REFLECTOR: Brake shudder - RG

[Pat Shea]

Al,

I chased the same the same shudder issue for months &
months. In the end, I had a grinding shop true up my
rotors and the shudder went away. I believe they were
about .005 out.

The shudder comes back, in a much milder state, every
50 hours or so of flying/landings. Now i just take a
sanding block to both sides of each rotor which cures
the problem. The explanation here is that brake pad
material builds up on the rotors. This can happen when
the rotors get hot, which they always do when landing
a 2,500lb plane at 75kts on a 3,000 foot runway...

Side note: I spoke to the owner of Matco at Osh so he
could "pass the word" to others having a similar
experience. I mentioned that I used emery cloth when
sanding the rotors. He cringed a little and explained
that emery cloth has silicon in it. Good to know... I
didn't notice any difference in braking performance,
but next time i plan on changing the pads, cleaning
the rotors, and using sandpaper without silicon.

I've had no noticeable movement of the main gears
(using the gear doors/wells as a reference) in the
last 180 hours. Also, I tighten the pivot bolts until
the they start to restrict the gear's up and down
movement (plane on jacks) and then loosen them only
slightly.     

Pat

    
--- Al Gietzen <ALVentures at cox.net> wrote:

> After the first few landings with the Matco brakes,
> I began to get 'shudder'
> of the main gear somewhere in the 40 - 30 kt range
> when applying the brakes
> on roll out.  This can be annoying, as well as cause
> a pretty good shake of
> the plane.  I'm told this is common with Velocitys. 
> There is a point of
> resonance involved here, and there must be a driving
> force.  
> 
>  
> 
> I recall someone posted here about just a few mils
> distortion of the rotors
> causing this, and milling the rotors true solved the
> problem.  Do I recall
> correctly, and did the problem stay solved? 
> Where/how did you get them
> trued up?
> 
>  
> 
> While investigating the issue, I found that the
> retracted position now the
> gear is about 1/8 - 3/16" further forward in the
> wells, which eliminated the
> clearance of the gear doors to the stake opening. 
> Is this a common
> occurrence?  I thought that perhaps the pivot bolts
> on my 1996 kit were not
> grade 8 and may be bent a bit, but they were grade
> 8.  I changed them out
> anyway, and found it eliminated a bit of play. 
> Examining the bolts shows
> that they were not very round, and the high spots
> were worn.  I think the
> new bolts are more true.
> 
>  
> 
> I also noted there was now about .010 - .015"
> fore-aft movement of the gear
> (the spacers originally fit very close), and the
> bolts were loosely
> tightened to allow them to rotate in the bushings,
> rather than the sleeve in
> the leg rotating on the bolts.  When I installed the
> new bolts I tightened
> them a bit more which reduced the clearance, but
> will mean that the bolts
> will not rotate in the bushings.  Any opinion on
> whether it matters?
> 
>  
> 
> Thanks,
> 
>  
> 
> Al
> 
>  
> 
>  
> 
> Thanks,
> 
>  
> 
> All
> 
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