Re: Brake pads fell off

mike wrote:

> What would one look for to preempt such a problem?

Rivetted brake shoes. Of course that means that the amount of availabe
friction lining material available for wear is approximately cut in
half. You have to throw away half your lining every time.

Chemical engineers developed some kind of bonding resin to glue the
friction material to the metal shoe in the 1940's or 1950's. I dunno
perzactly what it is, but it looks dark reddish brown, like some kind
of varnish. I don't even think it was catalyzed epoxy. It might have
been a catalyzed polyester resin.

The brake engineers are relying on the peel strength of the resin to
exceed the frictional drag applied by the rotating drum and I'm sure
they did all kinds of lab tests and came up with a safety factor of two
or three times the maximum drag in order to certify their resin as safe
for bonding whatever material they used to metal.

But, polyester resin will dry out over the years from exposure to heat
and dryness. Epoxies do better than that.

If you have doubts about the strength of bonding materials, consider
this: the pressure vessel that the Apollo astronauts rode to the Moon
and back into the Earth's atmosphere, experiencing 9 g's on
acceleration, and 11 g's on deceleration, was all bonded together by
epoxy glue, and it did not come apart...

.

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