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#1
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Tost brake bolt shears off
"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") -- Posted via a free Usenet account from http://www.teranews.com |
#2
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Tost brake bolt shears off
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 |
#3
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Tost brake bolt shears off
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 |
#4
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Tost brake bolt shears off
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 |
#5
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Tost brake bolt shears off
Chris Reed wrote:
I've never yet met a reliable glider wheel brake. You should meet a glider with a Cleveland wheel and brake, like those used on Schleicher gliders from the ASW 20 B/C and later. These are the same brakes used on thousands of airplanes, and they are effective and reliable. -- Eric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#6
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Tost brake bolt shears off
Ineffective brakes is one thing. Brakes where bolts shear off during normal
use is a completely different category. Mike Schumann "Bruce" wrote in message ... 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 -- Posted via a free Usenet account from http://www.teranews.com |
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