On Sep 1, 8:40 am, Jack Glendening wrote:
I am wondering if others have experienced the shearing of a Tost brake
bolt resulting in brake failure - I'm speaking about the bolt which
extends from the hub and is secured to the aircraft frame (not
the bolt which extends for the wire lever attachment). I experienced
such a failure on my latest landing with a month-old Tost unit - I was
puliing more strongly than usual on the brake but not nearly as hard
as I could, and certainly not as hard as I would if it had been an
emergency situation. I was amazed that such could produce a bolt
shear - I would have thought that some other brake part would fail
before such a
relatively thick bolt would, but I am no mechanic. It makes me wonder
about the quality of the parts Tost is using. Is this a known/common
point of failure?

Jack Glendening

Hi Jack - I believe you are talking about a 4.50 tire mechanical
(ie non-hydraulic) Tost brake? The wonder is not that the bolt
sheared, rather that your brake shoes (actually, the one shoe
doing any work) generated enough force to shear the thing.
I don't think this is a common point of failure (though another
post here recounts another incident). For these brake
assemblies modified to servo-actuate, the torque load
is carried through the cast aluminum hub from the cam
to this bolt, and the cast hub has been known to fail...

Make sure that the end of the bolt isn't sloppy where it
attaches to the gear fork, which maybe could provoke
a failure, replace the bolt, and never point the plane at
anything valuable whilst expecting this brake to stop it...

Hope this helps,
Best Regards, Dave "YO" ("Miss August")