REFLECTOR: Matco brakes

[gibbons]

Yes the axle flange was hitting the weld on the tube. I had to repair
both main gear legs with metal bootees.( cutting off about 6 inches of
leg and replacing it with a metal leg, in with Velocity sells them.) I
did tell Velocity about the problem so they would let other know about
the problem. The plane steers good now with out a lot of braking.
Barry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Monday, May 28, 2007 3:34 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: REFLECTOR: Matco brakes



Subject: Re: REFLECTOR: [SPAM] Re: Matco to cleveland brakes

 

Hello Folks

I've been having problem with my steering on my plane and some brake
problems. It turned out to be the Mattco brakes. The brake back plate
was hitting the axle. You can see this problem if you remove the back
plate and you will see it riding on the weld around the small pipe. This
made my brakes drag all the time, creating too much heat

Do you mean at the axle flange, or the tube the bolt goes through?  When
installing my Matcos I recall noting that issue and chamfering the
backing plate to make things work right.  Anyone installing the earlier
version Matcos should inspect carefully.

 

Here is the text of a memo I wrote to Velocity at the time, but never
had a response nor saw any notice:

 

To:      Duane/Scott Swing

@Fax:   407, 589-1893

From:    Al Gietzen

 

Date:     7/22/97

Re:        Matco Brakes and axle

 

When installing the Matco assembly I found that the weld buildup where
the lower guide tube for the cylinder bolt is welded into the torque
plate, interferes with the axle flange.  They are very close at that
lower corner and that weld prevents the torque plate from seating
properly, causing the torque plate to get slightly bent when the
mounting bolts are tightened; and results in binding on the bolts
holding the cylinder.  This could cause the brakes not to hold properly;
or more likely, cause them to not release completely when the peddle was
released, hence, brake drag and continued heating of the rotor. 

 

If this is common to the Matco assembly, a builder who did not notice
and grind it off could have some problems.  A definite QA problem on
these parts.

 

Also, I recall a safety note in Velocity Views a few issues back about
overheating of a gear leg, causing it to bend.  My quick analysis of the
heat transfer paths indicates that a significant amount of heat would
transfer across the small air gap between the rotor and the torque
plate.  This could be as important as to the rim, through the bearing
and the axle.

 

The air gap heat transfer could be reduced significantly by simply
reducing the size of the torque plate (increasing the gap).  A change
from 1/16" to 1/4" would cut that flow by more than a factor of 4.  The
path to the rim could be reduced by placing a spacer of insulating
material of some type at the three rotor-to-rim attach points (I haven't
looked into what that material might be).  This could also be important
to protect the tire.  It seems to me that by the time the leg got hot
enough to bend, the temperature of the rim would have to be scorching;
enough to damage the tire at the bead.

 

I think these fixes may be more effective than a heat dissipation plate
between the axle flange and the leg.  Of course it may be that the
designers intended the heat to transfer away from the rotor; which is
fine if it's mounted on a metal leg.

 

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