r e l a t i o n s h i p a n a l y s i s . Table 27 - Calculated relationships between average values during Inhaul and outhaul elements for: heart rate; noise l e v e l ; and mainline tension. Dependent Variable Eliminated Shift V a r i a b l e 2 Equation N S.E.y F* R 2 by the Stepwise Regression Method Heart Rate: 3 MR 72.6550 + 0.0122 (ISP) 300 4.0 . 14.2 0.04 INZ. IYD OUR 72.1340 + 0.0106 (OSP) 300 4.3 16.2 0.05 ONZ. OYD 4 IHR 29.8150 + 0.3910 (INZ) 311 4.5 53.0 0.15 IYD, ISP OHR 36.3890 + 0.3066 (ONZ) 311 4.5 46.8 0.13 IYD, OSP Noise Level: 1 1NZ 89.0080 - 0.0012 (IMT) 64 4.0 9.0 0.13 IYD, ISP ONZ 85.3200 - 0.0682 (OYD) -1- 0.0141 (OSP) 64 4.6 7.7 0.20 OMT 3 INZ 82.2110 + 0.0232 (IYD) + 0.0111 (ISP) 300 4.0 18.4 0.11 ONZ 84.0370 + 0.0135 (OSP) 300 4.6 23.2 0.07 OYD 4 INZ 81.4380 + 0.0089 (ISP) 311 7.7 0.02 IYD ONZ No variables In regression equation 311 NA NA NA ISP, IYD Mainline Tension: 1 IMT 3918.3000 + 13.8400 (IYD) - 5.1406 (ISP) 247 1191.1 22.8 0.16 OMT 758.1900 + 9.2121 (0YD) 247 590.5 46.9 0.16 OSP 2 IMT 3130.2000 -1- 20.2020 (IYD) 163 1178.8 21.6 0.12 ISP OMT 1452.0000 + 15.3860 (0YD) 163 784.2 25.5 0.14 OSP •Significant at the 0.05 probability l e v e l N - number of observations; S.E.y - standard error of estimate; F " F-teat; R - c o e f f i c i e n t of determination. During: ^Symbols for variables: Outhaul Inhaul Heart rate (bpm) OHR IHR Mainline speed (ra/min) OSP ISP Yarding distance (a) OYD IYD Noise level (dBA) ONZ INZ Mainline tension (kg) OMT IMT NA - not applicable - 150 -6. DISCUSSION 6.1 Computer—Interpreted Work-Cycles, Work-Elements and Element—Delays For the f i r s t time, grapple yarder work-cycles and work-elements were automatically determined using an e l e c t r o n i c Data Logger system. The average t o t a l work-cycle time ( i n c l u d i n g delays and yarding road change) was 1.320 min. (Under d i f f e r e n t study conditions, Sauder (1980b) reported averages for t o t a l work-cycle time of 1.61 min and 2.01 min for two s i m i l a r machines. C o t t e l l et a l . (1976), i n evaluating cable logging systems i n I n t e r i o r B r i t i s h Columbia and A l b e r t a , found an average t o t a l cycle time of 2.59 min for a grapple yarder machine.) Sauder (1980a) tested the e l e c t r o n i c Data Logger i n a standard highlead machine and reported an average t o t a l work-cycle time of 9.744 min. He also used pattern recognition computer programs to i d e n t i f y the work-cycles through a sequential search technique. The basic d i f f e r e n c e between t h i s research and Sauder*s approach was the implementation of a new data f i l t e r i n g and coding system (Figures 31 and 32) to e f f e c t i v e l y i d e n t i f y short-duration grapple yarder work elements at a higher proces-sing speed. Automation of work study i s a s i g n i f i c a n t c o n t r i b u t i o n to researchers and managers i n the f o r e s t industry. The t r a d i t i o n a l method (stopwatch) i s often d i f f i c u l t to apply to a fast moving machine with very short-duration work elements, e s p e c i a l l y i f d i f f e r e n t f a c t o r s are - 151 -to be simultaneously recorded. Also there are the problems of boredom, human e r r o r s , accuracy and cost often associated with continuous stop-watch studies. The i d e a l would be a low cost Data Logger ( r e l a t i v e to the p r i c e of a new logging machine) that could be factory i n s t a l l e d i n grapple yarders. The managers could not only p e r i o d i c a l l y reviexv- the work performance and ergonomic status of t h e i r machines, but could also monitor other s i g n i f i c a n t areas such as mechanical and hydraulic components. An important aspect of work study i s determination of delays and t h e i r causes. At the present, delays were determined by noting any abnormality or i n t e r r u p t i o n during execution of the standard work cy c l e . Thus a delay was timed and l a b e l l e d according to i t s place of occurrence within the work-cycle (e.g., inhaul delay). The cause or nature of delays was not automatically determined. To overcome t h i s problem a new information gathering device could be attached to the e l e c t r o n i c Data Logger to be used by the machine operator i n the cab and by his co-workers i n the f i e l d . The device could be a transmitter containing a keypad numbered from 0 to 9. Coded delay information could be e a s i l y transmitted to the Data Logger by the operator (landing or yarder mechanical delays) or by h i s co-workers ( f i e l d d e l a y s ) . The extra work should not i n t e r f e r e with these persons' a c t i v i t i e s due to the waiting involved i n almost a l l delays. - 152 -6.1.1 Grapple Travel Time Relationships One of the purposes of t h i s study was to determine the r e l a t i o n -ship between grapple t r a v e l time and yarding distance. Weak r e l a t i o n -ships are t y p i c a l l y detected i n cable logging studies ( C o t t e l l et^ a l . 1976, Souza 1980b). However, i t was hypothesized that yarding distance explained 70% (an a r b i t r a r y , r e l a t i v e high value for a sin g l e yarding v a r i a b l e ) or more of the v a r i a t i o n i n inhaul or outhaul time. The c o e f f i c i e n t s of determination for the regression equations obtained f o r a l l s h i f t s studied (Figure 36) supported the hypothesis. In f a c t , the degree of a s s o c i a t i o n between time and distance varied from 75% to 87%. Acceptance of the hypothesis i n d i c a t e d that ( f o r the conditions of t h i s study) yarding distance i s the most important v a r i a b l e a f f e c t i n g grapple t r a v e l time. Planning f o r grapple yarding operations should c a r e f u l l y consider the e f f e c t of yarding distance on time and producti-v i t y . 6.1.2 Hooking Time and Yarding Distance Relationship This r e l a t i o n s h i p was studied to test the hypothesis that hooking time increases as yarding distance increases. The diminished operator's depth perception and grapple c o n t r o l (due to r e s t r i c t e d a b i l i t y f o r l a t e r a l movement) at larger distances were pos s i b l e reasons f o r expect-ing t h i s r e l a t i o n s h i p . - 153 -Although the c o e f f i c i e n t s of l i n e a r c o r r e l a t i o n did not support the hypothesis, they showed a weakly p o s i t i v e l i n e a r r e l a t i o n s h i p between the two v a r i a b l e s . One possible reason for lack of support f o r the hypothesis was the r e s t r i c t e d range i n the yarding distance over the study period. 6.1.3 Execution Time of Work-Elements During the Shift The r e l a t i o n s h i p between time of the day and time spent accomplishing the d i f f e r e n t phases of the work-cycle was examined. It was hypothesized that, due to operator's f a t i g u e , the task execution time increases i n r e l a t i o n to the cumulative working time as the s h i f t progresses. Linear c o r r e l a t i o n a n a l y s i s showed no s t a t i s t i c a l support (at the 0.05 p r o b a b i l i t y l e v e l ) for the hypothesis. Time series p l o t s of work-element times (adjusted for yarding distance) showed no c y c l i c a l pattern over the s h i f t . P ossible explanations of t h i s r e s u l t could i n c l u d e : the tendency of operators to maintain a p a r t i c u l a r working rhythm during the day, as suggested by Grandjean (1981); t e r r a i n and f o r e s t conditions (assumed constant over the s h i f t , but could have changed, masking expected r e l a t i o n s h i p s ) ; and the fa c t that the grapple yarder work was not p a r t i c u l a r l y f a t i g u i n g f or the experienced operator over the scheduled s h i f t periods (see 6.2.1). More extensive studies would be required to examine the e f f e c t of cumulative working days or weeks on the time spent during execution of grapple yarding a c t i v i t i e s . - 154 -6.1.4. Production and Ergonomic Factors Within Work-Elements One of the purpose of t h i s study was to test the hypothesis that there i s no d i f f e r n c e i n the average value of operator's heart rate, noise l e v e l and mainline tension from element to element of the work cy c l e . At the 0.05 p r o b a b i l i t y l e v e l , the approximate test of e q u a l i t y of means when variances are heterogeneous (Sokal and Rohlf 1969) i n d i c a -ted that: a. There was no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e among work-element heart rate means. This showed that the l e v e l of s t r e s s placed on the operator remained constant during the execution of grapple yarding work elements. Also, due to the short duration of some work elements, i t was possible that heart rate during them was not completely independent of the in f l u e n c e of preceding elements. b. There was no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e between noise l e v e l means for most pai r s of work elements. Explanations for the higher noise l e v e l during outhaul on one s h i f t l i k e l y include engine and drum noise. Drums and engine were us u a l l y n o i s i e r at higher mainline speed during the outhaul element. c. Mainline tension during inhaul was s i g n i f i c a n t l y d i f f e r e n t from a l l other means, except for that of inhaul delay. This was p r i m a r i l y due to the e f f e c t s of log weight and the magni-tude of the dynamic forces which occurred during the trans-- 155 -po r t a t i o n of the load from the forest area to the roadside. Inhaul delay was commonly the r e s u l t of logs "hanging up" behind obstacles, accounting f o r high mainline tension during t h i s time element. 6.2. Comparison with the Standards Evaluation of operator's heart rate, noise and v i b r a t i o n l e v e l s allowed comparison with the recommended standards f o r safety, health, reduced comfort or fatigue-decreased p r o f i c i e n c y . Because of generally perceived poor workplace conditions i n logging operations, i t was hypothesized that representative values for. those v a r i a b l e s exceeded t h e i r respective standard l i m i t s . 6.2.1. Heart Rate The operator's average heart rate was well below the l i m i t ( r e s t i n g pulse plus 35 bpm) f o r continuous performance recommended by Grandjean (1981). Hence the workload of the grapple yarder operator, on the basis of p h y s i o l o g i c a l i n t e n s i t y , was rated "very low" according to Christensen ( c i t e d i n Grandjean (1981)). Other f o r e s t harvesting operations have been assessed f o r t h e i r degree of p h y s i o l o g i c a l stress placed on the operator. Smith et a l . (1982) on the basis of p h y s i o l o g i c a l i n t e n s i t y c l a s s i f i e d Southeastern United States forest harvesting operations under summer environmental - 156 -conditions as follows: a. chainsaw (landing operation) - heavy work; b. chainsaw ( f e l l i n g operation) - moderate to heavy work; c. cable skidder - moderate work; d. grapple skidder, feller-buncher and knuckle-boom loader -l i g h t work. 6.2.2. Noise L e v e l The c a l c u l a t e d Leq for the three s h i f t s studied were below the hearing r i s k l i m i t of 90 dBA adopted by the Workers' Compensation Board of B r i t i s h Columbia for an 8-hr s h i f t . However, these Leq approached or exceeded the 85 dBA 8-hr l i m i t proposed by Boivin jit a l . (1977) and Grandjean (1981). The noise l e v e l experienced by the grapple yarder operator was also much greater than the target l e v e l s of 70 - 75 dBA proposed by Axelsson (1981) for Swedish logging machines. It was recommended by WCB that the operator use hearing protec-t i o n to reduce the r i s k of hearing impairment. Since such p r o t e c t i o n could be annoying to some operators, other p o s s i b l e noise c o n t r o l measures could include: use of more e f f e c t i v e mufflers; p r o v i s i o n of s i l e n c e r s for a i r discharge from pneumatic co n t r o l valves (Brtiel & Kjaer 1982); better i n s u l a t i o n material i n the cab, e s p e c i a l l y the windows; an a i r c onditioning system; drums and engine enclosures; and proper l u b r i c a t i o n of the drums and gears. - 157 -Another f a c t o r that contributed to increase noise l e v e l i n the cab was the volume of the radio speaker used f o r crew communication. To overcome the background cab noise, the speaker volume was set at much higher l e v e l s than required for normal conversation. Speech comprehen-sion i s considered unimpaired when the background noise l e v e l i s at lea s t 10 dBA below the l e v e l of the speaker volume (Grandjean 1981). Other logging operations show higher noise l e v e l s than those obtained i n t h i s research. B o i v i n et a l . (1977) reported l e v e l s of 90 to 95 dBA f o r graders, front-end-loaders, and truck-mounted knuckle-boom loaders; 95 dBA or greater for skidders, t r a c t o r s and slasher-mounted knuckle-boom loaders. Reif and Howell (1973) and Howell (1974), studying the exposure to noise of operators of mechanical logging equipment i n B r i t i s h Columbia and Eastern Canada, reported the following average noise l e v e l s f o r the d i f f e r e n t machines studied: Noise Level (dBA) Machine B r i t i s h Columbia Eastern Canada Chainsaw 94 - 105 85 - 102 Rock d r i l l 96 Not ap p l i c a b l e F e l l e r - s h e a r s 83 - 95 Not a p p l i c a b l e Front-end-loaders 91 - 104 86 - 96 Boom loaders 83 - 100 87 - 94 Skidders 97 - 100 96 - 107 Trucks 88 - 91 72 - 95 Yarders 85 - 99 Not ap p l i c a b l e Harvesters Not a p p l i c a b l e 83 - 106 Slashers Not ap p l i c a b l e 82 - 93 - 158 -Also the r e s u l t s of an a c c o u s t l c a l study of machinery on logging operations i n Eastern Canada by Myles et^ a l . (1971) i n d i c a t e d average noise l e v e l s of 106, 104 and 106 dBA f o r chainsaws, skidders and loaders r e s p e c t i v e l y . Webb and Hope (1983) reported an average of 93.6 dBA for skidding operations i n Northern Ontario. 6.2.3 Vibration Acceleration The e f f e c t i v e d a i l y exposure to whole-body v i b r a t i o n of the grapple yarder operator was assessed using the equivalent exposure method (ISO 1978). The r e s u l t s showed that the v i b r a t i o n l e v e l s (X, Y, and Z d i r e c t i o n s ) were w e l l below the recommended ISO 8-hr "exposure l i m i t " for safety or health. However, observed l e v e l s were above the ISO 8-hr "reduced comfort boundary". A c c e l e r a t i o n l e v e l s i n the X di r e c t i o n exceeded the "fatigue-decreased p r o f i c i e n c y boundary" on most s h i f t s studied. X-acceleration was the most important d i r e c t i o n c o n t r i b u t i n g t o operator's "reduced comfort" and "fatigue-decreased p r o f i c i e n c y " , and i t was the most c r i t i c a l d i r e c t i o n i n terms of p o t e n t i a l r i s k to "safety or heal t h " . Z-acceleration was found to be the most c r i t i c a l d i r e c t i o n of a g r i c u l t u r a l t r a c t o r operators ( S j o f l o t 1971) and for truck d r i v e r s (La Dou 1980). Webb and Hope (1983) found higher X - a c c e l e r a t i o n l e v e l s f o r skidders. The r e l a t i v e l y high X-acceleration values appeared to be associated with the nature of the grapple yarding operation, since the forces developed to p u l l the logs coincide with the X - d i r e c t i o n . - 159 -F i e l d observations seemed to i n d i c a t e that the X-acceleration l e v e l s increased when the guyline was not used, e s p e c i a l l y f o r condi-t i o n s of heavy load and i n s u f f i c i e n t cable d e f l e c t i o n . Log dragging due to poor d e f l e c t i o n appears to be a major fa c t o r a f f e c t i n g the v i b r a t i o n a c c e l e r a t i o n r e s u l t s . More s p e c i f i c study would be needed to i s o l a t e the e f f e c t of each v a r i a b l e . V i b r a t i o n l e v e l s varied from s h i f t to s h i f t . P o s s i b l e explana-tions for t h i s v a r i a t i o n could include the stand c h a r a c t e r i s t i c s and ground conditions, as well as the degree of smoothness with which the operator handled the machine. Kindsvater (1982), t e s t i n g the v i b r a t i o n analyzer equipment i n the same machine used i n t h i s study, reported that the seat attenuated v i b r a t i o n l e v e l s i n the Z - d i r e c t i o n . He reported that the "sudden v a r i a t i o n i n the measured a c c e l e r a t i o n l e v e l s (and observed shock behavior i n the f i e l d ) i n d i c a t e a large c o n t r i b u t i o n from shock impulses (high crest f a c t o r ) , which may i n themselves play an important r o l e as str e s s inducing f a c t o r s " . The ISO standard (clause 3.3) i s v a l i d only for a crest f a c t o r of l e s s than 3. Future studies should be conducted to determine the crest f a c t o r i n the grapple yarding operation. Grapple yarder v i b r a t i o n l e v e l s were s i m i l a r to those reported by Axelsson (1981) and Hansson (1981) f or most modern Swedish machines. However, i f the grapple yarder cab was as comfortable as those i n Swedish machines the grapple yarder may have exhibited even lower v i b r a -t i o n l e v e l s . - 160 -Howat (1978) revealed that v i b r a t i o n l e v e l s f o r two of the three front-end-loaders he observed i n B r i t i s h Columbia exceeded the ISO recommended standard (ISO 1978) f o r "fatigue-decreased p r o f i c i e n c y " and for "exposure l i m i t " . According to Toyakawa e_t a l . (1981) v i b r a t i o n l e v e l s at the operator's seat of a Japanese yarder was lower than the l e v e l f o r "fatigue-decreased p r o f i c i e n c y " s t i p u l a t e d by ISO (1978). V i b r a t i o n l e v e l s w ell beyond the ISO l i m i t s (ISO 1978) were found by Webb and Hope (1983) for skidding operations i n Northern Ontario. 6.2.4 Effective Temperature The new e f f e c t i v e temperature l e v e l s were below the recommended standard values for low l e v e l of a c t i v i t y and l i g h t or medium c l o t h i n g during a l l s h i f t s studied, except s h i f t 4 where the measured value was within the l i m i t s . While the cab helped to keep the workplace environment closer to the comfort guidelines (Zerbe 1979), the use of a heater was u s u a l l y required during the winter and a (noisy) fan during the warmer summer days. An a i r conditioning system i n s t a l l e d i n the machine would properly maintain the e f f e c t i v e temperature at optimum comfort l e v e l s . In Sweden, the best r e s u l t s were achieved by combining the heating and c o o l i n g i n t o one system, with j o i n t a i r o u t l e t s s u f f i c i e n t l y d i s t r i b u t e d around i n the cab (Axelsson 1981). - 161 -6.2.5 Mainline Tension The mainline tension values exceeded the 14,000 kg safe working load (cable breaking strength of 42,000 kg/safety f a c t o r of 3) of the p a r t i c u l a r cable used f o r approximately 0.04% of the t o t a l time recorded. Momentary values of mainline tension exceeded the safe working load 12 times during one s h i f t , and 5 times during another. According to Carson and Jorgensen (1980) "the adopted safety f a c t o r of 3 i s assumed to be conservative enough to l i m i t the combined values of tension due to s t a t i c , dynamic and other sources of cable loading (e.g., bending)". For the conditions of t h i s study the actual safety f a c t o r was, an occasion, l e s s than 3. 6.3 Production and Ergonomic Factors R e l a t i o n s h i p s For the f i r s t time, r e l a t i o n s h i p s among production and ergonomic f a c t o r s have been studied i n a grapple yarding operation. The i n i t i a l hypotheses of no r e l a t i o n s h i p between work-cycle averages f o r the production and ergonomic variables were tested using l i n e a r c o r r e l a -t i o n . Regression a n a l y s i s i n d i c a t e d the degree of a s s o c i a t i o n among va r i a b l e s and the r e l a t i v e importance of the independent v a r i a b l e s i n terms of explaining v a r i a t i o n s i n the dependent v a r i a b l e . The analyses showed that the v a r i a b l e s were associated as follows: heart rate: with inhaul speed, X - a c c e l e r a t i o n and noise l e v e l ; - 162 -noise l e v e l : with v i b r a t i o n a c c e l e r a t i o n , l i n e speed and yarding distance; X-acceleration: with Y and Z-acceleration, mainline tension, inhaul speed and yarding distance; Y - a c c e l e r a t i o n : with X and Z- a c c e l e r a t i o n , mainline tension and yarding distance; Z-acceleration: with X and Y-a c c e l e r a t i o n , mainline tension, yarding distance and outhaul speed; mainline tension: with yarding distance and inhaul speed. The l i m i t e d range of the v a r i a b l e s encountered during the a c t u a l grapple yarding operation was one possible f a c t o r c o n t r i b u t i n g to the weak r e l a t i o n s h i p s ( r < 0.50) found between most p a i r s of v a r i a b l e s (Tables 20 to 23). However, these r e l a t i o n s h i p s showed how the v a r i -ables behaved during the yarding operation. The r e s u l t s cannot be used to examine cause and e f f e c t between v a r i a b l e s . Nevertheless some i n t e r e s t i n g observations can be made. For instance, i f the l e v e l s of v i b r a t i o n a c c e l e r a t i o n and noise which were associated with heart rate are diminished through improvement of machine design an even lower heart rate might be achieved. Noise l e v e l s were p o s i t i v e l y associated with v i b r a t i o n l e v e l s . Noise l e v e l was also p o s i t i v e l y c o r r e l a t e d with l i n e speed. To avoid lowering p r o d u c t i v i t y high l i n e speed should be maintained but the noise l e v e l could be diminished by better cab i n s u l a t i o n or better enclosure of the l i n e drums and engine. - 163 -Yarding distance and mainline tension were r e l a t e d to v i b r a t i o n a c c e l e r a t i o n . As yarding distance increased mainline tension increased, p o s s i b l y due to d i f f e r e n c e s i n t e r r a i n conditions along the yarding road. These conditions could have i n t e r f e r e d with the grapple's t r a v e l (e.g., dragging, p a r t i a l l y or f u l l y suspended above the ground). Yarding distance could show p o s i t i v e or negative c o r r e l a t i o n with v i b r a t i o n a c c e l e r a t i o n depending on the p o s i t i o n along the yarding road of the obstacles encountered. Since yarding distance Is a c o n t r o l l a b l e v a r i a b l e , i t can be managed to improve p r o d u c t i v i t y and i t s e f f e c t on ergonomic v a r i a b l e s . Mainline tension was p o s i t i v e l y c o r r e l a t e d with inhaul distance and i n v e r s e l y c o r r e l a t e d with inhaul speed. It appeared that heavy logs increased l i n e tension and decreased l i n e speed. The operator's v i s i b i -l i t y from the cab was another f a c t o r that could have a f f e c t e d the values of mainline tension. When the operator could not see a portion of the yarding road, a stump or a rock could be unexpectedly h i t by the moving logs producing high mainline tension. - 164 -7. SUMMARY AND CONCLUSIONS The objectives of t h i s study were to: (1) develop and test an automated data c o l l e c t i o n and compilation methodology for use i n f o r e s t harvesting operations; and (2) i n v e s t i g a t e production f a c t o r s (yarding distance, mainline tension and number of logs yarded per work cycle) and ergonomic f a c t o r s (operator's heart rate; noise l e v e l ; temperature; v i b r a t i o n a c c e l e r a t i o n i n the X, Y, and Z d i r e c t i o n s ) i n a c o a s t a l B r i t i s h Columbia grapple yarding operation. S p e c i f i c a l l y , the study was designed to: i n t e r p r e t and determine the machine work-cycle, i t s elements and delays; analyze task execution time; evaluate ergonomic f a c t o r s with respect to recommended standards; and determine r e l a t i o n s h i p s among v a r i a b l e s . An e l e c t r o n i c Data Logger system, s p e c i f i c a l l y developed for t h i s research, has been applied to simultaneous v a r i a b l e sampling during a c t u a l grapple yarding operations, confirming the a b i l i t y of t h i s equipment to properly function as a f i e l d research t o o l . The system allowed the v a r i a b l e s to be r e l a t e d to a s i n g l e time base and recorded on si n g l e magnetic medium for subsequent a n a l y s i s . The data compression technique, d i g i t a l recording and automatic computer analysis of the r e s u l t i n g data have made t h i s study f e a s i b l e . To the knowledge of t h i s i n v e s t i g a t o r , i t i s the f i r s t time t h i s approach has been employed i n an ongoing i n d u s t r i a l logging operation. Within the l i m i t s of t h i s study, i n t e r p r e t a t i o n of the analyzed data suggests the f o l l o w i n g : - 165 -A. Automatic i n t e r p r e t a t i o n and computation of grapple yarder work c y c l e s , work elements and element delays are p o s s i b l e and may have eliminated the majority of the problems a s s o c i -ated with t r a d i t i o n a l motion and time study techniques. Equipment accuracy of 0.001 min and automatic data recording have allowed i d e n t i f i c a t i o n of fast grapple yarding a c t i v i -t i e s never i d e n t i f i e d before. E a r l i e r studies have r e l i e d on grouping a l l a c t i v i t i e s occurring within a distance of 30 m from the yarder, creating a s i n g l e time element of s u f f i c i e n t length to be conveniently timed by stopwatch. However some d i f f i c u l t i e s remain with the automated data recording system. To avoid possible overflow problems due to l i m i t e d cassette recorder speed (2.5 events per second) yarding distance could not be recorded with accuracy greater than ± 4.2 m. Thus, d e f i n i t i o n of work-elements, which was p r i m a r i l y based on d i r e c t i o n and distance the grapple t r a v e l l e d , can be improved i f a f a s t e r data recording system i s used. Other d i f f i c u l t i e s i nclude: r e l a t i v e low proces-sing speed of the HP 9845B micro-computer; lack of an automa-t i c error checking routine for the work-cycle i n t e r p r e t a t i o n computer program; and lack of an automatic delay l a b e l l i n g device to record causes of delays. B. Results of the hypothesis t e s t i n g led to the following con-clu s i o n s : - 166 -Yarding distance explained more than 70% of the v a r i a t i o n i n grapple t r a v e l time when inhaul and outhaul delays were excluded. Hooking time did not s i g n i f i c a n t l y increase over the l i m i t e d range of yarding distance experienced during the study. Execution time of work elements did not increase i n r e l a -t i o n to the cumulative time worked, over the standard 8 hr s h i f t . There was no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e among most ergonomic f a c t o r s averaged across work elements and delays. The exceptions were: mainline tension (during inhaul and inhaul delay); and noise l e v e l (during outhaul), both of which showed s i g n i f i c a n t l y higher average values than f o r a l l the remaining components of the work c y c l e . When the r e s u l t s of t h i s study were compared with the recommended standards the following conclusions were made: - operator's average working heart rate was well below the continuous performance l i m i t ; - noise l e v e l s (Leq) were j u s t below the adopted WCB 8-hr hearing r i s k l i m i t of 90 dBA; - v i b r a t i o n a c c e l e r a t i o n l e v e l s i n the X, Y and Z d i r e c -t i o n s were well below the ISO 8-hr l i m i t f o r "preserva-t i o n of health or safety". However, observed l e v e l s - 167 -were f a r above the "reduced comfort" l i m i t and X -acceleration l e v e l s exceeded the "fatigue-decreased p r o f i c i e n c y boundary" f o r most s h i f t s studied; - new e f f e c t i v e temperature values were below the optimum comfort l e v e l (low l e v e l of a c t i v i t y and medium or l i g h t clothing) f o r most s h i f t s studied; - mainline tension values exceeded the cable safe working load for approximately 0.4% of the t o t a l recorded time (17 occasions over 2 s h i f t s ) . f. The production and ergonomic f a c t o r s , within the work-c y c l e , were s t a t i s t i c a l l y s i g n i f i c a n t associated as follows: heart rate: with inhaul speed, X-acceleration and noise l e v e l ; noise l e v e l : with a c c e l e r a t i o n , l i n e speed and yarding distance; X - a c c e l e r a t i o n : with Y and Z-acceleration, mainline tension, inhaul speed and yarding distance; Y - a c c e l e r a t i o n : with X and Z-acceleration, mainline tension and yarding distance; Z-acceleration: with X and Y - a c c e l e r a t i o n , mainline tension, yarding distance and outhaul speed; mainline tension: with yarding distance and inhaul speed. C. O v e r a l l , the grapple yarder studied was acceptable but not i d e a l i n terms of ergonomic design. However, i t was considered superior to most Canadian logging machines - 168 -p r i m a r i l y with respect to whole-body v i b r a t i o n and noise l e v e l at the operator's workplace. On the basis of heart rate l e v e l s the operation was considered not s t r e s s f u l to the healthy and experienced operator during the standard 8-hr s h i f t . V i b r a t i o n and noise l e v e l s were f a c t o r s s i g n i f i c a n t l y associated with the heart rate s t r e s s i n d i c a t o r . D. Analysis of r e l a t i o n s h i p s among ergonomic and production f a c t o r s provided better understanding of the complexity of the grapple yarding system. Successful improvement of the ergonomic c h a r a c t e r i s t i c s could depend not only on the correct i d e n t i f i c a t i o n of problematic f a c t o r s , but also on an o v e r a l l systems approach to c o r r e c t i v e measures taken upon a l l v a r i a b l e s adversely a f f e c t i n g the logging system. E. Based on an average t o t a l time per turn ( i n c l u d i n g delays) of 1.320 min and an average load volume of 1.2 m 3/turn, the man-machine system studied produced an average 55 m of logs per hour. Improvement of the workplace conditions i n terms of cab climate, noise and v i b r a t i o n l e v e l s could contribute to increased p r o d u c t i v i t y of t h i s operation. The number of hookup delays was also found to be high. Introduction of a portable video system to improve the opera-t o r ' s view of hooking a c t i v i t y through a video monitor i n s t a l l e d i n the machine cab could diminish hooking delay time and increase p r o d u c t i v i t y . - 169 -8 . RECOMMENDATIONS Based on the data and experience obtained by t h i s study i t i s recommended that: A. Measures should be taken to further reduce noise l e v e l (e.g. cab i n s u l a t i o n , drums and engine enclosure); to reduce whole-body v i b r a t i o n (e.g., improved seat); and to maintain a proper l e v e l of temperature and humidity (e.g., a i r condi-tioning) i n the cab of the machine studied. These improve-ments could diminish long-term health r i s k s , increase operator comfort and job s a t i s f a c t i o n , and increase p r o d u c t i -v i t y . Studies should be conducted to evaluate the perform-ance e f f e c t that may accompany these changes i n the workplace conditions. B. Long-term research should be c a r r i e d out to in v e s t i g a t e whether any long-term health problems a r i s e from prolonged exposure to the grapple yarding work environment. C. Study should be conducted to determine the e f f e c t on operator performance (time, production and ergonomic f a c t o r s ) accompanying the i n t r o d u c t i o n of a video system i n t o the grapple yarding operation. The system would provide addi-t i o n a l v i s u a l information to the operator v i a a monitor i n s t a l l e d i n the machine cab. The system should be tested f o r long yarding distances and d i f f i c u l t t e r r a i n conditions. Increases i n the operator's job s a t i s f a c t i o n and p r o d u c t i v i t y are expected. - 170 -Future research i n t h i s f i e l d should include: sampling a c r o s s - s e c t i o n of grapple yarders and t h e i r crews; and varying s i t e , stand, and c l i m a t i c conditions to allow a general evaluation of the production and ergonomic status of these machines. S i m i l a r studies are needed i n other f o r e s t machines. These studies could include a more d e t a i l e d a n a l y s i s of tension i n the d i f f e r e n t cables i n c l u d i n g guylines; and the i n v e s t i g a t i o n of other r e l a t i o n s h i p s such as l i n e tension and operator's heart rate. Future studies should also c o l l e c t more information on the operator involved. Further research could include: - Evaluation of the operator's health status; - Assessment of the operator's work load i n r e l a t i o n to his work capacity; - Evaluation of p o s s i b l e symptoms of fatigue and the operator's opinion about his workplace conditions. Coordinated e f f o r t among researchers, f o r e s t companies and machine manufacturers i s needed to implement changes i n e x i s t i n g machines or i n new machine design based on the s i g n i f i c a n t findings of ergonomic research. The grapple yarding crew should rotate jobs during the s h i f t to d i s t r i b u t e among them the operator cab exposure time, and the time f o r monotonous log spotting and yarding road change. C o l l e c t i v e agreements may l i m i t t h i s option, however. - 171 -G. The e l e c t r o n i c Data Logger should be modified to incorporate an analog or d i g i t a l meter di s p l a y to f a c i l i t a t e monitoring of the input s i g n a l s , and to adjust the threshold for each v a r i a b l e recorded, while o n - s i t e . Adjustment of the threshold would permit the best recording rate without causing the recording system to overflow. Another system improvement would be the use of a data recording system f a s t e r than the present rate of 2.5 events per second. An instrument should be designed to allow the Data Logger users to record information on the nature and cause of delays as well as on observed extraordinary events. To decrease the data processing and a n a l y s i s time, the p o s s i b i l i t y of developing more e f f i c i e n t computer programs should be i n v e s t i g a t e d . Also processing and analysis time could be decreased by using a f a s t e r and higher memory capa-c i t y micro-computer system, or by d i r e c t l y t r a n s f e r i n g the raw data to a large system such as the U n i v e r s i t y of B r i t i s h Columbia computer network. - 172 -9. G L O S S A R Y ANSI. American National Standard I n s t i t u t e . Correct e f f e c t i v e temperature (CET). A revised new e f f e c t i v e tempera-ture index i n which an adjustment i s made to allow f o r radiant heat ( M u r r e l l 1979). dB ( D e c i b e l ) . A nondimensional unit to express sound l e v e l s . I t i s a logarithm to the base 10 of the r a t i o of a measured quantity to an a r b i t r a r i l y chosen quantity. In audiometry a l e v e l of zero decibels represents roughly the weakest sound that can be heard by a person with good hearing. The d e c i b e l i s 1/10 of a Bel ( I r v i n and Graf 1979, Benwell and Repacholi 1979). dBA. A noise l e v e l reading i n decibels made on the A-weighted network (see Weighting network) of a sound l e v e l meter ( I r v i n and Graf 1979). D i r e c t i o n of V i b r a t i o n . D i r e c t i o n of v i b r a t i o n i s based on an orthogonal co-ordinate system having i t s o r i g i n at the l o c a t i o n of a person's heart (ISO 1978). The ISO designated d i r e c t i o n s are: Z- d i r e c t i o n ( l o n g i t u d i n a l or Z-axis): foot (or buttocks)-to-head; X - d i r e c t i o n (fore-and-aft or X a x i s ) : chest-to-back or anteroposterior; Y - d i r e c t i o n ( l a t e r a l or Y a x i s ) : r i g h t to l e f t side. Equivalent sound l e v e l . See Leq. External Yarding Distance. Distance between the grapple yarder and the backspar. "Fast" response. A " f a s t " response meter c h a r a c t e r i s t i c has a response time of approximately 0.1 sec (ANSI 1971a). FERIC. Forest Engineering Research I n s t i t u t e of Canada. Floating-Aperture Algorithm. A technique used to compress data sampled at a high f i x e d rate ^number of observations/unit time) which e l i -minates "redundant" samples occurring within the range of lower and upper l i m i t s established around a previously recorded value by a preset tolerance or threshold (Lawrence ^ t a l . 1982). The algo-rithm i s implemented i n the e l e c t r o n i c Data Logger software as follows: - 173 -1. I n i t i a l i z e 2. Update time 3. Read each analog input and i f data i s greater than the threshold put data and time on stack ( b u f f e r ) . 4. I f recorder i s not busy and data on stack, write data out to recorder. 5. Go to 2. Hertz (Hz). The unit of frequency. The number of times a cycle i s repeated i n a period of 1 s (Hammond 1978). Impact Noise. V a r i a t i o n i n sound presure l e v e l s where the time i n t e r v a l between peak pressure l e v e l s i s greater than 1 s (WCB 1980). Leq. Equivalent continuous sound l e v e l i n dBA. Leq i s the sound energy averaged over a stated period of time; that i s , i t i s the rms or mean l e v e l of the time varying noise ( I r v i n and Graf 1979). Inhaul Distance. Distance t r a v e l l e d by the grapple from the stump area (where hookup ended) to the landing. ISO. I n t e r n a t i o n a l Organization for Stan d a r i z a t i o n . Loudness L e v e l . The loudness l e v e l of a sound In question i s determined by the subjective comparison of the loudness of the sound to that of a 1000 Hz pure tone ( I r v i n and Graf 1979). The unit i s Phon. New E f f e c t i v e Temperature (ETx). A temperature index to represent combinations of dry-bulb temperature and r e l a t i v e humidity that generally produce the same l e v e l of skin "wetness" as caused by regular sweating (McCormick 1976). Noise L e v e l . See sound l e v e l . Octave. The i n t e r v a l between two tones, one of which has twice the f r e -quency of the other (Hammond 1978). Outhaul Distance. Distance t r a v e l l e d by the grapple from the landing to the stump area (where hookup s t a r t e d ) . Root Mean Square (rms) Value. The e f f e c t i v e value of a f l u c t u a t i n g quantity. The values of the quantity are squared and averaged; then the square root of t h i s average i s extracted (Hammond 1978). "Slow" Response. A "slow" response meter c h a r a c t e r i s t i c has a response time of approximately 1 sec (ANSI 1971a). Sound Pressure Level (SPL). Twenty times the logarithm to the base 10 of the r a t i o of the pressure of a sound to the reference pressure. The reference pressure i s 20 micronewtons per square meter or 0.00002 N/m2. The SPL unit i s the dB (ANSI 1971b). - 174 -Sound L e v e l . Weighted sound pressure l e v e l measured by use of a meter-ing c h a r a c t e r i s t i c and weighting A, B or C, as s p e c i f i e d i n the ANSI SI.4-1971 (ANSI 1971b). Sound l e v e l u nits are dBA, dBB or dBC (ANSI 1971a). Steady State Noise. Steady state noise means v a r i a t i o n s i n sound pres-sure l e v e l s where the time i n t e r v a l between the peak pressure l e v e l s i s 1 s or le s s (WCB 1980). Thermistors. Thermistors are semiconductors which behave as "thermal r e s i s t o r s " - that i s , r e s i s t o r s with a high ( u s u a l l y negative) temperature c o e f f i c i e n t (Anonymous 1970). Weighting. A prescribed frequency response provided i n a sound l e v e l meter (ANSI 1971b). Weighting Network. An e l e c t r o n i c c i r c u i t whose s e n s i t i v i t y varies with frequency the same way as does the human ear (Bruel & Kjaer undated-a). An e l e c t r o n i c network designated to be incorporated i n a sound l e v e l meter such that the l a t t e r conforms to a s p e c i f i e d weighting curve (Benwell and Repacholi 1979). The three weighting curves or networks are designated A, B and C, according to ANSI SI.4-1971 (ANSI 1971b). Weighting networks s e l e c t i v e l y discriminate against low and high frequencies i n accordance with the equal loudness contours subjec-t i v e l y developed (McCormick 1976). The A-network approximates the equal loudness curves at low SPLs and the C-network at high l e v e l s . However today only the A-network i s widely used since the B and C networks did not give good c o r r e l a t i o n to subjective tests (Bruel & Kjaer undated-a). Wet-Bulb Globe Temperature (WBGT). A temperature index computed by means of the following formula (FAO 1974, Hansson and Pettersson 1980): WBGT = 0.7Tw + 0.3Tg where: Tw = The psychrometric wet temperature (°C), measured by means of a v e n t i l a t e d and r a d i a t i o n i n s u l a t e d thermometer or psychro-meter. Tg = The globe temperature (°C), measured by means of a globe thermometer. Whole-Body V i b r a t i o n . V i b r a t i o n a c c e l e r a t i o n transmitted to the body as a whole through the supporting surface, namely, the feet of a standing person, the buttocks of a seated person or the supporting area of a r e c l i n i n g person (ISO 1978). Yarding Distance. Distance t r a v e l l e d by the grapple from the landing (haul road) to the stump area ( i . e . , maximum distance t r a v e l l e d by the grapple i n a given work-cycle). - 175 -10. LITERATURE CITED Ager, B. 1981. Design of work systems i n f o r e s t r y . 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In: Proceedings of the Seminar on Occupational Safety and Health and Applied Ergonomics on Highly Mechanized Logging Operations, Ottawa, Sept. 21-25/1981. ECE/FAO/ILO, Environment Canada D i s t r i b u t i o n Centre, Ottawa, pp. 505-517. Souza, A. P. 1983. Documentation of the Data Logger computer programs. The Univ. of B r i t i s h Columbia, Faculty of F o r e s t r y , Vancouver. (Unpublished). 105 pp. Teicher, W. H.; Arees, E. and R e i l l y , R. 1963. Noise and human performance, a psychophysiological approach. Ergonomics, 6_(1):-83-97. Thakor, N. V. 1978. R e l i a b l e R-wave det e c t i o n from ambulatory subjects. Biometric Science Instrumentation, (14):67-72. Toyokawa, K.; Okuda, Y. and I s h i i , K. 1981. Evaluation of f o r e s t machinery on human f a c t o r s , i n the case of a yarder. In: Proceed-ings of the XVII IUFRO World Congress, Ibaraki (Japan), August 1981. IUFRO, Div. 3, Ibaraki. p. 505. - 182 -van Loon, J. H. and Spoelstra, L. H. 1971. Heart rate and a n a l y s i s , used i n f i e l d studies. In: Methods i n ergonomic research In f o r e s t r y , IUFRO Seminar, SILVIFUTURUM, Hurdal (Norway), September 1971. IUFRO, Div. 3, Pub. 2, Hurdal. pp. 93-105. Vik, T. 1971. Measurement of work load during f o r e s t r y work. In: Methods i n ergonomic research i n f o r e s t r y , IUFRO Seminar, SILVIFUTURUM, Hurdal (Norway), September 1971. IUFRO, Div. 3, Pub. 2, Hurdal. pp. 109-122. von Gierke, H. E. 1965. On noise and v i b r a t i o n c r i t e r i a . Archives of  Environmental Health, (11): 327-339. WCB. 1980. Noise co n t r o l requirements. In: I n d u s t r i a l health and safety r e g u l a t i o n s . Workers' Compensation Board of B r i t i s h Columbia, Vancouver, pp. 13-5 to 13-6. Webb, R. D. G. and Hope, P. A. 1983. Ergonomics and skidder operations i n Northern Ontario: a preliminary i n v e s t i g a t i o n . In: Proceedings of the 64th Annual Meeting, Woodlands Section, CPPA, Toronto, March 1983. Woodlands Section, Canadian Pulp and Paper A s s o c i a t i o n , Montreal, pp. 97-102. Wencl, J . and Wenter, W. 1971. Pulsfrequenzmessungen mit Pulstelemeter bei Schlagerungsarbeiten mit Einmann-motorsagen. In: Methods i n ergonomic research i n f o r e s t r y , IUFRO Seminar, SILVIFUTURUM, Hurdal (Norway), September 1971. IUFRO, Div. 3, Pub. 2, Hurdal. pp. 77-90. Wencl, J . and Wenter, W. 1973. Die Ergonomie und ihre Anwendung bei der Waldarbeit. F o r s t l i c h e Bundesversuchanstalt (Informations- d i e n s t ) , (150):305-309. Zander, J. 1979. Ergonomics i n t r o p i c a l a g r i c u l t u r e and f o r e s t r y . In: Ergonomics i n t r o p i c a l a g r i c u l t u r e and f o r e s t r y , proceedings of the F i f t h IAAMRH/CIGR/IUFRO J o i n t Symposium, Wageningen (Netherlands), May 14-18/1979, ed. by J. H. van Loon; F. J . Staudt and J . Zander. IAAMRH/CIGR/IUFRO, Centre f o r A g r i c u l t u r a l P ublishing and Documenta-t i o n , Wageningen. pp. 11-17. Zerbe, W. 1979. Preliminary guide to ergonomic evaluation of logging equipment. Tech. Note No. TN-30, FERIC, Vancouver. 46 pp. - 183 -11. APPENDICES APPENDIX 1. GENERAL SPECIFICATIONS FOR THE MADILL 044 GRAPPLE YARDER Engine - GM V12-N71 Mark 20 (480 HP) Undercarriage - Track type Speed ~ 8 km/hr Turning radius.; • 5.5 m Swing c a p a b i l i t y - Yea Swing speed - 0 - 12 RPM Boom (tower) type ™ A-frame, f a b r i c a t e d s t e e l Height to top of f a l r l e a d - 18.3 tn Number of guy l i n e s - 1 - 2 Weight - 89357 kg Ground pressure •  ~ 1.55 kg/cm Grapple weight - 1500 kg M a d i l l 044 Drum Performances and C a p a c i t i e s Dimensions Operating Line P u l l Line P u l l Maximum Line Speed (cm) Capacity Low Gear High Gear Low Gear High Gear Drum (m) (mm) (kg) (kg) (m/raln (ra/raln) Main Flange 101.6 536 25 Bare 42071 Bare 21410 Bare 199 Bare 391 Core 40.6 423 29 Mid 25538 Mid 12997 Mid 328 Mid 644 Length 50.8 344 32 F u l l 18325 F u l l 9321 F u l l 456 F u l l 897 Haulback Flange 101.6 1371 16 Bare 46653 Bare 23723 Bare 195 Bare 382 Core 40.6 950 19 Mid 27692 Mid 14084 Mid 328 Mid 644 Length 50.8 701 22 F u l l 19709 F u l l 10025 F u l l 461 F u l l 905 Guyline Flange 76.2 88 32 Bare 32478 Bare 25061 Bare 184 Bare 362 Core 36.8 73 35 Mid 22998 Mid 17736 Mid 260 Mid 511 Length 25.4 - - F u l l 17804 F u l l 13721 F u l l 336 F u l l 661 Topping Flange 76.2 108 29 Bare 32750 Bare 25243 Bare 183 Bare 359 Core 36.8 160 25 Mid 22998 Mid 17736 Mid 260 Mid 511 Length 25.4 - - F u l l 17713 F u l l 13653 F u l l 338 F u l l 664 Tag Flange 101.6 1310 10 Bare 6872 Bare 6872 Bare 309 Bare 606 Core 66.0 731 13 Mid 5489 Mid 5489 Mid 386 Mid 759 Length 25.4 457 16 F u l l 4581 F u l l 4581 F u l l 464 F u l l 911 Straw Flange 76.2 2194 6 Bare 34700 Bare 24676 Bare 173 Bare 339 Core 36.8 975 10 Mid 22998 Mid 16352 Mid 260 Mid 511 Length 25.4 719 16 F u l l 17191 F u l l 10183 F u l l 348 F u l l 684 - 185 -APPENDIX 2. DATA CONVERSION PROCEDURES Conversion of recorded Data Logger counts to the appropriate unit of measurement was c a r r i e d out by the "PRPARE" program (Souza 1983). a. Yarding Distance To provide adjustments f o r the changing drum radius, an algorithm s i m i l a r to that developed by Pendlebury (1980) was used. Table Al presents the information needed to determine the yarding distance from the values generated by the r o t a t i o n a l movement of the drum and recorded by the Data Logger. Figure Al presents drum terminology and dimensions at the time of the study. The equation below uses the value found i n Table Al to c a l c u l a t e the yarding distance. D . = ( (Dc. - W. .) x K. . ) /Nt -HJ. . 3 J i j i j l j where: Dj = Yarding distance (m). DCj = Data Logger count ( j = 1 to N, where N i s the number of recorded observations). W^j = Maximum number of r e v o l u t i o n counts that precedes Dc^ ( i = 1 to n, where n i s the wrap number corresponding to D C J ) K . = C o i l length (m). Table A l . Determination of yarding distance from the values generated by the revolution of the drum and recorded by the Data Logger. Wrap Number, i C o i l Length, K (m) C o i l Diameter (m) Maximum counts number of up to the of wrap, re v o l u t i o n beginning W Length of Line up to Beginning of Wrap, (m) the Q 1 2 . 3 4 0 . 7 4 4 W l = 0 Qi - 0 2 2 . 1 8 0 . 6 9 3 w 2 = Nf x Nt « 2 = Q l + Nf x K l 3 2 . 0 2 0 . 6 4 2 W 3 = W2 + Nc x Nt Q 3 = Q 2 + Nc x K 2 4 1 . 8 6 0 . 5 9 1 W 4 = W3 + Nc x Nt Q 4 = Q 3 + Nc x V 5 1 . 7 0 0 . 5 4 1 W 5 = W4 + Nc x Nt Q 5 = % + Nc x K 4 n - - W n = W . + Nc n-l x Nt Q n - Qn-- 1 + Nc + K n - 1 Where: Nf = Number of c o i l s on the f i r s t wrap of a f u l l drum. Nt = Number of targets mounted on the drum. Nc = Maximum number of c o i l s on wrap (1 9 for th i s p a r t i c u l a r drum). - 187 -OOOO© ooooo 1ST. WRAP 5TH. WRAP 40.6 cm 0 0 6 6 0 H t - C O I L 19 COILS 0 0 0 • • • 0 0 0 • • • • • • • • * 660 oo© 74.4 cm 50.8 cm FIGURE A1. Schematic of the M a d i l l 044 m a i n l i n e drum showing c o i l s , wraps and f u l l drum wrap diameter. - 188 -Q = Length of l i n e up to the beginning of wrap i (m), Nt = Number of tar g e t s . The example below i l l u s t r a t e s the use of the algorithm. Assuming Dc = 55; Nf = 10 and Nt = 2, then, Wl = 0.0 W2 - 10 x 2 = 20 W3 = 20 + (19 x 2) = 58 Thus, the number of r e v o l u t i o n counts that precedes 55 i s 20 (W2 = 20). Therefore, 55 belongs to wrap number 2 which K equals to 2.18 m. The length of l i n e up to the beginning of wrap number 2 i s : Ql = 0.0 Q2 = 0.0 + 10 x 2.34 = 23 m When the values found above are inserted i n the distance equation, i t i s found: D - ((55-20) x 2.18)/(2) + 23 D = 61 m b. Number of Logs The number of logs was t a l l i e d d i r e c t l y from the number of times the log switch button was actuated. Since the number of logs was d i g i t a l l y recorded no conversion f a c t o r was needed. - 189 -c . Mainline Tension The recorded Data Logger count were converted to tension i n kg using the following equations based on theory given by Mason (1982): MLT = LCT/K where: LCT = (5000/255) x (R x Dc) / (G x Ve x C) and, K = 2 x SIN (ARCTAN (D + 1 - S)/12)) and, MLT = Mainline tension (kg) LCT = Load c e l l tension (kg) Dc - Data Logger count or output R » Load c e l l capacity (4,536 kg or 10,000 lb) G = Selected Ectron gain (50 or 100) Ve = Ectron e x c i t a t i o n voltage (7 V) C = Load c e l l output/Input constant (3 mV per V input) D = Cable diameter (1 i n ) S = Spacing (0.875 in) between the inner r i n g of the main sheave and the r i g h t side plate of the tensiometer (Figure A2). K = Tensiometer constant for a p a r t i c u l a r "spacing" (S) and cable diameter (D) - 190 -F I G U R E S A 2 . T e n s i o m e t e r s h o w i n g t h e c a b l e d e f l e c t i o n a d j u s t m e n t m e c h a n i s m a n d p l a c e o f d e f l e c t i o n m e a s u r e m e n t s ( " s p a c i n g " ) . - 191 -The data and equations above provide two s i m p l i f i e d versions of MLT: a) Gain of 50: MLT = 453.7276 x Dc b) Gain of 100: MLT = 226.8538 x Dc The tensiometer was c a l i b r a t e d and mainline tension was continuously measured during the operating day. d. Heart Rate The equation below converts the Data Logger recorded values to heart rate (Clark 1980b) i n beats per minute: Hr - 300 x Dc / 255 or Hr = 1.17647 x Dc where: Hr = Heart rate (bpm) Dc = Data Logger count e. Noise L e v e l The conversion equation f or the Data Logger noise counts i s : NL = RI + (Dc / 2.55) where: NL = Noise l e v e l (dBA) RI = I n f e r i o r l i m i t of the range used (dBA) Example: f o r 50 - 110 dBA range, RI = 50 Dc = Data Logger count - 192 -f . Vibraton A c c e l e r a t i o n V i b r a t i o n Data Logger values were converted to a c c e l e r a t i o n using the following equations: 1) Vx « 0.001076 x Dc 2) Vy - 0.001019 x Dc 3) Vz = 0.001034 x Dc Where: Dc represents Data Logger counts and Vx, Vy, and Vz corespond to v i b r a t i o n a c c e l e r a t i o n , i n g u n i t s f o r the X, Y, and Z axes, r e s p e c t i v e l y . g. Temperature and Humidity Recorded data values were converted to act u a l temperature using the following regression equations developed at the time the equipment was c a l i b r a t e d : DBT - 4.6708 + 12.118 x V - 0.99169 x V 2 WBT = 5.4237 + 12.011 x V - 0.98828 x V 2 or DBT - 4.6708 + 0.2376 x Dc - 0.000381 x Dc 2 WBT = 5.4237 + 0.2355 x Dc - 0.000380 x Dc 2 where: - 193 -DBT = Dry-bulb temperature (°C) WBT = Wet-bulb temperature (°C) Dc = Data Logger count V = Instrument output ( v o l t ) The c o e f f i c i e n t of determination and standard error of estimate f o r these equations are 0.99 and 0.49, r e s p e c t i v e l y . h. Relative Humidity R e l a t i v e humidity i n s i d e the machine cab was obtained using the following equations given by Black (undated): RH = 100 x e/e* and, e' - 0.6108 x A n t i l o g (7.5 x DBT / (DBT + 273.3)) e " = 0.6108 x A n t i l o g (7.5 x WBT / (WBT + 273.3)) e = e" - 0.066 (DBT - WBT) where: RH = Re l a t i v e humidity (%) e' = Saturation vapour pressure over water at dry-bulb temperature (kPa) e" = Saturation absolute vapour pressure at wet-bulb temperature (kPa) e = Actual water vapour pressure (kPa) DBT = Dry-bulb temperature (°C) WBT = Wet-bulb temperature (°C) - 194 -APPENDIX 3. FLOW CHARTS OF "TURNIN" COMPUTER PROGRAM AND ITS SUBROUTINES The "TURNIN" computer program (Souza 1983) allows the user to i n t e r p r e t the grapple yarder work-cycle, work-elements and delays. the program u t i l i z e s the data prepared and stored by the "PRPARE" program (Souza 1983). The user should i n s e r t the following data: a. Start-time and end-time of lunch i n t e r v a l . b. Delay " s e n s i t i v i t y l i m i t " for unhook and hookup (de f a u l t equals 0.8 min). c. Distance l i m i t between outhaul or inhual delays (default equals 10 m). d. Mainline speed (m/min) to determine the delay s e n s i t i v i t y l i m i t f o r outhaul and inhual (default equals 50 m/min). Usually, the program i s not able to i n t e r p r e t the l a s t 2 or 3 tuns i n a s h i f t . The user should examine the data set and enter the maximum (Dmax) and minimum (Dmin) yarding distance when asked by the computer. I f these values are not given the l a s t turns are ignored. The flow charts of the "TURNIN" computer program and i t s subroutines are shown i n Figures A3 to A12. - 195 -( START J DECLARE VARIABLES I INPUT FILE NAME I READ TITLE, NO. 'OF OBSERVATIONS AND LAST RECORDED TIME, I ( » ) CALL INTEPT SUB INTEPT > FIGURE A3. Flow chart of "TURNIN" computer program used to determine grapple yarder work c y c l e s , work- elements and delays. - 196 -SUB. INTEPT ^ DECLARE VARIABLES READ DISTANCE AND TIME DATA DETERMINE OUTHAUL START TIME AND START DISTANCE CALL DMAX DETERMINE HOOKING AREA L I M I T CALL OUTDEL D E T E R M I N E O U T H A U L E N D T I M E A N D E N D D I S T A N C E  S U B . DMAX > S U B . OUTOEL > CALL H O D . - S O B CALL KOSUCL orrrmiw E N D O F HOOUIf. E N D OF HOOHJ"> OCLAT M I O START OF I M A M . OI S T A K E SUB. HXL-SEIB S U B . Hoonta. ^ > C A L L moa O E T E R M I N E E N D OF I M I A U L A N D E N D O F I N H A U L D I S T A N C E CALL UDEL- S O B CALL UNMOOUtL C A L L S T O R E - C T C L E S U B . INOEL S U B . U O E L - S E H S S U B . S T O R E - G f C U •FIGURE A4 Flow chart of subroutine "INTEPT". This subroutine coordinates i n t e r p r e t a t i o n of work elements, delays and yarding distance. - 197 -SUB. DMAX DETERMINE MAXIMUM AND MINIMUM YARDING DISTANCE FOR CURRENT CYCLE YES DETERMINE LANDING LIMIT 1 ( RETURN ^ READ MAXIMUM AND/ MINIMUM YARDING/ DISTANCE STORE WORK-CYCLE TIME AND DISTANCE DATA ON S P E C I F I E D MASS STORAGE DEVICE DETERMINE LANDING LIMIT RETURN J OUTPUT WORK-CYCLE DATA ON PAPER R ON COMPUTER SCREEN FIGURE A5. Flow chart of subroutine "DMAX" used to determine yarding distance, and hooking and unhooking l i m i t s f o r each work c y c l e . - 198 -1 YES DETERMINE END OF OUTHAUL DELAY NO. j FIGURE A6. Flow chart of subroutine "OUTDEL.'^  used to determine outhaul delays.. - 199 -YES i _ DETERMINE START OF HOOKUP DELAY Q RETURN ^ FIGURE A7. Flow chart of subroutine "HDEL-SENS" used to determine hookup delays when grapple remained i n a c t i v e i n the stump area f o r greater than or equal to 0.8 min (delay " s e n s i t i v i t y " l i m i t ) . - 200 -FIGURE A8. Flow chart of subroutine "H00KDEL" used to determine hookup delays. - 201 -NO FIGURE A9. Flow chart of subroutine "INDEL" used to determine inhaul delays. - 202 -FIGURE A10. Flow chart of subroutine "UDEL-SENS" used to determine unhook delays when grapple remained i n a c t i v e i n the landing area f o r greater than or equal to 0.8 min (delay " s e n s i t i v i t y " l i m i t ) . - 203 -DETERMINE START OF UNHOOK DELAY INCREMENT COUNTER FIGURE A l l . Flow chart of subroutine "UNHOOKDEL" used to determine unhook delays. - 204 -SUB. STORE-CYCLE > SAVE THE FOLLOWING WORK-CYCLE INFORMATION: . START AND END TIME OF ELEMENTS . START AND END TIME OF DELAYS . MINIMUM AND MAXIMUM DISTANCE . DISTANCE OUTHAUL STARTED AND ENDED . DISTANCE INHAUL STARTED AND ENDED . NUMBER OF DELAYS PER ELEMENT . NUMBER OF ROAD CHANGE I INITIALIZE VARIABLES C I RETURN FIGURE A12. Flow chart of subroutine "STORE-CYCLE" used to store information f o r inte r p r e t e d work c y c l e s . - 205 -APPENDIX 4. COMPUTATION METHODS FOR COMPARING NOISE AND VIBRATION LEVELS WITH RECOMMENDED STANDARDS A. Noise L e v e l The following measures of noise l e v e l were evaluated using the "HISTOG" computer program (Souza 1983): a. Equivalent sound l e v e l (Leq) and i t s standard d e v i a t i o n (S.D.) To compare the measured value of noise l e v e l s with the I n d u s t r i a l Health and Safety Regulations (Section 13.21) of WCB (WCB 1980), the "equivalent sound l e v e l " f o r the time measurement period (8-hr s h i f t ) was c a l c u l a t e d . The following equation (ANSI 1971, Magrab 1975, I r v i n and Graf 1979) was used: Leq = 10 x Logio "N E 3=1 (L AO)" S.D. = 'N S P,L 2 - ( N S j=l 1/2 where: Leq = Equivalent continuous sound l e v e l over the measured period of time, 8 hr (dBA). - 206 -L. = Center of the cl a s s i n t e r v a l i n which L. and L J J represents the lower and upper cl a s s l i m i t s , r e s p e c t i v e l y (dBA). Thus Lj = (L' + L j + 1 ) / 2 , where j = 1, 2 N c l a s s e s . P. = F r a c t i o n of time spent i n the class i n t e r a l L.. 3 3 T. N P. = - r J and I P = 1 J N i=l j E T J ^ = Time spent i n (min). b. P r o b a b i l i t y of Exceedance (pj) The p r o b a l i t y that noise l e v e l exceeds Lj was c a l c u l a t e d using the expression: N j=l J N P2 = S P i . j=2 3 • N PN-1 = S P i j=N-l J - 207 -Percentage of Time (PSJ) Spent i n I n t e r v a l LJ Ps. = p. x 100 J 1 Ps represents the percentage of the measurement time f or which the noise l e v e l remained i n each class of dBA. Percentage of Time (Pej) Noise Level i n dBA Exceeded I n t e r v a l L e vel (Lj) or Cumultive Percentage of Time Pe.= p. x 100 J j The value of Pe i n d i c a t e s the percentage of the measurement time a c e r t a i n noise l e v e l i n t e r v a l was exceeded. Exposure Time (Et) The maximum d a i l y exposure time to conform with the i n d u s t r i a l Health and Safety Regulations (Section 13.21) of WCB (WCB 1980) i s given by: K x 10 9 " = 1 0(Leq/10) where: Et = Allowed d a i l y exposure time (hr) at the c a l c u l a t e d Leq. Leq = Leq for the time measurement period (dBA). K = 8 hr ( t o t a l time of exposure permitted at the 90 dBA l e v e l ) . - 208 -If the measured time exceeds the allowed exposure time, then the exposure i s considered to exceed the threshold l i m i t . f . Percentage of Noise Dose (D) Percentage of noise energy r e l a t e d to the reference value of 90 dBA for an 8 hr period i s given by: D = 100 x 10 ( L e « / 1 0 > x t 8 x 10' where: D = Noise dose (%) t = Actual time period of exposure to noise ( h r ) . Leq = Equivalent sound l e v e l (dBA). If D i s le s s than 100% the exposure i s within the recomended l i m i t s . B. V i b r a t i o n A c c e l e r a t i o n The measured v i b r a t i o n a c c e l e r a t i o n values were compared with the ISO l i m i t s shown i n Table A2 using the "Equivalent T o t a l Exposure Method" recommended by the ISO standard (ISO 1978). This method i s used when the rms a c c e l e r a t i o n amplitude varies appreciably with time, or when the t o t a l d a i l y exposure i s composed of several i n d i v i d u a l exposure times t ^ at d i f f e r e n t l e v e l s A^. The method assumes that v i b r a t i o n Table A2. Numerical values of vibration acceleration for the three human c r i t e r i a in the longitudinal (Z) and transverse (X, Y) directions. Human C r i t e r i a Fatigue-Decreased Proficiency Exposure Limit Reduced Comfort Boundary Boundary (FDP) (EL - 2 x FDP) (RC - FDP/3.15) Direction Direction Direction Exposure Time (min) X and Y (g) Z (g) X and Y (g) Z (g) X and Y (g) Z (g) 1 0.200 0.285 0.408 0.571 0.066 0.090 16 0.153 0.216 0.306 0.432 0.049 0.069 25 0.127 0.183 0.225 0.367 0.040 0.058 60 0.087 0.120 0.173 0.241 0.028 0.038 150 0.051 0.072 0.102 0.145 0.016 0.023 240 0.036 0.054 0.072 0.108 0.011 0.017 480 0.025 0.032 0.050 0.064 0.008 0.010 960 0.015 0.002 0.031 0.043 0.005 0.007 1440 0.010 0.014 0.020 0.028 0.003 0.004 The l i m i t 8 shown in this Table are those given by the ISO standard for healthy human beings in the frequency range of maximum whole-body acceleration sensitivity: 4 to 8 in the case of Z, and 1 to 2 Hz in the case of X and Y directions). - 210 -exposure at l e v e l for a time t^ i s equivalent to an exposure at a standard reference l e v e l A' f o r a time t^ (Figure A13). In other words, the procedure assumes the following r e l a t i o n s h i p s : or X X. 1 and t i x where t | = Equivalent exposure time (min). A^ = Measured value of v i b r a t i o n a c c e l e r a t i o n (g). t^ = Measured period of time corresponding to A^ (min). x^ = Permissible time corresponding to A^ (min). x' = Selected period of time at which the equivalent exposure time i s referenced ( i . e., 480 min or 8 h r ) . A' = Permissible v i b r a t i o n a c c e l e r a t i o n corresponding to x'. Summing a l l c a l c u l a t e d i n d i v i d u a l equivalent exposure times gives the equivalent t o t a l exposure time, which corresponds to A': N T' = where N = number of observations. - 211 -- 212 -If the cal c u l a t e d equivalent t o t a l exposure time (T') exceeds the selected period of time (T*), the v i b r a t i o n exposure exceeds the recommended standards. f o r each d i r e c t i o n (X, Y, and Z) using the "VIBEV" computer program (Souza 1983). found i n Table A2 were determined by l i n e a r i n t e r p o l a t i o n . For example, assume the s t a r t (RI) and the end (R2) of recording time (x-acceleration) equal 20.677 min and 20.844 min, r e s p e c t i v e l y , and: A = 0.027 g t =• R2 - RI = 0.167 min T* = 480 min The value of A^ equal to 0.027 g l i e s between 0.020 g and 0.031 g on Table A2. These tabulated a c c e l e r a t i o n values correspond to the permissible exposure times (T^) of 1440 and 960 min, r e s p e c t i v e l y . The corresponding permissible exposure time f o r 0.027 g was then found: The equivalent t o t a l exposure time was determined independently Values f o r permissible exposure time (T^) not s p e c i f i c a l l y 960 min 0.031 g 0.027 g 1440 min 0.020 g x - 960 + (1440 - 960) x (0.031 - 0.027) 0.031 - 0.020 - 1134.545 min = 0.167 480 and t! = 0.071 min 1134.545 LIST OF PUBLICATIONS Bower, R. W.; Souza, A. P. and Senft, J . F. 1976. Physical and mechanical properties of fast-grown, plantation Caribbean pine (Pinus caribaea) from B r a z i l , South America. Research B u l l e t i n No. 936, Purdue Univ., Agric. Exp. Station, West Lafayette, 6 pp. L e l l e s , J . G; Souza, A. P.; Barros, A. A. A.; e Valente, O.F. 1978. Rendimentos e custos no corte de eucaliptos com machado e motosserras. Revista Arvore, 2(1):20-26. L e l l e s , J . G.; Souza, A. P.; Clemente, V. M. e Valente, 0. F. 1978. Estudo das character^sticas da celulose k r a f t de Cunninghamia  lanceolata Lamb. Revista Arvore, 2(1):30-40. L e l l e s , J . G.; Reis, M. S.; Valente, 0. F.; e Souza, A. P. 1978. Durabilidade de moiroes preservados em condicoes de campo. Revista X r v o r e , 2(l):27-33. L e l l e s , J . G.; Valente, 0. F.; Souza, A. P. e Clemente, V. M. 1978. V a r i a b i l i d a d e da madeira de Cunninghamia lanceolata Lamb. Revista da  Madeira, (319):27-29. Souza, A. P.; L e l l e s , J . G.; Gomes, J . N. and e Valente, 0. F.. 1978. Um estudo de tempo e producao na explorac"ao de povoamentos j ovens de Douglas-fir com motosserra e "skidders". Revista Arvore, 2_(2)1:19. Gomes, J. M.; Brandi, R. M.; Cano, M. A. D. e Souza, A. P. 1978. E f e i t o do s a l antitranspirante e poda no endurecimento va seca de mudas de Eucalyptus grandis H i l l ex Maiden. Revista da F l o r e s t a , 9(2):18-24. Souza, A. P.; Del i a Lucia, R. M. e Rezende, G. C. 1979. Estudo da densidade basica da madeira de Eucalyptus microcoris F. Muell, da regiao de Dionfzio, MG. Revista Axvore, 3(1):16-27. Machado, C. C ; Souza, A. P. e Calado, M. A. L. 1981. Estudo de tempo e movimento para racionalizapab da exploracab f l o r e s t a l na regiao de Catende, PE. Ciencia e Cultura, 33(9):1222-1224. Souza, A. P.; C o t t e l l , P. L. and Lawrence, P. D. 1981. E l e c t r o n i c Data Logger for ergonomic studies i n mechanized logging operations. In: Proceedings of the Seminar on Occupational Health and Safety and Applied Ergonomics on Highly Mechanized Logging Operations, Ottawa, Sept. 21-25/1981. ECE/FA0/IL0, Environment Canada D i s t . Centre, Ottawa, pp. 505-515. 

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