VOLUNTEER YIELD, CRACKED GRAIN, DIRTY SAMPLE, CHANGING CONCAVES
One big reason for aftermarket combine concaves, rotor loss. This loss results from incomplete threshing, lack of capacity, and an overloaded separation section from stock concaves and grate assemblies. The problem happens because stock concaves are not open sufficiently to get enough threshed grain down and onto the augers and thus, overloading the separation grates from the volume of grain coming in. The overloaded separation section is then unable to capture all the threshed grain so it ends up being “thrown over the rotor” and spit out the back. This results in volunteer yield you see to the right. The higher the yield, the more chaff there is or the harder the crop is to thresh the WORSE the grain loss is, also known as “volunteer yield” as you can see.