Pulling Strength

[Otter 0]

Has anyone ever read any article, post or comment on the pulling strength (in kg./lb.) required by a jumper during an emergency procedure (release main/pull silver)? Is guess it might depend on the Gs involved.

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Alex / FLY4FUN Team - Curious? ready, set, CLICK!

[piisfish 135]

never tried it live, just in my riggers loft.
Guess when in situation, need more force. But on the ground was fine

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[vt1977 0]

I’m pretty sure the BPA rules state a maximum pull force of 22lbs on the reserve.

Vicki

[FrogNog 1]

Quote

Has anyone ever read any article, post or comment on the pulling strength (in kg./lb.) required by a jumper during an emergency procedure (release main/pull silver)? Is guess it might depend on the Gs involved.

I've seen theoretical numbers based on mechanical advantage of various 3-ring systems and suspended loads x G forces. There were footnotes about cleaning cutaway cables and flexing the 3-rings
I'm sure snippets of this are posted here somewhere.

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Pull.

[skydiverek 55]

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I've seen theoretical numbers based on mechanical advantage of various 3-ring systems and suspended loads x G forces. There were footnotes about cleaning cutaway cables and flexing the 3-rings
I'm sure snippets of this are posted here somewhere.

Thera ya go
http://www.relativeworkshop.com/support/tech_pullforce.html

and

http://www.relativeworkshop.com/support/tech_risers.html

Hope that helps.

[mjosparky 3]

Under TSO-C23d, both the main canopy release and the reserve actuation device must be not less than 5 lbf nor more than 22 lbf.
Sparky

My idea of a fair fight is clubbing baby seals

[nacmacfeegle 0]

G forces involved will normally only affect the cut away load/pull force during a spinning mal.
Some food for thought here...http://www.bpa.org.uk/skydive/pages/articles/dec03/cutting-away.html

Once you have got rid of the main the G forces should be dramatically reduced and the reserve pull should be straightforward. I think 22lbs (10kg) is the max allowed here in the UK, more usually its around the 12-16lb (5-7 kg) mark, on my gear anyways...

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He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson

[BlindBrick 0]

It's been a while since I read my Poynter's, but I remeber a section where they said the USAF did a test and virtually no one could pull 25 lbs or more of force.

-Blind

"If you end up in an alligator's jaws, naked, you probably did something to deserve it."

[mjosparky 3]

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It's been a while since I read my Poynter's, but I remeber a section where they said the USAF did a test and virtually no one could pull 25 lbs or more of force.

-Blind

I would think the would depend on the angle of the pull. Chest mount reserves must have a pull of 15 lbf. or less.
Sparky

My idea of a fair fight is clubbing baby seals

[SkySlut 0]

Odd you mention. While I was at the riggers course. 22 lbs. without the seal thread, by the way. I packed one up that was a real bitch to close...I thought that it would be really tight and a hard pull. When we did a pull test. I capped out at around 35 lbs. The rig was laying on the ground. We put the rig on and pulled it...well under the 22 lb pull force required. Easy to pull. Just thought that I would mention that the angle of the cable and its housings made a huge difference.

[FrogNog 1]

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It's been a while since I read my Poynter's, but I remeber a section where they said the USAF did a test and virtually no one could pull 25 lbs or more of force.

-Blind

I seem to remember that part said some people could pull significantly more than 25 pounds, but some people definitely could not. (And therefore the limit would have to be set about there or it would kill certain people.)

I guess I have to read my Poynter's too.

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Pull.

[billbooth 10]

Years ago, we mounted a High priced (1000 samples a second) digital scale on a the back of a harness, and connected it to a ripcord. From the standard reserve ripcord position, everyone could pull over 85 pounds with both hands...hell, one girl pulled over 100 pounds, and a few guys pulled over 150 pounds. "Soft" reserve handles generated forces nearly identical to metal handles. These numbers are from memory, but are probably pretty close.

From other tests with the same scale, I have learned that if you pull "quickly", from a "running start" (slack in the cable), the pull force necessary to open the same reserve container is up to 300% lower than if you apply the force gradually to the handle. Most riggers only have a spring loaded fish scale, and therefore must apply pull forces gradually in order to read the scale. So, what reads 30 pounds on the fish scale in the loft, will only be around 10 pounds when you actually pull your reserve in an emergency, because I don't know of anyone who applies ripcord pull force "gradually" while falling rapidly toward the earth.

[FrogNog 1]

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From other tests with the same scale, I have learned that if you pull "quickly", from a "running start" (slack in the cable), the pull force necessary to open the same reserve container is up to 300% lower than if you apply the force gradually to the handle.

You mean the force is up to 75% lower, right? (i.e. the larger force is up to 300% higher, or 4 times as much, so 4 - 1 = 3 which is 75% of 4.) Because if the pull force goes down by 300%, it would be negative.

I'm glad to hear this was tested, and what the result was. It makes me feel warm and fuzzy, actually.

And I agree with your assessment of typical real-world reserve handle pull technique. (I know I won't be getting out my fish scale after cutting away...)

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Pull.

[billbooth 10]

Whatever you said. I think I must have missed that chapter in high school math...percentage increase vs percentage decrease, or something like that. Anyway, you got the point.