REFLECTOR: Matco brakes

[Al Gietzen]

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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