The advantages accruing to this method of harvest may be limited 

 in areas where strong winds prevail during harvesttime because strong 

 winds can turn the windrows over and dump on the ground seed caught by 

 the plastic. 



COMBINES, COMPONENTS, OPERATION' 



The advantages gained from harvesting early, from efficient mowing, 

 from using a suction machine to reclaim shattered seed, or from baling 

 or windrowing onto plastic sheets cannot be fully realized unless the crop 

 is efficiently connbined. ARS -State scientists have explored this facet of 

 seed harvesting and the exploration results now make it possible to define 

 some of the elements of an ideal combine, to delineate how best to adjust 

 and operate combines, and to list other factors that should be considered 

 when seed are combined. A general review of how combines function will 

 make the presentation of the other information more meaningful. 



How Combines Function 



The combine header, consisting of the reel, the cutterbar with sickle, 

 an endless canvas or an auger, and other parts that make up the platform 

 cuts and feeds the crop into the machine. Various mechanisms can be 

 used to accomplish the feeding function. These include canvasses, augers, 

 feed cylinders, and slatted conveyor chains. When harvesting from swath 

 or windrow, the header may be replaced by a pickup attachnnent. 



The rubbing and beating action of the cylinder against the concaves, 

 which are stationary but nnay vary in number, remove seed from pods, 

 hulls, or florets. Grates, either between the concaves or behind the cylinder 

 or both, separate much of the threshed seed from the straw at the cylinder. 

 A beater, just back of the cylinder, maybe provided to strip the straw from 

 the cylinder and deflect it onto racks that move it to the rear or side of 

 the machine for disposal and at the same time agitate it to shake out the 

 threshed seed. Threshed seed, unthreshed seed hulls or pods, short pieces 

 of straw, chaff, and any extraneous nnaterial (weed seed, foreign seed) fall 

 on or are carried onto the chaffer. The chaffer may be mesh wire, a lip 

 sieve, an adjustable sieve, or combinations of these. Devices agitate it and 

 a fan and shutter, or fan and vane, assembly direct a current of air through 

 it. 



Threshed seed and small extraneous material work through the chaffer 

 onto another sieving assembly. Specific sieves for specific crops are usually 

 attainable or an adjustable sieve is used. Chaff and other light material are 

 blow^n off the chaffer and out of the machine. Some seed, unthreshed hulls 

 or pods (the tailings) work to the back of the chaffer and fall into the tailings 

 elevator, which carries them back to the cylinder to be rethreshed. 

 Threshed seed and other material are again subjected to air blasts and 

 agitation, which separate seed from any extraneous material. Threshed 

 seed, now cleaned, fall into the grain elevator and are carried to the grain 

 bin, truck, or sacking attachment. 



^ Additional details about combines appear in Farmers* Bulletin 1761, "Harvesting With Combines," avail- 

 able from the Office of Information, United States Department of Agriculture, Washington 25, D. C. 



