REFLECTOR: Main LG vibration on braking ...

[Ron Brown]

THANKS, Pat.

Excellent data points for the vibration and I believe you have nailed it - 
disks that are not perfectly straight and flat.  I pretty much tried many of 
the things you did except for the resurfacing.

I think it is a resonance problem that apparently is excited by a non 
perfect set of disks.  I measured mine and found less than .001, but 
apparently, that is enough to set up a bit of chatter that excites the gear.

Ronnie


----- Original Message ----- 
From: "Pat Shea" <xl340hp at yahoo.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Tuesday, February 01, 2005 7:21 PM
Subject: Re: REFLECTOR: Main LG vibration on braking ...


> Jim,
>
> I battled main gear vibration while braking in the
> 45-25 speed range on my XLRG for a while. I worked w/
> George at Matco trying all sorts things. These all had
> little or no affect:
>
> -Adjusting toe in/out
> -different pad material
> -Different calipers (upgraded to XT)
> -Different discs (different material)
> -Line restrictors/dampeners
> -Different tire pressures
> -Balancing the wheels/tires
> -Shimmed away any disc run-out
>
> I finally did what Scott Swing said to do early on,
> which was have the surfaces of the discs ground flat.
> I found a grinding shop (versus machine shop) that
> charged me $20 to grind both discs. My discs were only
> about .005 out and slightly bowl shaped (again, about
> .005 worth). This solved the problem. I didn't do this
> initially because I had sent my brakes to Matco for
> inspection and specifically asked them to verify that
> the discs were true - they said they were fine...
>
> Pat
>
> --- Jim Sower <canarder at frontiernet.net> wrote:
>
>> All,
>> There is a pretty extended discussion on the Cozy
>> list about Main Gear
>> vibration.  Seems as if the gear legs start
>> vibrating / oscillating
>> during braking from about 45 kts down to 30 kts or
>> thereabouts.  If you
>> let off the brakes at 45, coast down to 30 and
>> re-apply the brakes there
>> is no vibration.
>>
>> I was wondering if this might be a known  / well
>> known / common
>> phenomenon in the Velocity / RV communities.  Seems
>> as if it's fairly
>> common in all of the direct derivatives of Rutan
>> airplanes (EZ, Cozy,
>> Defiant).
>>
>> Inquiring minds need to know ... Jim S.
>
>>
>
>
>
>
>
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