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early failure. Specific tools are made to measure the tension of a V-belt drive
system. A Dodge® V-Belt Tension Tester, Browning® Belt Tension Checker
or equivalent an alternative should be used for tensioning V-belts. Check with
you local belt supplier.
Belt tension is measured by applying a force perpendicular to the belt at the
center point between motor and fan sheaves. The belt should deflect
1
⁄
64
of
the entire span, (measured sheave centerline to sheave centerline) when the
pressure shown in the table below is applied. Because belt tension is a func-
tion of the motor sheave diameter, it is necessary to inspect the motor sheave
to determine the diameter. If diameter markings are unreadable, measure the
sheave diameter at the bottom of the sheave grooves.
New belts (operating less than 8 hours) should be tensioned to the maximum
value. Tension after this period should use no less than the minimum value. If
the belt span was measured in inches, then use the pounds of force values.
If the belt span was measured in centimeters, then use the kilograms of force
values. If specific tensioning instructions are provided with your tensioning
tool, those instructions should be used instead.
Sheave Alignment:
Always shut off electrical power to the tower fan motor prior to
performing any inspections that may involve physical contact with
the mechanical or electrical equipment in or on the tower. Lock out
and tag out any electrical switches to prevent others from turning
the power back on. Service personnel must wear proper personal
protective clothing and equipment.
• The motor sheave is to be positioned as close as possible to the motor
in order to minimize torque on the motor bushings.
• The motor and fan sheaves may have grooves that are not used. The bot-
tom surface of the motor and fan sheaves must be aligned within
1
⁄
8
" of
Warning
maintenance
Motor Sheave
diameter
Used V-Belt
minimum
New V-Belt
maximum
3.4" - 4.2"
4.9 lb
7.2 lb
85cm - 105cm
2.2 kg
3.3 kg
4.4" - 5.6"
7.1 lb
10.5 lb
106cm - 140cm
3.2 kg
4.8 kg
5.8" - 8.6"
8.5 lb
12.6 l
141cm - 220 cm
3.9 kg
5.7 kg
