8200 SERIES TRACTORS 3A01.8
Engine - General
C . Viscostatic fan Description The engines are fitted with a cooling fan equipped with a viscostatic coupling. This device permits a gain in power in the order of 2 to 3 horsepower. The viscostatic coupling comprises three main parts: - the driving part driven by the engine and composed of a shaft (1) integral with a plate (2) fitted with annular grooves, - the driven part constituted by a hub (6) receiving the fan and the body (7) and equally fitted with annular grooves, - the regulating section comprising a thermostatic spring (3) that controls valve (4). The centre of the device contains a tank (5) filled with a viscous silicone fluid.
Operation When the temperature of the air passing through the radiator reaches a preset value, thermostatic spring (3) acts upon valve (4) which opens port a. The liquid is directed by centrifugal force to the annular grooves of hub (2) and body (7). The torque is transmitted through the internal friction of the extremely viscous liquid and its adherence to the inner walls. The fan is thus driven and permits a better air cooling of the radiator. The speed of the fan varies continuously over the whole range of regulation depending on the temperature. When the temperature of the air passing through the radiator drops, the spring closes the valve and stops the liquid from reaching the friction area. The fluid gradually returns to the tank (5) via channel b, the fan thus becomes de-clutched, leaving only residual resistive torque.
Issue 1
December 2000
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