REFLECTOR: Violent Shimmy Cause = Light Gun Oil Lubrication

[Brian Michalk]

Perhaps a damping grease would work better?
A damping grease is a dilatant, or shear thickening lubricant.  It has 
the property of exhibiting higher viscosity when under shear.

Almost all lubricants are the opposite.  Greases in particular are 
thixotropic.  They become solid at rest, and liquids under shear, which 
is the opposite of what we need.

I would like to try this one day.  Here is a link to a kit containing 
various samples:
http://www.lubekits.com/?load=grease

There may be other sources, perhaps motorcycle fork oil, chain grease, 
shock absorber oil or limited slip differential oil could be dilatant 
greases.


On 9/6/2011 9:13 AM, Brett Ferrell wrote:
> We replaced the phenolic with the nylon, so YES, we still use the 
> standard belleville washers, grease, and check them before each 
> flight, but we find that we can tighten the nut tighter and still 
> maintain pretty easy steering.  We also keep the tension higher since 
> Scott Swing visited, as he thought our nose wheel was 'too loose' at 
> what we believed was the prescibed tension.  I think the manual calls 
> for 15 pounds break-out, and with our test rig what felt right to 
> Scott measured about 25.
>
> We have the Mishler lock, but we do not use it.  It's probably fine, 
> but we heard a couple of stories that worried us, one person tossed 
> their nose pant and someone else's wheel got locked sideways and they 
> had some trouble controlling the plane with the pant cocked to one 
> side.  Scott S really likes the lock, though (or at least did) and 
> encouraged us to use it.  He may favor the dampener now, I'm not sure.
>
> We've been flying with the nylon nut for over a year and have really 
> liked it.  All of our "practical" flying has been done with it, but 
> I'd have to look at a log to say for sure how many hours.  It's 
> probably in the 30-40, but we have a ton of landings as it seems we're 
> always testing something (pants, vgs, props, whatever).  We certainly 
> don't have years and years on ours, but so far we have been happy.
>
> Brett
>
> 	-------Original Message-------
> From: Scott Derrick
> To: Brett Ferrell , Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Violent Shimmy Cause = Light Gun Oil Lubrication
> Sent: 06 Sep '11 08:47
>
> So Brett,
>
> No Belleville washers at all? Just a couple of thick nylon washers?
>
> How many hours/landings would you estimate?
>
> Do you still check the nose turning tension as part of preflight?
>
> Scott
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: Violent Shimmy Cause = Light Gun Oil Lubrication
> From: Brett Ferrell
> To: reflector
> Date: 09/06/2011 05:35 AM
>> I would definitely use the grease, but we've been flying the nylon 
>> nut solution for awhile and really like it.  It keeps a relatively 
>> usable break-out force but still has enough friction to damp out 
>> shimmy.  We think the airplane stays very steerable with this setup.
>> http://www.velocityxl.com/wiki/index.php?title=Nylon_Belleville_Anti-Shimmy
>>
>> Brett
>>
>>
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