Combines are a rolling physics experiment, and the Gleaner is a marvel. A combine's cleaning system works with two mechanisms: mechanical sieve action to separate based on particle size and pneumatics (air) to separate based on mass differential of particles (heavy vs. light matter). The Gleaner has the most powerful pneumatic system of any combine before or since, and thus relies less on the mechanical sieve action, allowing these machines to have smaller sieve areas than competitors, yet have superior cleaning performance. As you mentioned, the accelerator rolls are the key because they ARTIFICIAllY augment or increase the difference in weight between the chaff and the grain. Under gravity that all other combines use, these particles have a difference in weight equal to their mass times gravitational force (Force=Mass*Acceleration). The Gleaner uses this law brilliantly by not using gravity, but by supplying its own force equal to 4 times gravity with the accelerator rolls. Hence, the difference in weight is artificially multiplied by a factor of 4. SoIJ A larger difference in weight means you can put more air to a stream of chaff and grain. The grain will be relatively unaffected by this air blast, while a very high percentage of the trash (chaff),nearly 90% in some cases, is removed even before it touches a sieve. It is propelled out of the machine, leaving what little trash remains to be separated and cleaned by the sieves and air through the sieves. The hillside and slope compensating advantages of the accelerator rolls have already been discussed, but they are also the key component to the amazing pneumatic pre-cleaning power of this combine. Either no other manufacturer is smart enough to recognize the inherent simplicity and effectiveness of this design, or they are just too proud to copy it.
),now do the same drop and tilt your receiving bottom hand about 15 degrees. See, the grain will not even touch your hand. the same thing happens in the combine . Now THROW the grain toward your catch hand and if you have ever played any ball you can see that you can even throw the grain 90 degrees and hit your mark. The other advantage is the ability to turn up the air through the high speed grain and 'pre clean it' more so than any brand without accel rolls. Imagine cleaning popcorn you shell by hand and pouring it through an air blast from a window fan. If one turns the up fan high enough it will blow out the grain as well as the chaff. BUT if one accelerates the grain toward the catch pan it will not blow away the good stuff. The grain being thrown into the air blast helps as well. The grain always lands on the area in front of the shoe that has a layer of grain on it held by those little strips. This prevents grain damage. One can build the largest machine in the world cylinder wise, but if you can't keep it in the shoe on hillsides you can't utilize the capacity of the machine. (remember the pullout sections on some machines chaffer rear section to dump the stream of grain back top tailings on hillsidesIJ) This is the reason the roll lugs need to be kept in good shape is that if the grain looses its velocity it will be blown back mid-shoe and thus lose a bunch of capacity, loose its super powers and become mere mortal like all the others...