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2. Check alignment
Proper alignment is more critical for variable speed drive
sheaves than for conventional V-belt drives. Check belt
alignment whenever you maintain or replace belts or remove
or install sheaves.
This illustration (Figure A), shows the correct way to check
alignment between two variable speed drive sheaves.
Another illustration (Figure B), shows a belt misaligned. To
correct the alignment, move one sheave so that the straight
edge is equidistant from both sides of the narrow sheave. The
belt edges should also be equidistant from the straight edge.
RIGHT
The belt is parallel
to the straight edge
WRONG
Check for misalignment
and o"set distance “D”
Figure A: Properly Aligned
Figure B:
Misaligned
D/2
D/2
D
3. Identify correct belt
To select the correct belt, refer to the drive manufacturer’s
recommendations. The belt length is most critical on fixed
center drives with both pulleys variable since accurate length is
required to achieve precise drive speed variations. Belt length
with one variable and one fixed pulley is also critical as it affects
the allowable increase and decrease in center distances.
4. How to install belt
Take special care during the installation of variable speed belts
to avoid damage to the belts and sheaves. You may have to
open variator sheaves fully to facilitate installation. You may
also have to shorten the drive center distance to allow for easy
installation. Also, you may have to remove sheaves. After
assembly, return the drive center distance to normal and
recheck drive alignment.
5. Tension
Spring loaded sheaves, which apply the tension required
to handle the design load, govern variable speed
belt tensioning.
6. Belt guards
Belt guards ensure cleanliness and safety. Screened, meshed
or grilled guards are preferable because they allow for air
circulation and heat escape. Note: refer to
www.osha.org.
7. Idlers
Idlers are not recommended for variable speed drives.
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Specialty Belts
Installation Guide