Economic considerations are also important. Mechanization must make money 

 for the grower — enough money so he can afford to invest in the equipment needed. 

 AERD has estimated savings from mechanically harvesting and handling some 

 crops and how much a hypothetical grower must market to make mechanization 

 profitable {see p. 10-13). Individual growers, however, who encounter unusual dif- 

 ficulty in getting harvesting help may decide to mechanize even though mechaniza- 

 tion will not increase profits. 



Before mechanizing, growers should be certain of their markets. AERD advises 

 that not all processors and fresh fruit buyers will accept mechanically harvested 

 fruit. Many of them will, however, and most of them do — after establishing that the 

 quality of mechanically harvested crops equals or surpasses that of handpicked 

 crops. 



MECHANICAL HARVESTING — EQUIPMENT AND METHODS 



The fact that fruit can be dislodged from trees by shaking the trees led AERD 

 engineers and their collaborators to investigate, test, and develop mechanical shak- 

 ers and catching frames to mechanize the harvesting of fruit. Today mechanical 

 shakers and catching frames have been used to harvest thousands of tons of prunes 

 in California, millions of pounds of cherries and plums in Michigan, and blue- 

 berries in New Jersey and Michigan. Their use will undoubtedly be extended to 

 other crops as research learns more about them. 



The shaking force that is applied to trees creates an equal and opposite force 

 (the reaction force) that must be absorbed. This law of physics sometimes limits 

 the effectiveness of shakers. An important segment of AERD research deals with 

 this phenomenon. 



Hand-held Mechanical Shakers 



Hand-held mechanical shakers may be powered hydraulically, by compressed air, 

 or manually by turning a crank. They are essentially long poles or pipes that trans- 

 mit the shaking force from the powering mechanism to the tree. They are hooked 

 to or held against individual limbs and then activated. Their use may be exhausting 

 because they often have to be held shoulder high and because the operator must 

 absorb the reaction force. 



Hand-held Vibrators for Harvesting Blueberries 



Hand-held vibrators for harvesting blueberries are driven by electricity or com- 

 pressed air. The operator holds the vibrator against the blueberry bush and the 

 driving force vibrates fingers that separate the berries from the bush. The earliest, 

 experimental vibrators were converted from electric hoes. 



Boom Shakers 



Boom shaker units usually consist of a tractor or truck-mounted boom with a 

 claw (clamp) at the end. They can be maneuvered so the claw can be closed on a 

 main scaffold limb. Once in position the operator can shake the limb by activating 

 the eccentric on the powering mechanism that activates the boom. Under favorable 

 conditions, this is a very effective way of harvesting fruit. 



The mass of the truck or tractor, however, has to be greater than the mass of 

 the tree. If it isn't, the truck or tractor will shake more than the tree because of the 

 reaction force. 



