rotor_man
Guest
The hydrostatic drive in gleaner and most other combines is a big hydraulic motor, but no variable flow valve. The hydro pump is variable output and reversible. the more you advance the speed lever, the more oil the hydro pump puts out and the faster the hydraulic motor turns. When you pull the speed lever back to neutral where the pump puts out no oil, the hydraulic motor stops. Pulling the speed lever back reverses the oil flow from the pump which makes the hydraulic motor turn the opposite direction to make the combine back up. They have an oil cooler to control oil temp. these hydro systems work at very high pressure, up to 6000psi