HYDRAULICS THE C MODEL General Description The combine has three separate hydraulic circuits: traction hydraulics, the combined lifting and steering hydraulics and the low-pressure connection hydraulics. All the circuits use the same oil tank and filter. There are two pumps in the system. They are located at the rear of the engine in the distribution gear and form an entity. Hydrostatic steering and working hydraulics use a joint pump. Hydrostatic steering gets its oil by means of a priority valve. The valve always supplies the amount of oil needed in steering and the rest can be used in other working hydraulics. Traction hydraulics works in a closed circuit. The engine return oil returns straight into the pump. Connection hydraulics uses the feed oil in traction hydraulics. Depending on the specification, the combine may have 4WD. 4WD gets the oil from the main transmission by means of a connection valve on the rear axle. With the drive switched off the rear wheels rotate freely and there is no oil circulating in the final drives. There is also an oil cooler in the system located in the traction hydraulics return line before the filter. The cooler functions are controlled by means of a thermostat valve. The control valves in working hydraulics are electrically controlled and located at the front beneath the cab. There are two valves: the valve further front houses the control valves of table height and free circulation; the one further back houses the control valves of the reel lift and the turning of the unloading pipe. Movement speeds are regulated by restrictors at the control valve gates except for the table lowering speed, which can be adjusted by the operator. The control valve for connection hydraulics is also located on the left-hand side, below the oil tank. Pump output in working hydraulics is 27 l/min. Working pressure is restricted to 180 Bar. Pump output in traction hydraulics is 217 l/min. Maximum working pressure is 420 Bar. Feed pressure in traction hydraulics is approx. 25 Bar.
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