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MAINTENANCE
PVT System
The basic operation of the POLARIS PVT system is dependent on
engine speed and vehicle torque requirements. As engine speed
increases, the force exerted on the movable drive sheave by the
flyweights also increases. This, in turn, increases the amount of pinch
applied to the drive belt. Similarly, if the engine speed decreases, the
amount of centrifugal force decreases, reducing the amount of belt
pinch.
The approximate gear ratio difference between high and low range is
1:2.25. This difference in gearing affects the operation of the PVT,
especially at speeds less than 7 MPH (11 km/h), due to the system's
dependence on engine speed.
For example, when operating at a ground speed of 3 MPH (5 km/h) in
low range, the engine speed would be around 3000 RPM. This is well
above the engagement speed of 1600 - 1800 RPM. However, in high
range at 3 MPH (5 km/h), the engine would be running at only 1500
RPM. Whenever operating this close to the engagement speed, the
engine may be running at a speed too low to provide the pinch needed to
prevent belt slip. Belt slip is responsible for creating the excessive heat
that destroys belts, wears clutch components and causes outer clutch
covers to fail.
The air temperature in the clutch cover is substantially reduced by using
low range while operating at low ground speeds. Reducing the
temperature inside the clutch cover greatly extends the life of the PVT
components (belt, cover, etc.).
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