The Forage Harvester: Chopping Green Crop to a Set Length

Silage is green crop — grass, maize, legumes — packed tight and left to ferment so it keeps through winter. It keeps only if it is chopped short and evenly enough to pack out the air. For decades the crop was cut and carted to a stationary silage cutter at the silo. The field forage harvester does the chopping in the field: it picks up or cuts the crop, feeds it between rollers into a cutterhead of knives, and blows the chop up a spout into a trailer. Sir Charles Ross thought of joining a pick-up to an ensilage cutter and blower powered by an engine riding on the rig; Professor Floyd Duffee improved it; the Fox River Tractor Company tried a mower-type chopper in 1931 and sold a cutter-bar chopper from 1940, and in 1942 Gehl became the first to mass-produce forage harvesters. This rung works out the length of cut, the flywheel's reserve and the spout speed, and builds a paper-strip model that shows the length of cut directly.