Collecting frames for blueberries are smaller than those for tree fruit and 

 have no conveyor. They are moved from bush to bush by hand and the harvested 

 berries are poured from them into boxes. 



Some Operational Notes 



AERD research reveals that shaking periods of 3 to 5 seconds give the best 

 results. Increasing the shaking period does not always increase yields but it does 

 separate more trash and bruise more fruit. The amount of fruit on a tree does not 

 materially affect the time it takes to harvest it. 



When heavily laden limbs are harvested, shaking intervals of 1 or 2 seconds 

 should alternate with rest periods of approximately the same duration — to give 

 the fruit a chance to roll off the collecting surface. This procedure reduces strain 

 on the collecting unit and minimizes pocketing and bruising. 



Shaker claws should normally be attached to trees in such a way that the angle 

 between them and booms is 90 degrees. To make such an attachment, however, is 

 not always practical. When the angle deviates from 90 degrees, a force is created 

 that may cause the claw to slip. Points at which attachments should be made de- 

 pend on branch size, distribution of fruit, visibility, and the angle the limb makes 

 with the boom. Best results are usually obtained when attachments are made just 

 below the lowest major lateral branch on a given scaffold branch. 



The use of boom or inertia shakers does not appear to damage root systems. 



Various amplitudes and frequencies of shaker strokes have been tested. AERD 

 obtained best results in experimental cherry harvesting with a stroke of II/2 inches 

 and a frequency of 900 to 1,200 cycles a minute. 



Open trees on level ground with high heads and three or four scaffold branches 

 are the easiest to harvest mechanically. Branches that touch the collecting surface 

 do not shake enough to dislodge the fruit. Rows should be 20 to 24 feet apart and 

 vegetative ground cover no higher than 2 or 3 inches so the movement of equipment 

 will not be impeded. Interplants, especially apple interplants in cherry or plum 

 orchards, often increase mechanical harvesting difficulties by interfering with the 

 proper placement of catching frames. 



Other factors that affect harvesting efficiency (for which little research data has 

 been accumulated) include: Spraying, fertilizing, and varietal strains. 



Decelerator Strips and Cushioning Material 



Two common sources of bruising during the shaking operations are fruit strik- 

 ing other fruit and fruit striking hard surfaces of the catching frame. AERD re- 

 search approaches these problems through experimental use of decelerator strips 

 and cushioning material. 



Decelerator strips are canvas or other woven material, 3 to 6 inches wide, and 

 the same length as the catching frame. They are placed 4 to 5 inches over conveyors 

 or collecting surfaces (see fig. 1). If only one layer of strips is used, the strips are 

 usually angled 30 to 40 degrees similar to Venetian blinds. When two or more lay- 

 ers are used, the strips may be staggered at different elevations. California ex- 

 periments showed that deceleration strips prevented serious bruises in mechanically 

 harvested fruit having as much as 24 inch-pounds of energy at impact — a 0.13-pound 

 fruit falling I51/2 feet. 



