Replacing TOST release at 10K activations

Pretty sure it's in the manual.
(Not sure if it's manual for hook or glider!)

For a club glider assumption is 4 activations per launch, once to hook on
to tow to launchpoint, once to release when at launchpoint, once at start
of launch, once at top of launch.

So hook should be overhauled every 2500 launches or so.

Overhaul of our hooks normally costs 150-200 Euro, so about 0.16 Euro a
launch (2-hooks)

If you don't tow the glider around on the hooks you may be able to make a
case for only 2 activations per launch so saving yourself the vast sum of
0.08 per launch

KN


At 16:23 28 January 2014, 150flivver wrote:
Those of you with TOST hooks, how do you track the number of times the
release is activated? As I understand it, the mechanism has to be
rebuilt
when it's been exercised 10,000 times due to the main spring getting worn
out.

Another reason why I don't "check" the release before takeoff. I checked it
when I opened and closed it during hookup and will check it again at the top
of the launch. Checking it again before takeoff will probably be the last
time it functions properly and it will fail during the launch and I'll have
to land on tow (because the tug's release will also fail that day). At
today's rate, that's a savings of $1.09/launch!


"Kevin Neave" wrote in message
...
Pretty sure it's in the manual.
(Not sure if it's manual for hook or glider!)

For a club glider assumption is 4 activations per launch, once to hook on
to tow to launchpoint, once to release when at launchpoint, once at start
of launch, once at top of launch.

So hook should be overhauled every 2500 launches or so.

Overhaul of our hooks normally costs 150-200 Euro, so about 0.16 Euro a
launch (2-hooks)

If you don't tow the glider around on the hooks you may be able to make a
case for only 2 activations per launch so saving yourself the vast sum of
0.08 per launch

KN


At 16:23 28 January 2014, 150flivver wrote:
Those of you with TOST hooks, how do you track the number of times the
release is activated? As I understand it, the mechanism has to be
rebuilt
when it's been exercised 10,000 times due to the main spring getting worn
out.

On Tuesday, January 28, 2014 9:16:06 AM UTC-8, Dan Marotta wrote:
...Checking it again before takeoff will probably be the last
time it functions properly and it will fail during the launch and I'll have
to land on tow ...

Dan, the vast majority of Tost E85 nose hook failures are caused by failure of the torsion spring that keeps the hook closed. The result is that the hook will open just fine, it just won't close properly.

Thanks, Bob K.

So, what's the real test, Bob? Would simply giving it a good tug after
hookup disclose a failure? Or would it simply not close over the ring, once
installed by the wing runner? I have only a CG hook - wouldn't it suffer
the same failure mode?


"Bob Kuykendall" wrote in message
...
On Tuesday, January 28, 2014 9:16:06 AM UTC-8, Dan Marotta wrote:
...Checking it again before takeoff will probably be the last
time it functions properly and it will fail during the launch and I'll
have
to land on tow ...

Dan, the vast majority of Tost E85 nose hook failures are caused by
failure of the torsion spring that keeps the hook closed. The result is
that the hook will open just fine, it just won't close properly.

Thanks, Bob K.

On Wednesday, January 29, 2014 3:36:56 PM UTC-8, Dan Marotta wrote:

So, what's the real test, Bob? Would simply giving it a good tug after
hookup disclose a failure? Or would it simply not close over the ring, once
installed by the wing runner? I have only a CG hook - wouldn't it suffer
the same failure mode?

I'm sorry, I don't know the answer to that one.

The one failure I was directly involved with was where one side of the spring had broken, but the other side was intact. The result was that the hook appeared to function correctly, but it sprung open as soon as the towplane powered up. JJ can probably tell you more about this.

Bob K.

On Wednesday, January 29, 2014 6:17:11 PM UTC-7, Bob Kuykendall wrote:
On Wednesday, January 29, 2014 3:36:56 PM UTC-8, Dan Marotta wrote:



So, what's the real test, Bob? Would simply giving it a good tug after

hookup disclose a failure? Or would it simply not close over the ring, once

installed by the wing runner? I have only a CG hook - wouldn't it suffer

the same failure mode?



I'm sorry, I don't know the answer to that one.



The one failure I was directly involved with was where one side of the spring had broken, but the other side was intact. The result was that the hook appeared to function correctly, but it sprung open as soon as the towplane powered up. JJ can probably tell you more about this.



Bob K.

Same thing on CG hook, at least with two up. Pull on rope was not enough for the release to open. On another CG hook, release failure, but this was attributed to wear on one of the shafts. CG hooks get a lot of dirt, water (in come regions), and probably an annual cleaning.

Frank W.

I guess I could also examine one closely and try to figure it out!


"Bob Kuykendall" wrote in message
...
On Wednesday, January 29, 2014 3:36:56 PM UTC-8, Dan Marotta wrote:

So, what's the real test, Bob? Would simply giving it a good tug after
hookup disclose a failure? Or would it simply not close over the ring,
once
installed by the wing runner? I have only a CG hook - wouldn't it suffer
the same failure mode?

I'm sorry, I don't know the answer to that one.

The one failure I was directly involved with was where one side of the
spring had broken, but the other side was intact. The result was that the
hook appeared to function correctly, but it sprung open as soon as the
towplane powered up. JJ can probably tell you more about this.

Bob K.