REFLECTOR: Shimmy on landing

[Scott Derrick]

I bought a new nose tire from the factory a couple years ago.  On take 
off I though I noticed a vibration. On landing it was very noticeable.

The new tire was totally out of round!  The factory sent me a new one 
that was round as a tire is expected to be..  Further landings were as 
smooth as Doylie Cart.

Scott

Christopher Martin wrote:
> 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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