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Mechanical raspberry harvesting Nyborg, Erling Orvald 1970

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MECHANICAL RASPBERRY HARVESTING BY ERLING ORVALD NYBORG B.E., U n i v e r s i t y o f Saskatchewan, 1960 M.S., M i c h i g a n S t a t e U n i v e r s i t y , 1967 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n t h e Department o f M e c h a n i c a l E n g i n e e r i n g We a c c e p t t h i s t h e s i s as c o n f o r m i n g to' t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA F e b r u a r y , 1970 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r equ i r emen t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I ag ree tha t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . 1 f u r t h e r agree tha p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y pu rposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d tha t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t hou t my w r i t t e n p e r m i s s i o n . Department o f Mechanical Engineering The U n i v e r s i t y o f B r i t i s h Co lumbia Vancouve r 8, Canada Date A p r i l 20, 1970. ABSTRACT Raspberry growers i n the lower mainland of B r i t i s h Columbia are contending with i n c r e a s i n g production c o s t s and are f a c i n g problems i n o b t a i n i n g seasonal labour f o r f r u i t p i c k i n g . Since cost of hand h a r v e s t i n g represents a l a r g e p r o p o r t i o n of the t o t a l production c o s t , the purpose of t h i s research was to i n v e s t i g a t e the f e a s i b i l i t y of mechanical raspberry h a r v e s t i n g and to design a mechanical h a r v e s t i n g system s u i t a b l e f o r the lower mainland of B r i t i s h Columbia. A systematic design procedure, o r i e n t e d toward design and t e s t i n g of a bio-machine system, was employed and the s e l e c t e d design was based upon the p h y s i c a l and mechanical p r o p e r t i e s of the raspberry p l a n t and i t s f r u i t . An economic a n a l y s i s , comparing the mechanical h a r v e s t i n g system to present hand .harvesting methods was used to determine the necessary r e l a t i o n -ships among machine c o s t , machine c a p a c i t y and machine e f f i c i e n c y . The s e l e c t e d design f o r a mechanical raspberry h a r v e s t i n g system i n c l u d e d t o o l s f o r fe e d i n g , cane o r i e n t a t i o n , s e l e c t i v e h a r v e s t -i n g , f r u i t c o l l e c t i o n , f r u i t conveying and f r u i t storage. Mathematical models f o r these t o o l s were c o n s t r u c t e d , based on a s e r i e s of t e s t s determining p e r t i n e n t p h y s i c a l and mechanical p r o p e r t i e s of the raspberry p l a n t and f r u i t . In a d d i t i o n , t e s t s to d e f i n e f r u i t q u a l i t y were undertaken and the r e l a t i o n s h i p s among f r u i t q u a l i t y and s e l e c t i v e h a r v e s t i n g parameters were i n v e s t i g a t e d . The use of chemical growth, regulator's t o a l t e r f r u i t r e t e n t i o n f o r c e was a l s o i n v e s t i g a t e d . Force-deformation moduli, r e s u l t i n g from f l a t p l a t e compression t e s t s of r a s p b e r r y f r u i t , were found to be good i n d i c a t o r s o f f r u i t q u a l i t y . C o r r e l a t i o n s among f o r c e - d e f o r m a t i o n moduli and f r u i t p r o p e r t i e s i n d i c a t e d t h a t e i t h e r f r u i t r e t e n t i o n f o r c e or F/W r a t i o c o u l d be used as c o n t r o l v a r i a b l e s f o r a s e l e c t i v e h a r v e s t i n g t o o l . Prototype u n i t s f o r f e e d i n g , cane o r i e n t a t i o n and s e l e c t i v e h a r v e s t i n g t o o l s were designed and f a b r i c a t e d . The s e l e c t i v e h a r v e s t i n g t o o l was a f i x e d d i s p l a c e -ment shaker designed t o a p p l y equal maximum a c c e l e r a t i o n t o a l l f r u i t i n g p o r t i o n s o f the p l a n t , independent o f p l a n t p r o p e r t i e s . F/W r a t i o was used as the c o n t r o l v a r i a b l e f o r s e l e c t i v e har-v e s t i n g . L i m i t e d f i e l d t e s t i n g i n d i c a t e d t h a t the t o o l s f o r f e e d i n g , cane o r i e n t a t i o n and s e l e c t i v e h a r v e s t i n g c o u l d s a t i s f a c t o r i l y be used i n a mechanical r a s p b e r r y h a r v e s t i n g system. R e s u l t s a l s o • i n d i c a t e d t h a t mechanical h a r v e s t i n g c o u l d be s u b s t a n t i a l l y more p r o f i t a b l e than hand h a r v e s t i n g . The W i l l a m e t t e v a r i e t y of r a s p b e r r i e s as commonly grown i n B r i t i s h Columbia was found not e s p e c i a l l y s u i t a b l e f o r mechanical h a r v e s t i n g . Due to the h i g h r a t i o o f f r u i t r e t e n t i o n f o r c e to f r u i t stem s t r e n g t h i n the W i l l a m e t t e v a r i e t y , the q u a l i t y o f machine h a r v e s t e d f r u i t must be lower than the q u a l i t y o f hand h a r v e s t e d f r u i t . Since f r u i t r e t e n t i o n f o r c e i s dependent upon f r u i t v a r i e t y , i n v e s t i g a t i o n of p h y s i c a l p r o p e r t i e s o f o t h e r s u i t a b l e r a s p b e r r y v a r i e t i e s should be undertaken i n o r d e r t o f i n d a v a r i e t y having p r o p e r t i e s more compatible with mechanical har-v e s t i n g methods. TABLE OF CONTENTS Page LIST OF TABLES i x LIST OF FIGURES x i TERMINOLOGY x i v NOMENCLATURE x v i i i ACKNOWLEDGMENTS x x i i INTRODUCTION 1 P r e s e n t S t a t u s o f R a s p b e r r y P r o d u c t i o n i n B r i t i s h C olumbia 1 The need f o r h a r v e s t m e c h a n i z a t i o n 1 Scope and Purpose o f t h i s R e s e a r c h 2 • Review o f P r e v i o u s Work 2 C a t e g o r i e s o f h a r v e s t i n g systems 3 Methods o f f r u i t r e m o v a l 4 SYSTEMATIC DESIGN PROCEDURE 7 ANALYSIS OF THE PROCESS 10 Flow C h a r t 10 O p e r a t i o n a l Requirements o f t h e H a r v e s t i n g Machine 10 I n i t i a l c o n d i t i o n 10 F i n a l c o n d i t i o n 14 Economic A n a l y s i s o f R a s p b e r r y H a r v e s t i n g 14 Cost o f hand p i c k i n g 14 Y i e l d s and market p r i c e 15 E s t i m a t e d c o s t o f m e c h a n i c a l h a r v e s t i n g 15 The br e a k - e v e n p o i n t 18 Summary o f Machine Requirements 21 - v -Page TOOL ANALYSES 2 3 M e c h a n i z a t i o n o f the P r o c e s s 23 T o o l f o r F e e d i n g and Cane O r i e n t a t i o n 23 F u n c t i o n 23 Proposed d e s i g n 24 A n a l y s i s 25 Unknowns 27 T o o l f o r S e l e c t i v e H a r v e s t i n g 27 F u n c t i o n 27 Proposed d e s i g n 27 A n a l y s i s 29 Unknowns 30 T o o l f o r F r u i t C o l l e c t i o n and Conveying 31 F u n c t i o n 31 Proposed d e s i g n 31 A n a l y s i s 32 Unknowns 3 3 T o o l f o r F r u i t S t o r a g e 34 F u n c t i o n 34 Proposed d e s i g n 34 A n a l y s i s 34 Unknowns 35 Summary 3 5 ANALYSIS OF PRODUCT CHARACTERISTICS 36 Scope o f I n v e s t i g a t i o n 36 D i s t r i b u t i o n o f F r u i t on t h e R a s p b e r r y P l a n t 36 P h y s i c a l Dimensions o f R a s p b e r r y P l a n t s 39 - v i -Page P h y s i c a l Dimensions o f the Raspberry F r u i t and Stem 39 F r u i t Weight, Volume and D e n s i t y 40 Rate of F r u i t Removal 41 Term i n a l V e l o c i t y o f Raspberry F r u i t 41 F r u i t R e t e n t i o n Force 4 2 F/W R a t i o 45 St r e n g t h o f F r u i t Attachment System 4 6 F r u i t C o l o r 48 B r u i s i n g C h a r a c t e r i s t i c s o f Raspberry F r u i t 52 Force-Deformation C h a r a c t e r i s t i c s o f Raspberry F r u i t 53 F r u i t R i g i d i t y 55 Sugar Content of F r u i t 57 Comparison o f P r o p e r t i e s i n an Attempt t o Def i n e F r u i t Q u a l i t y 58 Dynamic Response o f Canes and F r u i t Attachment System 63 E l a s t i c Modulus o f Raspberry Canes 70 C o n t r o l o f P h y s i c a l P r o p e r t i e s - Growth Reg u l a t o r s 71 MATHEMATICAL MODELS FOR THE TOOLS 8 0 Completion o f the T o o l Analyses 80 T o o l f o r Feeding and Cane O r i e n t a t i o n 80 T o o l f o r S e l e c t i v e H a r v e s t i n g 84 T o o l f o r F r u i t C o l l e c t i o n and Conveying 88 T o o l f o r F r u i t Storage 91 DESIGN AND FABRICATION OF TOOLS 91 I n t r o d u c t o r y Remarks 9 3 T o o l f o r Feeding and Cane O r i e n t a t i o n 93 To o l f o r S e l e c t i v e H a r v e s t i n g 95 - v i i -Page F r u i t C o l l e c t i o n , Conveying and Storage 97 SYNTHESIS AND CONSTRUCTION OF THE MACHINE 99 Purpose of the Prototype Machine 99 Powering Systems 99 Frame and Supporting Members 102 T r e l l i s i n g M o d i f i c a t i o n 102 MACHINE EVALUATION 104 Scope o f Tes t 104 E v a l u a t i o n o f the Feeding and Cane O r i e n t a t i o n T o o l 104 E v a l u a t i o n o f the S e l e c t i v e H a r v e s t i n g T o o l 105 E v a l u a t i o n o f Machine C o n s t r u c t i o n 109 Concluding Remarks 110 OBSERVATIONS AND CONCLUSIONS 112 SUGGESTIONS FOR FURTHER STUDY 117 LITERATURE CITED 118 • • • - V11X -LIST OF TABLES T a b l e Page I R a s p b e r r y P r o d u c t i o n i n t h e Lower M a i n l a n d o f B r i t i s h Columbia 14 I I E s t i m a t e d Cost o f M e c h a n i c a l H a r v e s t i n g 17 I I I P h y s i c a l Dimensions o f the R a s p b e r r y F r u i t and i t s Attachment Stem 4 0 IV C a l c u l a t e d Rate o f F r u i t Removal f o r a S i n g l e Row H a r v e s t i n g Machine 41 V R e s u l t s o f Drop T e s t s 53 VI S i m p l e C o r r e l a t i o n s Among R i g i d i t y and F r u i t Dimensions 57 V I I S i m p l e C o r r e l a t i o n s Among F r u i t R e t e n t i o n F o r c e , F r u i t Weight and F r u i t Sugar C o n t e n t 58 V I I I S i m p l e C o r r e l a t i o n s Among F r u i t R e t e n t i o n F o r c e , F / W , R i g i d i t y and F o r c e - D e f o r m a t i o n M o d u l i 59 IX S i m p l e C o r r e l a t i o n s Among C o l o r I n d e x , F r u i t R e t e n t i o n F o r c e , F/W, R i g i d i t y and F o r c e - D e f o r m a t i o n M o d u l i f o r t h e F i r s t Day o f the 1968 H a r v e s t Season 62 X Si m p l e C o r r e l a t i o n s Among C o l o r Index, F r u i t R e t e n t i o n F o r c e , F/W, R i g i d i t y and F o r c e - D e f o r m a t i o n M o d u l i f o r t h e F i f t e e n t h Day o f t h e 1968 H a r v e s t Season 62 XI F l e x i b i l i t y M a t r i x , [ C ] , f o r a R a s p b e r r y Cane Loaded as a V e r t i c a l C a n t i l e v e r Beam 66 X I I Mass M a t r i x , ["m J , f o r a R a s p b e r r y Cane 67 X I I I Growth R e g u l a t o r Treatments 74 XIV V a r i a t i o n o f F r u i t R e t e n t i o n F o r c e w i t h Time as A f f e c t e d by Growth R e g u l a t o r Treatments 77 XV V a r i a t i o n o f F r u i t Weight w i t h Time as A f f e c t e d by Growth R e g u l a t o r Treatments 78 XVI F/W V a r i a t i o n w i t h Time as A f f e c t e d by Growth R e g u l a t o r Treatments 79 X V I I Means and S t a n d a r d D e v i a t i o n s o f F r u i t R e t e n t i o n F o r c e and F/W R a t i o Based on Data C o l l e c t e d i n 1968 85 - i x -T a b l e Page X V I I I C a l c u l a t e d Base M o t i o n A c c e l e r a t i o n f o r S e v e r a l L e v e l s o f F r u i t Removal E f f i c i e n c y 87 - x -LIST OF FIGURES i g u r e 1 S y s t e m a t i c d e s i g n p r o c e d u r e 2 D e f i n i n g t h e p r o c e s s 3 Flow c h a r t s f o r hand h a r v e s t i n g and f o r t h e p r o p osed m e c h a n i c a l h a r v e s t i n g system 4 A t y p i c a l row o f W i l l a m e t t e r a s p b e r r i e s 5 The r a s p b e r r y f r u i t 6 The e f f e c t o f machine pur c h a s e p r i c e on the b r e ak-even p o i n t f o r a machine c a p a c i t y o f one a c r e p e r hour 7 The e f f e c t o f machine c a p a c i t y on t h e b r e a k -even p o i n t f o r a machine p u r c h a s e p r i c e o f $3,500 8 T o o l f o r f e e d i n g and cane o r i e n t a t i o n 9 A r a s p b e r r y cane i d e a l i z e d as a t a p e r e d v e r t i c a l c a n t i l e v e r beam o f c i r c u l a r c r o s s s e c t i o n 10 T o o l f o r s e l e c t i v e h a r v e s t i n g 11 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t on a r a s p b e r r y p l a n t as measured upward from th e s o i l s u r f a c e 12 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t on a r a s p b e r r y p l a n t as measured outward from t h e c e n t e r o f t h e row o f p l a n t s 13 P h y s i c a l d i m e n s i o n s o f a r a s p b e r r y p l a n t 14 Nomenclature used i n T a b l e I I I 15 Method o f measuring f r u i t r e t e n t i o n f o r c e 16 Method o f h o l d i n g f r u i t i n t h e dynamometer 17 F r u i t r e t e n t i o n f o r c e v a r i a t i o n o v e r th e h a r v e s t season f o r 1967 and 1968 18 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t r e t e n t i o n f o r c e f o r 1968 19 C u m u l a t i v e d i s t r i b u t i o n o f F/W f o r 1968 - x i -F i g u r e Page 20 R a s p b e r r y f r u i t a t t a c h m e n t system 47 21 V a r i a t i o n o f f r u i t stem s t r e n g t h w i t h l o a d d i r e c t i o n 47 22 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t stem s t r e n g t h f o r a = 0° 47 23 S p e c t r o p h o t o m e t e r m o d i f i c a t i o n 50 24 T u r n t a b l e and e x t e r n a l l i g h t s o u r c e 50 2 5 Complete i n s t r u m e n t a t i o n f o r measuring e x t e r n a l c o l o r o f r a s p b e r r y f r u i t 51 26 V a r i a t i o n o f f r u i t c o l o r as d e t e r m i n e d by r e f l e c t a n c e measurements 51 27 Method o f l o a d i n g f r u i t i n I n s t r o n machine 54 28 T y p i c a l f o r c e - d e f o r m a t i o n c u r v e f o r r a s p b e r r y f r u i t s u b j e c t e d t o f l a t - p l a t e l o a d i n g a t 2 cm/min 54 29 I n s t r u m e n t a t i o n f o r me a s u r i n g f r u i t r i g i d i t y 56 30 F r u i t a t t a c h m e n t system i d e a l i z e d as a s i m p l e pendulum 64 31 Measurement o f t h e s t i f f n e s s i n f l u e n c e c o e f f i c i e n t s o f a r a s p b e r r y cane 65 32 C a l c u l a t e d modes o f v i b r a t i o n and c o r r e s p o n d i n g n a t u r a l f r e q u e n c i e s f o r two r a s p b e r r y canes 68 3 3 Randomized p l o t s f o r growth r e g u l a t o r t r i a l s 7 3 34 Spray boom f o r a p p l y i n g growth r e g u l a t o r s 7 3 35 E s t i m a t i n g t h e p o i n t o f c o n t a c t between t h e canes and t h e f e e d r o l l s 82 36 E s t i m a t i n g t h e d e f l e c t i o n o f t h e canes by t h e f e e d r o l l s 82 37 D e t e r m i n i n g cane t a p e r as a f u n c t i o n o f t h e p o i n t o f l o a d a p p l i c a t i o n 83 38 Base m o t i o n a p p l i e d t o t h e f e e d r o l l s 86 - x i i -F i g u r e Page 39 Maximum a c c e l e r a t i o n developed by a s l i d e r crank mechanism, wit h one f o o t c o n n e c t i n g rod l e n g t h , f o r s e v e r a l amplitudes and a range o f f r e q u e n c i e s 89 HO Feed r o l l f a b r i c a t i o n 94 41 Feed r o l l mounting and d r i v e t r a i n 94 42 Method of a p p l y i n g base motion to the feed r o l l s 96 43 Method o f v a r y i n g base motion amplitude 96 44 D r i v e t r a i n f o r a p p l y i n g the base motion 97 4 5 Nylon screens used as temporary c o l l e c t i o n and conveying t o o l s d u r i n g t e s t i n g of the t o o l s f o r f e e d i n g and s e l e c t i v e h a r v e s t i n g 98 46 P l a n view o f the h a r v e s t e r 100 47 Right view o f completed machine 101 48 Rear view o f completed machine 101 4 9 View o f machine e n t e r i n g a row. The m o d i f i e d t r e l l i s i n g system i s shown 103 « 50 106 51 106 52 106 53 F r u i t stem damage due to e x c e s s i v e base motion a c c e l e r a t i o n 108 54 The i n f l u e n c e o f f r u i t core shape on f r u i t r e t e n t i o n f o r c e 111 - x i i i -TERMINOLOGY A b s c i s s i o n l a y e r . - The r e g i o n on the f r u i t stem a t which n a t u r a l a b s c i s s i o n o c c u r s . A g g r e g a t e f r u i t . - A f r u i t formed by t h e r i p e n i n g t o g e t h e r o f a number o f s e p a r a t e o v a r i e s , a l l b e l o n g i n g t o a s i n g l e f l o w e r and a d h e r i n g as a u n i t on a common r e c e p t a c l e . A m p l i t u d e . - The maximum d i s p l a c e m e n t o f an o s c i l l a t i n g m o t i o n as measured from t h e mean p o s i t i o n . A n a l y s i s o f c o v a r i a n c e . - The a n a l y s i s o f c o v a r i a n c e as used i n t h i s s t u d y a p p l i e s t o a method o f comparing r e g r e s s i o n s i n m u l t i p l e c l a s s i f i c a t i o n s . I f t h e r e l a t i o n between Y and X i s o b t a i n e d f o r two i n d i v i d u a l t r e a t m e n t s , t h e model f o r the r e g r e s s i o n s i s Y i j = «i + 0 i X i j + «ij where i = 1,2 deno t e s t h e two t r e a t m e n t s . The method compares the r e s i d u a l v a r i a n c e s and °2^» compares t h e s l o p e s (3^ and ^ > a n d compares t h e e l e v a t i o n s o f t h e l i n e s «^ and • The p r o c e d u r e used i s o u t l i n e d on page 432 o f r e f e r e n c e ( 3 3 ) . A n a l y s i s o f v a r i a n c e . - A p r o c e s s by means o f which t h e t o t a l v a r i a n c e i n a co m p o s i t e sample i s a p p o r t i o n e d among the d i f f e r e n t f a c t o r s r e s p o n s i b l e f o r i t s g r o s s v a l u e . See, f o r example, pages 278 t o 436 o f r e f e r e n c e ( 2 8 ) . A n g l e modulus.- The a n g l e between t h e d e f o r m a t i o n a x i s and t h e i n i t i a l l i n e a r p o r t i o n o f t h e f o r c e - d e f o r m a t i o n c u r v e f o r r a s p b e r r y f r u i t compressed between p a r a l l e l f l a t p l a t e s a t a r a t e o f 2cm/min. Base m o t i o n . - The t y p e o f m o t i o n i m p a r t e d by a v i b r a t o r y h a r -v e s t i n g t o o l a t i t s p o i n t o f c o n t a c t w i t h a p l a n t . Break-even p o i n t . - The minimum n e c e s s a r y f r u i t r e m o v a l e f f i c i e n c y , i n p e r c e n t o f g r o s s f r u i t y i e l d , w h i c h must be a c h i e v e d by a m e c h a n i c a l h a r v e s t i n g machine, i n o r d e r t o o b t a i n t h e same g r o s s income from m e c h a n i c a l h a r v e s t i n g as i s p r e s e n t l y o b t a i n e d from hand h a r v e s t i n g . B r u i s i n g . - Damage t o p l a n t t i s s u e by e x t e r n a l f o r c e s c a u s i n g change i n t e x t u r e and/or e v e n t u a l c h e m i c a l a l t e r a t i o n o f c o l o r , f l a v o u r and t e x t u r e . B r u i s i n g does n ot break t h e s k i n . I n t h i s s t u d y , b r u i s e damage was e v a l u a t e d o n e - h a l f hour a f t e r l o a d i n g and was r e p o r t e d i n terms o f the maximum de p t h and mean w i d t h o f the b r u i s e d t i s s u e . - x i v -Cane.- The woody, p r o d u c t i v e , s e c o n d - y e a r growth o f t h e r a s p b e r r y p l a n t . Cane t a p e r . - When c o n s i d e r i n g a s p e c i f i c l e n g t h o f cane, cane t a p e r i s d e f i n e d as t h e mean r a d i u s o f t h e c r o s s - s e c t i o n o f the s m a l l end o f the cane d i v i d e d by t h e mean r a d i u s o f t h e c r o s s - s e c t i o n o f t h e l a r g e end o f t h e cane. C o e f f i c i e n t o f d e t e r m i n a t i o n . - In s i m p l e r e g r e s s i o n , t h e q u a n t i t y , r 2 , r e p r e s e n t i n g t h e f r a c t i o n o f t h e c o r r e c t e d sums o f s q u a r e s t h a t i s a t t r i b u t a b l e t o s i m p l e l i n e a r r e g r e s s i o n . See, f o r example, page 225 o f r e f e r e n c e ( 2 8 ) . C o e f f i c i e n t o f m u l t i p l e d e t e r m i n a t i o n . - I n m u l t i p l e r e g r e s s i o n , t h e q u a n t i t y , R 2 , r e p r e s e n t i n g the f r a c t i o n o f the sums o f s q uares o f t h e d e v i a t i o n s o f Y from i t s mean t h a t i s a t t r i b u t a b l e t o the r e g r e s s i o n . R 2 i s d e f i n e d as t h e sum o f s q u a r e s due t o r e g r e s s i o n d i v i d e d by t h e sum o f squares about th e mean. See, f o r example, page 402 o f r e f e r e n c e ( 3 3 ) . C o r e . - The r e c e p t a c l e on the end o f the f r u i t a t t a c h m e n t stem, around w h i c h t h e r a s p b e r r y f r u i t grows. D r u p e l e t s . - The i n d i v i d u a l r a s p b e r r y f r u i t l e t s , each o f w h i c h a r e formed from the r i p e n i n g o f s e p a r a t e o v a r i e s . The r a s p b e r r y f r u i t c o n s i s t s o f a number o f l o o s e l y bound d r u p e l e t s a t t a c h e d t o a c e n t r a l c o r e . , F i e l d e f f i c i e n c y . - The r a t i o o f e f f e c t i v e f i e l d c a p a c i t y t o t h e o r e t i c a l f i e l d c a p a c i t y . F i x e d d i s p l a c e m e n t s h a k e r . - A v i b r a t o r y h a r v e s t i n g t o o l i n w h i c h t h e a m p l i t u d e o f t h e a p p l i e d base m o t i o n i s c o n s t a n t . F r u i t f i r m n e s s . - The r e s i s t a n c e t o d e f o r m a t i o n o f f e r e d by a f r u i t under c o m p r e s s i v e l o a d . I n t h i s s t u d y , the t a n g e n t modulus o f t h e f o r c e - d e f o r m a t i o n c u r v e , r e s u l t i n g f r om c o m p r e s s i o n o f the f r u i t between p a r a l l e l f l a t p l a t e s a t a r a t e o f 2cm/min, was used as an i n d i c a t o r o f f r u i t f i r m n e s s . F r u i t r e t e n t i o n f o r c e . - The t e n s i l e f o r c e r e q u i r e d t o remove a r a s p b e r r y f r u i t from i t s c o r e . F r u i t r i g i d i t y . - I n t h i s s t u d y , r i g i d i t y was d e f i n e d as the a b i l i t y o f f r u i t t o t r a n s m i t m e c h a n i c a l v i b r a t i o n s . The i n t e n s i t y o f v i b r a t i o n s t r a n s m i t t e d t h r o u g h an i n d i v i d u a l f r u i t , compressed w i t h a f o r c e o f t e n grams between two p a r a l l e l d iaphragms, th e l o w e r diaphragm b e i n g e x c i t e d a t a f r e q u e n c y o f 250Hz, was used as an i n d i c a t o r o f f r u i t r i g i d i t y . -xv -Growth r e g u l a t o r . - An o r g a n i c compound which,when i n t r o d u c e d i n t o a p l a n t i n a r e l a t i v e l y s m a l l q u a n t i t y , i n d u c e s e f f e c t s on the growth p a t t e r n o f the p l a n t . I n e r t i a s h a k e r . - A v i b r a t o r y h a r v e s t i n g t o o l i n wh i c h t h e maximum f o r c e e x e r t e d by t h e a p p l i e d base m o t i o n i s c o n s t a n t . L i n e a r l i m i t . - The minimum l o a d a t wh i c h t h e f o r c e - d e f o r m a t i o n c u r v e , r e s u l t i n g from c o m p r e s s i n g r a s p b e r r y f r u i t between p a r a l l e l f l a t p l a t e s a t a r a t e o f 2cm/min, becomes non-l i n e a r . Mean.- The a r i t h m e t i c mean ,Mj o f a random sample o f indepe n d e n t o b s e r v a t i o n s . M u l t i p l e c o r r e l a t i o n c o e f f i c i e n t . - The square r o o t , R , o f t h e c o e f f i c i e n t o f m u l t i p l e d e t e r m i n a t i o n . P i c k i n g e f f i c i e n c y . - The p e r c e n t a g e o f mature f r u i t on a p l a n t w h i c h i s removed by a h a r v e s t e r . T h i s i s a l s o c a l l e d t he f r u i t r e m o v a l e f f i c i e n c y . PPM.- P a r t s p e r m i l l i o n . Random sample.- A sample c o n s i s t i n g o f in d e p e n d e n t o b s e r v a t i o n s w h i c h a r e drawn from a p o p u l a t i o n . R a s p b e r r y . - R a s p b e r r y , as used i n t h i s s t u d y , r e f e r s t o the American r e d r a s p b e r r y ( f a m i l y : Rosaceae, genus: Rubus, s p e c i e s : S t r i g o s u s , v a r i e t y : W i l l a m e t t e ) . Shoot.- The s u c c u l e n t , n o n - p r o d u c t i v e , f i r s t y e a r growth o f the r a s p b e r r y p l a n t . S i m p l e c o r r e l a t i o n c o e f f i c i e n t . - The square r o o t , r , o f the c o e f f i c i e n t o f d e t e r m i n a t i o n . S t a n d a r d d e v i a t i o n . - The s t a n d a r d d e v i a t i o n ,<r, o f a random sample o f i n d e p e d e n t o b s e r v a t i o n s , d e f i n e d as Stem.- The member a t t a c h i n g a r a s p b e r r y f r u i t t o an i n t e r m e d i a t e l i m b . (See f i g u r e 5) S t r o k e . - The maximum d i s p l a c e m e n t i m p a r t e d by t h e base m o t i o n . The s t r o k e i s t w i c e t h e a m p l i t u d e o f the m o t i o n . Tangent modulus.- The t a n g e n t o f the a n g l e modulus. where n = the number o f o b s e r v a t i o n s M = the sample mean - x v i -T o o l . - A d e v i c e w h i c h p e r f o r m s a b a s i c p r o c e s s f u n c t i o n . T r e l l i s . - A s u p p o r t i n g framework w i t h i n a r a s p b e r r y row. . The purpose o f the t r e l l i s i s t o p r e v e n t t h e p l a n t s from l o d g i n g . - x v i i -NOMENCLATURE A Machine purchase p r i c e , d o l l a r s A P r o i e c t e d f r u i t a r e a normal t o d i r e c t i o n o f m o t i o n P B Number o f men r e q u i r e d t o o p e r a t e a m e c h a n i c a l h a r v e s t -i n g system C F r u i t c o l o r i n d e x [C] F l e x i b i l i t y m a t r i x C^ O v e r a l l d r ag c o e f f i c i e n t [D] Dynamic m a t r i x E Modulus o f e l a s t i c i t y F F r u i t r e t e n t i o n f o r c e F Q F o r c e a p p l i e d t o f r u i t F, Minimum f o r c e t o damage f r u i t s u p p o r t system o r t o remove immature f r u i t F Upper l i m i t o f f r u i t r e t e n t i o n f o r c e o f mature f r u i t m ^ Drag f o r c e F/W R a t i o o f f r u i t r e t e n t i o n f o r c e t o f r u i t w e i g h t I Moment o f i n e r t i a o f cane c r o s s s e c t i o n a t s o i l s u r f a c e o I ( x ) Moment o f i n e r t i a o f cane c r o s s s e c t i o n p e r u n i t o f l e n g t h K A modulus r e l a t i n g f r u i t d e f o r m a t i o n t o c o m p r e s s i v e l o a d . F o r t h i s s t u d y , K = 20 y L Cane l e n g t h f r om s o i l s u r f a c e t o p o i n t o f l o a d a p p l i c a t i o n N, Numbers o f f r u i t on one p l a n t i n a o n e - h a l f - f o o t - t h i c k v e r t i c a l s l i c e N Numbers o f f r u i t on one p l a n t i n a o n e - f o o t - t h i c k v • h o r i z o n t a l s l i c e 0^ . A n n u a l machine overhead c o s t , d o l l a r s .0 H o u r l y o p e r a t i n g c o s t , d o l l a r s - x v i i i -P r o b a b i l i t y l e v e l , ( 1 - 6 ) , where 3 i s t h e l e v e l o f s i g n i f i c a n c e . P i s a l s o t h e t y p e I I e r r o r . S t a t i c c o m p r e s s i v e l o a d a p p l i e d t o f r u i t C o n c e n t r a t e d h o r i z o n t a l l o a d a p p l i e d t o a cane M u l t i p l e c o r r e l a t i o n c o e f f i c i e n t C o e f f i c i e n t of. m u l t i p l e d e t e r m i n a t i o n Forward speed, m i l e s p e r hour S t a n d a r d e r r o r o f t h e e s t i m a t e Sweeping m a t r i x d e v o i d o f t h e f r u i t mode Time, days R e l a t i v e v e l o c i t y between f a l l i n g f r u i t and s u r r o u n d i n g f l u i d Maximum a l l o w a b l e impact v e l o c i t y o f f r u i t s t r i k i n g a r i g i d s u r f a c e Upward v e l o c i t y o f a i r s u p p l i e d by an a i r c u s h i o n i n g system Forward v e l o c i t y o f machine T e r m i n a l v e l o c i t y o f f a l l i n g f r u i t Weight o f a s i n g l e f r u i t Dependent v a r i a b l e Mode o f v i b r a t i o n o f a r a s p b e r r y cane Column m a t r i x o f mode shape f o r t h e fun d a m e n t a l mode o f v i b r a t i o n Column m a t r i x o f mode shape f o r t h e second p r i n c i p a l mode o f v i b r a t i o n I n t e r c e p t o f s i m p l e r e g r e s s i o n e q u a t i o n A c c e l e r a t i o n o f f r u i t r e l a t i v e t o cane Sl o p e o f s i m p l e r e g r e s s i o n e q u a t i o n Cane t a p e r , ( r , / r ) r l o F r u i t d i a m e t e r - x i x -F r u i t d e f o r m a t i o n under c o m p r e s s i v e l o a d Maximum impact energy w h i c h a f r u i t can a b s o r b w i t h o u t b r u i s i n g A c c e l e r a t i o n due t o g r a v i t y F r u i t l e n g t h Maximum a l l o w a b l e f r e e f u l l d i s t a n c e w i t h o u t b r u i s i n g M a t r i x row M a t r i x column R a t i o o f c r a n k arm l e n g t h t o c o n n e c t i n g r o d l e n g t h F r u i t stem l e n g t h Mass o f a s i n g l e f r u i t Mass o f cane p e r u n i t o f l e n g t h D i a g o n a l mass m a t r i x Sample s i z e Feed r o l l speed, r e v o l u t i o n s p e r minute P L 2 / E I a o S i m p l e c o r r e l a t i o n c o e f f i c i e n t C o e f f i c i e n t o f d e t e r m i n a t i o n Feed r o l l r a d i u s Crank arm l e n g t h R a d i u s o f cane c r o s s s e c t i o n a t s o i l s u r f a c e R a d i u s o f cane c r o s s s e c t i o n a t p o i n t o f l o a d a p p l i c a t i o n Minimum s i g n i f i c a n t v a l u e o f r f o r P < 0.01 Minimum s i g n i f i c a n t v a l u e o f r f o r P < 0.05 Base m o t i o n d i s p l a c e m e n t Base m o t i o n v e l o c i t y Base m o t i o n a c c e l e r a t i o n - xx -Base m o t i o n a m p l i t u d e Time, seconds H e i g h t above s o i l s u r f a c e a t w h i c h cane d e f l e c t i o n i s measured D i s t a n c e from t h e c e n t e r o f t h e f r u i t row, o u t w a r d , f e e t D i s t a n c e above ground, f e e t H o r i z o n t a l cane d e f l e c t i o n a t h e i g h t , x, above s o i l s u r f a c e . H o r i z o n t a l d i s t a n c e ( i n c h e s ) b e h i n d t h e f r o n t o f t h e f e e d r o l l s a t w h i c h cane c o n t a c t o c c u r s A n g l e between f r u i t stem and i n t e r m e d i a t e p l a n t stem ( f i g u r e 21) L e v e l o f s i g n i f i c a n c e Tangent modulus A n g l e o f i n c l i n a t i o n o f f e e d r o l l s Mean o f a sample o f independent o b s e r v a t i o n s Mass d e n s i t y o f f l u i d Mass d e n s i t y o f f r u i t S t a n d a r d d e v i a t i o n o f a sample A n g l e Modulus Base m o t i o n f r e q u e n c y N a t u r a l f r e q u e n c y o f f r u i t a t t a c h m e n t system A n g u l a r v e l o c i t y o f f e e d r o l l s Fundamental ( f i r s t ) n a t u r a l f r e q u e n c y o f a r a s p b e r r y cane Second n a t u r a l f r e q u e n c y o f a r a s p b e r r y cane - x x i -ACKNOWLEDGMENTS T h i s r e s e a r c h was f i n a n c e d by Canada Department o f A g r i c u l t u r e . T e s t p l o t s were l o c a t e d a t t h e S m a l l F r u i t Sub-s t a t i o n , Canada Department o f A g r i c u l t u r e , A b b o t s f o r d , B r i t i s h C o l u m b i a . The a u t h o r w i s h e s t o thank t h e f o l l o w i n g p e o p l e f o r a d v i c e and a s s i s t a n c e . Dr. J . P. Duncan and Dr. V. J . Modi, M e c h a n i c a l E n g i n e e r i n g Department; P r o f e s s o r T. L. C o u l t h a r d , P r o f e s s o r E. L. Watson and Mr. W. G l e a v e , A g r i c u l t u r a l E n g i n e e r i n g D e p a r t -ment and Dr. G. W. E a t o n , P l a n t S c i e n c e Department, a l l a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . - x x i i -INTRODUCTION •Present S t a t u s o f R a s p b e r r y P r o d u c t i o n i n B r i t i s h Columbia R a s p b e r r y p r o d u c t i o n i n Canada i s a s m a l l i n d u s t r y when compared t o o t h e r t y p e s o f f a r m i n g b u t , n e v e r t h e l e s s , i t i s an i m p o r t a n t i n d u s t r y i n t h e l o w e r m a i n l a n d o f B r i t i s h C o l u m b i a . The o u t p u t v a l u e o f r a s p b e r r i e s from B r i t i s h Columbia exceeds t h a t o f t h e o t h e r Canadian p r o v i n c e s ( 1 2 ) ^ and 95 p e r c e n t o f t h i s o u t p u t comes from t h e l o w e r F r a s e r V a l l e y . I n 1967 t h e l o w e r m a i n l a n d p r o d u c t i o n o f r a s p b e r r i e s was 16.1 m i l l i o n pounds from 2150 a c r e s under c u l t i v a t i o n r e p r e s e n t i n g an e s t i m a t e d g r o s s v a l u e t o t h e growers o f 2.3 m i l l i o n d o l l a r s ( 5 ). F a v o u r a b l e e n v i r o n m e n t a l c o n d i t i o n s and p r o x i m i t y t o markets i n Vancouver and t h e U n i t e d S t a t e s make the l o w e r F r a s e r V a l l e y e s p e c i a l l y s u i t a b l e f o r r a s p b e r r y p r o d u c t i o n . The i n d u s t r y has o b t a i n e d a r e p u t a t i o n f o r h i g h q u a l i t y f r u i t and e f f i c i e n t methods o f p r o d u c t i o n , p r o c e s s i n g and m a r k e t i n g . The need f o r h a r v e s t m e c h a n i z a t i o n R a s p b e r r y growers a r e c o n t e n d i n g w i t h i n c r e a s i n g p r o d u c -t i o n c o s t s w h i c h a r e d i s p r o p o r t i o n a t e l y h i g h when compared t o market p r i c e s and a r e f a c i n g problems i n o b t a i n i n g s u i t a b l e s e a s o n a l p i c k i n g l a b o u r . Each y e a r t h e growers f i n d i t i n c r e a s i n g l y d i f f i c u l t t o a t t r a c t competent p i c k e r s a t wage r a t e s a l l o w i n g p r o f i t a b l e r e t u r n s . A p p r o x i m a t e l y 10,000 p i c k e r s a r e r e q u i r e d i n t h e l o w e r F r a s e r V a l l e y d u r i n g t h e month l o n g h a r v e s t season. The c o s t o f o b t a i n i n g and m a i n t a i n i n g t h i s 1 Numbers i n p a r e n t h e s e s r e f e r t o r e f e r e n c e s l i s t e d i n t h e l i t e r a t u r e c i t e d . - 1 -- 2 -l a b o u r f o r c e r e p r e s e n t s up t o 80 p e r c e n t o f t h e t o t a l c o s t o f p r o d u c t i o n . U n l e s s a more r e l i a b l e and e f f i c i e n t method o f h a r v e s t i n g can be found many growers may be f o r c e d o u t o f p r o d u c -t i o n . M e c h a n i z a t i o n o f t h e h a r v e s t i n g p r o c e s s may be a s o l u t i o n t o t h e problem Scope and Purpose o f t h i s R e s e a r c h The purpose o f t h i s r e s e a r c h p r o j e c t was t o i n v e s t i g a t e t h e f e a s i b i l i t y o f m e c h a n i c a l h a r v e s t i n g o f r a s p b e r r i e s and t o d e s i g n a p r o t o t y p e h a r v e s t i n g system w h i c h would be s u i t a b l e f o r c o n d i t i o n s p r e v a i l i n g i n t h e l o w e r m a i n l a n d o f B r i t i s h C o l u m b i a . S i n c e o v e r 65 p e r c e n t o f t h e l o w e r m a i n l a n d r a s p b e r r y a c r e a g e i s p l a n t e d t o the W i l l a m e t t e v a r i e t y ( 1 2 ) , o n l y t h i s v a r i e t y was c o n s i d e r e d . Review o f P r e v i o u s Work D u r i n g t h e p a s t decade much emphasis has been p l a c e d on m e c h a n i z a t i o n o f f r u i t and v e g e t a b l e p r o d u c t i o n ( 3 ). I n t h i s p e r i o d o v e r 500 pap e r s have been w r i t t e n on d i f f e r e n t a s p e c t s o f h a r v e s t m e c h a n i z a t i o n . At p r e s e n t o v e r 200 N o r t h A m e r i c a n f i r m s ( •+ ) a r e engaged i n m a n u f a c t u r i n g s p e c i a l i z e d h a r v e s t i n g machines and h a r v e s t i n g a i d s f o r v a r i o u s c r o p s . R e s e a r c h on m e c h a n i c a l h a r v e s t i n g o f cane f r u i t s h a s , however, been l i m i t e d and l i t t l e d a t a a r e a v a i l a b l e on t h e e n g i n e e r i n g p r o p e r t i e s o f cane f r u i t s n e c e s s a r y f o r d e s i g n o f a h a r v e s t i n g system. S e v e r a l a t t e m p t s ( 6 , 15) have been made a t d e s i g n i n g machines f o r h a r v e s t i n g cane f r u i t s . T h i s work has been l a r g e l y on a t r i a l and e r r o r b a s i s , u s i n g e x i s t i n g t o o l s d e s i g n e d f o r o t h e r c r o p s , and r e s u l t s a r e no t w e l l documented. E x p e r i m e n t s on o t h e r t y p e s o f c r o p s , however, y i e l d u s e f u l i n f o r m a t i o n f o r t h e i n i t i a l p l a n n i n g s t a g e o f a cane f r u i t h a r v e s t i n g system. C a t e g o r i e s o f h a r v e s t i n g systems E x i s t i n g f r u i t and v e g e t a b l e h a r v e s t i n g systems may be c a t e g o r i z e d on t h e b a s i s o f t h e p h y s i o l o g i c a l and m o r p h o l o g i c a l c h a r a c t e r i s t i c s o f t h e p l a n t b e i n g h a r v e s t e d : ( i ) Once-over system ( r e g e n e r a t i v e p l a n t ) : The f r u i t matures u n i f o r m l y a t one t i m e d u r i n g t h e growing s e a s o n . The p l a n t s u p p o r t i n g t h e f r u i t a t t a c h m e n t s y s t e m r e g e n e r a t e s , i t s e l f each y e a r . I n h a r v e s t i n g such c r o p s t h e complete p l a n t may be removed from the s o i l t o f a c i l i t a t e p r o c e s s i n g under c o n t r o l l e d c o n d i t i o n s w i t h i n t h e h a r v e s t i n g machine. T h i s i s the e a s i e s t t y p e o f h a r v e s t i n g system t o d e s i g n s i n c e damage t o the p l a n t and f r u i t s u p p o r t system can be t o l e r a t e d . Such machines have l o n g been used f o r h a r v e s t i n g s m a l l g r a i n s and r e c e n t l y have been d e s i g n e d f o r h a r v e s t i n g d e l i c a t e f r u i t s such as tomatoes ( 2 1 , 34) and cucumbers ( 3 5 ) . ( i i ) Once-over system ( n o n - r e g e n e r a t i v e p l a n t ) : The f r u i t matures u n i f o r m l y a t one t i m e d u r i n g t h e growing s e a s o n ; however, t h e p l a n t does n o t r e g e n e r a t e i t s e l f a n n u a l l y and hence p l a n t damage must be w i t h i n a c cep-t a b l e l e v e l s n o t t o a d v e r s e l y a f f e c t y i e l d i n f o l l o w i n g y e a r s . The p l a n t may not be removed from t h e s o i l f o r p r o c e s s i n g w i t h i n t h e h a r v e s t i n g machine. Such machines have been d e s i g n e d f o r h a r v e s t i n g c h e r r i e s ( 1 6 ) , n u t s (13) and many o t h e r t r e e f r u i t s , ( i i i ) S e l e c t i v e system: The f r u i t matures n o n - u n i f o r m l y o v e r a p r o l o n g e d p e r i o d . The h a r v e s t i n g machine must be a b l e t o d i s c r i m i n a t e between mature and immature f r u i t , r emoving t h e mature f r u i t and l e a v i n g t h e immature f r u i t f o r subsequent p a s s e s o f the h a r v e s t e r . The h a r v e s t e r must not damage the f r u i t s u p p o r t system o r t h e immature f r u i t . Such machines have been d e s i g n e d t o s a t i s f a c t o r i l y h a r v e s t c o t t o n , cucumbers ( 1 8 ) , c a n t a l o u p e ( 1 7 ) , mushrooms (29) and o t h e r u n e v e n l y m a t u r i n g p l a n t s . Methods o f f r u i t r e m o v a l To a c c o m p l i s h f r u i t r e m o v a l , a f o r c e g r e a t e r t h a n the f r u i t r e t e n t i o n f o r c e must be a p p l i e d t o t h e f r u i t o r t h e f r u i t a t t a c h m e n t stem must be s e v e r e d . Four main methods o f f r u i t r e m o v a l a r e used i n e x i s t i n g h a r v e s t i n g machines: ( i ) F r u i t r e m o v a l by i m p a c t : The f r u i t i s s t r u c k , . u s u a l l y by a r o t a t i n g drum w i t h such impact t h a t t h e energy i m p a r t e d t o t h e f r u i t i s g r e a t e r t h a n t h e energy r e q u i r e d f o r f r u i t r e m o v a l . T h i s method i s s u i t e d t o tough f r u i t s and has been s u c c e s s f u l l y used f o r hundreds o f y e a r s i n g r a i n h a r v e s t i n g . A l t h o u g h i n i t i a l d e s i g n s were by t r i a l and e r r o r , Kolganov ( l g ) i n d i c a t e s t h a t such systems have r e c e n t l y been a n a l y z e d based on the p h y s i o - m e c h a n i c a l p r o p e r t i e s o f g r a i n . - 5 -( i i ) F r u i t r emoval by i n e r t i a l f o r c e : Some type o f base m o t i o n i s a p p l i e d t o the p l a n t s t a l k o r f r u i t l i m b . I f t h e i n e r t i a l f o r c e d e v e l o p e d i n t h e f r u i t due t o a c c e l e r a t i o n exceeds t h e f r u i t r e t e n t i o n f o r c e , f r u i t r e m o v a l o c c u r s . T h i s method depends upon t h e v i b r a t i n g l i m b s t r u c t u r e t o t r a n s f e r a s u f f i c i e n t p o r t i o n o f the base m o t i o n a m p l i t u d e t o the f r u i t a t t a c h m e n t system t o cause detachment. Much work has r e c e n t l y been c o n d u c t e d on the modes o f v i b r a t i o n o f v a r i o u s p l a n t s t r u c t u r e s , t h e e f f e c t s o f t y p e o f base m o t i o n and p o i n t s o f a p p l i c a t i o n o f base m o t i o n , and time-dependent p r o p e r t i e s o f l i v e p l a n t m a t e r i a l . T h i s work has p r i m a r i l y been c o n c e n t r a t e d on t r e e f r u i t s ( c o f f e e , c h e r r i e s , o l i v e s , a p p l e s , n u t s ) . P h i l l i p s e t a l . (31) r e c e n t l y s i m u l a t e d t h e r e s p o n s e o f t r e e l i m b s w i t h s e c o n d a r y branches t o f o r c e d v i b r a t i o n by use o f f i n i t e element a n a l y s i s , ( i i i ) F r u i t r e m o v a l by t e n s i l e f o r c e ( s t r i p p i n g ) : A d i r e c t t e n s i l e f o r c e g r e a t e r t h a n t h e f r u i t r e t e n t i o n f o r c e i s e x e r t e d on the f r u i t . T h i s method i s s a t i s f a c t o r i l y used i n t h e h a r v e s t i n g o f e a r c o r n and some t y p e s o f c o t t o n . R e l a t i v e m o t i o n o f t h e p l a n t w i t h r e s p e c t t o s t a t i o n a r y s t r i p p i n g b a r s o r r o t a r y s t r i p p e r s causes f r u i t r emoval i f the e x e r t e d f o r c e i s g r e a t e r t h a n t h e f r u i t r e t e n t i o n f o r c e . An e x p e r i m e n t a l a u g e r - t y p e p i c k i n g head f o r oranges (20) and a s e l e c t i v e m e c h a n i c a l c a n t a l o u p e h a r v e s t e r (17) a r e b o t h based on - 6 -t h i s p r i n c i p l e , ( i v ) F r u i t removed by s h e a r : The stem a t t a c h i n g the f r u i t t o t h e s e c o n d a r y l i m b s i s c u t w i t h a s h e a r i n g d e v i c e and t h e stem does not s e p a r a t e from t h e f r u i t a t t h e a b s c i s s i o n l a y e r . The f e a s i b i l i t y o f such a d e v i c e depends on whether s e p a r a t i o n a t the a b s c i s s i o n l a y e r i s e s s e n t i a l f o r a c c e p t a b l e f r u i t . Such d e v i c e s a r e used f o r h a r v e s t i n g o f some v e g e t a b l e s (cabbage, l e t t u c e ) but c o u l d not be used f o r r a s p b e r r i e s s i n c e r e m o v a l o f t h e c o r e f rom t h e f r u i t i s e s s e n t i a l f o r an a c c e p t a b l e grade o f f r u i t . SYSTEMATIC DESIGN PROCEDURE The d e s i g n and development p r o c e d u r e used i n t h i s s t u d y f o l l o w s t h a t d e v e l o p e d by P e r s s o n (29,30) w h i c h i s o r i e n t e d t o -ward d e s i g n and t e s t i n g o f a machine system h a n d l i n g b i o l o g i c a l m a t e r i a l s . The s t e p s i n t h i s p r o c e d u r e a r e o u t l i n e d i n f i g u r e 1. The s t u d y i s i n i t i a l l y c a r r i e d o u t a t two l e v e l s . I n t h e f i r s t s t a g e , f l o w c h a r t s ( f i g u r e 2) o f p o s s i b l e sequences o f o p e r a t i o n s between i n i t i a l and f i n a l c o n d i t i o n s a r e c o n s t r u c -t e d and t h e most a p p r o p r i a t e sequence i s s e l e c t e d on the b a s i s o f economic c o n s i d e r a t i o n s , m e c h a n i c a l l i m i t a t i o n s and o t h e r p e r t i n e n t c r i t e r i a . The second s t a g e i s a d e t a i l e d d e s c r i p t i o n o f t h e phenomena o c c u r r i n g on each t r e a t m e n t d e v i c e ( t o o l ) o u t l i n e d i n t h e f l o w c h a r t . The i n p u t c o n d i t i o n s , o u t p u t c o n d i t i o n s and o p e r a t i o n a l r e q u i r e m e n t s o f each t o o l i n t h e p r o c e s s a r e d e t e r m i n e d and p r e l i m i n a r y t o o l a n a l y s i s i s under-t a k e n . The t o o l a n a l y s e s p r o b a b l y cannot be c o m p l e t e d a t t h i s s t a g e due t o l a c k o f i n f o r m a t i o n on t h e e n g i n e e r i n g p r o p e r t i e s o f t h e m a t e r i a l b e i n g p r o c e s s e d . T h i s l e a d s t o t h e t h i r d s t e p i n t h e p r o c e d u r e w h i c h i s d e t e r m i n a t i o n o f t h e p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f t h e m a t e r i a l , n e c e s s a r y t o complete th e t h e t o o l a n a l y s e s . T h i s a l l o w s t h e m a t h e m a t i c a l models o f t h e i n d i v i d u a l t o o l s t o be c o m p l e t e d . The f i n a l s t e p s i n v o l v e d e s i g n , f a b r i c a t i o n and t e s t i n g o f t h e i n d i v i d u a l t o o l s and i n c o r p o r a t i o n o f t h e t o o l s i n t o a machine f o r w h i c h c o n t r o l mechanisms and powering systems a r e s e l e c t e d as based on m a t e r i a l p r o p e r t i e s and o p e r a t i o n a l r e q u i r e m e n t s . The - 7 -- 8 -Analysis of Process Analysis of Tools Analysis of Product Mathematical Models of Tools Design and Testing of Tools Design of Control and Power Synthesis of Machine Evaluation of Machine F i g u r e 1 S y s t e m a t i c d e s i g n p r o c e d u r e Initial Condition Final Condition Tool 1 Machine System Tool 2 Tool 3 F i g u r e 2 Alternate Machine System D e f i n i n g t he p r o c e s s Tool 11 Tool 12 Tool 13 Tool 14 machine may now be f i e l d t e s t e d t o e v a l u a t e d u r a b i l i t y and f u n c t i o n a l p e r f o r m a n c e . T h i s r e s e a r c h p r o j e c t f o l l o w e d t h e o u t l i n e d p r o c e d u r e ; however, f u n c t i o n a l and d u r a b i l i t y e v a l u a t i o n s were l i m i t e d t o t r i a l s i n one l o c a t i o n on one r a s p b e r r y v a r i e t y d u r i n g a s i n g l e h a r v e s t s e a s o n . The r e m a i n i n g s e c t i o n s o f t h i s t h e s i s f o l l o w t h e s t e p s as o u t l i n e d i n f i g u r e 1. ANALYSIS OF THE PROCESS Flow Chart The flow charts (figure 3) compare hand harvesting with a proposed mechanical harvesting system. The i n i t i a l condition f o r both flow charts i s f r u i t at various stages of maturity on the plants; the f i n a l condition i s harvested f r u i t delivered to the processor. The flow chart f o r mechanical harvesting i s broken into elementary functions (tools) each of which are analyzed i n the following sections of the thesis by the procedure outlined i n figure 1. The proposed mechanical system contains two machines, one f o r harvesting and one f o r transporting f r u i t to the processing plant. Only the harvesting machine i s considered i n t h i s study. Operational Requirements of the Harvesting Machine  I n i t i a l condition The i n i t i a l analysis of the process must include a d e s c r i p t i o n of the morphology and physiology of the plant, the c u l t u r a l practices necessary for production and the plant environment. The machine must be designed to operate within t h i s framework. Figure 4 shows a t y p i c a l row of raspberries of the Willamette v a r i e t y . The raspberry plant has a perennial root system with b i e n n i a l s t a l k s . During the f i r s t year,the growth i s nonproductive shoots,growing up to eight feet i n height. The shoots which are pruned to four feet i n the spring of the second year now become known as canes. The canes grow to approximately s i x feet and bear f r u i t during the second year. - 10 -- 11 -HAND MACHINE Orient plant Select mature fruit Pick fruit Place in container Store in container Transport container Store containers Load Transport Unload Feed Orient Select Pick Collect Convey Store Transport Load Transport Unload F i g u r e 3 Flow c h a r t s f o r hand h a r v e s t i n g and f o r the proposed mechanical h a r v e s t i n g system - 12 -At the end of the second year, the canes die and i t i s common practice to remove the dead canes from the new shoots before the t h i r d year. Although the plants are productive i n a l l succeeding years, y i e l d decreases when the plants pass a c e r t a i n stage of development. I t i s therefore necessary to destroy plants a f t e r eight to twelve years and plant new stock. Raspberries are planted i n p a r a l l e l rows spaced at ten feet. Individual plants are spaced i n the rows at a distance of two and one h a l f feet, r e s u l t i n g i n hedge rows (figure 4) once the plants mature. Due to rank growth, weak and f l e x i b l e canes, weak root systems and a heavy load imposed on the canes by f r u i t and leaves, an a r t i f i c i a l support system i s necessary to prevent the plants from lodging. Most growers use a t r e l l i s i n g system composed of wooden posts and s t e e l support wires placed within the plant rows. The harvesting machine must be designed to cope with t h i s necessary c u l t u r a l p r a c t i c e . The raspberry f r u i t (figure 5) i s an aggregate f r u i t com-posed of loosely bound drupelets attached to a central core. As the f r u i t matures, attachment to the core weakens and the f r u i t may be removed from the core. F r u i t retention force decreases as the f r u i t ripens and when the f r u i t becomes overmature i t f a l l s from the plant. Raspberries mature unevenly over a t h i r t y day period. The most productive period i s the f i r s t twenty days of the harvest season. Picking i s required at least once every three days throughout the harvest season to avoid overmature f r u i t . The harvesting machine must therefore be of the s e l e c t i v e F i g u r e 5 The r a s p b e r r y f r u i t - 14 -type with the c a p a b i l i t y of removing f r u i t of desired maturity without appreciable plant damage. Each plant must be harvested at least ten times during the harvest season. F i n a l condition An acceptable f i n a l condition or end product of the harvesting machine depends upon the avai l a b l e market f o r d i f f e r e n t grades of f r u i t . High q u a l i t y f r u i t may be marketed fresh or may be processed p r i o r to marketing. F r u i t of lower q u a l i t y must be processed as jam, canned f r u i t or frozen f r u i t to prevent d e t e r i o r a t i o n . As i s shown in Table 1, over 95 percent of the raspberry production in the lower mainland (12) i s sold f o r processing rather than f o r d i r e c t consumption. This indicates that even i f a machine i s incapable of harvesting f r u i t s u itable f o r the fresh market, i t can s t i l l serve 95 percent of the industry. The f r u i t must, however, be acceptable at the processing plant. TABLE I RASPBERRY PRODUCTION IN THE LOWER MAINLAND OF BRITISH COLUMBIA Processed as Year Fresh F r u i t (lbs) Processed F r u i t (lbs.) Percent of Total  1961 350,000 6,886,000 95 1964 300,000 13,595,000 98 1965 300,000 14,671,000 98 Economic Analysis of Raspberry Harvesting  Cost of hand picking The cost of hand picking i n 1967 was f i v e cents per pound of f r u i t while i n 1969 i t varied from seven to ten cents per - 15 -pound. These f i g u r e s r e p r e s e n t o n l y the wages p a i d t o the p i c k e r s . A d d i t i o n a l expenses are a l s o i n c u r r e d by way o f i n c e n -t i v e s t o r e t a i n e x p e r i e n c e d p i c k e r s . For example, many growers p r o v i d e d a i l y t r a n s p o r t a t i o n to and from the urban c e n t e r (Vancouver) o r a p p r o p r i a t e l i v i n g q u a r t e r s on the farm. Y i e l d s and market p r i c e In the p e r i o d from 1962 t o 1967 average annual y i e l d s o f r a s p b e r r i e s marketed i n the lower mainland v a r i e d from 6450 t o 8660 pounds per acre (12). In t r i a l s on the e f f i c i e n c y o f hand p i c k i n g ( 6) i t was shown t h a t o n l y 80 p e r c e n t o f the f r u i t i s a c t u a l l y h a r v e s t e d . T h i s i n d i c a t e s t h a t the p o t e n t i a l average annual y i e l d may be o v e r 10,000 pounds per a c r e . Large f l u c t u a t i o n s o c c u r i n the s e l l i n g p r i c e of r a s p -b e r r i e s depending upon market c o n d i t i o n s . For example, i n 1967 the p r i c e of f r u i t s o l d to p r o c e s s i n g p l a n t s was t h i r t e e n cents per pound w h i l e i n 1969 i t ranged from twenty-seven t o t h i r t y c ents p e r pound. Est i m a t e d c o s t o f mechanical h a r v e s t i n g S i n c e the t o t a l c o s t i n c u r r e d by u s i n g a mechanical h a r v e s t i n g system r e s u l t s from overhead c o s t and o p e r a t i n g c o s t , both these c o s t s were es t i m a t e d i n o r d e r to determine d e s i g n l i m i t s f o r machine p r i c e and machine c a p a c i t y . Machine l i f e was e s t i m a t e d as t e n y e a r s , with d e p r e c i a t i o n computed on a s t r a i g h t l i n e b a s i s over t h i s p e r i o d . The t o t a l r e p a i r c o s t f o r the t e n y e a r p e r i o d was e s t i m a t e d as t h i r t y p e r c e n t o f the purchase p r i c e w h i l e charges f o r i n t e r e s t on investment f o r the same p e r i o d were taken as s i x p e r c e n t of the average investment. Annual i n s u r a n c e - 16 -costs were estimated as one-half percent of the machine purchase p r i c e . The r e s u l t i n g annual overhead cost i n d o l l a r s was 0 f = 0.165 A [1] where A = machine purchase p r i c e , d o l l a r s . Estimating the cost of f u e l and o i l at $0.50 per hour and the cost of labour at $1.50 per hour, the r e s u l t i n g hourly operating cost in d o l l a r s was 0 = 0.50 + 1.50 B [2] o where B = the number of men required to operate the machine. Based on these approximations, the cost of mechanical harvesting was determined over a range of machine pri c e s , machine cap a c i t i e s , picking e f f i c i e n c i e s and f r u i t y i e l d s . Table II presents the r e s u l t s of t h i s analysis f o r the upper and lower l i m i t s of the ranges considered. Since t h i s table i s based on a labour force of two men operating the machine f o r six hours per day f o r a t h i r t y day period, the annual operating cost i s $6 30 fo r any of the combinations presented. Annual overhead costs vary from $250 f o r the $1,500 machine to $1900 f o r the $11,500 machine. The machine capacities presented i n table II are f o r a single row machine operating with 100 percent f i e l d e f f i c i e n c y i n f r u i t rows spaced at ten feet. On t h i s basis, a machine operating at one-quarter mile/hour can harvest f i v e acres per season, while one operating at three miles/hour can harvest si x t y acres. TABLE I I - 17 -ESTIMATED COST OF MECHANICAL HARVESTING 1 Machine Forward C a p a c i t y P i c k i n g F r u i t P i c k i n g Purchase Speed (acre/hour) E f f i c i e n c y Y i e l d Cost P r i c e (mile/hour) (per c e n t ) ( l b . / a c r e ) ( c e n t s / l b . ) ( d o l l a r s ) 1,500 0.25 0.3 HO 6,000 7.4 1,500 0.25 0.3 40 10,000 4.5 1,500 0.25 0.3 100 6,000 3.0 1,500 0.25 0.3 100 10,000 1.8 1,500 3.00 3.3 40 6,000 0.6 1,500 3.00 3.3 40 10,000 0.4 1,500 3.00 3.3 100 6,000 0.2 1, 500 3.00 3.3 100 10,000 0.1 11,500 0.25 0.3 40 6,000 21.5 11,500 0.25 0.3 40 10,000 12.9 11,500 0.25 0.3 100 6,000 8.6 11,500 0.25 0.3 100 10 ,000 5.2 11,500 3.00 3.3 40 6,000 1.8 11,500 3.00 3.3 40 10,000 1.1 11,500 3.00 3.3 100 6,000 0.7 11,500 3.00 3.3 100 10,000 0.4 1 The p i c k i n g c o s t s i n t h i s t a b l e are based on overhead and o p e r a t i n g c o s t s as determined by equations [1] and [ 2 ] . I t i s assumed t h a t two men are r e q u i r e d t o operate the machine. The r e s u l t s are f o r a s i n g l e - r o w machine o p e r a t i n g a t 100 pe r c e n t f i e l d e f f i c i e n c y , s i x hours each day f o r a t h i r t y day p e r i o d , w i t h each p l a n t being p i c k e d once every t h r e e days. - 18 -The break-even p o i n t • The machine p i c k i n g c o s t s as presented i n t a b l e I I r e p r e s e n t the machine c o s t p e r pound of h a r v e s t e d f r u i t f o r each combination o f machine f a c t o r s . These f i g u r e s cannot be d i r e c t l y compared to the per-pound-cost p a i d t o hand p i c k e r s s i n c e hand p i c k i n g e f f i c i e n c y and f r u i t market p r i c e must a l s o be c o n s i d e r e d . Machine p i c k i n g c o s t s were compared t o hand p i c k i n g c o s t s by use o f a break-even p o i n t ( f i g u r e s 6 and 7). The break-even p o i n t was d e f i n e d as the necessary machine p i c k -i n g e f f i c i e n c y ( p ercent of gross f r u i t y i e l d ) which must be achieved t o o b t a i n the same gross income from machine h a r v e s t i n g as i s p r e s e n t l y o b t a i n e d from hand h a r v e s t i n g . For t h i s comparison, i t was assumed t h a t the o n l y d i f f e r e n c e i n c o s t f o r the two h a r v e s t i n g methods o c c u r r e d d u r i n g the a c t u a l h a r v e s t o p e r a t i o n . Other p r o d u c t i o n c o s t s were assumed t o be c o n s t a n t . The c o s t o f hand p i c k i n g was c o n s i d e r e d t o be t e n cents p e r pound o f h a r v e s t e d f r u i t w h i l e hand p i c k i n g e f f i c i e n c y was e s t i m a t e d as 80 p e r c e n t o f the gross f r u i t y i e l d . I t was f u r t h e r assumed t h a t machine h a r v e s t e d f r u i t had the same market va l u e as hand h a r v e s t e d f r u i t . F i g u r e 6 shows the e f f e c t o f machine purchase p r i c e on the break-even p o i n t f o r a machine c a p a c i t y o f one acre per hour. At t h i s machine c a p a c i t y , break-even p o i n t i s not s t r o n g l y depen-dent upon purchase p r i c e f o r the range o f f r u i t y i e l d s expected i n the lower mainland. Break-even p o i n t f o r f r u i t market p r i c e of t h i r t y c e n t s per pound i s approximately 55 p e r c e n t , w h i l e f o r a market p r i c e o f 20 cen t s p e r pound i t i s approximately 4 2 _ 19 -. f r 0 „ market price - 20 -** Machine capacity , acre/hour * Fruit market price 3.0  L_ L £ _ 800 100 Fruit Yield (pound/acre) Figure 7 The e f f e c t of machine capacity on the break-even point fo r a machine purchase price of $3,500. - 21 -p e r c e n t . As i s shown i n f i g u r e 7, bre a k - e v e n p o i n t i s s t r o n g l y dependent upon machine c a p a c i t y f o r c a p a c i t i e s below one a c r e p e r h o u r . F o r c a p a c i t i e s above one a c r e p e r hour t h e br e a k - e v e n p o i n t i s n e a r l y c o n s t a n t f o r t h e range o f y i e l d s e x p e c t e d i n the l o w e r m a i n l a n d . F i g u r e 7 i s based on a machine p u r c h a s e p r i c e o f $3,500; however, n e a r l y s i m i l a r r e s u l t s can be e x p e c t e d f o r a l l machines w i t h i n t h e c o s t range p r e s e n t e d i n f i g u r e 6. Summary o f Machine Requirements Based on p l a n t c h a r a c t e r i s t i c s and economic c o n s i d e r a t i o n s , as o u t l i n e d above, t h e f o l l o w i n g f a c t o r s s h o u l d be c o n s i d e r e d i n d e s i g n o f a h a r v e s t i n g system: ( i ) I n d i v i d u a l p l a n t s must be p i c k e d a t l e a s t t e n t i m e s d u r i n g t h e h a r v e s t s e a s o n . P l a n t damage must be c o n t r o l l e d so t h a t t h e c u m u l a t i v e damage f o r t h e whole h a r v e s t season i s w i t h i n a c c e p t a b l e l i m i t s , ( i i ) F r u i t t r e l l i s i n g systems a r e n e c e s s a r y i n t h e l o w e r m a i n l a n d . The machine must be d e s i g n e d t o o p e r a t e w i t h i n the t r e l l i s i n g framework, ( i i i ) A machine w h i c h h a r v e s t s f r u i t s u i t a b l e o n l y f o r p r o c e s s i n g w i l l s e r v e o v e r 95 p e r c e n t o f t h e l o w e r m a i n l a n d r a s p b e r r y i n d u s t r y , ( i v ) Machine c a p a c i t y s h o u l d be a t l e a s t one a c r e p e r hour. T h i s r e p r e s e n t s a f o r w a r d speed o f a t l e a s t one m i l e p e r hour. A machine w i t h a c a p a c i t y o f one a c r e p e r hour can h a r v e s t a p p r o x i m a t e l y twenty a c r e s p e r se a s o n , ( v ) F o r t h e range o f y i e l d s e x p e c t e d i n t h e l o w e r - 22 -mainland and f o r machine c a p a c i t i e s above one acre per hour, the break-even p o i n t i s not s t r o n g l y dependent upon machine purchase p r i c e w i t h i n the p r i c e range of $1,500 t o $11,500. I t must be noted t h a t f o r low f r u i t y i e l d s and low machine c a p a c i t i e s , break-even p o i n t i s s t r o n g l y dependent upon machine purchase p r i c e , ( v i ) Although a machine w i t h gross s e a s o n a l p i c k i n g e f f i c i e n c y o f 40 to 60 p e r c e n t may be e c o n o m i c a l l y f e a s i b l e , much h i g h e r p r o f i t s than are p r e s e n t l y o b t a i n e d are p o s s i b l e w i t h a machine of h i g h p i c k i n g e f f i c i e n c y . TOOL ANALYSES M e c h a n i z a t i o n o f t h e P r o c e s s The i n d i v i d u a l components o f t h e f l o w c h a r t f o r mechani-c a l h a r v e s t i n g ( f i g u r e 3) r e p r e s e n t t h e b a s i c p r o c e s s f u n c t i o n s . One o r more t o o l s may be r e q u i r e d t o p e r f o r m a g i v e n f u n c t i o n . C o n v e r s e l y , a s i n g l e t o o l may have more t h a n one f u n c t i o n . I n t h e f o l l o w i n g s e c t i o n o f t h e d e s i g n p r o c e d u r e , t h e t o o l s s e l e c t e d t o mechanize the p r o c e s s a r e o u t l i n e d ; o p e r a t i o n a l r e q u i r e m e n t s , i n p u t c o n d i t i o n s and o u t p u t c o n d i t i o n s f o r each t o o l a r e s t a t e d ; p r e l i m i n a r y t o o l a n a l y s i s i s c o n d u c t e d and t h e unknown p l a n t and f r u i t p r o p e r t i e s , n e c e s s a r y f o r t o o l d e s i g n , a r e l i s t e d . T o o l f o r F e e d i n g and Cane O r i e n t a t i o n . F u n c t i o n T h i s t o o l mechanizes t h e f i r s t two b a s i c p r o c e s s f u n c t i o n s dn t h e f l o w c h a r t . I t s r e q u i r e m e n t s a r e as f o l l o w s : I n p u t c o n d i t i o n . - Rows o f r a s p b e r r y p l a n t s c o n t a i n e d w i t h i n a t r e l l i s i n g s u p p o r t s t r u c t u r e . Output c o n d i t i o n . - P l a n t s d e l i v e r e d t o t h e s e l e c t i o n t o o l w i t h t h e canes s u i t a b l y s u p p o r t e d and w i t h t h e f r u i t p o s i t i o n e d t o a l l o w t h e s e l e c t i o n t o o l t o f u n c t i o n . O p e r a t i o n a l r e q u i r e m e n t s . - C u m u l a t i v e damage t o the c a n e s , s h o o t s , f o l i a g e and f r u i t i n g p o r t i o n s must be w i t h i n a c c e p t a b l e l i m i t s a f t e r a t l e a s t t e n s u c c e s s i v e p a s s e s o f t h e t o o l , spaced a t t h r e e day i n t e r v a l s . The t o o l s h o u l d be c a p a b l e o f f u n c t i o n i n g w i t h i n a range o f f o r w a r d speeds above one m i l e p e r hour and i t s d e s i g n must be c o m p a t i b l e w i t h a s u i t a b l e t r e l l i s i n g system. - 23 -- 24 -Proposed design The s e l e c t i o n t o o l must scan a l l f r u i t bearing portions of the plant. Since f r u i t i s d i s t r i b u t e d throughout most of the plant, the primary requirement of the feeding and cane o r i e n t a t i o n t o o l i s to concentrate the f r u i t i n g portions within fixed l i m i t s , thereby determining the size of the s e l e c t i o n t o o l and i t s p o s i t i o n i n g on the machine. A proposed t o o l f o r feeding and cane o r i e n t a t i o n which meets th i s requirement i s i l l u s t r a t e d i n figure 8. Inclined, aggressive r o l l s , r o t a t i n g i n opposite d i r e c t i o n s , are positioned on each side of the raspberry row. As the machine passes down the row, the r o l l s gather and compress the plant. R o l l v e l o c i t y i s synchronized with forward speed i n order to hold the canes upright as the r o l l s pass the plants. side view Y Y rear v i e w Figure 8 Tool f o r feeding and cane o r i e n t a t i o n . - 25 -F r o n t and r e a r r o l l s p a c i n g i s a d j u s t a b l e t o accommodate v a r i a -t i o n i n p l a n t d i m e n s i o n s , t o o b t a i n t h e d e s i r e d c o n c e n t r a t i o n between t h e r o l l s and t o p e r m i t t h e r o l l s t o pass t h e t r e l l i s i n g s u p p o r t p o s t s . A n a l y s i s F o r s y n c h r o n i z a t i o n o f r o l l v e l o c i t y w i t h speed o f f o r w a r d t r a v e l , t h e h o r i z o n t a l component o f t h e t a n g e n t i a l r o l l v e l o c i t y must be t h e same magnitude as t h e f o r w a r d v e l o c i t y but o f o p p o s i t e s i g n . Assuming t h a t no s l i p p i n g o c c u r s between t h e f e e d r o l l s and canes and u s i n g c o n s i s t e n t u n i t s o f measurement, the n e c e s s a r y a n g u l a r v e l o c i t y o f t h e f e e d r o l l s ( f i g u r e 8) i s w- = -V / r . s i n 9 [3] f g f where V = f o r w a r d v e l o c i t y o f h a r v e s t i n g machine r^. = f e e d r o l l r a d i u s 9 = f e e d r o l l i n c l i n a t i o n The r e a c t i o n f o r c e between t h e canes and t h e f e e d r o l l s may be e s t i m a t e d based on t h e f l e x u r a l c h a r a c t e r i s t i c s o f the canes. Assuming a cane t o be e l a s t i c , c o n s i d e r i n g i t as a v e r t i c a l t a p e r e d c a n t i l e v e r beam w i t h c i r c u l a r c r o s s s e c t i o n ( f i g u r e 9) and a p p l y i n g s i m p l e beam t h e o r y w i t h a c o n s i s t e n t s e t o f u n i t s , t h e e q u a t i o n o f f l e x u r e i s ^ s P a CL - x) m d x 2 EI [1 - £ (1 - c ) ] 4 O L where E = e l a s t i c modulus o f cane m a t e r i a l I = moment o f i n e r t i a o f cane c r o s s s e c t i o n a t ° s o i l s u r f a c e P a = h o r i z o n t a l l o a d a p p l i e d t o cane a t d i s t a n c e , L, above s o i l s u r f a c e c = cane t a p e r _ r a d i u s o f cane c r o s s s e c t i o n a t l o a d p o i n t r a d i u s o f cane c r o s s s e c t i o n a t s o i l s u r f a c e y = h o r i z o n t a l cane d e f l e c t i o n a t d i s t a n c e , x, above s o i l s u r f a c e I n t e g r a t i n g e q u a t i o n [ 4 ] and a p p l y i n g boundary c o n d i t i o n s s a t i s f y i n g a c a n t i l e v e r beam, t h e r e s u l t i n g e x p r e s s i o n i s 3 \ E I ( l - c ) 3 / x ( l - c ) 2 [ l ~ ( l - c ) ] 6 [ l - f ( l - c ) ] 2 c x ( l - c ) 2L + £ - I C5] 3L 6 2 where the n o m e n c l a t u r e i s as p r e v i o u s l y d e f i n e d . The t o t a l r e a c t i o n f o r c e between t h e f e e d r o l l s and the compressed canes can be e s t i m a t e d by s u c c e s s i v e l y a p p l y i n g e q u a t i o n [ 5 ] t o a l l t h e canes i n c o n t a c t w i t h t h e r o l l s a t one i n s t a n t . Cane d e f l e c t i o n , p o i n t o f l o a d a p p l i c a t i o n and cane t a p e r d i f f e r f o r each cane due t o the i n c l i n a t i o n o f the f e e d " r o l l s . Pa" c = riAo 7777777] Tt ro r F i g u r e 9 A r a s p b e r r y cane i d e a l i z e d as a t a p e r e d v e r t i c a l c a n t i l e v e r beam o f c i r c u l a r c r o s s s e c t i o n . - 27 -Unknowns The f o l l o w i n g p l a n t c h a r a c t e r i s t i c s must be d e t e r m i n e d b e f o r e a n a l y s i s o f the f e e d i n g and cane o r i e n t a t i o n t o o l can be c o m p l e t e d : ( i ) Mean p l a n t d i m e n s i o n s , ( i i ) F r u i t d i s t r i b u t i o n on c a n e s, ( i i i ) Mean cane d i m e n s i o n s and cane d e n s i t y p e r p l a n t , ( i v ) E l a s t i c modulus o f cane m a t e r i a l , (v) S u s c e p t i b i l i t y o f p l a n t s t o m e c h a n i c a l damage. T o o l f o r S e l e c t i v e H a r v e s t i n g F u n c t i o n T h i s t o o l mechanizes t h e f r u i t s e l e c t i o n f u n c t i o n and t h e f r u i t p i c k i n g f u n c t i o n on t h e f l o w c h a r t and has t h e f o l l o w i n g r e q u i r e m e n t s : I n p u t C o n d i t i o n . - P l a n t s h e l d by t h e f e e d r o l l s . Output C o n d i t i o n . - Mature f r u i t o f a c c e p t a b l e q u a l i t y . O p e r a t i o n a l R e q u i r e m e n t s . - T h i s t o o l must s e l e c t and p i c k mature f r u i t w h i l e l e a v i n g immature f r u i t on t h e p l a n t . The r a t e o f s e l e c t i o n and p i c k i n g must be h i g h enough t o a l l o w machine speeds o v e r one m i l e p e r h our. The h a r v e s t e d f r u i t must be o f a c c e p t a b l e q u a l i t y w h i l e damage t o immature f r u i t , canes and f o l i a g e must be w i t h i n a c c e p t a b l e l i m i t s . A l t h o u g h t h e p i c k i n g t o o l s h o u l d remove a l l o f t h e mature f r u i t a t each h a r v e s t d a t e , economic a n a l y s i s i n d i c a t e s t h a t h a r v e s t i n g e f f i c i e n c i e s as low as f o r t y p e r c e n t may be a c c e p t a b l e . Proposed d e s i g n The t o o l f o r s e l e c t i v e h a r v e s t i n g must scan th e p l a n t s i n the r e g i o n d i r e c t l y above the feed r o l l s , s e l e c t i n g and r e -moving the mature f r u i t as the p l a n t s are d e l i v e r e d by the feed r o l l s . Since f r u i t q u a l i t y , f r u i t c o l o r and f r u i t r e t e n t i o n f o r c e are a l l a f u n c t i o n of f r u i t m a t u r i t y i t i s assumed t h a t the d e s i r e d q u a l i t y o f h a r v e s t e d f r u i t may be o b t a i n e d by s e l e c t i n g f r u i t w i t h i n c e r t a i n l i m i t s o f c o l o r or f r u i t r e t e n t i o n f o r c e . Although s e l e c t i v e cane 777 •Pa(t) V7777 F i g u r e 10 T o o l f o r s e l e c t i v e h a r v e s t i n g . hand p i c k i n g i s based p r i m a r i l y on f r u i t c o l o r , the d e n s i t y of f o l i a g e makes mechanical c o l o r s e n s i n g d i f f i c u l t . S e l e c t i o n based on f r u i t r e t e n t i o n f o r c e i s r e a d i l y mechanized and has the added advantage of combining the s e l e c t i o n f u n c t i o n and p i c k i n g f u n c t i o n i n t o one t o o l . F i g u r e 10 i l l u s t r a t e s the proposed d e s i g n o f a s e l e c t i v e h a r v e s t i n g t o o l which operates on the b a s i s o f f r u i t r e t e n t i o n f o r c e . A v i b r a t o r y motion i s imparted to the p l a n t s i n the r e g i o n d i r e c t l y above the feed r o l l s . By c o n t r o l l i n g the frequency and amplitude o f the a p p l i e d base motion, a d e s i r e d l e v e l o f i n e r t i a l f o r c e i s developed i n the f r u i t . F r u i t removal occurs i f the developed i n e r t i a l f o r c e exceeds the f r u i t r e t e n t i o n f o r c e . - 29 -A n a l y s i s The f o r c e a p p l i e d to the f r u i t support system must be w i t h i n the f o l l o w i n g l i m i t s : m a d where F = upper l i m i t o f f r u i t r e t e n t i o n f o r c e o f mature f r u i t F = a p p l i e d f o r c e F = f o r c e r e q u i r e d to remove immature f r u i t o r to damage the f r u i t support system. Using Newton's second p r i n c i p l e , w i t h a c o n s i s t e n t s e t o f u n i t s , the i n e r t i a l f o r c e developed i n the f r u i t as the r e s u l t o f a p p l i e d base motion i s F _ W a f [7] a " g where a^. = a c c e l e r a t i o n o f the f r u i t W = f r u i t weight g = a c c e l e r a t i o n due to g r a v i t y S i n c e f o r f r u i t removal the i n e r t i a l f o r c e must equal f r u i t r e t e n t i o n f o r c e , the necessary a c c e l e r a t i o n i s a f = (I) g [8] where F/W = f r u i t r e t e n t i o n f o r c e / f r u i t weight A p p l y i n g simple harmonic base motion to the canes above the feed r o l l s and assuming t h a t a l l the base motion displacement i s imparted t o the f r u i t , the displacement, v e l o c i t y and a c c e l e r a t i o n o f the f r u i t a r e , r e s p e c t i v e l y s = s s i n (w,t) [9] o D s = s w.cos (w, t ) [10] O D D s = _S q w b 2 s i n ( u ) b t ) [11] - 30 -where Sq = base m o t i o n a m p l i t u d e t = t i m e , seconds = base m o t i o n f r e q u e n c y , r a d i a n s / s e c o n d As can be seen from c o m p a r i s o n o f e q u a t i o n s [ 9 ] , [ 1 0 ] and [ 1 1 ] t h e a c c e l e r a t i o n i s maximum when the base m o t i o n i s a t maximum d i s p l a c e m e n t and z e r o v e l o c i t y . I f t h e base m o t i o n i s a p p l i e d t o the canes so t h a t no r e l a t i v e d i s p l a c e m e n t can o c c u r between the base m o t i o n mechanism and t h e ca n e s , t h e maximum 2 a c c e l e r a t i o n o f t h e f r u i t r e l a t i v e t o t h e canes i s s <u. . T h i s o b i s t r u e o n l y f o r f r u i t c l o s e t o t h e f e e d r o l l s . Cane d i s p l a c e -ment a t p o i n t s d i s t a n t f r om t h e p o i n t o f base m o t i o n a p p l i c a t i o n w i l l be d i m i n i s h e d due t o i n t e r n a l and e x t e r n a l damping and t h e f l e x u r a l s t r e n g t h o f t h e canes. C o n v e r s e l y , a m p l i t u d e m a g n i f i c a -t i o n can be e x p e c t e d i f a p p l i e d f r e q u e n c y i s a t t h e r e s o n a n t f r e q u e n c y o f t h e canes and base m o t i o n i s a p p l i e d t o an a n t i n o d e . Unknowns The unknown p h y s i c a l and m e c h a n i c a l p r o p e r t i e s n e c e s s a r y f o r d e s i g n o f t h e s e l e c t i v e h a r v e s t i n g t o o l a r e : ( i ) The s t a t i s t i c a l d i s t r i b u t i o n o f f r u i t w e i g h t ( i i ) The s t a t i s t i c a l d i s t r i b u t i o n o f f r u i t r e t e n t i o n f o r c e . ( i i i ) The s t a t i s t i c a l d i s t r i b u t i o n o f F/W r a t i o ( i v ) The modes o f v i b r a t i o n and n a t u r a l f r e q u e n c i e s o f bo t h t h e canes and t h e f r u i t a t t a c h m e n t system (v) S u s c e p t i b i l i t y o f t h e f r u i t a ttachment system t o m e c h a n i c a l damage ( v i ) The r e l a t i o n s h i p s among f r u i t c o l o r , f r u i t r e t e n t i o n f o r c e , f r u i t m a t u r i t y and f r u i t q u a l i t y - 31 -( v i i ) A b a s i c d e f i n i t i o n o f f r u i t q u a l i t y i s r e q u i r e d . , P r e s e n t s t a n d a r d s f o r f r e s h r a s p b e r r i e s ( 8 ) as s e t by t h e Canadian Government S p e c i f i c a t i o n s Board a r e : " R a s p b e r r i e s s h a l l be f r e s h l y p i c k e d , c l e a n , sound, mature, r i p e but f i r m , o f good c o l o r , and f r e e from mold, mildew o r o t h e r decay, c o r e s , stems, l e a v e s , d i r t o r o t h e r f o r e i g n m a t e r i a l , g r e e n o r d r i e d f r u i t , and s h a l l be whole and f a i r l y u n i f o r m i n s i z e and not l e s s t h a n o n e - h a l f i n c h i n d i a m e t e r " . These s t a n d a r d s do not a d e q u a t e l y d e f i n e f r u i t q u a l i t y . T o o l f o r F r u i t C o l l e c t i o n and Conveying F u n c t i o n T h i s t o o l w hich mechanizes t h e c o l l e c t i o n and c o n v e y i n g f u n c t i o n s on the f l o w c h a r t has t h e f o l l o w i n g r e q u i r e m e n t s : I n p u t C o n d i t i o n . - Mature f r u i t w h i c h has been removed from t h e p l a n t by t h e s e l e c t i v e h a r v e s t i n g t o o l . Output C o n d i t i o n . - F r u i t d e l i v e r e d t o t h e f r u i t s t o r a g e t o o l . ' O p e r a t i o n a l R e q u i r e m e n t s . - The c o l l e c t i o n and c o n v e y i n g t o o l must c o l l e c t f r u i t as i t f a l l s from th e s e l e c t i v e h a r v e s t i n g t o o l and convey i t t o the s t o r a g e t o o l w h i l e m a i n t a i n i n g f r u i t damage a t an a c c e p t a b l e l e v e l . Conveyor c a p a c i t y must be g r e a t enough t o accommodate f o r w a r d speeds above one m i l e p e r hour i n c r o p s y i e l d i n g up t o 10,000 pounds p e r a c r e . P roposed d e s i g n A b e l t c o n v e y o r o r o s c i l l a t i n g c o n v e y o r , o f s u f f i c i e n t w i d t h and l e n g t h t o c o l l e c t a l l t h e f r u i t f a l l i n g from t h e s e l e c t i v e h a r v e s t i n g t o o l , i s p l a c e d a d j a c e n t t o each f e e d r o l l . The f a l l i n g f r u i t , w h i c h i s i n t e r c e p t e d by t h e c o n v e y o r , i s d e l i v e r e d t o t h e f r u i t s t o r a g e t o o l . The impact v e l o c i t y o f - 32 -the f r u i t s t r i k i n g t h e c o n v e y o r , t h e d e p t h o f f r u i t on t h e con-v e y o r , t h e c o n v e y o r m a t e r i a l and the f r u i t v e l o c i t y as i t l e a v e s t h e c o n v e y o r must be based on t h e b r u i s i n g c h a r a c t e r i s t i c s o f the r a s p b e r r y f r u i t . A n a l y s i s The impact v e l o c i t y o f the f r u i t s t r i k i n g t h e conv e y o r s u r f a c e and o f t h e f r u i t e n t e r i n g t h e s t o r a g e t o o l must be l i m i t e d t o p r e v e n t f r u i t b r u i s i n g . The maximum a l l o w a b l e f r e e f a l l h e i g h t i s h = e./W [ 1 2 ] a b where e, = t h e maximum impact energy w h i c h t h e f r u i t can a b s o r b w i t h o u t b r u i s i n g W = t h e w e i g h t o f a s i n g l e f r u i t S i m i l a r l y , t h e maximum a l l o w a b l e i m p act v e l o c i t y i s V = (2 e K / m ) 1 / 2 [ 1 3 ] a D where m = t h e mass o f a s i n g l e f r u i t I f f r u i t f r e e f a l l h e i g h t i s g r e a t e r t h a n h t h e n p r o v i s i o n must be made t o l i m i t t h e impact v e l o c i t y t o V . T h i s cL c o u l d be done by a l l o w i n g the f r u i t t o f a l l i n a more v i s c o u s f l u i d t h a n a i r o r by s u p p l y i n g an a i r c u s h i o n i n g system. As g i v e n by Mohsenin ( 2 5 ) , t h e d r a g f o r c e on f r e e l y f a l l i n g f r u i t may be e s t i m a t e d as F = C, A p . V 2/2 [14] r d p- f where A = t h e p r o j e c t e d f r u i t a r e a normal t o the P d i r e c t i o n o f m o t i o n C d = t h e o v e r a l l d r a g c o e f f i c i e n t , u n i t l e s s V = t h e v e l o c i t y o f t h e f r u i t r e l a t i v e t o t h e s u r r o u n d i n g f l u i d - 33 -p = the mass d e n s i t y o f the su r r o u n d i n g f l u i d In t h i s r e l a t i o n s h i p , the o v e r a l l drag c o e f f i c i e n t i s d e f i n e d as C d = 2 W ( »p - P f ' [15] V t 2 A p p p " f where V = t e r m i n a l v e l o c i t y o f the f a l l i n g f r u i t W = the weight o f a s i n g l e f r u i t P = the mass d e n s i t y o f the f r u i t P Assuming t h a t the r a s p b e r r y f r u i t i s s p h e r i c a l (C = 0.5) and n o t i n g t h a t a t t e r m i n a l v e l o c i t y the drag f o r c e equals the f r u i t weight, the estimated t e r m i n a l v e l o c i t y o f r a s p b e r r y f r u i t i s V t = (W( pp - p f ) / A p ) 1 / 2 [16] The necessary upward a i r v e l o c i t y s u p p l i e d by the a i r c u s h i o n i n g system then i s V = V. - V [17] e t a where V and V. are as d e f i n e d i n equations [13] and [16] r e s p e c t i v e l y . Conveyor dimensions must be based on f r u i t d i s t r i b u t i o n on the canes and on the maximum expected f r u i t y i e l d f o r a s p e c i f i c h a r v e s t date. Unknowns The f o l l o w i n g f r u i t p r o p e r t i e s are unknown: ( i ) The aerodynamic p r o p e r t i e s o f the r a s p b e r r y f r u i t ( i i ) The s t a t i s t i c a l d i s t r i b u t i o n s o f f r u i t weight, f r u i t d e n s i t y and p r o j e c t e d a r e a o f the f r u i t ( i i i ) The b r u i s i n g c h a r a c t e r i s t i c s o f r a s p b e r r y f r u i t ( i v ) The q u a n t i t y and d i s t r i b u t i o n o f f r u i t on t h e canes a t t h e peak o f the h a r v e s t season. T o o l f o r F r u i t S t o r a g e F u n c t i o n T h i s t o o l s t o r e s t h e h a r v e s t e d f r u i t on the machine t o p e r m i t c o n t i n u o u s o p e r a t i o n o f t h e h a r v e s t e r f o r a c e r t a i n l e n g t h o f t i m e . I t s r e q u i r e m e n t s a r e : In p u t C o n d i t i o n . - F r u i t l e a v i n g t h e c o n v e y i n g t o o l . Output C o n d i t i o n . - F r u i t c o n t a i n e r s f i l l e d t o a s u i t a b l e d e p t h . O p e r a t i o n a l R e q u i r e m e n t s . - F r u i t c o n t a i n e r s s h o u l d be e v e n l y f i l l e d . F i l l i n g d e p th must be l i m i t e d by t h e r e s i s t a n c e t o b r u i s i n g o f t h e l o w e r f r u i t l a y e r and by t h e e f f e c t o f i n - t r a n s i t v i b r a t i o n s on f r u i t damage. The t o o l must have s u f f i c i e n t s t o r a g e c a p a c i t y t o a l l o w c o n t i n u o u s o p e r a t i o n f o r an a c c e p t a b l e l e n g t h o f t i m e . Down t i m e , f o r r e moving a s e t o f f u l l c o n t a i n e r s and p l a c i n g a s e t o f empty c o n t a i n e r s on t h e machine, s h o u l d be m i n i m a l . Proposed D e s i g n I n d i v i d u a l f r u i t c o n t a i n e r s o s c i l l a t e s l o w l y beneath t h e co n v e y o r d i s c h a r g e t o p e r m i t u n i f o r m f i l l i n g . When one c o n t a i n e r i s f i l l e d t o a s u i t a b l e d e p t h , i t i s removed from beneath t h e conveyo r d i s c h a r g e and r e p l a c e d w i t h an empty c o n t a i n e r . S t o r a g e space t o accommodate a s u i t a b l e number o f f r u i t c o n t a i n e r s i s p r o v i d e d on the machine. A n a l y s i s The maximum r a t e o f f r u i t e n t e r i n g t h e s t o r a g e t o o l w i l l be d e t e r m i n e d i n the f i n a l a n a l y s i s o f t h e f r u i t c o n v e y i n g t o o l . The n e c e s s a r y s t o r a g e c a p a c i t y w i l l be d e t e r m i n e d by t h e r a t e o f f r u i t e n t e r i n g t h e s t o r a g e t o o l and by t h e a l l o w a b l e d e p t h o f f i l l o f each s t o r a g e c o n t a i n e r . Assuming a l i n e a r r e l a t i o n s h i p between f r u i t d e f o r m a t i o n and c o m p r e s s i v e l o a d , t h e a l l o w a b l e l o a d on t h e bottom l a y e r o f f r u i t i n a c o n t a i n e r i s P = K d [18] c c where K = a modulus r e l a t i n g f r u i t d e f o r m a t i o n t o c o m p r e s s i v e l o a d . d = a l l o w a b l e f r u i t d e f o r m a t i o n , c The d e p t h o f f i l l w i l l be l i m i t e d by t h e a l l o w a b l e f r u i t d e f o r m a t i o n and by t h e e f f e c t s o f i n - t r a n s i t v i b r a t i o n s on f r u i t damage. Unknowns The f o l l o w i n g p l a n t and f r u i t p r o p e r t i e s must be d e t e r m i n e d b e f o r e s t o r a g e t o o l d e s i g n may be c o m p l e t e d ; ( i ) The q u a n t i t y o f f r u i t on t h e canes a t t h e peak o f t h e h a r v e s t season. ( i i ) The d e f o r m a t i o n c h a r a c t e r i s t i c s o f f r u i t under c o m p r e s s i v e l o a d . ( i i i ) The e f f e c t o f i n - t r a n s i t v i b r a t i o n s on f r u i t damage. Summary The f o u r t o o l s which were d e s c r i b e d above a r e r e q u i r e d t o mechanize a l l t h e f u n c t i o n s on t h e f l o w c h a r t . A n a l y s i s o f t h e t o o l s i s i n c o m p l e t e . D e l i m i t a t i o n o f t h e p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f t h e r a s p b e r r y p l a n t and i t s f r u i t i s n e c e s s a r y b e f o r e t h e m a t h e m a t i c a l models f o r t h e t o o l s can be c o m p l e t e d . The n e x t s e c t i o n o f t h e t h e s i s t h e r e f o r e p r e s e n t s t h e r e s u l t s o f measurements d e t e r m i n i n g t h e s e p r o p e r t i e s . ANALYSIS OF PRODUCT CHARACTERISTICS Scope o f I n v e s t i g a t i o n T h i s c h a p t e r p r e s e n t s t h e r e s u l t s o f measurements d e t e r m i n i n g the p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f t h e r a s p b e r r y p l a n t and i t s f r u i t . I n a d d i t i o n t o d e t e r m i n i n g t h e d a t a r e q u i r e d f o r c o m p l e t i o n o f t h e t o o l a n a l y s e s , an i n v e s t i -g a t i o n on t h e c o n t r o l o f p h y s i c a l p r o p e r t i e s , by t h e use o f c h e m i c a l growth r e g u l a t o r s , was a l s o u n d e r t a k e n . Due t o l a r g e v a r i a b i l i t y i n t h e p r o p e r t i e s o f b i o l o g i c a l m a t e r i a l s , s t a t i s -t i c a l a n a l y s e s were used t o i n t e r p r e t t h e d a t a . The f o l l o w i n g r e s u l t s a r e based on a n a l y s e s o f t h e W i l l a m e t t e v a r i e t y o f r a s p b e r r i e s grown a t t h e S m a l l F r u i t Sub-s t a t i o n o f t h e Canada Department o f A g r i c u l t u r e a t A b b o t s f o r d , B r i t i s h C o l u m b i a . C u l t u r a l p r a c t i c e s used on t h e t e s t p l o t s were s i m i l a r t o t h o s e used by c o m m e r c i a l growers i n t h e l o w e r m a i n l a n d . D i s t r i b u t i o n o f F r u i t on t h e R a s p b e r r y P l a n t The numbers o f f r u i t on s u c c e s s i v e o n e - f o o t - t h i c k h o r i z o n t a l s l i c e s were c o u n t e d on n i n e t e e n randomly s e l e c t e d p l a n t s midway t h r o u g h t h e 1968 h a r v e s t . S i m i l a r l y , t h e numbers o f f r u i t i n o n e - h a l f - f o o t - t h i c k v e r t i c a l s l i c e s , f r o m t h e c e n t e r o f t h e row outward, were c o u n t e d on f o u r t e e n p l a n t s . U s i n g t h e method o f l e a s t s q u a r e s and s t e p w i s e r e g r e s s i o n p r o c e d u r e , t h e b e s t f i t p o l y n o m i a l s o f numbers o f f r u i t v e r s u s d i s t a n c e were d e t e r m i n e d . The p o l y n o m i a l o f b e s t f i t d e s c r i b i n g t h e v e r t i c a l f r u i t d i s t r i b u t i o n was N = -9.04+17.40X -0.09x 4 , R 2=0.64, n=114, v v v ' S =11.2 [ 1 9 ] y - 36 -- 37 -f o r t h e range 0. 5 < < 5.5 where N = numbers o f f r u i t on one p l a n t i n a o n e - f o o t -t h i c k h o r i z o n t a l s l i c e from (x -0.5) f t . t o (x + 0 . 5 ) ' f t . V x v = d i s t a n c e above s o i l s u r f a c e , f t . I n t h e case o f h o r i z o n t a l f r u i t d i s t r i b u t i o n , t h e b e s t f i t p o l y n o m i a l was N h = 0.67+42.31x h-15.53x h 3+3.62x h 4, R 2=0.63, n=84, S =8.49 [20] y f o r t h e range 0.25 < x h < 2.75 where N, = Numbers o f f r u i t on.one p l a n t i n a o n e - h a l f -f o o t - t h i c k v e r t i c a l s l i c e from (x,-0.25) f t . t o (x, + 0.25) f t . n n x, = d i s t a n c e from t h e c e n t e r o f t h e row, o u t w a r d , f t . Distance Above Soil Surface(feet) F i g u r e 11 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t on a r a s p b e r r y p l a n t as measured upward from t h e s o i l s u r f a c e . 0 1 2 3 Distance Outward from Center of Row (feet) F i g u r e 12 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t on a r a s p b e r r y p l a n t as measured outward from the c e n t e r o f t h e row o f p l a n t s . E x p r e s s i o n s f o r t h e c u m u l a t i v e d i s t r i b u t i o n f u n c t i o n s , w h i c h were o b t a i n e d by i n t e g r a t i n g e q u a t i o n s [ 1 9 ] and [ 2 0 ] , a r e shown i n f i g u r e s 11 and 12. From f i g u r e 11 i t can be seen t h a t i n o r d e r t o o b t a i n a l l o f t h e f r u i t , a p o r t i o n o f t h e p l a n t from 0.5 t o 5.5 f e e t h i g h must be h a r v e s t e d . E i g h t y p e r c e n t o f the f r u i t i s l o c a t e d i n a t h r e e - f o o t - t h i c k s l i c e w h i l e s i x t y p e r c e n t i s c o n t a i n e d i n a t w o - f o o t - t h i c k s l i c e ( f r o m 2.25 t o "4.25 f e e t ) . F i g u r e 12 shows t h a t a l l o f t h e f r u i t i s l o c a t e d i n a s i x f o o t wide p o r t i o n o f t h e p l a n t . E i g h t y p e r c e n t o f t h e f r u i t i s con-t a i n e d i n two 1.5 f e e t - t h i c k v e r t i c a l s l i c e s on each s i d e o f t h e p l a n t w h i l e s i x t y p e r c e n t i s l o c a t e d i n two o n e - f o o t - t h i c k v e r t i c a l s l i c e s ( f r o m 0.75 t o 1.75 f e e t on each s i d e o f t h e c e n t e r o f t h e f r u i t r o w ) . - 3 9 -P h y s i c a l Dimensions o f R a s p b e r r y P l a n t s , The average s i z e o f r a s p b e r r y p l a n t s a t h a r v e s t i s shown i n f i g u r e 13. P l a n t h e i g h t may depend s l i g h t l y upon p r u n i n g p r a c t i c e s and w i d t h may depend upon t r e l l i s i n g methods. The p o r t i o n o f t h e p l a n t above 5.5 f e e t i n h e i g h t i s u n p r o d u c t i v e c o n s i s t i n g o f f l e x i b l e s h o o t s . S i n c e t h e s e may be r e a d i l y d e f l e c t e d as t h e h a r v e s t e r p a s s e s o v e r them, machine c l e a r a n c e o f l e s s t h a n s i x f e e t i s s u f f i c i e n t . The p l a n t w i d t h a t t h e s o i l s u r f a c e ranges from t h r e e t o t e n i n c h e s . A l t h o u g h t h e maximum p l a n t w i d t h i s o v e r s i x f e e t , the p o r t i o n o f t h e p l a n t above one f o o t i n h e i g h t may be r e a d i l y compressed i n t o a f o u r i n c h t h i c k v e r t i c a l s l i c e . Each p l a n t c o n t a i n s from t h r e e t o t e n p r o d u c t i v e canes w i t h a s i m i l a r number o f s h o o t s . P h y s i c a l Dimensions o f t h e R a s p b e r r y F r u i t and i t s Attachment Stem  The p h y s i c a l d i m e n s i o n s o f t h e r a s p b e r r y f r u i t and the stem a t t a c h i n g i t t o t h e p l a n t a r e g i v e n i n T a b l e I I I . The n o m e n c l a t u r e used i n t h i s T a b l e i s d e f i n e d i n f i g u r e 14. 60 in. Stem Fruit F i g u r e 13 P h y s i c a l d i m e n s i o n s o f a r a s p b e r r y p l a n t F i g u r e 14 Nomenclature used i n T a b l e I I I - 4 0 -TABLE III PHYSICAL DIMENSIONS OF THE RASPBERRY FRUIT AND ITS ATTACHMENT STEM Mean Standard Deviation Stem length (4), cm 3.07 0.65 F r u i t length (h), cm 2.17 0.23 F r u i t diameter (d), cm - maximum 1.97 0.15 - minimum 1.88 0.14 Fr u i t Weight, Volume and Density Based on 124 samples and data gathered by McLeod (22) i n 1967, the weight of a single f r u i t was 4.19 1 - 0.97 grams. Based on 90 samples and data c o l l e c t e d i n 1968, f r u i t weight was 3.52 - 0.97 grams. For the 1968 data, the simple l i n e a r regression of f r u i t weight on time of harvest was determined as W = 3.01+0.07T, r 2=0.12, n=90, Sy= 0,92 [21] for the range 1 < T < 15 where T = time i n days, T=l being the f i r s t day of harvest W = weight of a single f r u i t , grams In order to determine f r u i t volume and density, i n d i v i d u a l f r u i t s were weighed successively i n both a i r and water, as outlined by Mohsenin (24). F r u i t volume was calculated as the quotient of the weight of water displaced by a submerged f r u i t and the density of the water. F r u i t density was then determined as the quotient of f r u i t weight divided by f r u i t volume. Based on 124 samples 1 In the following pages, the r e s u l t s + o f i n d i v i d u a l determina-tions are reported as the mean (u) - the standard deviation (a). - 41 -+ 3 the volume o f a s i n g l e r a s p b e r r y f r u i t i s 4.07 - 0.97 cm , w h i l e + 3 i t s d e n s i t y i s 1.04 - 0.12 gm/cm . Rate o f F r u i t Removal Based on e q u a t i o n [ 1 9 ] , mean f r u i t w e i g h t and a s p a c i n g o f 2.5 f e e t between a d j a c e n t p l a n t s i n a row, t h e r a t e o f f r u i t r e m o v a l f o r one pass o f a s i n g l e row h a r v e s t i n g machine was d e t e r m i n e d . T a b l e IV shows t h e number o f f r u i t p e r p l a n t a t v a r i o u s h e i g h t i n t e r v a l s and t h e r e s u l t i n g r a t e o f h a r v e s t i n g i n pounds o f f r u i t p e r minute a t a f o r w a r d speed o f one m i l e p e r h o u r , assuming 100 p e r c e n t p i c k i n g e f f i c i e n c y . The t a b l e i s based on f r u i t d i s t r i b u t i o n a t t h e peak o f t h e h a r v e s t s e a s o n , and r e p r e s e n t s a y i e l d o f 1925 pounds p e r a c r e f o r one p i c k i n g . TABLE IV CALCULATED RATE OF FRUIT REMOVAL FOR A SINGLE ROW HARVESTING MACHINE. P l a n t H e i g h t I n t e r v a l Number o f F r u i t Rate o f F r u i t Removal ( f e e t above s o i l ) on One P l a n t ( l b s / m i n u t e o f f r u i t a t f o r w a r d speed o f 1 m i l e / h o u r ) 0.5 t o 1.5 8.2 2.3 1.5 t o 2.5 24.1 6.8 2.5 t o 3.5 35.4 9.9 3.5 t o 4.5 36.7 10. 2 4.5 t o 5.5 20.6 5.8 T o t a l P l a n t 125. 0 35. 0 T e r m i n a l V e l o c i t y o f R a s p b e r r y F r u i t The t e r m i n a l v e l o c i t y o f r a s p b e r r i e s i n a i r was e s t i m a t e d u s i n g e q u a t i o n [ 1 6 ] , w i t h A based on mean f r u i t d i a m e t e r ( T a b l e I I I ) . T h i s v a l u e f o r V was t h e n s u b s t i t u t e d i n t o e q u a t i o n [ 1 5 ] , u s i n g the mean v a l u e s o f f r u i t w e i g h t and f r u i t d e n s i t y , t o v e r i f y t h e c h o i c e o f C^. Based on t h e s e c a l c u l a t i o n s , t h e t e r m i n a l v e l o c i t y and d r a g c o e f f i c i e n t were 3960 f e e t / m i n u t e and 0.5 r e s p e c t i v e l y . F r u i t R e t e n t i o n F o r c e F r u i t r e t e n t i o n f o r c e was d e t e r m i n e d u s i n g a C h a t t i l o n t y pe DPP1 hand dynamometer ( a c c u r a c y - 3 gm). The dynamometer ( f i g u r e 15) was m o d i f i e d t o mount on a s u r v e y o r ' s t r i p o d . A s p r i n g l o a d e d s c i s s o r s clamp, h a v i n g jaw s u r f a c e s c o a t e d w i t h w a t e r p r o o f s i l i c o n c a r b i d e paper, was used t o c l a s p t h e f r u i t stem. A s l o t t e d r i n g ( f i g u r e 16) w i t h s l o t w i d t h o f 9.5 mm was used t o a p p l y t h e l o a d t o t h e f r u i t . The l o a d was a p p l i e d t h r o u g h a screw mechanism t o a v o i d impact l o a d i n g . S i n c e t h e f r u i t was h e l d i n a v e r t i c a l p o s i t i o n , f r u i t w e i g h t was added t o dynamometer r e a d i n g t o o b t a i n f r u i t r e t e n t i o n f o r c e . The mean v a l u e o f t h e f r u i t r e t e n t i o n f o r c e o b t a i n e d i n 1968 from n i n e t y random samples was 254.0 - 146.5 gm. McLeod (22) o b t a i n e d a v a l u e o f 162.8 - 100 gm i n a s i m i l a r e x p e r i m e n t i n 1967. S i m p l e r e g r e s s i o n a n a l y s i s o f f r u i t r e t e n t i o n f o r c e on h a r v e s t t i m e r e s u l t e d i n the f o l l o w i n g r e g r e s s i o n e q u a t i o n f o r t h e 1967 d a t a . F = 218.4-6.9T, r 2 = 0 . 1 6 , n=397, S y=91.9 [ 2 2 ] f o r t h e range 1 <T < 16 F o r t h e 1968 d a t a the s i m p l e r e g r e s s i o n e q u a t i o n was F = 347.7-13.4T, r 2=0.19, n=90, S y=132.9 [23] f o r t h e range 1 < T < 15. - 43 -Figure 15 Method of measuring Figure 16 Method of holding f r u i t r e t e n t i o n f r u i t i n the dyna-force mometer where F = f r u i t r e t e n t i o n f o r c e , grams T = time, days, where T=l i s the f i r s t day of harvest. Equations [22] and [23], which are p l o t t e d i n f i g u r e 17, were compared using the a n a l y s i s of covariance (33). This t e s t i n d i c a t e d that slopes were s i g n i f i c a n t l y d i f f e r e n t at P < 0.01 and l e v e l s were s i g n i f i c a n t l y d i f f e r e n t at P < 0.005. A f u r t h e r t e s t f o r homogeneity of r e s i d u a l variances revealed that the variances were s i g n i f i c a n t l y d i f f e r e n t at P < 0.005 i n d i c a t i n g that the two d i s t r i b u t i o n s were from d i f f e r e n t populations and that comparison i s not j u s t i f i e d . From the above r e s u l t s i t may be concluded that f r u i t r e t e n t i o n f o r c e , 0 * first day of harvest season i i i i i i i 0 6 8 10 Time (days) 12 14 16 F i g u r e 17 F r u i t r e t e n t i o n f o r c e v a r i a t i o n o v e r t h e h a r v e s t season f o r 1967 and 1968 100 § 80 a 60 f 40 z > D E 3 u 20 0 A harvest tirr:3,days 100 200 300 400 500 Upper Limit of Fruit Retention Force (grams) 600 F i g u r e 18 C u m u l a t i v e d i s t r i b u t i o n o f f r u i t r e t e n t i o n f o r c e f o r 1968 f o r f r u i t o f e q u a l m a t u r i t y , d e c r e a s e s as t h e h a r v e s t season p r o g r e s s e s . F u r t h e r m o r e , f r u i t r e t e n t i o n f o r c e appears t o be dependent upon growth c o n d i t i o n s i n a s p e c i f i c y e a r . F i g u r e 18 shows t h e c u m u l a t i v e d i s t r i b u t i o n f u n c t i o n o f f r u i t r e t e n t i o n f o r c e f o r t h e f i r s t day o f t h e h a r v e s t s e a s o n , the l a s t day o f t h e h a r v e s t season and f o r t h e whole h a r v e s t s e a s o n , based on t h e 1968 d a t a . The mean f r u i t r e t e n t i o n f o r c e on the f i r s t day o f h a r v e s t was 290.8 - 101.8 gm w h i l e on the l a s t day o f h a r v e s t , t h e mean f r u i t r e t e n t i o n f o r c e was 162.2 -142.2 gm, each v a l u e b e i n g based on e i g h t e e n measurements. F/W R a t i o F/W r a t i o was o b t a i n e d by combining t h e d a t a on f r u i t r e t e n t i o n f o r c e and f r u i t w e i g h t . Mean F/W f o r 1968 based on 90 samples was 82.8 - 65.1 w h i l e i n 1967 i t was 52.7 - 84.5, based on 124 measurements. The s i m p l e r e g r e s s i o n o f F/W on h a r v e s t t i m e f o r t h e 1968 d a t a i n d i c a t e d t h a t F/W d e c r e a s e d s i g n i f i c a n t l y w i t h i n c r e a s e i n t h e t i m e o f h a r v e s t . F/W = 128.0-6.5T, r 2 = 0 . 2 2 , n=90, S y=57.8 [24] f o r t h e range 1 < T < 15 where F/W = f r u i t r e t e n t i o n f o r c e / f r u i t w e i g h t T = t i m e i n d a y s , T=l b e i n g t h e f i r s t day o f h a r v e s t . Based on the 1968 d a t a and 18 measurements f o r each day, mean F/W was 96.2 - 44.8 on t h e f i r s t day o f t h e h a r v e s t s e a s o n , and was 46.4 - 43.3 on t h e l a s t day o f measurement (T=15). F i g u r e 19 shows t h e c u m u l a t i v e d i s t r i b u t i o n f u n c t i o n o f F/W f o r t h e 1968 h a r v e s t season. 100 200 300 Upper Limit of F/W F i g u r e 19 C u m u l a t i v e d i s t r i b u t i o n o f F/W f o r 1968 S t r e n g t h o f F r u i t A ttachment System The weakest p a r t o f t h e f r u i t a t t a c h m e n t system o c c u r s a t t h e p o i n t where t h e f r u i t stem a t t a c h e s t o the i n t e r m e d i a t e p l a n t stem ( f i g u r e 2 0 ) . Stem s t r e n g t h i s a f u n c t i o n o f d i r e c t i o n o f l o a d a p p l i c a t i o n ( f i g u r e 21) b e i n g g r e a t e s t when th e l o a d i s a p p l i e d upward ( a = 180°) p a r a l l e l t o t h e p l a n t stem and l e a s t when th e l o a d i s a p p l i e d downward p a r a l l e l t o t h e p l a n t stem (a = 0°). S i n c e the d i r e c t i o n o f l o a d a p p l i c a t i o n on t h e f r u i t stem i n a v i b r a t o r y h a r v e s t i n g machine i s unknown, measurement o f stem s t r e n g t h was based on a l o a d d i r e c t i o n o f a = 0°, r e s u l t i n g i n d e t e r m i n a t i o n o f minimum s t r e n g t h . Randomly s e l e c t e d samples, p i c k e d a t two d a t e s d u r i n g t h e 1969 h a r v e s t s e a s o n , were l o a d e d i n an I n s t r o n t e s t i n g machine. Stem s t r e n g t h was t a k e n as t h e 47 -1 0 0 0 Upper Limit of Stem Strength (grams) F i g u r e 22 Cum u l a t i v e d i s t r i b u t i o n o f f r u i t stem s t r e n g t h f o r a = 0° - 48 -maximum r e a d i n g on t h e f o r c e - d e f o r m a t i o n c u r v e i n each c a s e . Based on 132 samples, t h e mean and s t a n d a r d d e v i a t i o n o f stem s t r e n g t h was 177.1 - 164.3 grams. The c u m u l a t i v e d i s t r i b u t i o n f u n c t i o n f o r stem s t r e n g t h i s shown i n f i g u r e 22. One f u r t h e r t e s t was conducted i n o r d e r t o d e t e r m i n e t h e s i g n i f i c a n c e o f stem s t r e n g t h i n m e c h a n i c a l h a r v e s t i n g . A l l t h e mature f r u i t on one p l a n t was hand p i c k e d by a p p l y i n g a d i r e c t t e n s i l e f o r c e t o the f r u i t w h i l e m a i n t a i n i n g a ( f i g u r e 21) a t a p p r o x i m a t e l y 90°. In a t o t a l o f 63 f r u i t , 70 p e r c e n t were de t a c h e d from the c o r e w h i l e 3 0 p e r c e n t f a i l e d a t t h e stem w i t h t h e r e s u l t t h a t t h e c o r e and stem remained a t t a c h e d t o t h e h a r v e s t e d f r u i t . I n a c t u a l p r a c t i c e , hand p i c k i n g i s w i t h a r o l l i n g m o t i o n o f t h e f i n g e r s i n o r d e r t o l o o s e n the f r u i t from the c o r e . I n a v i b r a t o r y h a r v e s t e r , however, f r u i t r e m o v a l r e s u l t s from a p p l i c a t i o n o f a t e n s i l e f o r c e on t h e f r u i t . From the above t e s t i t appears t h a t f r u i t stem s t r e n g t h may l i m i t t h e e f f e c t i v e n e s s o f a m e c h a n i c a l h a r v e s t e r i n W i l l a m e t t e r a s p b e r r i e s . F r u i t C o l o r S e l e c t i v e h a r v e s t i n g o f r a s p b e r r i e s by hand i s based on f r u i t c o l o r . The human eye d i s t i n g u i s h e s between immature, mature and overmature f r u i t on the b a s i s o f c o l o r d i f f e r e n c e s . Measurement o f the s u r f a c e c o l o r o f r a s p b e r r i e s was, t h e r e f o r e , c o n d u c t e d i n an attempt t o d e t e r m i n e t h e r e l a t i o n s h i p between c o l o r and o t h e r f r u i t p r o p e r t i e s . An H i t a c h i P e r k i n - E l m e r model 139 UV-VIS s p e c t r o p h o t o -meter w i t h d i f f u s e r e f l e c t a n c e a t tachment was used f o r measuring f r u i t c o l o r . S i n c e c o l o r measurement i s a d e s t r u c t i v e t e s t w i t h t h i s i n s t r u m e n t ( c r u s h e d sample p l a c e d i n a g l a s s c e l l ) t h e s p e c t r o p h o t o m e t e r was m o d i f i e d t o n o n - d e s t r u c t i v e l y measure the e x t e r n a l c o l o r o f r a s p b e r r y f r u i t . A F i b r o x , n o n - c o h e r e n t , f i b r e o p t i c l i g h t p i p e , 4 5.7 cm l o n g x 6.2 mm d i a m e t e r , was used t o t r a n s m i t r e f l e c t e d l i g h t from t h e f r u i t t o t h e i n t e g r a t i n g sphere on t h e s p e c t r o p h o t o m e t e r . A 15 power m i c r o s c o p e eye-p i e c e was a t t a c h e d t o the i n t e g r a t i n g sphere i n p l a c e o f t h e sample h o l d e r ( f i g u r e 23) w i t h t h e end o f t h e l i g h t p i p e i n s e r t e d i n t o t h e e y e p i e c e tube a t a d i s t a n c e so t h a t the cone o f l i g h t emerging from t h e l i g h t p i p e c o m p l e t e l y f i l l e d t h e l e n s viewed by t h e i n t e g r a t i n g s p h e r e . (The a p e r t u r e a n g l e o f t h e l i g h t p i p e was 33°). I n d i v i d u a l f r u i t were p l a c e d u p r i g h t on.a 1.5 i n c h d i a m e t e r t u r n t a b l e ( f i g u r e 24) c o a t e d w i t h b l a c k s i l i c o n c a r b i d e paper >(Behr-Manning No. 2204 t u f b a k d u r i t e p a p e r ) . The o u t e r end o f t h e l i g h t p i p e was p l a c e d 1.5 i n c h e s above th e s u r f a c e o f the t u r n t a b l e . O r i g i n a l l y , t h e i n t e r n a l monochromatic l i g h t s o u r c e i n t h e s p e c t r o p h o t o m e t e r was used t o i l l u m i n a t e t h e f r u i t , t h r o u g h t h e l i g h t p i p e . That p o r t i o n o f t h e l i g h t w hich was r e f l e c t e d from t h e f r u i t and was i n t e r c e p t e d by t h e o u t e r end o f t h e l i g h t p i p e , r e t u r n e d t h r o u g h t h e p i p e t o t h e i n t e g r a t i n g s p h e r e . Even though t h e i n t e r n a l l i g h t s o u r c e was a d j u s t e d t o 5200 nm, t h e wave l e n g t h most r e a d i l y t r a n s m i t t e d by t h e l i g h t p i p e * s e n s i t i v i t y o f t h e s p e c t r o p h o t o m e t e r was t o o low t o s a t i s f a c t o r i l y d i s t i n g u i s h c o l o r d i f f e r e n c e s . A 17 w a t t e x t e r n a l w h i t e l i g h t s o u r c e ( f i g u r e 24) was t h e r e f o r e d i r e c t e d o n t o th e f r u i t by means o f an i n c l i n e d m i r r o r . W i t h t h i s - 50 -F i g u r e 2 3 S p ectrophotometer F i g u r e 24 T u r n t a b l e and e x t e r -m o d i f i c a t i o n n a l l i g h t s o u r c e m o d i f i c a t i o n , c o l o r d i f f e r e n c e s were d i s c e r n i b l e . C a l i b r a t i o n o f the s p e c t r o p h o t o m e t e r was by means o f a s t a n d a r d w h i t e powder c e l l and the b l a c k s u r f a c e on the t u r n t a b l e . The s p e c t r o p h o t o -meter was a d j u s t e d f o r a r e a d i n g o f 100 p e r c e n t r e f l e c t a n c e w i t h t h e w h i t e powder c e l l r o t a t e d t o i n t e r c e p t the l i g h t from t h e i n t e r n a l s o u r c e and w i t h no f r u i t on t h e t u r n t a b l e , a p r o c e d u r e s i m i l a r t o t h e s t a n d a r d c a l i b r a t i o n method f o r t h i s s p e c t r o -photometer. ^ C a l i b r a t i o n and c o l o r measurements were conducted i n a darkroom. By r o t a t i n g t h e t u r n t a b l e , b oth maximum and minimum r e f l e c t a n c e r e a d i n g s were t a k e n f o r each f r u i t . The complete i n s t r u m e n t a t i o n f o r measuring c o l o r i s shown i n f i g u r e 25. C o l o r i n d e x was d e f i n e d as t h e mean o f the maximum and minimum r e f l e c t a n c e r e a d i n g s f o r each f r u i t and ranged from 8 5 - 51 -F i g u r e 25 Complete i n s t r u m e n t a t i o n f o r measuring e x t e r n a l c o l o r o f r a s p b e r r y f r u i t -•Color Index F i g u r e 26 V a r i a t i o n i n f r u i t c o l o r as de t e r m i n e d by r e f l e c t a n c e measurements - 52 -f o r overmature f r u i t , s u i t a b l e o n l y f o r p r o c e s s i n g , t o 105 f o r f i r m f r u i t , s u i t a b l e f o r t h e f r e s h market ( f i g u r e 2 6 ) . As i s d i s c u s s e d l a t e r , c o r r e l a t i o n s among c o l o r and o t h e r f r u i t p r o p e r t i e s ( T a b l e s IX and X) were h i g h l y s i g n i f i c a n t . B r u i s i n g C h a r a c t e r i s t i c s o f Ra s p b e r r y F r u i t Drop t e s t s were c o n d u c t e d t o d e t e r m i n e t h e r e s i s t a n c e o f r a s p b e r r y f r u i t t o m e c h a n i c a l damage. F r u i t , w i t h stem and. c o r e a t t a c h e d , were dropped onto a smooth r i g i d F o r m i c a s u r f a c e from p r e d e t e r m i n e d h e i g h t s . The stem p r e v e n t e d t h e f r u i t from t u m b l i n g as i t f e l l , making i t p o s s i b l e t o d e t e r m i n e t h e p o i n t o f i m p a c t . B r u i s i n g damage was a s s e s s e d v i s u a l l y t h i r t y m i n u t e s a f t e r t h e drop. C o l o r i n d e x was used as a measure o f f r u i t m a t u r i t y i n o r d e r t o a s s e s s t h e b r u i s i n g c h a r a c t e r i s t i c s o f f r u i t a t d i f f e r e n t s t a g e s o f m a t u r i t y . The e x t e n t o f b r u i s i n g was d e t e r m i n e d by mea s u r i n g the d e p t h and d i a m e t e r o f each b r u i s e . R e s u l t s o f drop t e s t s a r e r e p o r t e d i n T a b l e V. Assuming damage t o one d r u p e l e t as an a c c e p t a b l e l e v e l o f b r u i s i n g , t h e maximum f r e e f a l l h e i g h t f o r a f r u i t o f c o l o r i n d e x 100 was 8 cm whereas f o r a f r u i t o f c o l o r i n d e x 90, i t was 4 cm. The maximum impact energy (e^) whi c h may be absorbed by a f r u i t o f c o l o r i n d e x 90 may be e s t i m a t e d as (4) (5) = 20 gm cm B a s i n g t h e r e s u l t on a mean f r u i t w eight o f 3.52 - 0.97 gm t h e a l l o w a b l e f r e e f a l l h e i g h t (h ) from e q u a t i o n [ 1 2 ] i s ct 20/(3.52+ 0.97) = 4.5 cm S i m i l a r l y , from e q u a t i o n [ 1 3 ] , t h e a l l o w a b l e impact v e l o c i t y (V f l) i s - 53 -( 2 ( 2 0 ) ( 9 8 1 ) / ( 3 . 5 2 + 0.97)) 1/2 Q 1 1 . 1 = 94 cm/sec 1 = 187 f t / m i n TABLE V RESULTS OF DROP TESTS H e i g h t o f Drop (cm) F r u i t Weight, i n c l u d i n g Stem and Core (gm) C o l o r Index R e s u l t 8 5.0 100 One d r u p e l e t b r u i s e d 8 5.0 90 Three d r u p e l e t s b r u i s e d 15 5.2 100 ' Three d r u p e l e t s b r u i s e d 15 5.9 90 B r u i s e d i a m e t e r 6 mm 30 5.0 100 B r u i s e d i a m e t e r 12 mm 3 mm deep. 30 5.0 90 B r u i s e d i a m e t e r 15 mm 6 mm deep. 75 4.5 100 B r u i s e d i a m e t e r 15 mm 6 mm deep. 75 5.6 90 Complete f r u i t b r u i s e d . F o r c e - D e f o r m a t i o n C h a r a c t e r i s t i c s o f R a s p b e r r y F r u i t As was p r e v i o u s l y m e n t i o n e d , q u a l i t y o f r a s p b e r r y f r u i t i s a t p r e s e n t p o o r l y d e f i n e d . F o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s o f r a s p b e r r y f r u i t were i n v e s t i g a t e d i n o r d e r t o more a c c u r a t e l y d e f i n e q u a l i t y and t o r e l a t e f r u i t p r o p e r t i e s t o f r u i t c o l o r and f r u i t r e t e n t i o n f o r c e . F o r c e - d e f o r m a t i o n c u r v e s were o b t a i n e d by p l a c i n g t h e f r u i t u p r i g h t between two f l a t p l a t e s on an I n s t r o n t e s t i n g machine ( f i g u r e 27) and a p p l y i n g a c o m p r e s s i v e l o a d a t a 1 V and h , as d e t e r m i n e d above, a r e based on a f r u i t w eight o f Si cl " t h e mean p l u s one s t a n d a r d d e v i a t i o n o f the f r u i t w e i g h t d i s -t r i b u t i o n . E i g h t y f o u r p e r c e n t o f the i n d i v i d u a l measures d e f i n i n g a normal d i s t r i b u t i o n have v a l u e s l e s s t h a n (u + a) whereas 97.5 p e r c e n t have v a l u e s l e s s t h a n (u + 2 a ) . - 54 -F i g u r e 2 7 Method o f l o a d i n g f r u i t i n I n s t r o n machine Fruit Deformation (millimeters) F i g u r e 28 T y p i c a l f o r c e - d e f o r m a t i o n c u r v e f o r r a s p b e r r y f r u i t s u b j e c t e d t o f l a t - p l a t e l o a d i n g a t 2 cm/min. - 55 -r a t e o f two cm/min. No a t t e m p t was made t o d e t e r m i n e t h e t i m e dependent p r o p e r t i e s o f t h e f r u i t ; o n l y one r a t e o f l o a d i n g was used. A t y p i c a l f o r c e - d e f o r m a t i o n c u r v e f o r r a s p b e r r y f r u i t i s shown i n f i g u r e 28. Three c h a r a c t e r i s t i c m o d u l i were o b t a i n e d from each c u r v e : t h e a n g l e modulus ( t h e a n g l e between t h e l o w e r l i n e a r p o r t i o n o f t h e c u r v e and t h e " d e f o r m a t i o n a x i s ) , t h e t a n g e n t modulus ( t h e t a n g e n t o f t h e above a n g l e ) and t h e l i n e a r l i m i t ( t h e minimum l o a d a t w h i c h t h e c u r v e became n o n - l i n e a r ) . C o r r e l a t i o n s among f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s and o t h e r f r u i t p r o p e r t i e s , w h i c h a r e p r e s e n t e d i n T a b l e V I I I , a r e d i s -c u s s e d l a t e r . Based on t h e u n i t s o f measurement which d e f i n e d t h e f o r c e - d e f o r m a t i o n c u r v e s , t h e r e l a t i o n s h i p between compres-s i v e l o a d and f r u i t d e f o r m a t i o n was P = d (20Y) [25] c c where P c . = c o m p r e s s i v e l o a d , gm d = f r u i t d e f o r m a t i o n , mm c ' Y = t a n g e n t modulus ( T a b l e V I I I ) F o r t h e s e u n i t s o f measurement, K ( e q u a t i o n [18]) has a v a l u e o f 20y. F r u i t R i g i d i t y I n an a t t e m p t t o measure f r u i t q u a l i t y , an a p p a r a t u s s i m i l a r t o t h a t d e v e l o p e d by Nybom and d e s c r i b e d i n r e f e r e n c e (24) was used. I n d i v i d u a l r a s p b e r r i e s were p l a c e d u p r i g h t between the diaphragms o f two earphones ( f i g u r e 29). The upper earphone e x e r t e d a c o m p r e s s i v e f o r c e o f t e n grams on t h e f r u i t w h i l e t h e l o w e r earphone was e x c i t e d a t a f r e q u e n c y o f 250 Hz by a s i g n a l - 56 -g e n e r a t o r . V i b r a t i o n s t r a n s m i t t e d t h r o u g h the f r u i t t o the upper earphone g e n e r a t e d an a l t e r n a t i n g c u r r e n t which was a m p l i f i e d by an A-C a m p l i f i e r and r e a d on an ammeter. The ammeter r e a d i n g was d e f i n e d as f r u i t r i g i d i t y . C o r r e l a t i o n s among r i g i d i t y and o t h e r f r u i t p r o p e r t i e s a r e p r e s e n t e d i n T a b l e V I I I and are d i s c u s s e d l a t e r . As i s shown i n Table VI r i g i d i t y r e a d i n g s were s i g n i f i -c a n t l y c o r r e l a t e d w i t h f r u i t d i m e n s i o n s a t P < 0.01. - 57 -TABLE VI SIMPLE CORRELATIONS AMONG RIGIDITY AND FRUIT DIMENSIONS F r u i t F r u i t Maximum Minimum Weight Length F r u i t F r u i t D i a m e t e r Diameter R i g i d i t y 1.00 F r u i t Weight -0.42 1.00 F r u i t L e n g t h -0.44 0.79 1.00 Maximum F r u i t D i a m e t e r -0.30 0.72 0.62 1.00 Minimum F r u i t D i a m e t e r -0.22 0.80 0.63 0.72 1.00 n = 144 r 0 . 05 = 0.16 r 0 . 0 1 = ° ' 2 1 Sugar Content o f F r u i t I n a f u r t h e r a t t e m p t t o r e l a t e f r u i t p r o p e r t i e s , s u g a r con-t e n t was measured on 141 randomly s e l e c t e d samples d u r i n g two days a t t h e b e g i n n i n g o f t h e 1968 h a r v e s t . Sugar c o n t e n t was d e t e r m i n e d i n the f i e l d w i t h a Z e i s s model 0/8 5 hand s u g a r r e f r a c t o m e t e r , w h i c h measures s u g a r on t h e b a s i s o f d i f f e r e n c e s i n i n d i c e s o f r e f r a c t i o n o f s u g a r s o l u t i o n s . S i m p l e c o r r e l a t i o n s among f r u i t r e t e n t i o n f o r c e , f r u i t w e i g h t and suga r c o n t e n t a r e p r e s e n t e d i n T a b l e V I I . S i n c e s u g a r c o n t e n t measurement was a d e s t r u c t i v e t e s t , c o r r e l a t i o n s between s u g a r c o n t e n t and f o r c e -d e f o r m a t i o n c h a r a c t e r i s t i c s were not o b t a i n e d . As can be seen from the t a b l e , t h e s i m p l e c o r r e l a t i o n o f f r u i t r e t e n t i o n f o r c e on f r u i t s ugar c o n t e n t was not s i g n i f i c a n t a t P 5 0.05. - 58 -TABLE V I I SIMPLE CORRELATIONS AMONG FRUIT RETENTION FORCE, FRUIT WEIGHT AND FRUIT SUGAR CONTENT Mean F r u i t R e t e n t i o n F o r c e (gm) F r u i t Weight (gm) F r u i t Sugar Content ( p e r c e n t ) 303 .0 5.1 S t a n d a r d D e v i a t i o n F r u i t R e t e n t i o n F r u i t 10. 2 n = 141 152.0 0.75 1.75 r 0 . 05 Force 1.00 0.12 0.14 = 0.16 1.00 0. 21 r 0 . 0 1 = ° ' 2 1 F r u i t Weight Sugar Content 1. 00 Comparison o f F r u i t P r o p e r t i e s i n an Attempt t o D e f i n e F r u i t ; Q u a l i t y  I n hand g r a d i n g r a s p b e r r i e s , t h e g r a d e r bases h i s d e c i s i o n p r i m a r i l y on f r u i t c o l o r and on f i r m n e s s o f f r u i t as d e t e r m i n e d by f e e l i n g t h e f r u i t w i t h h i s f i n g e r s . Both o f t h e s e parameters i n f l u e n c e t h e a c c e p t i b i l i t y o f the f r u i t a t t h e consumer l e v e l . An immature f r u i t i s o f l i g h t c o l o r and f e e l s f i r m between the f i n g e r s w h i l e an overmature f r u i t i s o f dark c o l o r and i s s o f t . S i n c e a m e c h a n i c a l h a r v e s t e r must s e l e c t i v e l y h a r v e s t f r u i t o f a c c e p t a b l e q u a l i t y , t h e r e l a t i o n s h i p between f r u i t p r o p e r t i e s was s t u d i e d i n o r d e r t o o b t a i n a par a m e t e r w h i c h c o u l d be used f o r m e c h a n i c a l f r u i t s e l e c t i o n . T a b l e V I I I p r e s e n t s s i m p l e c o r r e l a t i o n s among f r u i t - 59 -r e t e n t i o n f o r c e , F/W, r i g i d i t y and f o r c e - d e f o r m a t i o n m o d u l i f o r a random sample o f 90 f r u i t c o l l e c t e d on f i v e d i f f e r e n t days d u r i n g t h e 1968 h a r v e s t season. As can be s e e n , f r u i t r e t e n t i o n f o r c e and F/W a r e b o t h s i g n i f i c a n t l y c o r r e l a t e d w i t h f o r c e -d e f o r m a t i o n c h a r a c t e r i s t i c s o f the f r u i t . The h i g h e s t c o r r e l a -t i o n e x i s t s w i t h t h e t a n g e n t modulus. The t a n g e n t modulus may be c o n s i d e r e d as an e l a s t i c modulus i n d i c a t i n g how f i r m l y t h e i n d i v i d u a l d r u p e l e t s a r e h e l d t o g e t h e r and hence i s a good i n d i c a t o r o f f r u i t f i r m n e s s as measured by hand. As can a l s o be seen from t h e t a b l e , r i g i d i t y as measured by t r a n s m i s s i o n o f v i b r a t i o n i s p o o r l y c o r r e l a t e d w i t h f r u i t r e t e n t i o n f o r c e o r o t h e r f r u i t p r o p e r t i e s . TABLE V I I I SIMPLE CORRELATIONS AMONG FRUIT RETENTION FORCE, F/W, RIGIDITY AND FORCE-DEFORMATION MODULI F r u i t R e t e n t i o n F o r c e (gm) R i g i d i t y -F/W (ampxlO -" 3) A n g l e Modulus ( d e g r e e s ) Tangent Modulus L i n e a r L i m i t (gm) Mean 254.0 82.7 440.0 50.0 1. 32 189.0 S t a n d a r d D e v i a t i o n 146.0 65.0 190.0 12.2 0. 54 71.0 F r u i t R e t e n t i o n F o r c e 1.00 F/W 0.88 1.00 R i g i d i t y 0.15 0.23 1.00 A n g l e Modulus 0.66 0.57 0.17 1.00 Tangent Modulus 0.68 0.61 0.15 0.96 1.00 L i n e a r L i m i t 0.59 0.49 0.03 0.76 0.81 1.00 n = 90 r 0 . 0 5 = 0.22 r 0 . 0 1 = 0.28 - 60 -T a b l e s IX and X p r e s e n t s i m p l e c o r r e l a t i o n s among f r u i t c o l o r i n d e x , f r u i t r e t e n t i o n f o r c e , F/W, r i g i d i t y and f o r c e -d e f o r m a t i o n m o d u l i f o r 144 random samples p i c k e d on t h e f i r s t day and on the f i f t e e n t h day o f the 1968 h a r v e s t season. As can be seen from t h e s e t a b l e s , s i g n i f i c a n t c o r r e l a t i o n s e x i s t among c o l o r i n d e x , f r u i t r e t e n t i o n f o r c e , F/W and f o r c e - d e f o r m a t i o n m o d u l i f o r b o t h days o f measurement. The s i m p l e l i n e a r r e g r e s -s i o n s o f f r u i t r e t e n t i o n f o r c e and F/W on c o l o r i n d e x f o r the f i r s t day o f t h e h a r v e s t season were F = 1335.6+17.7C, r 2 = 0 . 2 9 , n = 144, S y = 133.1 [26] F/W = -205.2+3.2C, r 2 =0.08, n = 144, S y = 53.3 [27] f o r t h e range 84.5 < C < 109.0 where F = f r u i t r e t e n t i o n f o r c e , g r a m s F/W = f r u i t r e t e n t i o n f o r c e / f r u i t w e i g h t C = f r u i t c o l o r i n d e x S i m i l a r l y , f o r t h e f i f t e e n t h day o f t h e h a r v e s t season t h e r e g r e s s i o n e q u a t i o n s were F = 1728.7+21.7C, r 2 = 0 . 2 8 , n = 144, S y = 113.4 [ 2 8 ] F/W = 488.0 + 6.2C, r 2 = 0 . 2 6 , n = 144, S y = 34.1 [29] f o r t h e range 84.0 < C < 100.0 The s i m p l e l i n e a r r e g r e s s i o n s o f i n d i v i d u a l f o r c e - d e f o r m a t i o n m o d u l i on c o l o r i n d e x were a l s o o b t a i n e d . Comparison o f s i m i l a r r e g r e s s i o n e q u a t i o n s , f o r t h e f i r s t and f i f t e e n t h day o f the h a r v e s t s e a s o n , u s i n g t h e a n a l y s i s o f c o v a r i a n c e (33) r e v e a l e d t h a t s i m i l a r r e g r e s s i o n s were homogeneous w i t h r e s p e c t t o r e s i d u a l v a r i a n c e and d i d not have s i g n i f i c a n t l y d i f f e r e n t s l o p e s . L e v e l s f o r t h e two days o f measurement were, however, s i g n i f i c a n t l y d i f f e r e n t . F o r example, t h e s i m p l e l i n e a r r e g r e s s i o n s o f t a n g e n t modulus on c o l o r i n d e x f o r t h e f i r s t and f i f t e e n t h day, r e s p e c t i v e l y , were Y = -5.16+0.07C, r 2 = 0.33, n = 144, S y = 0.51 [30] f o r t h e range 84.5 <C<109.0 Y = -4.54+0.06C, r 2 = 0.17, n = 144, S = 0.47 [ 3 1 ] ' y f o r t h e range 84.0<C<100.0 where Y = t a n g e n t modulus C = f r u i t c o l o r i n d e x A l t h o u g h the s l o p e s o f t h e above e q u a t i o n s a r e not s i g n i f i c a n t l y d i f f e r e n t , t h e l e v e l s a r e s i g n i f i c a n t l y d i f f e r e n t a t P < 0.005. T h i s i n d i c a t e s t h a t the t a n g e n t modulus f o r f r u i t s o f e q u a l c o l o r d e c r e a s e s as t h e h a r v e s t season p r o g r e s s e s . S i n c e t h e t a n g e n t modulus i s an i n d i c a t o r o f how f i r m l y t h e i n d i v i d u a l d r u p l e t s a r e bound t o g e t h e r , i t a l s o i s measure o f how f i r m l y t h e f r u i t i s a t t a c h e d t o t h e c o r e . T h i s e x p l a i n s t h e r e a s o n f o r the p r e v i o u s l y r e p o r t e d s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n between f r u i t r e t e n t i o n f o r c e and t i m e o f h a r v e s t . Due t o the s i g n i f i c a n t c o r r e l a t i o n s among f r u i t r e t e n t i o n f o r c e , F/W, f r u i t c o l o r and t a n g e n t modulus, i t may be c o n c l u d e d t h a t b o t h f r u i t r e t e n t i o n f o r c e and F/W a r e i n d i r e c t i n d i c a t o r s o f f r u i t q u a l i t y . A machine which h a r v e s t s s e l e c t i v i t y on the b a s i s o f f r u i t r e t e n t i o n f o r c e l e v e l o r F/W l e v e l w i l l a l s o h a r v e s t on t h e b a s i s o f f r u i t q u a l i t y . - 62 -TABLE IX SIMPLE CORRELATIONS AMONG COLOR INDEX, FRUIT RETENTION FORCE, F/W, RIGIDITY AND FORCE-DEFORMATION MODULI FOR THE FIRST DAY OF THE 1968 HARVEST SEASON. C o l o r Index F r u i t R e t e n t i o n F o r c e F/W R i g i d - i t y A n g l e Tangent Modulus Modulus L i n e a r 1 L i m i t C o l o r Index 1.00 F r u i t R e t e n t i o n F o r c e 0.54 1.00 F/W 0. 28 0.73 1.00 R i g i d i t y 0.02 0.10 0.32 1.00 A n g l e Modulus 0.53 0.63 0.43 0.26 1.00 Tangent Modulus 0.57 0.69 0.52 0.24 0.93 1.00 L i n e a r L i m i t 0. 54 0. 62 0.42 0.08 0.74 0.87 1.00 n = 144 r 0 . 0 5 = ° ' 1 6 r 0 . 0 1 = ° ' 2 1 TABLE X SIMPLE CORRELATIONS AMONG COLOR INDEX, FRUIT RETENTION FORCE, F/W, RIGIDITY AND FORCE-DEFORMATION MODULI FOR THE FIFTEENTH DAY OF THE 1968 HARVEST SEASON. C o l o r Index 1.00 F r u i t R e t e n t i o n F o r c e 0.53 1.00 F/W 0. 51 0.95 1.00 R i g i d i t y 0.33 0. 30 0.40 1. 00 A n g l e Modulus 0.35 0.68 0.68 0. 39 1. 00 Tangent Modulus 0.41 0.73 . 0.72 0. 36 0. 95 1. 00 L i n e a r L i m i t 0.47 0.73 0.70 0. 36 0. 82 0. 87 1.00 n = 144 r 0 . 0 5 = ° ' 1 6 r 0 . 0 1 = ° ' 2 1 1 T h i s h e a d i n g a p p l i e s t o t h e columns i n both T a b l e IX and T a b l e X. - 63 -Dynamic Response o f Canes and F r u i t Attachment System The r a s p b e r r y p l a n t i s a complex s t r u c t u r e c o n s i s t i n g o f ca n e s , s h o o t s , i n t e r m e d i a t e l i m b s , f r u i t a t t achment members and f o l i a g e . As w i t h most b i o l o g i c a l m a t e r i a l s , m e c h a n i c a l p r o p e r t i e s o f t h e canes and l i m b s may be time dependent when s u b j e c t e d t o dynamic l o a d i n g s i n c e b o t h i n t e r n a l damping and e x t e r n a l damping may be e x p e c t e d . I n a d d i t i o n , p r o p e r t i e s a r e i n f l u e n c e d by e x i s t i n g e n v i r o n -m e n t a l c o n d i t i o n s , r e s u l t i n g i n l a r g e v a r i a t i o n even w i t h i n one f i e l d o f f r u i t . S i n c e many a p p r o x i m a t i o n s must be made i n dynamic a n a l y s i s o f such a system, r e s u l t s may be used o n l y as a rough g u i d e f o r d e s i g n . I n a n a l y z i n g t h e dynamic r e s p o n s e o f t h e r a s p b e r r y p l a n t , t h e f o l l o w i n g s i m p l i f y i n g a s s u m p t i o n s were made: The p l a n t was c o n s i d e r e d as two s e p a r a t e systems, t h e f r u i t a t t a c h m e n t system and t h e c e n t r a l p l a n t cane w h i c h s u p p o r t s t h e f r u i t a t t a c h m e n t system. The canes were assumed t o have e l a s t i c p r o p e r t i e s . I n t e r n a l and e x t e r n a l damping were not c o n s i d e r e d . The method o f a n a l y z i n g t h e v i b r a t o r y c h a r a c t e r i s t i c s o f the r a s p b e r r y f r u i t a t t a c h m e n t system was s i m i l a r t o t h a t used by Wang (37) f o r c o f f e e f r u i t . Wang c o n s i d e r e d the c o f f e e - c h e r r y p e d u n c l e system as a c a n t i l e v e r beam w i t h a c o n c e n t r a t e d end mass. N a t u r a l f r e q u e n c y was e s t i m a t e d by measuring t h e s p r i n g c o n s t a n t o f t h e p e d u n c l e and a n a l y z i n g as a s i m p l e spring-mass system. S i n c e t h e s p r i n g c o n s t a n t o f t h e stem ( f i g u r e 30) a t t a c h i n g the r a s p b e r r y t o the sec o n d a r y l i m b s t r u c t u r e i s n e g l i g i b l e , t h e f r u i t - s t e m system was a n a l y z e d as a s i m p l e pendulum. On t h i s b a s i s , t h e e s t i m a t e d n a t u r a l f r e q u e n c y o f t h e f r u i t a t t achment - 64 -system was where g h n [ g / U + 0 . 5 h ) ]1 / 2 a c c e l e r a t i o n due t o g r a v i t y f r u i t l e n g t h f r u i t stem l e n g t h [ 3 2 ] Based on t h e d i m e n s i o n s r e p o r t e d i n T a b l e I I I and a f r u i t w e i g h t o f 3.52 - 0.97 gm, t h e e s t i m a t e d n a t u r a l f r e q u e n c y o f the f r u i t a t t a c h m e n t system v a r i e d from 135 t o 164 c y c l e s p e r minute. I f base m o t i o n i s a p p l i e d t o t h e cane and not t o the f r u i t a t t a c h m e n t system, i n v e s t i g a t i o n o f t h e modes o f v i b r a t i o n o f t h e canes i s i m p o r t a n t . F r i d l e y and A d r i a n (13) s u g g e s t t h a t optimum d e s i g n f r e q u e n c y o f a f r u i t h a r v e s t i n g system s h o u l d be a n a t u r a l f r e q u e n c y o f t h e t r e e system. A d r i a n e t a l (1) showed a m p l i t u d e m a g n i f i c a t i o n a t r e s o n a n t f r e q u e n c i e s i n c o n t r o l l e d t e s t s on o l i v e S t e m l i m b s when base m o t i o n was a p p l i e d a t an a n t i n o d e . The method o f i n f l u e n c e c o e f f i c i e n t s (36) was used t o e s t i m a t e t h e modes and f r e -q u e n c i e s o f two s e l e c t e d r a s p b e r r y canes. S i n c e t h e r e F i g u r e 30 F r u i t a t tachment system i s a l a r g e v a r i a t i o n i n cane i d e a l i z e d as a s i m p l e pendulum. s i z e , two canes o f d i f f e r e n t Fruit - 65 -p h y s i c a l appearance were s e l e c t e d , one r e p r e s e n t i n g the l a r g e s t d i a m e t e r o f f r u i t b e a r i n g canes and the o t h e r r e p r e s e n t i n g t h e s m a l l e s t d i a m e t e r . The canes were removed from the f i e l d i n the s p r i n g o f 1969, j u s t as l e a f buds were b e g i n n i n g t o emerge. An epoxy base was c a s t on the r o o t end o f each cane t o f a c i l i t a t e h o l d i n g w h i l e measurements were conducted. Each cane was d i v i d e d i n t o e i g h t s t a t i o n s spaced a t s i x i n c h i n t e r v a l s a l o n g i t s l e n g t h . The canes were h e l d v e r t i c a l l y ( f i g u r e 31) and s t i f f n e s s i n f l u e n c e c o e f f i c i e n t s were determined by measuring the d e f l e c t i o n a t a l l s t a t i o n s w h i l e a h o r i z o n t a l l o a d o f 200 grams was s u c c e s s i v e l y a p p l i e d t o each s t a t i o n . The f l e x i b i l i t y m a t r i x r e s u l t i n g from one such t e s t i s shown i n T a b l e XI . The v a l u e s p r e s e n t e d i n the t a b l e a r e the F i g u r e 31 Measurement o f the s t i f f n e s s i n f l u e n c e c o e f f i c i e n t s o f a r a s p b e r r y cane. - 66 " d e f l e c t i o n s i n i n c h e s r e s u l t i n g from t h e s u c c e s s i v e a p p l i c a t i o n o f a l o a d o f 200 grams a t 6 i n c h i n t e r v a l s up t h e cane. ( C i j i s t h e d e f l e c t i o n a t s t a t i o n j r e s u l t i n g from l o a d a p p l i c a t i o n a t s t a t i o n i . ) As can be seen, t h e f l e x i b i l i t y m a t r i x i s n e a r l y symmetric i n d i c a t i n g t h a t f o r s t a t i c l o a d s o f s h o r t d u r a t i o n , t h e m a t e r i a l i n t h e r a s p b e r r y canes may be c o n s i d e r e d e l a s t i c . A f t e r d e t e r m i n a t i o n o f t h e i n f l u e n c e c o e f f i c i e n t s , a s m a l l d e f o r m a t i o n was o b s e r v e d i n t h e cane upon l o a d r e m o v a l . The cane r e l a x e d , r e t u r n i n g t o z e r o p o s i t i o n a f t e r t h i r t y m i n u t e s . TABLE XI FLEXIBILITY MATRIX,[C], FOR A RASPBERRY CANE LOADED AS A VERTICAL CANTILEVER BEAM. 1 2 3 4 5 6 7 8 1 0.02 0. 04 0. 08 0.11 0.16 0.19 0. 21 0.25 2 0.05 0.15 0.22 0. 30 0.40 0. 51 0.60 0.65 3 0.08 0.22 0.40 0.60 0.84 1.05 1.26 1.40 4 0.11 0.32 0. 61 0.92 1.38 1.76 2.17 2. 50 5 0.15 0.40 0. 84 1. 37 2.02 2.62 3.29 3.90 6 0.19 0.51 1. 06 1.74 2.66 3. 65 4 . 50 5.45 7 0.20 0.62 1. 28 2.18 3.29 4.55 6.08 7.60 8 0. 24 0.69 1.44 2.45 3.90 5.50 7.62 9.70 A f t e r d e t e r m i n a t i o n o f t h e f l e x i b i l i t y m a t r i x , the cane was c u t i n t o p i e c e s midway between each s t a t i o n and each p i e c e was weighed. For e s t i m a t i o n o f modes and n a t u r a l f r e q u e n c i e s , t h e mass o f t h e cane was c o n s i d e r e d t o be lumped a t each o f t h e e i g h t s t a t i o n s , r e d u c i n g t h e i n f i n i t e degree o f freedom system t o a d i s c r e t e system w i t h e i g h t degrees o f freedom. T a b l e X I I p r e s e n t s t h e mass m a t r i x f o r the same cane as d e s c r i b e d i n T a b l e X I . The v a l u e s p r e s e n t e d i n T a b l e X I I a r e t h e w e i g h t s , i n grams, w h i c h were c o n s i d e r e d lumped a t each s t a t i o n . TABLE X I I MASS MATRIX,Cm v ] , FOR A RASPBERRY CANE 1 V j 1 2 3 4 5 6 7 8 1 16.7 2 10.6 3 9.5 4 6.9 5 7.2 6 7.7 7 7.8 8 5.5 In o r d e r t o e s t i m a t e the modes o f v i b r a t i o n o f t h e canes and the c o r r e s p o n d i n g n a t u r a l f r e q u e n c i e s , a p r o c e s s o f m a t r i x i t e r a -t i o n ( 3 6 ) was used. U s i n g a c o n s i s t e n t s e t o f u n i t s , t h e mode o f v i b r a t i o n i s ( Z ^ = co-j2 [C] P n u ] { Z ^ = U l 2 [D] {Z 1> [33] where {Z^} = t h e column m a t r i x f o r t h e f i r s t mode [C] = the f l e x i b i l i t y m a t r i x ( T a b l e X I ) [ vnu]= t h e d i a g o n a l mass m a t r i x ( T a b l e X I I ) [D] = [C] [ v r r u ] = t h e dynamic m a t r i x o)^ = t h e f u n d a m e n t a l ( f i r s t ) n a t u r a l f r e q u e n c y o f th e cane  1 These d a t a a p p l y t o t h e same cane f o r which t h e f l e x i b i l i t y m a t r i x was p r e s e n t e d i n T a b l e X I . Cane 1 Cane 2 1 r First Mode -o Q. E < -o CD N ~o E o Z -1 1 2 3 4 A distance above soil surface (feet) CO - 1 L F i g u r e 32 C a l c u l a t e d modes o f v i b r a t i o n and c o r r e s p o n d i n g n a t u r a l f r e q u e n c i e s f o r two r a s p b e r r y canes. - 69 -The l a s t column o f t h e dynamic m a t r i x was n o r m a l i z e d and used as an i n i t i a l a p p r o x i m a t i o n f o r t h e mode shape. A p p l i c a t i o n o f t h e i t e r a t i v e p r o c e d u r e shown i n e q u a t i o n [33] r e s u l t e d i n convergence t o the f i r s t p r i n c i p l e mode and y i e l d e d t h e f u n d a -m e n t a l f r e q u e n c y , co^. F o r d e t e r m i n a t i o n o f t h e second mode and the second n a t u r a l f r e q u e n c y , a sweeping m a t r i x , d e v o i d o f t h e f i r s t mode, was used i n t h e i t e r a t i v e p r o c e d u r e . {Z 2> = t o 2 2 [ D ] [ S 1 ] {Z 2> [34] where {Z,,} = t h e column m a t r i x f o r t h e second mode [S^ ] = t h e sweeping m a t r i x to 2 = t h e second n a t u r a l f r e q u e n c y o f t h e cane The f i r s t two modes and c o r r e s p o n d i n g r e s o n a n t f r e q u e n c i e s f o r t h e two r a s p b e r r y canes a r e p r e s e n t e d i n f i g u r e 32. The c a l c u l a t e d r e s o n a n t f r e q u e n c i e s o f t h e two canes were 185 and 218 c y c l e s p e r minute f o r t h e f i r s t mode and 786 and 1032 c y l e s p e r minute f o r t h e second mode. The i n c l u s i o n o f f r u i t and l i m b mass and damping would r e d u c e t h e s e f r e q u e n c i e s c o n s i d e r a b l y . Due t o t h e s i m p l y i n g a s s u m p t i o n s used i n t h e s e d e t e r m i n a t i o n s , the r e s u l t i n g v a l u e s a r e not i n d i c a t i v e o f t h e a c t u a l dynamic r e s p o n s e o f t h e complete p l a n t . The r e s u l t s a r e , however, u s e f u l i n d e s i g n i n g a h a r v e s t i n g machine. The l a r g e d i f f e r e n c e s o b s e r v e d between t h e two canes i n d i c a t e t h a t a t t e m p t i n g t o d e s i g n a h a r v e s t i n g machine w h i c h o p e r a t e s a t a r e s o n a n t f r e q u e n c y o f the p l a n t system i s i m p r a c t i c a l . F u r t h e r m o r e , a p p l i c a t i o n o f base m o t i o n t o o n l y one p a r t o f the canes ( f i g u r e 10) i s a l s o i m p r a c t i c a l s i n c e t h e r e s u l t i n g i n e r t i a l f o r c e d e v e l o p e d i n t h e f r u i t i n g p o r t i o n s w i l l be v a r i a b l e , depending upon t h e p r o p e r t i e s o f t h e i n d i v i d u a l canes. E l a s t i c Modulus o f R a s p b e r r y Canes The e l a s t i c modulus o f the two canes s t u d i e d i n the p r e v i o u s s e c t i o n was e s t i m a t e d by b o t h an energy method and by a n u m e r i c a l s o l u t i o n o f the E u l e r e q u a t i o n f o r l a r g e d e f l e c t i o n s o f t a p e r e d beams. The energy s o l u t i o n was based on R a y l e i g h ' s method (36) f o r d e t e r m i n a t i o n o f t h e f u n damental f r e q u e n c y o f a c o n t i n u o u s system. The fundamental f r e q u e n c y as o b t a i n e d from the m a t r i x i t e r a t i o n p r o c e d u r e was s u b s t i t u t e d i n t o R a y l e i g h ' s f o r m u l a t i o n and t h e r e s u l t i n g e q u a t i o n was s o l v e d f o r the e l a s t i c modulus. E = (UK) 2 [/ Lm(x) Z 2 dx / / L I ( x ) ( ^ - | ) 2 dx] [35] o ' o M x ' where I ( x ) = moment o f i n e r t i a o f the cane c r o s s s e c t i o n p e r u n i t o f l e n g t h L = t o t a l l e n g t h o f t h e cane Z = mode shape m(x)= mass o f the cane p e r u n i t o f l e n g t h = f u n d a m e n t a l f r e q u e n c y o f t h e cane The canes were c o n s i d e r e d as t a p e r e d c a n t i l e v e r beams o f c i r c u l a r c r o s s s e c t i o n . I ( x ) and m(x) were d e t e r m i n e d by p l o t t i n g the v a l u e s o f cane d i a m e t e r and cane mass f o r each o f the e i g h t s t a t i o n s used i n d e t e r m i n i n g the f l e x i b i l i t y m a t r i x 2 and f i t t i n g s t r a i g h t l i n e s . A p a r a b o l i c mode shape, Z = C^ x , s a t i s f y i n g t h e boundary c o n d i t i o n s f o r a c a n t i l e v e r beam, was chosen. The r e s u l t i n g e s t i m a t e s o f e l a s t i c modulus f o r the two 2 canes shown i n f i g u r e 32 were 295,000 l b / i n f o r cane 1 and 469,000 l b / i n 2 f o r cane 2. - .71 -A second e s t i m a t e o f the e l a s t i c modulus was o b t a i n e d by use o f n u m e r i c a l s o l u t i o n s o f the E u l e r e q u a t i o n f o r l a r g e d e f l e c t i o n s o f t r u n c a t e d cones w i t h c o n c e n t r a t e d end l o a d s , as p r e s e n t e d by D i e n e r e t a l ( l i ) # The t a b u l a t e d s o l u t i o n s , which were used by t h e s e a u t h o r s i n s t u d y i n g t h e d e f l e c t i o n o f a p p l e l i m b s , a r e o f t h e form o where E = e l a s t i c modulus I = moment o f i n e r t i a o f c r o s s s e c t i o n a t r o o t o f l i m b L = l i m b l e n g t h P A = c o n c e n t r a t e d l o a d a p p l i e d a t l i m b t i p q = P L 2 / E . I M a / o c = t a p e r o f l i m b = t i p r a d i u s / r o o t r a d i u s y = d e f l e c t i o n o f l i m b t i p S u b s t i t u t i n g a p p r o p r i a t e v a l u e s o f I , P , L, y and c f o r O ' cl t h e two r a s p b e r r y c a n e s , i n t o t h e t a b u l a t e d s o l u t i o n s r e s u l t e d 2 i n e s t i m a t e s o f e l a s t i c modulus o f 255,000 l b s / i n and 463,000 2 l b s / i n f o r canes 1 and 2 r e s p e c t i v e l y . C o n t r o l o f P h y s i c a l P r o p e r t i e s - Growth R e g u l a t o r s The f o l l o w i n g d i s c u s s i o n does n ot d i r e c t l y p e r t a i n t o d e s i g n o f a m e c h a n i c a l h a r v e s t e r but i s i n c l u d e d s i n c e i t may s i g n i f i c a n t l y a f f e c t t h e performance o f m e c h a n i c a l h a r v e s t i n g systems f o r r a s p b e r r i e s . S i n c e t h e h i g h r a t i o o f f r u i t r e t e n -t i o n f o r c e t o f r u i t stem s t r e n g t h may s e r i o u s l y l i m i t t h e p i c k i n g e f f i c i e n c y o f a m e c h a n i c a l h a r v e s t e r , an at t e m p t was - 72 -made t o reduce f r u i t r e t e n t i o n f o r c e t h r o u g h the use o f c h e m i c a l growth r e g u l a t o r s . U n r a t h and Kenworthy (2 3) s u c c e s s f u l l y used growth r e g u l a t o r s t o reduce t h e f r u i t r e t e n t i o n f o r c e o f c h e r r i e s . A s i m i l a r t e c h n i q u e was a p p l i e d t o r a s p b e r r i e s i n an att e m p t t o improve the s u i t a b i l i t y o f t h e p l a n t s t o m e c h a n i c a l h a r v e s t i n g . S i n c e no p u b l i s h e d r e s u l t s on the use o f growth r e g u l a t o r s on r a s p b e r r i e s c o u l d be o b t a i n e d , growth r e g u l a t o r s were s e l e c t e d on the b a s i s o f t h e i r e f f e c t on o t h e r f r u i t . A randomized b l o c k c o n s i s t i n g o f f o u r t e e n p l o t s ( f i g u r e 33) each h a v i n g t e n p l a n t s , was used f o r t h e growth r e g u l a t o r t r i a l s . The s e l e c t e d growth r e g u l a t o r s were s u c c i n i c a c i d 2 , 2 - d i m e t h y l -h y d r a z i d e ( A l a r ) and a m i x t u r e o f e q u a l p a r t s o f 2,4, 5 - t r i c h l o r o p h e n o x y p r o p i o n i c a c i d (2,4,5-TP) and n a p h t h e l e n e a c e t i c a c i d (NAA). Three c o n c e n t r a t i o n s o f each o f the growth r e g u l a t o r s were a p p l i e d t o i n d i v i d u a l p l o t s a t two d i f f e r e n t a p p l i c a t i o n d a t e s as shown i n T a b l e X I I I . Growth r e g u l a t o r s were a p p l i e d u s i n g a s e m i - c i r c u l a r s p r a y boom ( f i g u r e 34) w i t h f o u r No. 650067 T - J e t s p r a y n o z z l e s spaced t o a p p l y r e l a t i v e l y u n i f o r m c o v e r a g e on t h e f r u i t b e a r i n g p o r t i o n o f t h e p l a n t s . Two such booms were used t o a v o i d p o s s i b l e m i x i n g o f growth r e g u l a t o r s . The s p r a y s o l u t i o n was p l a c e d i n t h e l i q u i d t a n k on the boom end ( f i g u r e 34) and a i r a t 40 p s i g was a p p l i e d t o t h e t a n k w i t h a p o r t a b l e a i r compressor. The r e s u l t i n g r a t e o f d i s c h a r g e o f each s p r a y boom was 1000 cc/m i n . The c o n c e n t r a t i o n o f A l a r p l a c e d i n t h e s p r a y t a n k was 1000 ppm w h i l e the c o n c e n t r a t i o n o f 2,4,5-TP+NAA was 20 ppm. I n o r d e r t o o b t a i n the low c o n c e n t r a t i o n s - 73 -F i g u r e 3 3 Randomized p l o t s f o r growth r e g u l a t o r t r i a l s F i g u r e 34 Spray boom f o r a p p l y i n g growth r e g u l a t o r s ( T a b l e X I I I ) 250 cc o f t h e s o l u t i o n was a p p l i e d t o t h e s e l e c t e d 10 p l a n t p l o t , w h i l e t o o b t a i n t h e medium c o n c e n t r a t i o n s , 500 cc was a p p l i e d and f o r t h e h i g h c o n c e n t r a t i o n s , 1000 cc was a p p l i e d . T h i s was a c c o m p l i s h e d by making one f i f t e e n second pass o f the s p r a y boom o v e r a p l o t f o r low c o n c e n t r a t i o n s , two pas s e s (30 seconds) f o r i n t e r m e d i a t e c o n c e n t r a t i o n s , and f o u r p a s s e s (one minute) f o r h i g h c o n c e n t r a t i o n s . TABLE X I I I GROWTH REGULATOR TREATMENTS Treatment P l o t Number Growth C o n c e n t r a t i o n A p p l i c a t i o n Number (see F i g . 3 3 ) R e g u l a t o r (p.p.m.) Date 1 3 check 0 2 4 A l a r 1000 June 17 3 16 A l a r 2000 June 17 4 2 A l a r 4000 June 17 5 15 2,4,5-TP+NAA 20 June 17 6 6 2,4,5-TP+NAA 40 June 17 7 8 2,4,5-TP+NAA 80 June 17 8 7 check 0 9 11 A l a r 1000 June 28 10 1 A l a r 2000 June 28 11 13 A l a r 4000 June 28 12 9 2,4,5-TP+NAA 20 June 28 13 10 2,4,5-TP+NAA 40 June 28 14 14 2,4,5-TP+NAA 80 June 28 Three p l a n t s i n each p l o t were s e l e c t e d f o r c o m p a r a t i v e p u r p o s e s . On each o f f i v e days d u r i n g the h a r v e s t s e a s o n , t h r e e - 75 -f r u i t were p i c k e d a t random from each s e l e c t e d p l a n t i n each p l o t . F r u i t r e t e n t i o n f o r c e , f r u i t weight, f r u i t c o l o r , r i g i d -i t y and f o r c e - d e f o r m a t i o n c h a r a c t e r i s t i c s were determined f o r each f r u i t . A n a l y s i s o f v a r i a n c e t e s t s were conducted, comparing the measured v a r i a b l e s o f the growth r e g u l a t o r treatments. R e s u l t s o f the t e s t s i n d i c a t e d t h a t both types o f growth r e g u l a -t o r s s i g n i f i c a n t l y a f f e c t e d f r u i t r e t e n t i o n f o r c e , f r u i t c o l o r and f r u i t weight. The type o f growth r e g u l a t o r , i t s c o n c e n t r a t i o n and i t s time o f a p p l i c a t i o n a l l a f f e c t e d f r u i t r e t e n t i o n f o r c e . Furthermore, the e f f e c t was dependent upon time o f h a r v e s t . S i n c e f r u i t r e t e n t i o n f o r c e , f r u i t weight and F/W a l l i n f l u e n c e h a r v e s t e r d e s i g n , the e f f e c t o f growth r e g u l a t o r s on these parameters was i n v e s t i g a t e d more f u l l y . The simple r e g r e s s i o n s o f f r u i t r e t e n t i o n f o r c e on h a r v e s t time were d e t e r -mined (Table XIV) f o r each treatment. The a n a l y s i s o f c o v a r i a n c e (33) was used t o compare the r e g r e s s i o n f o r each growth r e g u l a t o r treatment t o the p o o l e d r e g r e s s i o n f o r treatments 1 and 8. T h i s a n a l y s i s compared homogeneity o f r e s i d u a l v a r i a n c e , s l o p e and l e v e l o f the two r e g r e s s i o n l i n e s i n o r d e r to f i n d s i g n i f i c a n t d i f f e r e n c e s . S i m i l a r comparisons were made f o r f r u i t weight (Table XV) and F/W (Table XVI). Tables XIV, XV, XVI are based on 90 o b s e r v a t i o n s f o r the check and 4 5 o b s e r v a t i o n s f o r each growth r e g u l a t o r treatment. The f i r s t column i n each t a b l e r e p r e s e n t s the treatment as shown i n T a b l e X I I I . The f o u r t h column i s the i n t e r c e p t and the f i f t h column i s the s l o p e o f the r e g r e s s i o n e q u a t i o n , Y = a + bT, where Y i s the dependent v a r i a b l e named i n the t i t l e o f the t a b l e . - 76 -The r e g r e s s i o n e q u a t i o n s a p p l y f o r the i n t e r v a l , 1 < T < 15, where T i s t i m e i n days and (T = 1) i s t h e f i r s t day o f h a r v e s t . The n i n t h , t e n t h and e l e v e n t h columns i n each t a b l e i n d i c a t e r e s u l t s o f t h e c o v a r i a n c e a n a l y s i s . In c a s e s where the homo-g e n e i t y o f r e s i d u a l v a r i a n c e show a s i g n i f i c a n t d i f f e r e n c e , t h e t e s t s f o r s l o p e and l e v e l a r e not v a l i d . The r e s u l t s o f the c o v a r i a n c e a n a l y s i s i n d i c a t e t h a t t h e use o f growth r e g u l a t o r s c o u l d s i g n i f i c a n t l y a f f e c t t h e p e r f o r -mance o f a m e c h a n i c a l h a r v e s t e r . F o r example, t r e a t m e n t s 3 and 14 s i g n i f i c a n t l y r e d u c e d f r u i t r e t e n t i o n f o r c e w h i l e t r e a t m e n t s 5, 11 and 14 s i g n i f i c a n t l y r e d u c e d F/W, f o r the e a r l y p a r t o f the h a r v e s t s e a s o n . S i n c e t h e h i g h e s t r a t i o o f f r u i t r e t e n t i o n f o r c e t o stem s t r e n g t h o c c u r s e a r l y i n t h e h a r v e s t s e a s o n , t h e s e t r e a t m e n t s c o u l d p o s s i b l y i n c r e a s e t h e p i c k i n g e f f i c i e n c y - o f a m e c h a n i c a l h a r v e s t e r d u r i n g t h e f i r s t p a r t o f the h a r v e s t . F u r t h e r t r i a l s a r e n e c e s s a r y b e f o r e any f i r m c o n c l u s i o n s may be drawn. TABLE XIV VARIATION OF FRUIT RETENTION FORCE WITH TIME AS AFFECTED BY GROWTH REGULATOR TREATMENTS Treatment Mean Standard (gm) Deviation S i g n i f i -cance of r S Significance of Covariance Anal-Homogeneity Slope T ' S 1 S I y of Variance e v e Check (pooled) 254 .0 146. 5 347. 7 -13.4 -.43 P< 0. 01 132. 9 — • -2 282 . 6 150. 8 382. 6 -14.3 -.45 P< 0.01 136. 3 NS NS P < 0. 25 3 280 .3 126. 7 287 . 3 - 1.0 -.04 NS1 128. 1 NS P < 0. 025 NS 4 389 .7 181. 1 452. 7 - 9.0 -.23 NS 178 . 1 NS NS P < 0. 005 5 289 . 2 132. 8 316. 8 - 4.0 -.14 NS 133. 0 NS P < 0. 10 P < 0. 25 6 315 .1 126. 3 392. 3 -11.0 -.41 P< 0.01 116. 3 P < 0. 25 NS P < 0. 01 ' 7 280 .6 122. 1 350. 6 -10.0 -.39 P< 0. 01 113. 8 P < 0. 25 NS NS -j i 9 287 .7 180. 1 386. 6 -14.1 -.37 P< 0.01 169. 1 NS NS P < 0. 25 10 266 .1 148. 1 310. 0 - 6.3 -.20 NS 146. 7 NS P < 0. 25 NS 11 288 .2 162. 2 344. 4 - 8.0 -.23 NS 159. 5 NS NS P < 0. 25 12 264 .9 143. 1 375. 8 -15.8 -.52 P< 0.01 123. 2 NS NS NS 13 3 39 .0 185. 9 445. 2 -15.2 -.39 P< 0.01 173. 4 NS NS P < 0. 005 14 292 .1 143. 1 273. 6 2.6 .09 NS 144. 2 NS P < 0. 005 P ^ 0. 25 1 NS indicates no s i g n i f i c a n t difference between the pooled check and the growth regulator treatment at P < 0.25 TABLE XV. VARIATION OF FRUIT WEIGHT WITH TIME AS AFFECTED BY GROWTH REGULATOR TREATMENTS Treatment Mean Sta n d a r d (gm) D e v i a t i o n S i g n i f i -cance o f r S S i g n i f i c a n c e o f C o v a r i a n c e A n a l -Homogeneity S l o p e L e v e l o f V a r i a n c e Check ( p o o l e d ) 3, .52 0. 97 3, .01 0, .07 .35 P < 0.01 0. 92 — --•-2 3, .92 1. 46 4, .10 -0, .03- .09 NS 1. 48 NS P < 0, .05 P < 0, .10 3 2. .76 1. 21 1, .80 0. .14 .54 P < 0.01 1. 03 NS P < 0, .10 P < 0, .005 4 4, .14 0. 83 4, .15 -0, .00- .01 NS 0. 84 NS P < 0, .05 P < 0. .005 5 3, .33 1. 16 3, .43 -0, .01- .06 NS 1. 18 NS P < 0. .05 NS i 6 4, .08 0. 76 4, .14 -0, .01- .05 NS 0. 77 P < 0.25 P < 0, .025 P < 0. ,005 « 7 3, .94 0. 95 4 , .57 -0, .09- .45 P < 0.01 0. 86 NS P < 0, ,005 P < 0, .025 ' 9 4, .64 0. 82 4, ,95 -0. , 04-.26 NS 0. 80 NS P < 0. .005 P < 0, .005 10 3, .98 0. 94 4. .16 -0, .02- .12 NS 0. 94 NS P < 0. ,01 P < 0. ,10 11 3. .85 0. 96 3. .83 0. ,00 .01 NS 0. 97 NS P < 0. .10 P < 0. ,10 12 4 . ,29 0. 89 4. , 33 -0. ,00- .03 NS 0. 90 NS P < 0. ,05 P < 0. ,005 13 4. ,32 1. 14 4. ,40 -0. ,01- .04 NS 1. 15 NS P < 0, ,05 P < 0. ,005 14 3. ,51 1. 41 3. ,85 -0. ,05- .16 NS 1. 41 NS P < 0. ,01 NS TABLE XVI F/W VARIATION WITH TIME AS AFFECTED BY GROWTH REGULATOR TREATMENTS Treatment Mean S t a n d a r d S i g n i f i - - S i g n i f i c a n c e o f C o v a r i a n c e A n a l -(gm) D e v i a t i o n . n c Homogeneity S l o p e ^ s : L S ^ 6 a b r r -S c ,,6 . J * L e v e l y o f V a r i a n c e Check ( p o o l e d ) 82.8 65.1 128.0 -6.5 -.47 P < 0.01 57.8 --•-2 93.5 105.1 143.4 -7.1 -.32 P < 0.05 100.6 NS NS NS 3 127.1 86.2 174.9 -6.8 -.38 P < 0.01 80.8 NS NS P < 0.005 4 98.0 50.8 117.4 -2.8 -.26 NS 49.6 P < 0. 25 P < 0. 10 P < 0.25 5 101.4 75.1 110.3 -1.3 -.08 NS 76.0 NS P < 0. 05 P < 0.25 1 6 80.8 36.3 96.8 -2.3 -.30 P < 0.05 35.1 P < 0.005 " P < 0. 05 CD NS i 7 74.8 37.5 84.5 -1.4 -.17 NS 37.3 P < 0.005 P < 0. 025 NS 9 64.1 43.0 85.1 -3.0 -.33 P < 0.05 41.1 P < 0.005 P < 0. 10 P < 0.10 10 71.3 45.8 81.7 -1.5 -.15 NS 45.8 P < 0.05 P < 0. 025 NS 11 82.4 68 .0 94.7 -1.8 -.12 NS 68.3 NS P < 0. 10 NS 12 65.8 39.9 93.3 -3.9 -.47 P < 0.01 35.6 P < 0. 005 P < 0. 25 P < 0.10 13 82.7 47.4 108 .5 -3.7 -.37 P < 0.01 44.9 P < 0.05 P < 0. 25 NS 14 103.1 78.2 101.7 0.2 .01 NS 67.4 NS P < 0, 01 P < 0.10 MATHEMATICAL MODELS FOR THE TOOLS C o m p l e t i o n o f t h e T o o l A n a l y s e s I n t h i s c h a p t e r , t h e e l e m e n t a r y t o o l a n a l y s e s and t h e a n a l y s i s o f t h e p r o d u c t c h a r a c t e r i s t i c s a r e combined i n o r d e r t o o b t a i n m a t h e m a t i c a l models r e p r e s e n t i n g t h e performance o f each t o o l i n t h e p r o c e s s . The r e s u l t i n g e q u a t i o n s d e t e r m i n e t h e d e s i g n s p e c i f i c a t i o n s o f t h e i n d i v i d u a l t o o l s . T o o l f o r F e e d i n g and Cane O r i e n t a t i o n F i g u r e 11 i n d i c a t e s t h a t t h e t o t a l f r u i t b e a r i n g p o r t i o n o f th e r a s p b e r r y p l a n t i s l o c a t e d i n a 5 f o o t h e i g h t i n t e r v a l . S e l e c t i n g a v a l u e o f 45° f o r 8 ( f i g u r e 8) t h e maximum n e c e s s a r y f e e d r o l l l e n g t h i s 5 / s i n (45°) = 7.1 f t . S e l e c t i n g an e x t e r n a l f e e d r o l l d i a m e t e r o f 4 i n c h e s w i t h Q = 4 5°, f rom e q u a t i o n [ 3 ] t h e n e c e s s a r y r e l a t i o n s h i p between f e e d r o l l r o t a t i o n and f o r w a r d speed i s • • r i r = 118.8S [ 3 5] where n^ = f e e d r o l l speed, r e v o l u t i o n s p e r minute S = f o r w a r d speed o f h a r v e s t i n g machine, m i l e s p e r hour L e t t i n g x = L , i n e q u a t i o n [ 5 ] and s o l v i n g f o r P , t h e cl r e s u l t i n g e s t i m a t e o f t h e h o r i z o n t a l r e a c t i o n f o r c e between a s i n g l e cane and a f e e d r o l l i s P a = [3yEI c ( l - c ) 3 ] / [ ( l - 3 c + 3 c 2 - c 3 ) L 3 ] [ 3 6 ] c l U where L = t h e d i s t a n c e above t h e s o i l s u r f a c e a t whi c h t h e f e e d r o l l c o n t a c t s a cane, y = t h e h o r i z o n t a l cane d e f l e c t i o n a t the l o a d p o i n t , and E, I and c a r e as p r e v i o u s l y d e f i n e d . Due t o t h e - 80 -i n c l i n a t i o n o f t h e f e e d r o l l s , L, y and c depend upon t h e p o s i t i o n on t h e f e e d r o l l s a t which c o n t a c t w i t h each i n d i v i d u a l cane o c c u r s . The t o t a l r e a c t i o n f o r c e between t h e canes and f e e d r o l l s depends upon t h e t o t a l number o f canes i n c o n t a c t a t any i n s t a n t . Assuming a maximum number o f t e n canes and t e n s h o o t s p e r p l a n t and c o n s i d e r i n g a f e e d r o l l l e n g t h o f 7.1 f e e t and a p l a n t s p a c i n g o f 2.5 f e e t , a maximum o f 40 canes and s h o o t s w i l l be i n c o n t a c t w i t h t h e f e e d r o l l s . Assuming t h a t t h e f l e x u r a l p r o p e r t i e s o f t h e s h o o t s a r e s i m i l a r t o t h o s e o f t h e canes and n o t i n g t h a t one f e e d r o l l compresses o n l y h a l f o f t h e p l a n t , t h e t o t a l r e a c t i o n f o r c e on one f e e d r o l l w i l l r e s u l t from c o n t a c t w i t h 20 c a n e s . Assuming t h a t t h e 20 canes a r e e q u a l l y spaced a t 3 i n c h e s down the row, t h e h e i g h t ( i n c h e s ) above ground a t w h i c h a f e e d r o l l c o n t a c t s a cane ( f i g u r e 35) i s L = 6 + z [ 3 7 ] where z = t h e h o r i z o n t a l d i s t a n c e ( i n c h e s ) b e h i n d t h e f r o n t o f t h e f e e d r o l l a t w h i c h cane c o n t a c t o c c u r s Based on a p l a n t w i d t h o f 10 i n c h e s a t ground l e v e l and 60 i n c h e s a t t h e 5.5 f o o t h e i g h t , assuming a l l canes a r e so o r i e n t e d and f u r t h e r assuming t h a t i t i s d e s i r e d t o compress a l l p l a n t s t o an 8 i n c h w i d t h a t t h e 0.5 f o o t l e v e l and a 4 i n c h w i d t h a t t h e 5.5 f o o t l e v e l , i t can be shown by g e o m e t r i c a l i n t e r p r e t a t i o n ( f i g u r e 36) t h a t t h e h o r i z o n t a l cane d e f l e c t i o n ( i n c h e s ) i s y = 3.8 + 0.504z [38] where z i s as p r e v i o u s l y d e f i n e d . - 82 C U < U <J D M-1_ ZJ CO o to cu > < cu ( J c o Feed roll centerline 1 2 3 4 Distance Behind Front of Feed Rolls (feet) F i g u r e 3 5 E s t i m a t i n g t h e p o i n t o f c o n t a c t between t h e canes and t h e f e e d r o l l s cu cu C U u o 5-D 3 3 CO o CO cu 5 < cu w c o 0 -3 .original « 101 oriental cane orientation (final cane 6 , 0 'orientation _2 _1 ° 0 ° 1 2 Distance Outward from Center of Row (feet) F i g u r e 36 E s t i m a t i n g the d e f l e c t i o n o f t h e canes by t h e f e e d r o l l s - 83 -Cane t a p e r , as d e f i n e d i n e q u a t i o n [ 5 ] , i s a l s o a f u n c t i o n o f t h e d i s t a n c e above ground a t wh i c h l o a d i n g o c c u r s . F i g u r e 37 shows a r a s p b e r r y cane r e p r e s e n t e d as a t a p e r e d c i r c u l a r c a n t i -l e v e r beam. The d i m e n s i o n s used i n t h i s f i g u r e a r e t h o s e o f t h e same cane as d e s c r i b e d i n T a b l e s XI and X I I and r e p r e s e n t t h e l a r g e s t e x p e c t e d s i z e o f r a s p b e r r y canes. By g e o m e t r i c a l i n t e r -p r e t a t i o n o f f i g u r e 37, cane t a p e r may be d e f i n e d as c = 0.95 - 0.0088z [ 39] where z i s as p r e v i o u s l y d e f i n e d . S u b s t i t u t i n g v a l u e s f o r L, y and c as g i v e n i n e q u a t i o n s [ 3 7 ] , [ 3 8 ] , and [39] r e s p e c t i v e l y , i n t o e q u a t i o n [ 3 6 ] , P now becomes t h e l o a d on t h e f e e d r o l l a t any d i s t a n c e z measured F i g u r e 37 D e t e r m i n i n g cane t a p e r as a f u n c t i o n o f t h e p o i n t o f l o a d a p p l i c a t i o n - 84 -r e a r w a r d from th e f r o n t end o f t h e f e e d r o l l . The t o t a l l o a d imposed by twenty canes e v e n l y spaced a t 3 i n c h e s a l o n g t h e 5 f o o t h o r i z o n t a l l e n g t h o f t h e f e e d r o l l i s E v a l u a t i n g e q u a t i o n [40] based on I - 0.0052 i n 2 ° and E = 455,000 l b / i n ( d a t a f o r t h e same cane as d e s c r i b e d i n f i g u r e 3 7 ) , t h e t o t a l h o r i z o n t a l r e a c t i o n f o r c e between one f e e d r o l l and the canes i t compresses was e s t i m a t e d a t 249 l b s . The r e a c t i o n f o r c e v a r i e d from 118 l b s . a t t h e f r o n t o f t h e f e e d r o l l t o 0.3 5 l b s . a t t h e r e a r o f t h e f e e d r o l l . Even though e q u a t i o n [36] u n d e r e s t i m a t e s t h e l o a d f o r l a r g e d e f l e c t i o n s , due t o s i m p l e beam t h e o r y , t h e above c a l c u l a t e d v a l u e f o r t o t a l r e a c t i o n f o r c e can be e x p e c t e d t o be h i g h s i n c e i t was assumed t h a t a l l canes and s h o o t s were o f maximum r i g i d i t y , were s u b j e c t e d t o maximum p o s s i b l e d e f l e c t i o n and were r i g i d l y a t t a c h e d t o t h e s o i l s u r f a c e . A n a l y s i s o f cane p r o p e r t i e s i n d i c a t e d l a r g e v a r i a t i o n s i n s i z e , r i g i d i t y and modes o f v i b r a t i o n o f i n d i v i d u a l c a n e s . I f base m o t i o n i s a p p l i e d t o a f i x e d p o i n t on each cane, r e s u l t a n t d i s p l a c e m e n t s a t e q u a l d i s t a n c e s f r om th e p o i n t o f a p p l i c a t i o n w i l l d i f f e r a c c o r d i n g t o t h e p r o p e r t i e s o f t h e i n d i v i d u a l canes. S i n c e maximum a c c e l e r a t i o n d e v e l o p e d a t any p o i n t i n a cane depends upon b o t h f r e q u e n c y and d i s p l a c e m e n t , th e i n e r t i a l f o r c e d e v e l o p e d i n t h e f r u i t w i l l depend upon cane p r o p e r t i e s . I n e r t i a l f o r c e must, however, be c o n t r o l l e d w i t h i n t h e l i m i t s s e t by e q u a t i o n [ 6 ] . T h i s can be a c c o m p l i s h e d o n l y by a p p l y i n g b o t h known d i s p l a c e m e n t and known f r e q u e n c y t o a l l f r u i t b e a r i n g — ,57,60 t o t a l [ 4 0 ] z = 0 , 3 , — T o o l f o r S e l e c t i v e H a r v e s t i n g - 85 -p o r t i o n s o f t h e p l a n t , i n d i c a t i n g t h a t base m o t i o n s h o u l d be a p p l i e d t o a l l the p l a n t . One method o f o b t a i n i n g t h i s d e s i r e d r e s u l t i s by a p p l y i n g t h e base m o t i o n t o t h e f e e d r o l l s ( f i g u r e 38). A l l f r u i t b e a r i n g p o r t i o n s w i l l t h e n be s u b j e c t e d t o the same maximum d i s p l a c e m e n t a t the same f r e q u e n c y as t h e r o l l s pass t h e p l a n t s . Both i n e r t i a s h a k e r s and f i x e d d i s p l a c e m e n t s h a k e r s a r e commonly used f o r base m o t i o n a p p l i c a t i o n i n t r e e f r u i t h a r v e s t -i n g . S i n c e the d i s p l a c e m e n t produced by an i n e r t i a s h a k e r i s a f u n c t i o n o f the r e s i s t i n g l o a d , the maximum a c c e l e r a t i o n produced by an i n e r t i a s h a k e r depends upon p h y s i c a l p r o p e r t i e s o f t h e p l a n t . A f i x e d d i s p l a c e m e n t s h a k e r appears t o be p r e f e r a b l e f o r s e l e c t i v e h a r v e s t i n g o f r a s p b e r r i e s s i n c e i t w i l l produce c o n s t a n t maximum base m o t i o n d i s p l a c e m e n t , i n d e p e n d e n t o f t h e p l a n t c h a r a c t e r i s t i c s . Both t h e f r u i t r e t e n t i o n f o r c e and the F/W r a t i o , f o r f r u i t o f s i m i l a r q u a l i t y , d e c r e a s e d u r i n g t h e h a r v e s t season as i s shown by e q u a t i o n s [23] and [ 2 4 ] , The f o r c e r e q u i r e d f o r f r u i t r e m o v a l t h e r e f o r e depends upon the s p e c i f i c d a t e o f h a r v e s t , i n d i c a t i n g t h a t t h e a p p l i e d base m o t i o n must be a d j u s t e d t o s u i t t h e t i m e o f h a r v e s t . The e x p e c t e d v a r i a t i o n o f f r u i t r e t e n t i o n f o r c e and F/W r a t i o i s summarized i n T a b l e X V I I . TABLE X V I I MEANS AND STANDARD DEVIATIONS OF FRUIT RETENTION FORCE AND F/W RATIO BASED ON DATA COLLECTED IN 1968 F i r s t Day o f F i f t e e n t h Day o f H a r v e s t Season H a r v e s t Season F r u i t R e t e n t i o n F o r c e (gm) 291 - 102 162 - 142 F/W R a t i o 96 - 45 46 - 4 3 - 86 -Po(t) F i g u r e 38 Base m o t i o n a p p l i e d t o t h e f e e d r o l l s S i x t y e i g h t p e r c e n t o f t h e measures d e f i n i n g a normal d i s t r i b u t i o n f a l l w i t h i n t h e range o f t h e mean - one s t a n d a r d d e v i a t i o n , w h i l e 95 p e r c e n t f a l l w i t h i n t h e range o f t h e mean - two s t a n d a r d d e v i a t i o n s . Hence, 84 p e r c e n t o f t h e measures have v a l u e s l e s s t h a n t h e sum o f t h e mean p l u s one s t a n d a r d d e v i a t i o n , and 97.5 p e r c e n t have v a l u e s l e s s t h a n t h e mean p l u s two s t a n d a r d d e v i a t i o n s . The e s t i m a t e d r e q u i r e d base m o t i o n a c c e l e r a t i o n s f o r 50, 84 and 97.5 p e r c e n t f r u i t r e m o v a l , based on the F/W d i s t r i b u t i o n s and e q u a t i o n [ 8 ] , a r e g i v e n i n T a b l e X V I I I . The n e c e s s a r y a c c e l e r a t i o n s f o r o t h e r l e v e l s o f f r u i t r e m o v a l may be e s t i m a t e d by a p p l y i n g e q u a t i o n [ 8 ] t o t h e c o r r e s -p o n d i n g v a l u e s o f F/W t a k e n from t h e c u m u l a t i v e d i s t r i b u t i o n c u r v e s i n f i g u r e 19. TABLE X V I I I CALCULATED BASE MOTION ACCELERATION FOR SEVERAL LEVELS OF FRUIT REMOVAL EFFICIENCY F r u i t Removal F i r s t "Day o f H a r v e s t F i f t e e n t h Day o f H a r v e s t R e q u i r e d Base R e q u i r e d Base L v c m u v a i Upper L i m i t M o t i o n A c c e l - Upper L i m i t M o t i o n A c c e l -<.percent; Q f p / w e r a t i o n o f F/W e r a t i o n ( f t / s e c 2 ) ( f t / s e c 2 ) 50 84 97.5 96 141 186 3090 4540 5980 46 89 132 1480 2860 4250 The c o l l e c t e d d a t a on f r u i t stem s t r e n g t h a r e not d i r e c t l y a p p l i c a b l e t o d e s i g n o f the p i c k i n g t o o l s i n c e t h e l o a d i n g used i n d e t e r m i n a t i o n o f stem s t r e n g t h i s n o t n e c e s s a r i l y t h e same as a c t u a l stem l o a d i n g d u r i n g m e c h a n i c a l h a r v e s t i n g . F i g u r e 22 shows t h e c u m u l a t i v e d i s t r i b u t i o n o f minimum stem s t r e n g t h ( ot = o°) and hence does n o t g i v e a r e l i a b l e e s t i m a t e o f F^ i n e q u a t i o n [ 6 ] , The t r i a l s on hand p i c k i n g by d i r e c t t e n s i l e f o r c e i n d i c a t e d t h a t i f a l l t h e mature f r u i t i s removed, 30 p e r -c e n t o f t h e f r u i t may have stem damage. I t i s t h e r e f o r e a p p a r e n t t h a t t o p r e v e n t stem damage, f r u i t r e m o v a l e f f i c i e n c y f o r one pass o f t h e h a r v e s t e r must be l e s s t h a n 70 p e r c e n t . O v e r a l l f r u i t r e m o v a l e f f i c i e n c y , c o n s i d e r i n g t h e whole s e a s o n , may be g r e a t e r but o n l y w i t h a d e c r e a s e i n o v e r a l l q u a l i t y o f t h e h a r v e s t e d f r u i t . S i n c e f r u i t r e t e n t i o n f o r c e d e c r e a s e s w i t h f r u i t m a t u r i t y , t h e f r u i t r e m a i n i n g a f t e r one pass o f t h e h a r v e s t e r may be p i c k e d a t a l a t e r d a t e but t h e q u a l i t y o f the r e s u l t i n g f r u i t w i l l be r e d u c e d . S i n c e c o l o r i n d e x i s an i n d i c a t o r o f f r u i t q u a l i t y , t h e a c c e l e r a t i o n r e q u i r e d t o remove f r u i t o f r e d u c e d q u a l i t y may be e s t i m a t e d . F o r example, u s i n g - 88 -e q u a t i o n s [ 2 6 ] and [ 2 8 ] w i t h a f r u i t c o l o r i n d e x o f 85, f r u i t r e t e n t i o n f o r c e i s e s t i m a t e d as 164 grams on the f i r s t day o f h a r v e s t and 110 grams on t h e l a s t day o f h a r v e s t . S i m i l a r l y , u s i n g e q u a t i o n s [27] and [29] w i t h a c o l o r i n d e x o f 85, F/W i s e s t i m a t e d as 67 on t h e f i r s t day o f h a r v e s t and 38 on t h e l a s t day o f h a r v e s t . C o r r e s p o n d i n g r e q u i r e d a c c e l e r a t i o n s f o r f r u i t 2 remo v a l a r e o n l y 2160 and 1220 f t / s e c , r e s p e c t i v e l y . A s i m p l e d e v i c e f o r a p p l y i n g f i x e d d i s p l a c e m e n t base mo t i o n t o t h e f e e d r o l l s i s a s l i d e r c r a n k mechanism. The maxi-mum a c c e l e r a t i o n d e v e l o p e d by a s l i d e r c r a n k mechanism i s ,£L,V = ( A ) H ) 2 r c (1 - k) [ 4 1 ] max D s where k = c r a n k l e n g t h / c o n n e c t i n g r o d l e n g t h r = c r a n k l e n g t h s = a n g u l a r v e l o c i t y o f c r a n k The n e c e s s a r y a m p l i t u d e and f r e q u e n c y f o r f r u i t r e m o v a l may be de t e r m i n e d by c o m b i n i n g e q u a t i o n s [ 8 ] and [ 4 1 ] . F i g u r e 39 shows t h e maximum a c c e l e r a t i o n d e v e l o p e d by a s l i d e r c r a n k mechanism, w i t h a c o n n e c t i n g r o d l e n g t h o f one f o o t , f o r s e v e r a l f i x e d a m p l i t u d e s and a range o f f r e q u e n c i e s . F/W has a l s o been p l o t t e d on t h e o r d i n a t e by r e l a t i n g maximum a c c e l e r a t i o n and F/W t h r o u g h e q u a t i o n [ 8 ] , T h i s f i g u r e may be used f o r d e t e r m i n i n g t h e base m o t i o n c h a r a c t e r i s t i c s which w i l l d e v e l o p t h e r e q u i r e d a c c e l e r a -t i o n s l i s t e d i n T a b l e X V I I I . T o o l f o r F r u i t C o l l e c t i o n and Conveying From t h e r e s u l t s o f drop t e s t s d e t e r m i n i n g t h e b r u i s i n g c h a r a c t e r i s t i c s o f r a s p b e r r y f r u i t , i t was found t h a t i f t h e f r e e f a l l d i s t a n c e o f t h e f r u i t i s g r e a t e r t h a n 4.5 cm, t h e impact Frequency (cycles per minute) F i g u r e 39 Maximum a c c e l e r a t i o n d e v e l o p e d by a s l i d e r c r a n k mechanism, w i t h one f o o t c o n n e c t i n g r o d l e n g t h , f o r s e v e r a l a m p l i t u d e s and a range o f f r e q u e n c i e s . The c o r r e s p o n d i n g upper l i m i t o f F/W r a t i o f o r f r u i t r e m o v a l i s a l s o p l o t t e d on t h e o r d i n a t e - 90 -v e l o c i t y must be l i m i t e d t o l e s s t h a n 94 cm/sec (187 f t / m i n ) . S i n c e base motion i s a p p l i e d t o f e e d r o l l s , t h e c o l l e c t i o n t o o l may be no h i g h e r t h a n t h e f e e d r o l l s i f i t i s t o i n t e r c e p t a l l t h e h a r v e s t e d f r u i t . A l t h o u g h most f r u i t removal s h o u l d o c c u r i n t h e r e g i o n o f maximum a c c e l e r a t i o n d i r e c t l y above t h e f e e d r o l l s , i t i s a p p a r e n t t h a t f r u i t w i t h low r e t e n t i o n f o r c e may be removed w h i l e t h e f e e d r o l l s a r e s t i l l a t a c o n s i d e r a b l e d i s t a n c e . A c u s h i o n i n g system, t o l i m i t t h e impact v e l o c i t y o f f r u i t s t r i k i n g t h e c o l l e c t i o n t o o l , t h e r e f o r e appears t o be mandatory. S u b s t i t u t i n g t h e v a l u e s f o r t e r m i n a l v e l o c i t y and a l l o w a b l e impact v e l o c i t y i n t o e q u a t i o n [ 1 7 ] , t h e n e c e s s a r y upward a i r v e l o c i t y s u p p l i e d by a c u s h i o n i n g a i r s t r e a m i s (3960 - 187) * 3800 f t / m i n . Minimum a c c e p t a b l e conveyor s i z e may be e s t i m a t e d from T a b l e s I I I and IV. I f s o r t i n g o r c l e a n i n g s h o u l d t a k e p l a c e on a c o n v e y o r , t h e maximum a l l o w a b l e c o n c e n t r a t i o n o f f r u i t i s a s i n g l e l a y e r o r l e s s . A h a r v e s t i n g r a t e o f 35 l b / m i n ( T a b l e IV) r e p r e s e n t s 7 5 i n d i v i d u a l f r u i t p e r second based on an i n d i v i d u a l f r u i t w e i g h t 3.52 gm. Conveyor d i s c h a r g e v e l o c i t y must be no g r e a t e r t h a n 94 cm/sec t o p r e v e n t b r u i s i n g o f f r u i t e n t e r i n g t h e s t o r a g e t o o l . Assuming a c o n v e y o r v e l o c i t y o f 94 cm/sec and a mean f r u i t d i a m e t e r o f 2.0 cm ( T a b l e I I I ) , a c o n v e y o r o f two cm w i d t h w i l l d e l i v e r 47 i n d i v i d u a l f r u i t p e r second. T h e r e f o r e , t o d e l i v e r a s i n g l e l a y e r o f f r u i t , t h e co n v e y o r w i d t h must be a t l e a s t f o u r cm. S i n c e the d a t a i n T a b l e IV a r e based on a f o r w a r d speed o f one m i l e / h o u r , c o n v e y o r w i d t h f o r h i g h e r speeds o f t r a v e l must be i n c r e a s e d a c c o r d i n g l y . - 91 -T o o l f o r F r u i t S t o r a g e The p e r m i s s i b l e d e p t h o f r a s p b e r r i e s i n a c o n t a i n e r may be e s t i m a t e d by a p p l y i n g e q u a t i o n [ 1 8 ] , n o t i n g t h a t from t h e f o r c e -d e f o r m a t i o n d a t a , K has a v a l u e o f 20Y. The mean and s t a n d a r d d e v i a t i o n o f t a n g e n t modulus from T a b l e V I I I a r e 1.32 and 0.54 r e s p e c t i v e l y . S i n c e s o f t f r u i t may be on t h e bottom l a y e r i n a c o n t a i n e r , a good e s t i m a t e o f r f o r d e t e r m i n i n g the a l l o w a b l e c o m p r e s s i v e l o a d on t h e bottom f r u i t l a y e r i s (1.32 - 0.54) = 0.78 S i n c e b r u i s i n g o f one d r u p e l e t ( T a b l e V) r e p r e s e n t s a b r u i s e depth o f a p p r o x i m a t e l y 1 mm, an o v e r a l l d e f o r m a t i o n o f 1 mm on the l o w e r l a y e r o f f r u i t i n a c o n t a i n e r w i l l n o t r e s u l t i n b r u i s i n g as t h i s r e p r e s e n t s t o t a l d e f o r m a t i o n t h r o u g h o u t the d i a m e t e r o f t h e f r u i t . On t h i s b a s i s , t h e a l l o w a b l e c o m p r e s s i v e l o a d on a s i n g l e f r u i t i s (1) (20) (0.78) = 15.6 gm U s i n g a mean f r u i t w e i g h t o f 3.52 gm and n e g l e c t i n g b r i d g i n g o r i n t e r a c t i o n between i n d i v i d u a l f r u i t , t h i s r e p r e s e n t s 4 l a y e r s o f f r u i t i n t h e c o n t a i n e r . S i n c e average f r u i t d i a m e t e r i s 2 cm, c o n t a i n e r f i l l i n g d e p th must not exceed 8 cm. The n e c e s s a r y s t o r a g e t o o l c a p a c i t y may be e s t i m a t e d from T a b l e IV. A h a r v e s t i n g r a t e o f 35 l b / m i n r e p r e s e n t s 4500 i n d i v i d u a l f r u i t p e r mi n u t e . Based on a mean f r u i t d i a m e t e r o f 2cm and a f i l l i n g d e p th o f 4 l a y e r s o f f r u i t , a c o n t a i n e r w i t h 2 2 s u r f a c e a r e a o f 4500 cm (700 i n ) w i l l be f i l l e d e v e r y m i n u t e . T h i s e s t i m a t e i s based on a f r u i t r e moval e f f i c i e n c y o f 100 p e r -c e n t f o r a f o r w a r d speed o f 1 m i l e p e r hour a t t h e peak o f the - 92 -h a r v e s t season. The e f f e c t o f i n - t r a n s i t v i b r a t i o n s on r a s p b e r r y f r u i t s t o r e d i n c o n t a i n e r s was not e v a l u a t e d . O ' B r i e n e_t a l (26 ,27 ) , i n s t u d i e s on t r a n s p o r t damage t o c l i n g peaches and tomatoes, found t h a t l i m i t i n g v e r t i c a l a c c e l e r a t i o n s t o l e s s t h a n 0.2g red u c e d t r a n s p o r t damage t o a c c e p t a b l e l e v e l s . As s o i l s u r f a c e c o n d i t i o n s i n r a s p b e r r y f i e l d s a r e v e r y u n i f o r m and h a r v e s t e r d e s i g n speed i s one m i l e / h o u r , e x p e c t e d v e r t i c a l a c c e l e r a t i o n s a r e l e s s t h a n 0.2g. The o n l y p r o b a b l e i n - t r a n s i t v i b r a t i o n damage i s i n t r a n s p o r t o f f r u i t from the f i e l d t o t h e p r o c e s s i n g p l a n t . DESIGN AND FABRICATION OF TOOLS I n t r o d u c t o r y Remarks T h i s c h a p t e r summarizes t h e d e s i g n and f a b r i c a t i o n o f the t o o l s s e l e c t e d t o mechanize the p r o c e s s . T o o l d e s i g n was based on t h e s p e c i f i c a t i o n s g i v e n i n t h e p r e v i o u s c h a p t e r w h i l e t h e m a t e r i a l s and methods used were t h o s e w h i c h would a l l o w f a b r i c a -t i o n i n a s m a l l machine shop. No at t e m p t was made t o c r e a t e optimum t o o l d e s i g n s . The purpose o f p r o t o t y p e t o o l s was t o t e s t t h e b a s i c d e s i g n p r i n c i p l e s and t o check t h e v a l i d i t y o f the assu m p t i o n s made d u r i n g the t o o l a n a l y s e s . T o o l f o r F e e d i n g and Cane O r i e n t a t i o n The s e l e c t e d f e e d r o l l i n c l i n a t i o n was 45° w h i l e the s e l e c t e d l e n g t h was 6 f e e t . The f r o n t end o f t h e f e e d r o l l s was d e s i g n e d t o o p e r a t e 1 f o o t above t h e s o i l s u r f a c e . A l t h o u g h f i g u r e 11 i n d i c a t e s t h a t the v e r t i c a l f r u i t d i s t r i b u t i o n b e g i n s a t 0.5 f e e t above t h e s o i l s u r f a c e , t h e l o w e r p o r t i o n o f t h e d i s t r i b u t i o n i s caused by canes w h i c h have grown o u t w a r d , away from t h e c e n t e r o f t h e row. G a t h e r i n g and c o m p r e s s i n g t h e s e canes between the f e e d r o l l s w i l l e f f e c t i v e l y r a i s e t h e l o w e r end o f v e r t i c a l f r u i t d i s t r i b u t i o n c u r v e s above t h e one f o o t l e v e l . Each f e e d r o l l was f a b r i c a t e d by w e l d i n g f o u r , 1/8 i n c h x 2 i n c h x 72 i n c h l o n g , c o l d r o l l e d s t e e l f l a t s i n t h e c o n f i g u r a -t i o n shown i n f i g u r e 40. One i n c h d i a m e t e r , c o l d r o l l e d s t e e l s t u b s h a f t s were i n s e r t e d i n t o each end o f the f a b r i c a t e d s e c t i o n and welded i n p l a c e . The o u t e r s u r f a c e s o f each f e e d r o l l were c o v e r e d w i t h o n e - h a l f i n c h foam r u b b e r a t t a c h e d w i t h c o n t a c t cement. The t o t a l w e i g h t o f each f e e d r o l l was a p p r o x i m a t e l y - 9 3 -F i g u r e 41 Feed r o l l mounting and d r i v e t r a i n - 95 -25 pounds. . The f e e d r o l l s were each a t t a c h e d t o upper and l o w e r sway-b a r s ( f i g u r e 41) by means o f s e l f - a l i g n i n g b a l l b e a r i n g s i n f l a n g e c a r t r i d g e s . The r a d i a l l o a d r a t i n g o f t h e s e l e c t e d b e a r i n g s was 1680 l b a t 100 rpm. T h i s c o r r e s p o n d s t o t h e i n e r t i a l l o a d i n g d e v e l o p e d i n t h e b e a r i n g s f o r a maximum base 2 mot i o n a c c e l e r a t i o n a t 4300 f t / s e c . The f e e d r o l l s were t i m e d 90° o u t o f phase and d r i v e n t h r o u g h a r o l l e r - c h a i n - a n d - g e a r d r i v e t r a i n ( f i g u r e 41) f o r c i n g them t o r o t a t e i n o p p o s i t e d i r e c t i o n s . F r o n t and r e a r f e e d r o l l c l e a r a n c e c o u l d be a d j u s t e d i n d e p e n d e n t l y by r o t a t i o n o f t h e swaybars about t h e i r upper p i v o t p o i n t s . T o o l f o r S e l e c t i v e H a r v e s t i n g O s c i l l a t o r y m o t i o n was a p p l i e d t o the f e e d r o l l s w i t h f o u r s y n c h r o n i z e d c r a n k and c o n n e c t i n g r o d mechanisms, one a t each end o f each f e e d r o l l ( f i g u r e 4 2 ) . The c o n n e c t i n g r o d s , w h i c h had a l e n g t h o f 1 f o o t between p i v o t p o i n t s were f a b r i c a t e d by a t t a c h -i n g s e l f - a l i g n i n g , d o u b l e row, b a l l b e a r i n g , r o d ends t o each end o f 8 i n c h l e n g t h s o f o n e - i n c h s t e e l p i p e . The s e l e c t e d r o d ends had a r a d i a l l o a d l i m i t o f 7090 l b . The c o n n e c t i n g r o d s were a t t a c h e d t o t h e f e e d r o l l swaybars 1 f o o t below t h e i r upper p i v o t p o i n t s . The c r a n k end o f each c o n n e c t i n g r o d was a t t a c h e d t o a s t e e l d i s k c e n t e r e d on a s h a f t ( f i g u r e 4 3 ) . Tapped h o l e s spaced a t 0.25, 0.50, 0.75, 1.00 and 1.25 i n c h e s from t h e c e n t e r o f r o t a t i o n o f t h e d i s k were used f o r a t t a c h i n g t h e c o n n e c t i n g r o d s . T h i s c r e a t e d a p o s s i b l e range o f s t r o k e s from 0.5 t o 2.5 i n c h e s i n 0.5 i n c h i n c r e m e n t s . A l t h o u g h t h i s base m o t i o n d e v i a t e s - 96 -F i g u r e 43 Method o f v a r y i n g t h e base motion a m p l i t u d e s l i g h t l y from s l i d e r c r a n k m o t i o n , t h e d e v i a t i o n f o r t h e range o f s t r o k e s used i s i n s i g n i f i c a n t and t h e c u r v e s p r e s e n t e d i n f i g u r e 39 a r e a p p l i c a b l e . The f o u r c r a n k s were d r i v e n and s y n c h r o n i z e d by means o f a r o l l e r - c h a i n d r i v e t r a i n ( f i g u r e 4 4 ) . The c r a n k s were t i m e d so t h a t t h e l a t e r a l o s c i l l a t i o n o f b o t h f e e d r o l l s was i n phase. F r u i t C o l l e c t i o n , C o nveying and S t o r a g e The p r i m a r y purpose o f the p r o t o t y p e h a r v e s t e r was t o t e s t t h e t o o l s f o r f e e d i n g , cane o r i e n t a t i o n and s e l e c t i v e h a r v e s t i n g . No a ttempt was made t o d e s i g n c o l l e c t i o n , c o n v e y i n g and s t o r a g e t o o l s based on t h e i r p r o posed m a t h e m a t i c a l models. F a b r i c a t i o n o f t h e s e t o o l s may be l o g i c a l l y u n d e r t a k e n a f t e r t e s t i n g and e v a l u a t i o n o f t h e f e e d i n g and s e l e c t i v e h a r v e s t i n g t o o l s . T h i s F i g u r e 44 D r i v e t r a i n f o r a p p l y i n g the base m o t i o n - 98 -a v o i d s unnecessary c o s t i n the i n i t i a l d e s i g n s t a g e s and s i m p l i -f i e s t e s t i n g o f i n d i v i d u a l t o o l s by e l i m i n a t i n g p o s s i b l e i n t e r -a c t i o n . A s i m p l e c o l l e c t i o n and c o n v e y i n g d e v i c e ( f i g u r e 45) c o n s i s t i n g o f n y l o n s c r e e n s , p a s s i n g from the f e e d r o l l sway-ba r s t o the machine frame, was used as a t o o l f o r c o l l e c t i o n and c o n v e y i n g d u r i n g e v a l u a t i o n o f the f e e d i n g and s e l e c t i v e h a r v e s t i n g t o o l s . F r u i t which was i n t e r c e p t e d by the o s c i l l a t i n g s c r e e n s was conveyed t o s t a t i o n a r y s t o r a g e c o n t a i n e r s p l a c e d a t the f r o n t end o f the s c r e e n s . F i g u r e 45 N y l o n s c r e e n s used as temporary c o l l e c t i o n and c o n v e y i n g t o o l s d u r i n g t e s t i n g o f t h e t o o l s f o r f e e d i n g and s e l e c t i v e h a r v e s t i n g . SYNTHESIS AND CONSTRUCTION OF THE MACHINE Purpose o f the P r o t o t y p e Machine As was p r e v i o u s l y s t a t e d , o n l y t h e f e e d i n g , cane o r i e n t a -t i o n and s e l e c t i v e h a r v e s t i n g t o o l s were d e s i g n e d and f a b r i c a t e d on t h e b a s i s o f t h e proposed m a t h e m a t i c a l models. The purpose o f t h e p r o t o t y p e h a r v e s t i n g machine was t o e v a l u a t e the p e r f o r m -ance o f t h e s e t o o l s . T h e c o m p l e t e d machine c o n s i s t e d o f a frame t o s u i t a b l y p o s i t i o n t h e t o o l s i n r e l a t i o n t o t h e p l a n t s , p o w e r i n g systems f o r b o t h f o r w a r d movement and base m o t i o n a p p l i c a t i o n , c o n t r o l systems t o p e r m i t a d j u s t m e n t o f t h e d e s i g n p a r a m e t e r s , d r i v e t r a i n s and s u p p o r t i v e members. Temporary c o l l e c t i o n , c o n v e y i n g and s t o r a g e t o o l s , as p r e v i o u s l y d e s c r i b e d , were a l s o i n c o r p o r a t e d i n the machine. The machine frame was d e s i g n e d t o accommodate the p r oposed t o o l s f o r f r u i t c o l l e c t i o n , c o n v e y i n g and s t o r a g e . I n c o r p o r a t i o n o f t h e s e t o o l s i n t o t h e machine i s a l o g i c a l f i n a l s t e p a f t e r e v a l u a t i o n o f t h e f e e d i n g and h a r v e s t i n g t o o l s . P owering Systems A h a r v e s t i n g machine may be e i t h e r s e l f - p r o p e l l e d o r t r a i l - t y p e . I n t h e l a t t e r c a s e , power i s s u p p l i e d by a t r a c t o r t o w i n g t h e machine, w h i l e i n t h e f o r m e r c a s e , m o t i v e power i s s u p p l i e d by a power u n i t p l a c e d on the h a r v e s t e r . S i n c e the p r o t o t y p e machine s e r v e d o n l y as a c a r r y i n g frame f o r e v a l u a t i o n o f t h e f e e d i n g and h a r v e s t i n g t o o l s , a t r a i l - t y p e c o n s t r u c t i o n was s e l e c t e d due t o l o w e r c o s t and d e s i g n s i m p l i c i t y . The machine was towed w i t h a Massey Ferguson model 65 t r a c t o r w i t h t h e f e e d r o l l s b e i n g d r i v e n from th e t r a c t o r power t a k e - o f f . - 9 9 -F i g u r e 4 6 P l a n view o f t h e h a r v e s t e r - 101 -F i g u r e 4 8 Rear view o f completed machine - 102 -T h i s t r a c t o r was s e l e c t e d as i t had a power t e k e - o f f d r i v e n from t h e t r a n s m i s s i o n , p e r m i t t i n g a u t o m a t i c s y n c h r o n i z a t i o n o f f e e d r o l l speed w i t h speed o f f o r w a r d t r a v e l . The t r a c t o r power t a k e - o f f c o m p l e t e d one r e v o l u t i o n f o r each 21 i n c h e s o f f o r w a r d t r a v e l , n e c e s s i t a t i n g a d r i v e t r a i n r a t i o o f 2.38/1 t o s a t i s f y e q u a t i o n [ 3 5 ] . A s m a l l power u n i t , mounted on t h e h a r v e s t e r , a c t e d as a p o w e r i n g system f o r t h e base m o t i o n . The r e a s o n f o r u s i n g a s e p a r a t e power u n i t f o r base m o t i o n a p p l i c a t i o n was i n o r d e r t o r e a d i l y o b t a i n a l a r g e range o f f r e q u e n c i e s d u r i n g t e s t r u n s . I f a s u i t a b l e base m o t i o n f r e q u e n c y c o u l d be e s t a b l i s h e d , base m o t i o n c o u l d a l s o be powered by the t r a c t o r . Frame and S u p p o r t i n g Members The machine was s u p p o r t e d on two pneumatic wheels and a p i n n e d c o n n e c t i o n a t the t r a c t o r drawbar. Welded r e c t a n g u l a r h o l l o w s t e e l s e c t i o n s (2 i n c h x 2 i n c h x 3/16 i n c h t h i c k ) were used f o r t h e frame members s u p p o r t i n g t h e t o o l s . No assessment o f t h e s t r u c t u r a l s t r e n g t h o f t h e frame was u n d e r t a k e n . A p l a n v iew o f t h e h a r v e s t e r i s shown i n f i g u r e 46, w h i l e two views o f t h e c o mpleted machine a r e shown i n f i g u r e s 47 and 48. T r e l l i s i n g M o d i f i c a t i o n The t r e l l i s i n g system c u r r e n t l y used was not s u i t a b l e f o r t h e h a r v e s t e r s i n c e the s i z e o f p o s t s used t o s u p p o r t the t r e l l i s w i r e s i s o f t e n more t h a n s i x i n c h e s i n d i a m e t e r . T h i s c o u l d cause p o s s i b l e i n t e r f e r e n c e between the f e e d r o l l s and t h e p o s t s . The t r e l l i s i n g system used i n t h e h a r v e s t i n g t e s t p l o t was m o d i f i e d by u s i n g 2 i n c h x 2 i n c h x 36 i n c h h i g h bean p o l e s i n F i g u r e 4 9 View o f machine e n t e r i n g a row. The m o d i f i e d t r e l l i s i n g system i s shown. MACHINE EVALUATION Scope o f T e s t The complete assessment o f machine performance n e c e s s i t a t e s b o t h f u n c t i o n a l t e s t s and d u r a b i l i t y t e s t s . S i n c e l o a d s imposed on a h a r v e s t i n g machine a r e n e a r l y i m p o s s i b l e t o d u p l i c a t e i n a l a b o r a t o r y , a d u r a b i l i t y t e s t must u s u a l l y be co n d u c t e d by o p e r a t i n g t h e machine f o r a s u i t a b l e p e r i o d o f t i m e i n a c t u a l f i e l d c o n d i t i o n s . S i m i l a r l y , c o mplete f u n c t i o n a l e v a l u a t i o n must be t h e r e s u l t o f many hours o f o p e r a t i o n i n d i v e r s e f i e l d c o n d i t i o n s , i n o r d e r t o a s s e s s performance i n a l a r g e v a r i e t y o f f i e l d and c r o p c o n d i t i o n s . Only one 2 0 0 - f o o t - l o n g row o f r a s p b e r r i e s was a v a i l a b l e f o r f i e l d t r i a l s d u r i n g 1969. No d u r a b i l i t y e v a l u a t i o n c o u l d , t h e r e f o r e , be u n d e r t a k e n and o n l y a c u r s o r y assessment o f f u n c t i o n a l performance c o u l d be c o m p l e t e d . S i m i l a r l y , no assessment o f t h e e f f e c t o f f r u i t v a r i e t y c o u l d be u n d e r t a k e n s i n c e o n l y t h e W i l l a m e t t e v a r i e t y was a v a i l a b l e f o r t e s t p u r p o s e s . The r e s u l t s p r e s e n t e d i n t h e f o l l o w i n g d i s c u s s i o n were o b t a i n e d from s i n g l e r u n s f o r each machine s e t t i n g . S i n c e r e p l i c a t e r u n s a r e u s u a l l y r e q u i r e d f o r r e l i a b l e a ssessment, t h e r e s u l t s must be t r e a t e d a c c o r d i n g l y . E v a l u a t i o n o f t h e F e e d i n g and Cane O r i e n t a t i o n T o o l P o s s i b l e i n t e r a c t i o n between t o o l s was e l i m i n a t e d by not power i n g t h e s e l e c t i v e h a r v e s t i n g t o o l d u r i n g assessment o f t h e f e e d i n g and cane o r i e n t a t i o n t o o l . On t h e b a s i s o f l i m i t e d t e s t s , p erformance o f t h e t o o l f o r f e e d i n g and cane o r i e n t a t i o n was s a t i s f a c t o r y . The f e e d r o l l s e f f e c t i v e l y c o n c e n t r a t e d t h e p l a n t s a t t h e p o i n t o f base m o t i o n a p p l i c a t i o n and h e l d t h e canes i n a - 104 -- 105 -v e r t i c a l p o s i t i o n i n d e p e n d e n t o f t h e speed o f f o r w a r d t r a v e l . S y n c h r o n i z a t i o n o f f e e d r o l l r o t a t i o n w i t h f o r w a r d speed was a c h i e v e d . No v i s i b l e p l a n t damage o c c u r r e d f o r a range o f f o r -ward speeds up t o t h r e e m i l e s p e r hour. A l o w e r s p a c i n g o f e i g h t i n c h e s between e x t e r n a l r o l l s u r f a c e s and an upper s p a c i n g o f f o u r i n c h e s r e s u l t e d i n s u f f i c i e n t c o n t a c t w i t h t h e p l a n t s and a l l o w e d t h e r o l l s t o pass t h e m o d i f i e d t r e l l i s i n g system w i t h no i n t e r f e r e n c e . F i g u r e s 50, 51 and 52 i l l u s t r a t e t he a c t i o n o f t h e f e e d r o l l s d u r i n g o p e r a t i o n . E v a l u a t i o n o f t h e S e l e c t i v e H a r v e s t i n g T o o l The method o f a p p l i c a t i o n o f base m o t i o n was s a t i s f a c t o r y . F r u i t b e a r i n g p o r t i o n s o f t h e canes appeared t o r e c e i v e e q u i v a -l e n t d i s p l a c e m e n t s as t h e h a r v e s t e r p a s s e d down t h e row, i n d i c a t i n g t h a t the maximum a c c e l e r a t i o n produced i n t h e f r u i t i n g zone c o u l d be q u i t e c l o s e l y c o n t r o l l e d . The p r e d i c t i o n o f p o s s i b l e f r u i t stem damage, as i n d i c a t e d by t h e measurements o f p h y s i c a l p r o p e r t i e s , was v e r i f i e d d u r i n g f i e l d t e s t i n g o f the s e l e c t i v e h a r v e s t i n g t o o l . From the m a t h e m a t i c a l model f o r t h i s t o o l ( f i g u r e 39) i t can be seen t h a t v a r i o u s c o m b i n a t i o n s o f s t r o k e and f r e q u e n c y may be used t o produce the same maximum a c c e l e r a t i o n . Wang (37) i n s t u d i e s on m e c h a n i c a l c o f f e e h a r v e s t i n g c o n c l u d e d t h a t c o m b i n a t i o n s o f h i g h f r e q u e n c i e s and low a m p l i t u d e s were p r e f e r a b l e t o low f r e q u e n c i e s and h i g h a m p l i t u d e s s i n c e p l a n t d e f l e c t i o n i s s m a l l e r and s h a k i n g t i m e i s r e d u c e d . Both o f t h e s e f a c t o r s may s i g n i f i c a n t l y i n f l u e n c e p l a n t damage. Due t o the s m a l l p l o t s i z e o n l y l i m i t e d assessment o f t h e above v a r i a b l e s c o u l d be c o m p l e t e d . R e s u l t s - 106 -F i g u r e 52 - 107 -and c o n c l u s i o n s based on l i m i t e d t e s t i n g o f the s e l e c t i v e h a r v e s t i n g t o o l may be summarized as f o l l o w s : ( i ) Only f i f t y p e r c e n t o f t h e mature f r u i t c o u l d be removed w i t h no damage t o t h e f r u i t stems i n t h e e a r l y p a r t o f the h a r v e s t s e a s o n . T h i s was a c c o m p l i s h e d w i t h a maximum base 2 m o t i o n a c c e l e r a t i o n o f 2600 f t / s e c , r e s u l t i n g from a 1 i n c h s t r o k e a t a f r e q u e n c y o f 2700 c y c l e s p e r minute. The r e m a i n i n g mature f r u i t c o u l d be removed on subsequent p a s s e s a t l a t e r d a t e s but o n l y w i t h r e d u c t i o n i n f r u i t q u a l i t y . I n s i m i l a r t r i a l s t o w ard the end o f t h e h a r v e s t s e a s o n , a p p r o x i m a t e l y s i x t y f i v e p e r c e n t o f t h e mature f r u i t c o u l d be removed w i t h no a p p r e c i a b l e f r u i t stem damage. 2 ( i i ) I n c r e a s i n g t h e a c c e l e r a t i o n above 2600 f t / s e c i n t h e e a r l y p a r t o f t h e h a r v e s t season i n c r e a s e d f r u i t r e m o v a l but a l s o i n i t i a t e d f a i l u r e o f t h e f r u i t stems. F or example, a 2 maximum a c c e l e r a t i o n o f 4100 f t / s e c , r e s u l t i n g from a s t r o k e o f two i n c h e s a t a f r e q u e n c y o f 2200 c y c l e s p e r m i n u t e , removed a p p r o x i m a t e l y 8 5 p e r c e n t o f t h e mature f r u i t but the r e s u l t i n g f r u i t sample c o n t a i n e d 10 p e r c e n t f r u i t w i t h stems a t t a c h e d , some l e a v e s and some immature f r u i t . The r e q u i r e d a c c e l e r a t i o n s and r e s u l t i n g f r u i t r e moval agree q u i t e c l o s e l y w i t h t h e p r e d i c t e d v a l u e s p r e s e n t e d i n Ta b l e X V I I I . ( i i i ) The f u l l e x t e n t o f t h e damage caused by a p p l y i n g e x c e s s i v e base m o t i o n a c c e l e r a t i o n i s not i m m e d i a t e l y a p p a r e n t . A l t h o u g h f r u i t w i t h stems a t t a c h e d may be o b s e r v e d i n t h e c o l l e c t e d f r u i t , some o f the f r u i t may s u f f e r stem damage but remain a t t a c h e d t o the canes. T h i s f r u i t s u b s e q u e n t l y d i e s and - 108 -i s not a v a i l a b l e a t l a t e r h a r v e s t d a t e s . F i g u r e 53 i l l u s t r a t e s such damage. ( i v ) High f r e q u e n c i e s and low a m p l i t u d e s appeared t o be p r e f e r a b l e t o low f r e q u e n c i e s and h i g h a m p l i t u d e s when p l a n t damage was c o n s i d e r e d . I t was not p o s s i b l e t o conduct s u f f i c i e n t t e s t s on the a v a i l a b l e p l o t t o determine s u i t a b l e l i m i t s o f f r e q u e n c y and a m p l i t u d e . S i m i l a r l y , r e s u l t s on t h e optimum l e n g t h o f time o f base motion a p p l i c a t i o n were i n c o n -c l u s i v e . S i n c e f o r w a r d speeds d u r i n g t e s t runs were one m i l e p e r hour, the s e l e c t i v e h a r v e s t i n g t o o l can be ex p e c t e d t o meet the n e c e s s a r y c a p a c i t y r e q u i r e m e n t s o f one a c r e p e r hour, as p r e v i o u s l y d e t e r m i n e d . F i g u r e 53 F r u i t stem damage due t o e x c e s s i v e base motion a c c e l e r a t i o n - 109 -(v) A l t h o u g h i t i s p o s s i b l e t o remove a l l t h e mature f r u i t on a p l a n t f o r each pass o f the h a r v e s t e r by a p p l y i n g s u f f i c i e n t base m o t i o n a c c e l e r a t i o n , t h i s i s not f e a s i b l e f o r two r e a s o n s . Hand s o r t i n g o f the f r u i t i s r e q u i r e d b e f o r e the p r o c e s s o r w i l l a c c e p t i t . S e c o n d l y , t h e f r u i t removed d u r i n g s o r t i n g and t h e damaged green f r u i t r e m a i n i n g on the p l a n t s w i l l r e d u ce t h e t o t a l y i e l d f o r t h e season. A more l o g i c a l s o l u t i o n a ppears t o be r e m o v a l o f f rom 50 t o 65 p e r c e n t o f t h e mature f r u i t a t each pass o f t h e h a r v e s t e r , t h e r e m a i n i n g f r u i t b e i n g a l l o w e d t o mature b e f o r e r e m o v a l . T h i s w i l l r e s u l t i n a h i g h o v e r a l l f r u i t removal e f f i c i e n c y f o r t h e whole season but w i t h reduced f r u i t q u a l i t y . E v a l u a t i o n o f Machine C o n s t r u c t i o n The p r i m a r y r e a s o n s f o r u s i n g t r a i l - t y p e c o n s t r u c t i o n f o r t h e h a r v e s t i n g machine were re d u c e d c o s t and d e s i g n s i m p l i c i t y , when compared t o a s e l f - p r o p e l l e d machine. A l t h o u g h t h e purpose o f t h e machine was t o s e r v e as a c a r r i e r frame d u r i n g t o o l e v a l u a t i o n , i t s performance i n d i c a t e d t h a t such a d e s i g n c o u l d p o s s i b l y be used f o r a c o m m e r c i a l r a s p b e r r y h a r v e s t i n g machine. A s e l f - p r o p e l l e d machine has advantages where m a n e u v e r a b i l i t y i s i m p o r t a n t and when t o o l s r e q u i r e a h i g h l e v e l o f s u p e r v i s i o n . S i n c e r a s p b e r r y rows a r e s t r a i g h t , a p u l l - t y p e machine i s s u f f i c i e n t l y m a neuverable, i f h e a d l a n d s a r e o f s u f f i c i e n t w i d t h t o a l l o w u n o b s t r u c t e d t u r n i n g . F u r t h e r m o r e , t h e f e e d i n g and s e l e c t i v e h a r v e s t i n g t o o l s r e q u i r e l i t t l e s u p e r v i s i o n , once t h e y have been a d j u s t e d t o s u i t c r o p c o n d i t i o n s . The f i n a l c h o i c e between a t r a i l - t y p e o r s e l f - p r o p e l l e d machine must be based on t h e l e v e l o f s u p e r v i s i o n r e q u i r e d f o r t h e f r u i t s t o r a g e - 110 -t o o l once i t has been i n c o r p o r a t e d i n t h e machine. I f an o p e r a t o r i s r e q u i r e d t o s u p e r v i s e and c o n t r o l t h e f r u i t s t o r a g e t o o l , a s e l f p r o p e l l e d machine would be a l o g i c a l c h o i c e . C o n c l u d i n g Remarks A l t h o u g h performance o f t h e p r o t o t y p e h a r v e s t e r met d e s i g n e x p e c t a t i o n s and the use o f such a machine i n W i l l a m e t t e r a s p -b e r r i e s would be e c o n o m i c a l l y b e n e f i c i a l , o t h e r r a s p b e r r y v a r i e t i e s may be b e t t e r s u i t e d t o m e c h a n i c a l h a r v e s t i n g . The r e t e n t i o n f o r c e , c o l o r and f i r m n e s s o f mature r a s p b e r r y f r u i t a r e s t r o n g l y dependent upon f r u i t v a r i e t y ( 1 0 ) . V i s u a l o b s e r v a -t i o n o f the f r u i t a t t achment systems o f s e v e r a l d i f f e r e n t r a s p b e r r y v a r i e t i e s i n d i c a t e d t h a t two v a r i e t i e s , C h i e f and Red Radabout, have f r u i t c o r e s which a r e much s h a l l o w e r t h a n the c o r e s i n t h e W i l l a m e t t e v a r i e t y ( f i g u r e 5 4 ) . L i m i t e d c o m p a r i s o n i n d i c a t e d t h a t due t o the c o r e c o n f i g u r a t i o n t h e f r u i t r e t e n t i o n f o r c e , f o r f r u i t o f s i m i l a r c o l o r and f i r m n e s s , was a p p r e c i a b l y l o w e r f o r t h e s e v a r i t i e s t h a n f o r t h e W i l l a m e t t e v a r i e t y . The r e c e n t l y d e v e l o p e d M a t s q u i v a r i e t y i s a l s o r e p o r t e d t o have l o w e r f r u i t r e t e n t i o n f o r c e t h a n the W i l l a m e t t e v a r i e t y ( 7 ) . The n e x t l o g i c a l s t e p i n development o f a r a s p b e r r y h a r v e s t i n g system t h e r e f o r e s h o u l d be i n v e s t i g a t i o n o f p h y s i c a l p r o p e r t i e s o f o t h e r s u i t a b l e v a r i e t i e s o f r a s p b e r r i e s t o f i n d a v a r i e t y w i t h a l o w e r r a t i o o f f r u i t r e t e n t i o n f o r c e t o f r u i t stem s t r e n g t h . A b r e e d i n g program aimed a t d e v e l o p i n g a r a s p b e r r y v a r i e t y more s u i t a b l e f o r m e c h a n i c a l h a r v e s t i n g s h o u l d a l s o be u n d e r t a k e n . F u r t h e r work on t h e use o f growth r e g u l a t o r s w i t h the aim - I l l -o f r e d u c i n g f r u i t r e t e n t i o n f o r c e i s a l s o i n d i c a t e d . I n i t i a l t r i a l s i n d i c a t e d t h a t s u i t a b l e growth r e g u l a t o r t r e a t m e n t s c o u l d s i g n i f i c a n t l y a l t e r f r u i t r e t e n t i o n f o r c e and i t s v a r i a t i o n o v e r t h e h a r v e s t season. A l t h o u g h no machine t r i a l s were co n d u c t e d on t h e p l o t s r e c e i v i n g growth r e g u l a t o r t r e a t m e n t s , measurement o f p h y s i c a l p r o p e r t i e s i n d i c a t e d t h a t growth r e g u l a t o r t r e a t m e n t s c o u l d be b e n e f i c i a l . Treatment 14 ( T a b l e XIV) f o r example, c o u l d p o s s i b l y i n c r e a s e f r u i t r e m o v a l a t t h e b e g i n n i n g o f t h e h a r v e s t s e a s o n , s i n c e i t s i g n i f i c a n t l y r e d u c e d f r u i t r e t e n t i o n f o r c e e a r l y i n t h e h a r v e s t season. Willamette variety Other varieties F i g u r e 54 The i n f l u e n c e o f f r u i t c o r e shape on f r u i t r e t e n t i o n f o r c e OBSERVATIONS AND CONCLUSIONS The f o l l o w i n g i s a summary o f t h e n a t u r e and scope o f t h e c o m pleted s t u d y , t h e r e s u l t s o f t h e e x p e r i m e n t a l i n v e s t i g a t i o n s and t h e subsequent c o n c l u s i o n s . The s t u d y a p p l i e s s p e c i f i c a l l y t o r a s p b e r r y p r o d u c t i o n i n t h e B r i t i s h Columbia l o w e r m a i n l a n d . C o n c l u s i o n s a r e based on r e s u l t s o b t a i n e d from i n v e s t i g a t i o n o f the W i l l a m e t t e v a r i e t y o f r a s p b e r r i e s . Other r a s p b e r r y v a r i e t i e s may be e x p e c t e d t o produce q u i t e d i f f e r e n t r e s u l t s . 1. A s y s t e m a t i c d e s i g n p r o c e d u r e , o r i e n t e d toward d e s i g n and t e s t i n g o f a b i o l o g i c a l - m a c h i n e - s y s t e m was used t o d e v e l o p a m e c h a n i c a l r a s p b e r r y h a r v e s t i n g system. The s e l e c t e d d e s i g n was based on t h e p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f t h e r a s p b e r r y p l a n t and t h e e x i s t i n g economic c o n d i t i o n s i n t h e r a s p b e r r y i n d u s t r y . 2. An economic s t u d y , comparing p r e s e n t hand h a r v e s t i n g methods i n t h e l o w e r m a i n l a n d t o a t h e o r e t i c a l m e c h a n i c a l h a r v e s t i n g system i n d i c a t e d t h a t : (a) A machine w i t h g r o s s s e a s o n a l f r u i t r e m o v a l e f f i c i e n c y o f 40 t o 60 p e r c e n t w i l l s a t i s f a c t o r i l y compete w i t h t h e p r e s e n t c o s t o f hand h a r v e s t i n g . (b) Machine c a p a c i t y s h o u l d be a t l e a s t one a c r e p e r hour. T h i s r e p r e s e n t s a minimum d e s i g n speed o f one m i l e p e r h our. ( c ) F o r the range o f y i e l d s e x p e c t e d i n t h e l o w e r m a i n l a n d , t h e b r e a k - e v e n p o i n t i s not s t r o n g l y dependent upon machine p u r c h a s e p r i c e , f o r p r i c e s under $11,500, p r o v i d e d t h a t machine c a p a c i t y i s a t l e a s t one a c r e - 112 -p e r hour. (d) A machine which h a r v e s t s f r u i t s u i t a b l e o n l y f o r p r o c e s s i n g w i l l s e r v e o v e r 95 p e r c e n t o f the i n d u s t r y . Measurement o f t h e p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f the r a s p b e r r y p l a n t and i t s f r u i t was u n d e r t a k e n i n o r d e r t o d e t e r m i n e p e r t i n e n t d e s i g n p a r a m e t e r s . R e s u l t s may be summarized as f o l l o w s : (a) The r e s u l t s o f t h i s i n v e s t i g a t i o n w i l l p r o v i d e u s e f u l i n f o r m a t i o n f o r t h e d e s i g n o f b o t h f i e l d and p r o c e s s -i n g equipment f o r cane f r u i t s . (b) C o r r e l a t i o n s among f r u i t p r o p e r t i e s and t h e f o r c e -d e f o r m a t i o n m o d u l i o b t a i n e d from f l a t p l a t e l o a d i n g o f t h e r a s p b e r r y f r u i t , i n d i c a t e d t h a t t a n g e n t modulus and f r u i t c o l o r a r e d i r e c t i n d i c a t o r s o f f r u i t q u a l i t y . ( c ) S i g n i f i c a n t c o r r e l a t i o n s among f r u i t r e t e n t i o n f o r c e , F/W r a t i o , f r u i t c o l o r and f o r c e - d e f o r m a t i o n m o d u l i showed t h a t b o t h f r u i t r e t e n t i o n f o r c e and F/W r a t i o a r e i n d i r e c t i n d i c a t o r s o f f r u i t q u a l i t y . D e s i g n o f a s e l e c t i v e h a r v e s t i n g t o o l c o u l d be based on e i t h e r o f t h e s e p a r a m e t e r s . (d) S i n c e f r u i t r e t e n t i o n f o r c e and F/W r a t i o were n e g a t i v e l y c o r r e l a t e d w i t h h a r v e s t t i m e , a s e l e c t i v e h a r v e s t i n g d e v i c e e m p l o y i n g e i t h e r o f t h e s e p a r a -meters must be a d j u s t e d t o s u i t the d e s i r e d s e l e c t i o n l e v e l f o r t h e p a r t i c u l a r h a r v e s t day. (e) F r u i t r e t e n t i o n f o r c e and F/W r a t i o appear t o be dependent upon e n v i r o n m e n t a l c o n d i t i o n s and may v a r y - 114 -s i g n i f i c a n t l y from season t o season. ( f ) The W i l l a m e t t e v a r i e t y o f r a s p b e r r i e s was found t o have a h i g h r a t i o o f f r u i t r e t e n t i o n f o r c e t o f r u i t stem s t r e n g t h . On t h e b a s i s o f t h e s e measurements, i t was shown t h a t t h e f r u i t removal e f f i c i e n c y d u r i n g a s i n g l e pass o f a m e c h a n i c a l h a r v e s t e r must be l e s s t h a n 70 p e r c e n t , i f damage t o t h e f r u i t a t t a c h m e n t system i s t o be w i t h i n a c c e p t a b l e l i m i t s . High o v e r a l l e f f i c i e n c y may be o b t a i n e d but o n l y by h a r v e s t i n g f r u i t o f r e d u c e d q u a l i t y . (g) Due t o low f r u i t stem s t r e n g t h and h i g h f r u i t r e t e n t i o n f o r c e , t h e f o r c e a p p l i e d t o t h e f r u i t by a m e c h a n i c a l r a s p b e r r y h a r v e s t i n g system must be c l o s e l y c o n t r o l l e d t o p r e v e n t f r u i t stem damage and t o o b t a i n maximum a l l o w a b l e e f f i c i e n c y o f f r u i t r e m o v a l . T h i s i n d i c a t e s t h a t i f v i b r a t o r y h a r v e s t i n g methods a r e used, base m o t i o n must be a p p l i e d t o t h e complete f r u i t i n g zone o f t h e p l a n t . The wide v a r i a t i o n i n f l e x u r a l s t r e n g t h and s i z e o f t h e r a s p b e r r y canes i n d i c a t e s t h a t a p p l i c a -t i o n o f base m o t i o n t o a f i x e d p o i n t on t h e canes i s not f e a s i b l e . 4. M a t h e m a t i c a l models f o r t h e v a r i o u s t o o l s r e q u i r e d i n a m e c h a n i c a l r a s p b e r r y h a r v e s t i n g system were c o n s t r u c t e d , based on t h e p h y s i o - m e c h a n i c a l p r o p e r t i e s o f t h e p l a n t and i t s f r u i t . The t o o l s c o n s i d e r e d were a t o o l f o r f e e d i n g and cane o r i e n t a t i o n , a t o o l f o r s e l e c t i v e h a r v e s t i n g , a t o o l f o r f r u i t c o l l e c t i o n and c o n v e y i n g and a t o o l f o r - 115 -f r u i t s t o r a g e . 5. F u l l s c a l e models o f t h e f e e d i n g and cane o r i e n t a t i o n t o o l and the s e l e c t i v e h a r v e s t i n g t o o l were f a b r i c a t e d and i n c o r p o r a t e d i n t o a p r o t o t y p e h a r v e s t e r . L i m i t e d f i e l d t e s t i n g i n d i c a t e d t h a t t o o l performance met d e s i g n expec-t a t i o n as p r e d i c t e d by measurement o f p h y s i c a l p r o p e r t i e s o f t h e r a s p b e r r y p l a n t . T e s t r e s u l t s i n d i c a t e d t h e f o l l o w i n g l i m i t a t i o n s on m e c h a n i c a l h a r v e s t i n g o f W i l l a m e t t e r a s p b e r r i e s : (a) Due t o a c o m b i n a t i o n o f h i g h f r u i t r e t e n t i o n f o r c e and low f r u i t stem s t r e n g t h , o n l y 50 p e r c e n t o f the mature f r u i t c o u l d be removed i n one pass o f the h a r v e s t e r a t t h e b e g i n n i n g o f t h e h a r v e s t season w i t h o u t f r u i t stem damage. L a t e i n the h a r v e s t season a p p r o x i m a t e l y 6 5 p e r c e n t o f t h e mature f r u i t c o u l d be removed i n one pass o f t h e h a r v e s t e r w i t h o u t f r u i t stem damage. The f r u i t r e m a i n i n g on t h e p l a n t s a f t e r one pass o f the h a r v e s t e r c o u l d be s a t i s f a c t o r i l y removed on subsequent p a s s e s a t l a t e r d a t e s , a s f r u i t r e t e n t i o n f o r c e d e c r e a s e s w i t h i n c r e a s e d m a t u r i t y . (b) O v e r a l l f r u i t r e m o v a l e f f i c i e n c y may approach 100 p e r -c e n t f o r t h e whole h a r v e s t season even though maximum a l l o w a b l e f r u i t r e m o v a l e f f i c i e n c y i s much l o w e r f o r a s p e c i f i c h a r v e s t d a t e . ( c ) The q u a l i t y o f f r u i t o b t a i n e d by a m e c h a n i c a l h a r v e s t i n g w i l l be l o w e r t h a n the q u a l i t y o b t a i n e d by hand p i c k i n g . T h i s i s due t o t h e f a c t t h a t t h e f r u i t must, on the whole, be more mature f o r removal by m e c h a n i c a l methods. The f r u i t o b t a i n e d by m e c h a n i c a l h a r v e s t i n g w i l l , t h e r e f o r e , be s u i t a b l e o n l y f o r p r o c e s s i n g ; i t w i l l not be s u i t a b l e f o r the f r e s h f r u i t market. (d) I n s p i t e o f low f r u i t r e m o v a l e f f i c i e n c y and reduced f r u i t q u a l i t y , use o f t h i s m e c h a n i c a l h a r v e s t i n g system c o u l d be e c o n o m i c a l l y b e n e f i c i a l when compared w i t h t h e c o s t o f hand h a r v e s t i n g . I n i t i a l t r i a l s on the use o f two c h e m i c a l growth r e g u l a t o r s i n d i c a t e d t h a t growth r e g u l a t o r a p p l i c a t i o n c o u l d s i g n i f i -c a n t l y i n f l u e n c e t h e f r u i t r e t e n t i o n f o r c e and F/W r a t i o . The e f f e c t o f the growth r e g u l a t o r was found t o be dependent upon t h e ty p e o f r e g u l a t o r , i t s d a t e o f a p p l i c a -t i o n and i t s c o n c e n t r a t i o n . The p r o p e r use o f growth r e g u l a t o r s c o u l d p o s s i b l y improve t h e performance o f a m e c h a n i c a l h a r v e s t e r i n W i l l a m e t t e r a s p b e r r i e s . A l t h o u g h m e c h a n i c a l h a r v e s t i n g o f W i l l a m e t t e r a s p b e r r i e s was shown t o be e c o n o m i c a l l y b e n e f i c i a l , and t h e proposed h a r v e s t e r d e s i g n c o u l d be used f o r h a r v e s t m e c h a n i z a t i o n , t h e W i l l a m e t t e v a r i e t y i s n o t e s p e c i a l l y s u i t a b l e f o r m e c h a n i c a l h a r v e s t i n g . C u r s o r y e x a m i n a t i o n o f t h e f r u i t a t t a chment systems o f o t h e r r a s p b e r r y v a r i e t i e s i n d i c a t e d t h a t s e v e r a l v a r i e t i e s may be much more s u i t a b l e f o r m e c h a n i c a l h a r v e s t i n g . SUGGESTIONS FOR FURTHER STUDY A l t h o u g h i t has been shown t h a t m e c h a n i c a l h a r v e s t i n g o f the W i l l a m e t t e v a r i e t y o f r a s p b e r r i e s i s f e a s i b l e , the h i g h r a t i o o f f r u i t r e t e n t i o n f o r c e t o f r u i t stem s t r e n g t h l i m i t s f r u i t r e m o v a l e f f i c i e n c y and r e d u c e s the o v e r a l l q u a l i t y o f machine h a r v e s t e d f r u i t . The f o l l o w i n g i n v e s t i g a t i o n s a r e t h e r e f o r e proposed f o r f u t u r e s t u d y : 1. Measurement o f t h e p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f o t h e r s u i t a b l e v a r i e t i e s o f r a s p b e r r i e s s h o u l d be under-t a k e n i n an attempt t o f i n d a v a r i e t y h a v i n g a l o w e r r a t i o o f f r u i t r e t e n t i o n f o r c e t o f r u i t stem s t r e n g t h . 2. F u r t h e r i n v e s t i g a t i o n s h o u l d be conducted c o n c e r n i n g the p o s s i b i l i t y o f l o w e r i n g f r u i t r e t e n t i o n f o r c e t h r o u g h t h e use o f growth r e g u l a t o r s . 3. A r a s p b e r r y b r e e d i n g program s h o u l d be i n i t i a t e d w i t h t h e aim o f d e v e l o p i n g a v a r i e t y s u i t a b l e f o r m e c h a n i c a l h a r v e s t i n g . An i d e a l v a r i e t y would have a low r a t i o o f f r u i t r e t e n t i o n f o r c e t o f r u i t stem s t r e n g t h , would have f r u i t t h a t matured u n i f o r m l y and would have s u f f i c i e n t cane s t r e n g t h t o e l i m i n a t e t h e need f o r a t r e l l i s i n g system. - 117 -LITERATURE CITED 1. A d r i a n , P.A., F r i d l e y , R. B. and L o r e n z e n , C. " F o r c e d V i b r a t i o n o f a Tree Limb." T r a n s a c t i o n s o f the ASAE,8:(4), p. 473-475, ( 1 9 6 5 ) . 2. American S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s . A n n o t a t e d  B i b l i o g r a p h y o f t h e E n g i n e e r i n g P r o p e r t i e s o f B i o l o g i c a l  M a t e r i a l s . S t . J o s e p h , M i c h i g a n : American S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s , S p e c i a l P u b l i c a t i o n SP-03-67, pp. 103, ( 1 9 6 7 ) . 3. American S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s . 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" M e c h a n i c a l C o f f e e H a r v e s t i n g " , T r a n s a c t i o n s  o f the ASAE, 8 : ( 3 ) , p. 400-405, (1965). 

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