Forums: Skydiving: Gear and Rigging:
Reserve pin tension questions

 


johnmatrix  (D 9999)

Oct 26, 2012, 6:32 PM
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Reserve pin tension questions Can't Post

Is it possible to create a hard pull from pin tension alone? Or would pin tension just contribute to other possible problems with the cable, cable housing, to cause a hard pull?

Of course varying pin tension will require more or less strength to pull the pin, but what would it take to put enough tension on the pin to cause a catastrophically hard pull?

Is it possible to close a reserve (e.g with a leverage device) so tightly that a main pilot chute would not be able to pull the pin - e.g via an RSL/Skyhook when cutting away from a high-speed malfunction like a baglock?


riggerrob  (D 14840)

Oct 26, 2012, 7:42 PM
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Re: [johnmatrix] Reserve pin tension questions [In reply to] Can't Post

According to the American Federal Air Regulations, pull force on a ripcord should be between 5 pounds and 22 pounds. Any more than that is not airworthy,

Those pull forces are measured when pulling the ripcord handle in the easiest direction relative to the ripcord housing, so if you tried hard enough, you could increase the pull force by pulling in the wrong direction, (e.g. perpendicular to the end of the ripcord housing).


riggerrob  (D 14840)

Oct 26, 2012, 7:46 PM
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Re: [johnmatrix] Reserve pin tension questions [In reply to] Can't Post

In reply to:
...

Is it possible to close a reserve (e.g with a leverage device) so tightly that a main pilot chute would not be able to pull the pin - e.g via an RSL/Skyhook when cutting away from a high-speed malfunction like a baglock?

....................................................................

A collapsed main pilot chute might not pull hard enough (5 to 22 pounds) to pull an RSL/Skyhook.

If that happens, you would need to pull your reserve ripcord (just like the old days) or pray that your Cypres is turned on.

Sarcastic humour !!!!


mark  (D 6108)

Oct 27, 2012, 6:54 PM
Post #4 of 17 (1887 views)
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Re: [riggerrob] Reserve pin tension questions [In reply to] Can't Post

In reply to:
Those pull forces are measured when pulling the ripcord handle in the easiest direction relative to the ripcord housing, so if you tried hard enough, you could increase the pull force by pulling in the wrong direction, (e.g. perpendicular to the end of the ripcord housing).

The newest TSO standards (C23c/AS8015A, 1984 and later) say the maximum pull force should be measured in the direction giving the highest pull forces under normal operation. This would probably be straight out from the chest. Whether that would be perpendicular to the ripcord housing would depend on the rig design. For sure you'd get a higher pull force if you tried pulling straight up, but that wouldn't be a normal direction.

On the other hand, the 5-pound minimum pull force is measured in the direction of easiest pull.

Mark


pchapman  (D 1014)

Oct 27, 2012, 7:31 PM
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Re: [mark] Reserve pin tension questions [In reply to] Can't Post

In reply to:
giving the highest pull forces under normal operation.

Nice point.
Then one gets into whether a weird pull direction is defined as normal operation or not, so the rules aren't very helpful! Just about any pack job could fail the test if one pulls the handle into the harness pocket...

Riggers don't try to get a high pull force when testing after a repack; we normally try to get the lowest possible number given the tight rigs today.


riggerrob  (D 14840)

Oct 28, 2012, 8:36 AM
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Re: [pchapman] Reserve pin tension questions [In reply to] Can't Post

In reply to:
... a repack; we normally try to get the lowest possible number given the tight rigs today.

........................................................................

Yes.
I normally aim for a reserve ripcord pull-force in the "high teens" ... 17 to 19 pounds.
Sometimes an especially tight reserve will test at more than 20 pounds, but it usually settles to the teens by the time I re-measure pull force the next day.


johnmatrix  (D 9999)

Oct 28, 2012, 4:05 PM
Post #7 of 17 (1744 views)
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Re: [riggerrob] Reserve pin tension questions [In reply to] Can't Post

What do you use to test it without pulling the pin?


riggerrob  (D 14840)

Oct 28, 2012, 7:21 PM
Post #8 of 17 (1698 views)
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Re: [johnmatrix] Reserve pin tension questions [In reply to] Can't Post

In reply to:
What do you use to test it without pulling the pin?

...................................................................

A fisherman's scale and a gentle technique.
Hah!
Hah!

It is a gentle technique that all riggers are well-practiced in, but most first-timers will flail miserably. The outcome - of most newbies - resembles an explosion in a pilot-chute factory!
Hah!
Hah!

Seriously, ask your local rigger to demonstrate te technique - for measuring ripcord pull forces - the next time you see him/her during a quiet afternoon.


koppel  (F License)

Oct 28, 2012, 7:27 PM
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There is a tool that prevents the pin from being pulled entirely whilst checking the pull forces with a fish scale


johnmatrix  (D 9999)

Oct 28, 2012, 10:31 PM
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Re: [koppel] Reserve pin tension questions [In reply to] Can't Post

Thanks - I know I've seen one somewhere in my travels through online gear stores.

I will travel to the sacred loft and ask for an audience with the Great Rigger Equal of Heaven. The Prophecy shall be fulfilled. Shall it not come to pass, I will search online, and upon discovering an image of the secret artifact, state the words 'Oh, that's interesting'.


mark  (D 6108)

Oct 29, 2012, 4:34 AM
Post #11 of 17 (1656 views)
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Re: [johnmatrix] Reserve pin tension questions [In reply to] Can't Post

http://www.paragear.com/....asp?group=162#M5995

Mark


theonlyski  (D License)

Oct 29, 2012, 10:52 AM
Post #12 of 17 (1604 views)
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Re: [johnmatrix] Reserve pin tension questions [In reply to] Can't Post

You mentioned a skyhook and I just wanted to point out that the tool linked above probably wont help much because of the different pin used on Vectors. (provided you have a Vector)


ctrph8  (D License)

Oct 29, 2012, 11:22 AM
Post #13 of 17 (1586 views)
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Re: [johnmatrix] Reserve pin tension questions [In reply to] Can't Post

I don't use Cypres silicone very often but one afternoon I played with the idea of whether I could create a hard pull scenario if there was silicone on the very top of the loop. In short, I couldn't. To be fair, I didn't try very many times to do this and was leery of putting my rig through that more than those few times.

I never came to any real conclusions other than the thought that it has some effect in the moment and that I didn't know much beyond what I'd seen that afternoon.

Has anyone played with this? If so, does anyone know if the effects of the silicone can wear off so that it could be a pull within the limits at the time of packing but get harder to pull later?




In reply to:
Is it possible to create a hard pull from pin tension alone? Or would pin tension just contribute to other possible problems with the cable, cable housing, to cause a hard pull?

Of course varying pin tension will require more or less strength to pull the pin, but what would it take to put enough tension on the pin to cause a catastrophically hard pull?

Is it possible to close a reserve (e.g with a leverage device) so tightly that a main pilot chute would not be able to pull the pin - e.g via an RSL/Skyhook when cutting away from a high-speed malfunction like a baglock?


riggerrob  (D 14840)

Oct 29, 2012, 11:52 AM
Post #14 of 17 (1578 views)
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Re: [ctrph8] Reserve pin tension questions [In reply to] Can't Post

No!
But I do know that when you spill Cypres silicone lubricant on the floor, it makes for lots of frivolity, pratfalls, slap stick, ... better than bananananana peels ... , etc.
Hah!
Hah!


JerryBaumchen  (D 1543)

Oct 29, 2012, 3:40 PM
Post #15 of 17 (1550 views)
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Re: [mark] Reserve pin tension questions [In reply to] Can't Post

Hi Mark,

You beat me to it. Tongue

The first time I saw one of these tools was at the Parachutes de France booth at the '93 Symposium.

It is my understanding that Dave DeWolf now makes them for people to obtain. I believe he exclusively sells them via ParaGear.

JerryBaumchen


johnmatrix  (D 9999)

Oct 30, 2012, 2:31 PM
Post #16 of 17 (1470 views)
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Re: [theonlyski] Reserve pin tension questions [In reply to] Can't Post

Well spotted sir - thanks.


(This post was edited by johnmatrix on Oct 30, 2012, 2:33 PM)


johnmatrix  (D 9999)

Oct 30, 2012, 2:32 PM
Post #17 of 17 (1467 views)
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Re: [riggerrob] Reserve pin tension questions [In reply to] Can't Post

Have you ever used it for other purposes? ....more devious purposes?



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