Fig 7. Travel of grain and straw through the combine (John Deere)

The cutting unit includes the reel (A), the cutter bar and sickle (B), and the platform and canvas (C). The platform canvas, in connection with the upper feeder canvas (D), feeds the cut grain evenly into the cylinder (E).

Threshing is accomplished at the cylinder (E) and the concaves (F). Perhaps 75 percent of the separation of threshed grain from straw is also accomplished there because threshed grain sifts through the concave openings to the grain pan (K).

But some grain is mixed with the straw leaving the rear of the cylinder. This mixture is confined to the straw rack (I) by the beater (G) and by two deflectors (H). The front end of the straw rack, in the model illustrated, is fitted with a chaffer section; and the rear end of this straw rack has large cells or openings. The threshed grain falls through these openings to the grain conveyor (J). This conveyor carries the grain and chaff forward and delivers it to the grain pan (K).

The air blast from the fan (N) is directed by the deflector (O) against the adjustable chaffer (L), which is located toward the rear of the grain pan. This air blast also strikes the shoe sieve (M). It blows light chaff and bits of straw out the rear, but the grain falls through the shoe sieve (M) and down to the grain auger (S). This auger carries it across the bottom of the combine to the elevator (T), from which it is delivered to the grain tank or bagging attachment.

Some grain and unthreshed heads, mixed with chaff, are usually carried off the ends of the chaffer (L) and the shoe sieve (M). But this material, called "tailings", will not be blown out if you have made the adjustments correctly. It falls into the tailings auger (P). This auger carries the tailings across the machine to the tailings elevator (Q). This elevator delivers the tailings through to another auger (R), which returns them to the cylinder for rethreshing.