REFLECTOR: Shimmy on landing

[Christopher Martin]

Chuck,

That is an interesting point and believe you are correct. I never flew in
the plane but I did spin the wheel up to about 40 MPH. As the wheel spun
down the nose gear began a vibration at about 30MPH and built into a severe
shaking of the entire plane within a few seconds. It was not shimmying back
and forth as in the case of the shopping cart castered wheel which we are
all so familiar with. I can amend my observation to a vibration of the out
of balance nose wheel being transmitted into the main airframe structure by
the nose gear which resulted in ripping out the nose gear bushings. After
he repaired the nose gear he still had the shaking which we corrected by
replacing the out of round nose wheel tire and then balancing.

Later on, in a normal landing the nose gear failed not from vibration or
shaking but from a broken weld which had fatigued in the earlier
vibration/shimmys incident. So, another lesson learned is that after you
fix the problem, make sure the rest of the system has not been damaged by
the severity of the earlier vibration induced shimmy.

Christopher Martin
christophercmartin at earthlink.net



> [Original Message]
> From: Chuck Jensen <cjensen at dts9000.com>
> To: <christophercmartin at earthlink.net>; Velocity Aircraft Owners and
Builders list <reflector at tvbf.org>
> Date: 4/10/2006 5:21:19 AM
> Subject: RE: REFLECTOR: Shimmy on landing
>
> Christopher,
>
> Are you sure the fellow you were referencing had shimmy, and not
> vibration from an out of round and/or out of balance wheel.  Two
> entirely different animals.  I suppose the out of balance/round may make
> one more susepctible to shimmy (side to side swinging of the nose
> wheel), but a shimmy can 'degear' the nose pretty fast on the first, or
> after a few events, whereas the out of round problem is highly annoying,
> even alarming, but is much less of a gear removal threat than true
> shimmy.  IMUO (in my uneducated opinion).
>
> Chuck Jensen
>
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Christopher Martin
> Sent: Monday, April 10, 2006 1:36 AM
> To: Velocity Aircraft Owners and Builders list; Velocity Aicraft Owners
> and Builder list
> Subject: RE: REFLECTOR: Shimmy on landing
>
> I was surprised that no one mentioned wheel balance.
>
> While it is absolutely required to have proper tension on the bevel
> washers
> it is also mandatory to balance the nose wheel to prevent shimmy. An out
> of
> balance wheel will create a peak shimmy at a specific speed and then
> diminish. One of our fellow velocity pilots had a significant shimmy
> problem which he couldn't correct. He tried everything. I picked up the
> nose of the plane and slid a saw horse under it , then spun up the wheel
> with a tire spinner, as the wheel spun down it started to shake and then
> built into a significant shaking of the whole plane. Not only was it out
> of
> balance it was also out of round. We replaced the front tire and
> balanced
> the wheel and tire. It completely eliminated the shimmy. If you don't
> have
> the equipment, take the wheel and tire over to a tire shop and ask them
> to
> balance it.
>
> Christopher Martin
> christophercmartin at earthlink.net
>
>
>
> > [Original Message]
> > From: RICHARD J VANDERSTEEN <rvandersteen at sbcglobal.net>
> > To: Velocity Aicraft Owners and Builder list <reflector at tvbf.org>
> > Date: 4/8/2006 8:49:00 PM
> > Subject: REFLECTOR: Shimmy on landing
> >
> > Any advice on what to check after a shimmy event on
> > landing an XL-RG.
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