Piper Navajo PA-31 Service Manual page 48

PIPER NAVAJO SERVICE MANUAL
2-39a. TIRE BALANCING.
Proper balancing is critical for the life of the aircraft tires. Ifa new tire is balanced upon installation it will
usually remain balanced for the life of the tire without having any shimmy or flat spots. and an inexpensive
balancer can be made that will balance almost any tire for light aircraft. (Refer to Paragraph 2-39b for
fabrication instruction.) Balance the tire as follows:
a.
Mount the tire and tube (if one is used) on the wheel, but do not install the securing bolts. Install the
wheel bearings in the wheel: then, using the -7 bushings, -6 spacers, and -5 nuts. install the wheel-tire assembly
on the -8 pipe. Secure the -5 nuts finger-tight so that the wheel halves touch each other. Be sure the bolt holes
are aligned! Insert the -4 axle through the -8 pipe and place the wheel in the center of the balancer. Make sure
the axle is only on the chamfered edges of the balancer and that it is at 90
°
to the side of the balancer.
b.
Release the tire. If it is out of balance it will rotate, coming to rest with the heaviest point on the
bottom. Tape a 1 2 ounce patch across top center of the tire. Rotate the tire 45° and release it again. If the tire
returns to the same position. add a I ounce patch and again rotate the tire and release it. Continue this
procedure until the tire is balanced.
c.
When balance is attained, put a chalk mark on the sidewall directly below the patch. Use one mark
for each half ounce of weight needed. Mark the valve stem location on the tire and the opposite wheel halt to
assure reassembly in the same position. Remove the wheel from the balance stand, break it down, and clean the
tire with toluol. Apply a coat of patch cement to both the patch and the inside center of the tire inline with the
chalk marks. When the cement has dried, install the patches making certain they are on the center line of the
tire and aligned with the chalk marks on the sidewall. Burnish the patches to remove trapped air. etc.
d.
When reassembling the wheel, powder the inside of the tire. Mount the tire on the valve side of the
wheel in the same position it was in when it was balanced. Install the other wheel half. aligning thechalk marks.
Install the bolts and tighten to required torque, then air the tire and recheck the balance. The wheel should not
be more that 1 2 ounce out of balance.
2-39b. CONSTRUCTION OF TIRE BALANCER. (Refer to Figure 2-11)
a.
The following instructions will help in building the balancer: chamfer top edges of -3 sides. leaving
1 16 inch flat on top inboard edge. Rivet -2 tee's to -3 sides using AN470-AD5 rivets' 2" spacing. Use
AN426-AD5 rivets 2" center to center to secure -2 tee's to -1 base. If tee extrusion is unavailable. heavy angle
extrusion could be used. -3 sides must be paralled and vertical.
b
The -4 axle must slide through the -8 pipe. The -5 nuts were made by reaming the existing threads in
the AN365-624 nuts with an R drill. then tapping with a 1 8-27 pipe tap
c. The -6 spacers were made from 1 2 inch aluminum tubing. The two lengths of spacers are suitable
for balancing most any aircraft wheel.
d.
The -7 bushing may be benchmade from one inch phenolic or aluminum using a 1-1 2 inch hole saw
to cut out the larger diameter. By inserting a 1 /4 inch long threaded bolt through the pilot hole and securing
with a washer and nut, a drill press and file may be used to make the off-set on the bushing. The turned down
part should just slide inside the beanng race. Ream the pilot hole to slide over the -8 pipe threads.
e.
The -8 pipe was made from a piece of I 8 inch black pipe and threaded wth a 1 8-27 pipe die. Thread
3 inches in from each end of the pipe.
Revised: 1/29/82
HANDLING AND SERVICING
1B24