REFLECTOR: wheel shimmy

Thu Feb 19 11:48:02 CST 2009

Just a input here related to nose gear shimmy.  I have found that on a 
number of the nose gear struts that have come out of the factory the threads 
on the end of the shaft are too long.  Or there are too many.  So make sure 
that none of the thread can get into the bushing area.  If they do the 
threads get transferred to the bushing and the bushing is no longer a pivot 
but a jack screw.  With weight on it, it can't pivot.  It can only go up or 
down.
Also if you have the lighter weight beveled washers they have a spacer 
inside of them to make up side clearance.  When they are compressed to the 
14+lbs you could be trying to compress the spacer and not the washers.  I 
found this out the hard way when every time I went to fly, I found the 
tension had loosened.  After I changed out to thicker washers the problem 
went away because the spacer was no longer needed.  So before further flight 
make sure that the spacer is not being compressed, this is the piece of 
tubing between the ID of the washers and the strut.  With the lighter 
washers they can compress to a point that you are now bottoming the washers 
and now trying to compress the spacer.  Then the washers become useless.
Dave
N32XL
----- Original Message ----- 
From: "Velocity" <velocityxl at fastmail.fm>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Thursday, February 19, 2009 9:08 AM
Subject: Re: REFLECTOR: wheel shimmy


> :it's difficult to get the plane exactly straight with the runway
>
> So the dampener idea really would not solve this problem of steering 
> right?
> Sounds like steerable nose wheel is what is really needed. I remember some
> one had made a steerable nose wheel once using a servo motor.
> Any idea on how it worked out?
>
> Also there is the locking nose wheel which looks good . That way the 
> tension
> can be quite low making steering easier?
> Still have to stab the brakes to get it to turn though.
>
> Any one played with changing the caster amount?
>
> Ron
>
> ----- Original Message ----- 
> From: <aminetech at bluefrog.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Thursday, February 19, 2009 10:49 AM
> Subject: Re: REFLECTOR: wheel shimmy
>
>
>> Another issue with the tension at 14 lbs or so, is that it's difficult to
>> get the plane exactly straight with the runway and that results in the
>> need for braking during takeoff.  Not a good thing if takeoff distance is
>> critical.
>>
>> John
>>
>> --- scott at tnstaafl.net wrote:
>>
>> From: Scott Derrick <scott at tnstaafl.net>
>> To: Velocity <velocityxl at fastmail.fm>,        Velocity Aircraft Owners 
>> and
>> Builders list <reflector at tvbf.org>
>> Subject: Re: REFLECTOR: wheel shimmy
>> Date: Thu, 19 Feb 2009 09:30:19 -0700
>>
>> Ron,
>>
>> I have about 450 hours of flying on my V.  With the bellevue washer
>> system.
>>
>> It is adequate, but certainly not optimal.  The problems for me are,
>>
>> 1.)  Hard to turn. Specifically hard to break into a turn, once the
>> wheel breaks free it turns fairly easily, leading to the next problem.
>> The tighter you have teh bellevue washers the harder to initiate a turn.
>>
>> 2.) In tight situations, its easy to over turn so that the wheel is now
>> near 90 degrees and then its tough to get it to straighten out.
>> Sometimes I've had to get out and kick the nose tire straight before
>> continuing a taxi.
>>
>> 3.) Bellevue's continuing tendency to loosening up.  Even though I check
>> it before every flight I have had it loosen up to much and then get a
>> bit of shimmy on landing, not a good feeling, especially for passengers
>> who imagine the worst.  As some have mentioned,  how you land and how
>> much weight on the nose can influence if you get a shimmy or not.
>>
>> A system that did not require constant maintenance/attention and
>> provided easier turning would be a great addition.  The bellevues have
>> simplicity and proven performance on their side, which in airplanes is a
>> big big plus.
>>
>> Scott
>>
>> Velocity wrote:
>>> Now being on this list for over 10 years now I know this issue keeps
>>> coming
>>> up. It seems
>>> the answer usually goes to set the tension on the front wheel to 14 lbs
>>> of
>>> pull or something like that
>>> and you should not have a problem. Is this not true? I have heard that
>>> this
>>> should be
>>> on the preflight check list. Does this number change and really need to
>>> be
>>> adjusted regularly?
>>> If so maybe  we just need to find the way to get the tension to stay
>>> within
>>> a range that works.
>>> Or perhaps  there are people that feel that there is a better mouse trap
>>> out
>>> there and are working
>>> toward a simpler/ better design for the front wheel which is great. So 
>>> is
>>> there a steering Issue?
>>> Or is there a real problem that needs to be addressed? Just wondering
>>> because I have not
>>> had the joy yet of being in the front seat and seeing for my self. One 
>>> of
>>> these days, One of these
>>> days.
>>>
>>> Ron
>>>
>>>
>>>
>>>
>>>
>>> ----- Original Message ----- 
>>> From: "Sid Knox" <sbjknox at earthlink.net>
>>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>> Sent: Wednesday, February 18, 2009 11:56 PM
>>> Subject: Re: REFLECTOR: wheel shimmy
>>>
>>>
>>>
>>>> From: "Scott Derrick" <scott at tnstaafl.net>
>>>>
>>>>> Sid,
>>>>> Can you give an update on the damper? Working well?
>>>>>
>>>> Working great.  Never a hint of shimmy.  The big nut is tight only
>>>> enough
>>>> to
>>>> take up any slack.  With damper disconnected, completely free of
>>>> friction.
>>>>
>>>>
>>>>> How many landings on the system?
>>>>>
>>>> Several dozen since install in Spring of 2006.
>>>>
>>>>
>>>>> Did you ever put external stops on it so the damper wouldn't bottom
>>>>> out?
>>>>>
>>>> No.  I can make the sharp 120 degree turn on the narrow taxiway leading
>>>> to
>>>> my ramp no problem.
>>>>
>>>>
>>>>> Ever miss not having a fulling castoring nose wheel?
>>>>> Scott
>>>>>
>>>> Not yet.  I simply pick up the nose and walk it around if needed.  With
>>>> no
>>>> passenger(s) inside of course... its too heavy for me otherwise.
>>>> Pushing
>>>> backwards is easier too without the tendency for the wheel to caster
>>>> around
>>>> backwards.
>>>>
>>>> Sid
>>>>
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>>>
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>>
>>
>>
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>
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