Tost brake bolt shears off

Jack,
I believe you are describing the *anti-rotation* bolt
and I have seen them shear off when the hub was improperly
installed. This bolt must be mated with its receptical
on the side of the landing gear or the hub will spin
when brakes are applied, resulting in the hub spinning
almost 360 degrees before hitting the landing gear
with sufficient force to shear off the bolt.

This bolt must be mated before installing the axle
when re-installing the wheel. While we're talking about
wheels and tires, if after changing the tire, the axle
doesn't slide easily through the hub, you have probably
*pinched* the tube in between the hub halves.
JJ


At 00:48 03 September 2007, wrote:
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')