Page 25 - Goodyear2011PTMaintenanceManual

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Poly-V ® Belt
INSTALLATION GUIDE
IDLERS
Even though Poly-V® belts are designed to handle idlers
better than most other power transmission belts, idlers
will reduce belt life and should be avoided. Idlers put an
additional bending stress point on the belts, which reduces
the belt’s horsepower rating and its life. The smaller the
idler, the greater this stress and the shorter the belt’s life.
If the drive design requires an idler, observe the following
design recommendations.
Inside Idler
A V-grooved idler located on the inside of the belts on the
slack side of the drive is preferable to a back side idler.
Locate the idler near the large sheave to avoid reduction
of the arc of contact with the small sheave. Note that
the size of the V-idler pulley should be equal to or larger
(preferably) than the diameter of the small sheave.
Back Side Idler
A back side idler increases the arc of contact on both
sheaves. However, such an idler also forces a backward
bend in the Poly-V® belt, which contributes to unwanted
wear such as rib cracking and premature failure. If a back
side idler is the only option, follow two guidelines: (1) make
sure the diameter of the fat idler pulley is at least 1.5 times
the diameter of the small sheave and (2) locate the back
side idler as close as possible to the small sheave.
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Kiss Idler
Unlike the back side idler, the kiss idler does not penetrate the belt
span and create a back bend. Consequently, the kiss idler does not
contribute to premature failure. The kiss idler can help control belt
vibration and whip on drives subject to shock and pulsating loads.
When using a kiss idler, make sure the diameter of the fat pulley is
at least 1.5 times the diameter of the small sheave.