Tost brake bolt shears off

Jack Glendening wrote:

at this point is that there is a nut on that bolt at the brake case
(as a spacer?) and the shearing occurred just outside that nut.

I don't have a tost wheel in front of me right now, but I'm certain that
there is *no* nut on that bolt as a *spacer* (maybe a washer, I can't
remember). There is a nut on that bolt outside the "receptical" to
secure that bolt. So if your mechanic installed that bolt inside that
"receptical" (e.g. as a spacer), it's pretty clear that the bolt would
slip out, the plate would rotate and that bolt would eventually be
sheared off.

Just a guess based on your description, I may have understood you
completely wrong.

John Smith wrote:
Just a guess based on your description, I may have understood you
completely wrong.

To clarify, immediately next to the shear is a thin bolt (shiny, new
looking), then the large drum case - i.e. the bolt is outside the
case. I have since learned from Tom Stowers that the nut is standard,
so my guess that it might be a spacer was wrong (I was thrown off by
my inspection of the _old_ brake parts, given to me after the new
installation, which does not have any such nut outside the hub, so I
incorrectly guessed that perhaps the bolt threaded into the hub itself -
for whatever reason that old nut was not included with the old parts.)

Jack

"never point the plane at anything valuable whilst expecting this brake to
stop it..."??????????

Brakes need to work reliably. If there is more than one incident of this
type, there needs to be a service bulletin or AD issued to fix the problem.

Mike Schumann

wrote in message
oups.com...
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")




--
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Jack Glendening wrote:

To clarify, immediately next to the shear is a thin bolt (shiny, new
looking), then the large drum case - i.e. the bolt is outside the
....

I fear that without a picture I won't understand what you're talking about.

Anyone who relies on the ineffectual brake fitted to most older gliders is an
optimist of note.

On the 4.00 X 4 hub common to these aircraft you have a couple of square
centimetres of friction material, with non energising shoes trying to stop
around 300 - 350kg of glider moving at anything up to 100km/h. Most are good for
one retardation only, at best, then they fade severely.

In my experience, with a lot of fettling work one can achieve a brake that is
reliably weak - which is a whole lot better than the alternative. But experience
indicates that one should still discount it ever working effectively in an
emergency.

You would be distressed to see how much damage you can cause at walking speed
with a 15m single seater. Just think what a 26m+ motorised uber bug smasher
could do with all it's inertia. (although they tend to have halfway decent disk
brakes these days)

In any case the man has it right - Don't point your glider at anything you
intend to keep, especially on a downhill. There is no need to provoke Murphy.

Mike Schumann wrote:
"never point the plane at anything valuable whilst expecting this brake to
stop it..."??????????
snip

My open Cirrus (1968, probably 400kg with me on board) has the 400 x 4
wheel and Tost brake.

The main purpose of the brake is to stop the glider overrunning the
aerotow rope in the Up slack/All out transition.

It also makes a scraping noise if I use it after landing.

I've never yet met a reliable glider wheel brake. I suspect the worst
kind are those which work *almost* all the time (K21 comes to mind)
because then you might get into the habit of pointing the glider at
expensive objects!

Bruce wrote:
Anyone who relies on the ineffectual brake fitted to most older gliders
is an optimist of note.

On the 4.00 X 4 hub common to these aircraft you have a couple of square
centimetres of friction material, with non energising shoes trying to
stop around 300 - 350kg of glider moving at anything up to 100km/h. Most
are good for one retardation only, at best, then they fade severely.

In my experience, with a lot of fettling work one can achieve a brake
that is reliably weak - which is a whole lot better than the
alternative. But experience indicates that one should still discount it
ever working effectively in an emergency.

You would be distressed to see how much damage you can cause at walking
speed with a 15m single seater. Just think what a 26m+ motorised uber
bug smasher could do with all it's inertia. (although they tend to have
halfway decent disk brakes these days)

In any case the man has it right - Don't point your glider at anything
you intend to keep, especially on a downhill. There is no need to
provoke Murphy.

Mike Schumann wrote:
"never point the plane at anything valuable whilst expecting this
brake to stop it..."??????????
snip

I agree, would someone please post a picture of this.



Thanks,



Larry

"zero one"

"John Smith" wrote in message
:

Jack Glendening wrote:

To clarify, immediately next to the shear is a thin bolt (shiny, new
looking), then the large drum case - i.e. the bolt is outside the
...

I fear that without a picture I won't understand what you're talking about.

I must say that I almost agree. I have had 4 gliders. My Astir CS had
a tost brake that was bad. My ASW17 had a tost brake that was a bad joke
considering the mass of the 17. My ASW22 had a disc brake that worked
pretty well after bleeding but it just did not like to stay bled.
Amazingly, the tost drum brake on my Ventus C works like a champ. I can
put the glider on its nose if I want.

Chris Reed wrote:
My open Cirrus (1968, probably 400kg with me on board) has the 400 x 4
wheel and Tost brake.

The main purpose of the brake is to stop the glider overrunning the
aerotow rope in the Up slack/All out transition.

It also makes a scraping noise if I use it after landing.

I've never yet met a reliable glider wheel brake. I suspect the worst
kind are those which work *almost* all the time (K21 comes to mind)
because then you might get into the habit of pointing the glider at
expensive objects!

Bruce wrote:
Anyone who relies on the ineffectual brake fitted to most older
gliders is an optimist of note.

On the 4.00 X 4 hub common to these aircraft you have a couple of
square centimetres of friction material, with non energising shoes
trying to stop around 300 - 350kg of glider moving at anything up to
100km/h. Most are good for one retardation only, at best, then they
fade severely.

In my experience, with a lot of fettling work one can achieve a brake
that is reliably weak - which is a whole lot better than the
alternative. But experience indicates that one should still discount
it ever working effectively in an emergency.

You would be distressed to see how much damage you can cause at
walking speed with a 15m single seater. Just think what a 26m+
motorised uber bug smasher could do with all it's inertia. (although
they tend to have halfway decent disk brakes these days)

In any case the man has it right - Don't point your glider at anything
you intend to keep, especially on a downhill. There is no need to
provoke Murphy.

Mike Schumann wrote:
"never point the plane at anything valuable whilst expecting this
brake to stop it..."??????????
snip

I had my Nimbus drum brake reworked by Vintage Brake and, so far, it stops
the glider fine. However, I had a brake cable fail four flights ago. After
coasting to a stop I crawled under the wing with close-up glasses and found
a frayed cable end with the swaged thingie missing.

As a stopgap, since the Salida camp was coming up, I swaged another end on
the frayed cable and it works OK - so far. I searched for replacement cable
parts and found them at a motorcycle rebuilding shop. I'll need to braze
on a cable termination for the stick brake grip and swage on a solid ball at
the brake lever but it should be an easy project.

Lesson: There's lots of ways for a brake to fail. "Don't aim at anything you
want to keep".

Bill Daniels


"Bob Backer" wrote in message
...
I must say that I almost agree. I have had 4 gliders. My Astir CS had a
tost brake that was bad. My ASW17 had a tost brake that was a bad joke
considering the mass of the 17. My ASW22 had a disc brake that worked
pretty well after bleeding but it just did not like to stay bled.
Amazingly, the tost drum brake on my Ventus C works like a champ. I can
put the glider on its nose if I want.

Chris Reed wrote:
My open Cirrus (1968, probably 400kg with me on board) has the 400 x 4
wheel and Tost brake.

The main purpose of the brake is to stop the glider overrunning the
aerotow rope in the Up slack/All out transition.

It also makes a scraping noise if I use it after landing.

I've never yet met a reliable glider wheel brake. I suspect the worst
kind are those which work *almost* all the time (K21 comes to mind)
because then you might get into the habit of pointing the glider at
expensive objects!

Bruce wrote:
Anyone who relies on the ineffectual brake fitted to most older gliders
is an optimist of note.

On the 4.00 X 4 hub common to these aircraft you have a couple of square
centimetres of friction material, with non energising shoes trying to
stop around 300 - 350kg of glider moving at anything up to 100km/h. Most
are good for one retardation only, at best, then they fade severely.

In my experience, with a lot of fettling work one can achieve a brake
that is reliably weak - which is a whole lot better than the
alternative. But experience indicates that one should still discount it
ever working effectively in an emergency.

You would be distressed to see how much damage you can cause at walking
speed with a 15m single seater. Just think what a 26m+ motorised uber
bug smasher could do with all it's inertia. (although they tend to have
halfway decent disk brakes these days)

In any case the man has it right - Don't point your glider at anything
you intend to keep, especially on a downhill. There is no need to
provoke Murphy.

Mike Schumann wrote:
"never point the plane at anything valuable whilst expecting this brake
to stop it..."??????????
snip

"Bob Backer" wrote in message
...
I must say that I almost agree. I have had 4 gliders. My Astir CS had a tost
brake that was bad. My ASW17 had a tost brake that was a bad joke considering
the mass of the 17. My ASW22 had a disc brake that worked pretty well after
bleeding but it just did not like to stay bled.

Hah! Finally we have found something that the 2-33 does well. Every one I
have ever flown would stop on a dime.

Vaughn