5
SRSH IO&M
B51142-004
Replacing Pulleys and Belts
1. Clean the motor and fan shafts.
2. Loosen the motor plate mounting bolts to relieve the belt
tension. Remove the belt.
3. Loosen the pulley setscrews and remove the pulleys from
the shaft. If excessive force is required to remove the pul
-
leys, a three-jaw puller can be used. This tool, however,
can easily warp a pulley. If the puller is used, inspect the
trueness of the pulley after it is removed from the shaft.
The pulley will need replacement if it is more than 0.020
inch out of true.
4. Clean the bores of the pulleys and place a light coat of oil
on the bores.
5. Remove any grease, rust or burrs from pulleys.
6.
Place the fan pulley on the fan shaft and the motor pulley
on the motor shaft. Damage to the pulleys can occur when
excessive force is used in placing the pulleys on their re
-
spective shafts.
7. After the pulleys have been correctly placed back onto
their shafts, tighten the pulley setscrews.
Belt and Pulley Installation
Belt tension is determined by the sound of the belts when
the fan is first started. The belts will produce a loud squeal,
which dissipates after the fan is operating at full capacity. If
belt tension is too tight or too loose, lost efficiency and dam-
age may occur.
1. Loosen motor plate adjustment bolts and slide motor plate
so that belts easily slip into the grooves on the pulleys.
Never pry, roll, or force the belts over the rim of the pulley.
2. Slide motor plate until proper tension is reached. For prop
-
er tension, a deflection of approximately 1/4” per foot of
center distance should be obtained by firmly pressing the
belt. Refer to
Figure 1
.
3. Lock the motor plate adjustment bolts in place
4. Ensure pulleys are properly aligned. Refer to
Figure 2
.
Pulley Alignment
Pulley alignment is adjusted by loosening the motor pulley
setscrew and by moving the motor pulley on the motor shaft.
Figure 2
indicates where to measure the allowable gap for
the drive alignment tolerance. All contact points (indicated by
WXYZ) are to have a gap less than the tolerance shown in the
table. When the pulleys are not the same width, the allowable
gap must be adjusted by half of the difference in width.
Figure
3
illustrates using a carpenter’s square to adjust the position
of the motor pulley until the belt is parallel to the longer leg of
the square.
Tolerance
Center
Distance
Maximum
Gap
Up thru 12”
1/16”
12” up
through 48”
1/8”
Over 48”
1/4”
OFFSET
ANGULAR
OFFSET/ANGULAR
A
W
X
Y
Z
B
CENTER
DISTANCE
(CD)
GAP
GAP
Bearing Replacement
The fan bearings are pillow block
type ball bearings.
1. Remove the old bearing.
2. Remove any burrs from the
shaft by sanding.
3. Slide new bearings onto the
shaft to the desired location
Fig‑
ure 3
and loosely mount bear
-
ings onto the bearing support.
Bearing bolts and setscrews
should be loose enough to allow
shaft positioning.
4. Correctly position the wheel and
tighten the bearing bolts securely to the bearing support.
5. Align setscrews bearing to bearing and secure tightly to
the shaft.
NOTICE! Never tighten both pairs of setscrews be-
fore securing bearing mounting bolts. This may
damage the shaft.
6.
Inspect the wheel position again. If necessary, readjust
by loosening the bearing bolts and setscrews and repeat
from step 5.
Wheel Replacement
1. Drill two holes approximately centered between the shaft
and the edge of the hub OD with the following dimensions:
•
1/4” diameter
•
3/8” to 1/2” deep
•
180° apart in face of hub
2.
Tap 1/4” holes to 5/16” thread with the 5/16” hole tap. Do
not drill or tap any larger than recommended.
3. Screw the puller arms into the tapped holes full depth of
threads (3/8” to 1/2” approximately). Align center of pull-
er with center of shaft. Make certain all setscrews in hub
(normally a quantity of two) are fully removed. Work puller
slowly to back wheel off the shaft.
Figure 1
Figure 2
1 foot
1/4 inch
