Combines Rubber Accelerator Rolls and Wobble Box

It has to do with the basic combine design. The Gleaner rotor is crossways in the combine so all the grain coming from the rotor is in a relatively narrow line across the combine, the problem is that most of it is coming on the right end under the threshing part of the rotor where most of the threshing_separation takes place. That causes them to install "distribution" augers to try to spread the grain evenly across the shoe. The accelerator rolls are under the dist. auger and they throw the grain downward through a strong blast of air, which is a good idea. Gets rid of a good deal of the chaff before it gets to the chaffer and helps on hillsides. Also, the old Gleaner conventional machines also had a somewhat similar double airblast setup that blasted the grain and chaff as it came off of the thresher raddle chain on its way to the shoe. I also suspect they have a patent of the accel. rolls too. But on other combines with cylinders_walkers or length wise rotors the grain is separated over a much longer area for and aft in the combine and it would be difficult to gather it all up and spread it out like Gleaner does. Clear as mud, right. The Wobble box is the mechanical device that turns rotary motion into reciprocating motion to operate the sickle. A much improved version of the old crank and pitman rod arrangement that used to be used to drive the sickle back and forth.

As John W said, the accelerator rolls allow a huge volume of air to preclean the threshed grain before it falls on the sieve. I often say that there is no excuse for any straw or chaff on the sieves of a properly set Gleaner in good wheat. The link shows a side view and the chaff coming from the machine. This machine has no chaff spreader other than the integral one that only relies on the blast of air through the material as it falls to the sieve. The fact that the heavy grain has been speeded up by the rolls means that a much higher velocity and volume of air can pre-clean it and not blow it out the rear of the machine. Ed in Montana