Piper COMANCHE PA-24-180 Service Manual page 590

PIPER COMANCHE SERVICE MANUAL
9-91. Methods Of Checking Generateo Or Alternator Belt Tenien.
a. If properly installed, tensioned and checked periodically, the generator or alternator drive
belt will give very satisfactory service. However, an improperly tensioned belt will wear rapidly
and may slip and reduce generator or alternator output. Consequently, a belt should be checked
for proper tension at the time it is installed, again after 25 hours operation and each 100 hours
thereafter
b. There are two satisfactory methods of checking belt tension; however the first method
described will be found preferable by most maintenance personnel because it is technically sim-
ple. and requires little time for accomplishment.
1. Torque Method: This method of checking belt tension consists of measuring the torque
required to slip the belt at the small pulley and is arcomplished as follows:
(a) Apply a torque indicating wrench to the nut that attaches the pulley to the generator
or alternator and turn it in a clockwise direction. Observe the torque shown on the
wrench at the instant the pulley slips.
(b) Check the torque indicated in step (2) with torque specified in the followingchart.
Width of Torque Indicated at
Belt Condition Generator or Alternator Pulley
3,8 inch New 11 to 13 ft. lbs.
3/8 inch Used 7 to 9 ft. lbs.
1/2 inch New 13 to 15 ft. lbs.
1, 2 inch Used 9 to 11 ft. lbs.
NOTE
The higher tension specified for a new belt is to compensate for
the initial stretch hat takes place as soon as it is operated. These
higher tension values should not be applied to belts which pre-
viously have been used.
2. Deflection Method: Belt tension may be checked by measuring the amountof deflection
caused by a predetermined amount of tension; this is accomplished in the following manner
(a) Attach the hook of a small spring-scale to the belt at the approximate mid-point
between the ring gear support and the generator or alternator.
(b) Pull on the scale until a reading of 14 pounds is obtained. (10 pounds for used
belts)
(c) Measure 'he distance the belt has moved with the 10 to 14 oound load applied The
distance (deflection) should be 3. 16 inch If less than 5/16 inch. the belt is too right.
ELECTRICAL SYSTEM
ISSUED: 8/18/72
3 C20