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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 flat 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.
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 flat pulley is at least 1.5 times the diameter of the
small sheave.
The following few sections detail other
issues that could arise during a Poly-V® belt
drive installation:
14. Belt guards
Poly-V® belt drive guards ensure cleanliness and safety.
Screened, meshed or grilled guards are preferable because
they allow for air circulation and heat escape.
15. 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.
Driven
Driver
Driver
Driven
Driven
Driver
32
Banded Belts
Installation Guide