Nose wheel shimmy

[JFLEISC]

I read an interesting thread where someone pointed out that all shimmy
preventitive devices are designed to stop something that has already started,
and that wheel balancing may stop a shimmy from ever starting. Makes sense, but
my question is; What, if any, is the normal method of balancing aircraft tires,
how is it done, and what kind of weights or counter balance device is used?

Jim

[JDupre5762]

>From: (Dan Thomas)

> I couldn't find a balancing machine to do such small wheels.

There are balancing devices, I can't call them machines, available. A good
aircraft tool catalog will probably have one. I think Goodyear made one
specifically for small aircraft wheels but others are of similar design and
basically are a pair of brackets that hold a threaded axle with sealed bearings
at each end. There are two threaded cones that are sused to trap the wheel
assembly on the axle and the axle is then placed onto the brackets so that the
bearings support the axle. Spin the wheel to warm the bearings and then stop
the wheel and rotate it 90 degrees and see it moves. Adhesive lead weights are
used on the light side of the wheel to correct the imbalance. You should be
able to rotate the wheel to any point and it will not settle to any other
point.

> Cessna recommends wheel balancing and says their dealers
>have the equipment. I've called dealers and they've never heard of it.

The Cessna style of balancing is more static than the other and consists of a
shaft with a point and an arbor that is placed into the wheel with a bubble
level in the end of the arbor. Weights are added until the bubble is centered.
It is important to set the arbor properly in each size of wheel. In twenty
years of aircraft maintenance only one shop out of dozens I have known or
worked in ever had the Cesssna set up.

John Dupre'

[Aaron Coolidge]

JDupre5762 > wrote:
:>From: (Dan Thomas)

:> I couldn't find a balancing machine to do such small wheels.
<snip>

:> Cessna recommends wheel balancing and says their dealers
:>have the equipment. I've called dealers and they've never heard of it.

: The Cessna style of balancing is more static than the other and consists of a
: shaft with a point and an arbor that is placed into the wheel with a bubble
: level in the end of the arbor. Weights are added until the bubble is centered.
: It is important to set the arbor properly in each size of wheel. In twenty
: years of aircraft maintenance only one shop out of dozens I have known or
: worked in ever had the Cesssna set up.

I have a static wheel balancer intended for motorcycles and such, and I
attempted to use it to balance my nosewheel. It works on the principle
John described, ie, a bubble level and a conical point. The problem I ran
into is that the balancer is really made for wheels where the weight is
much further from the center than an aircraft wheel, in other words,
larger diameter wheels. I was unable to balance my nosewheel, and solved
the shimmy by buying a new nosewheel tire.
--
Aaron Coolidge