Pulling on chest Straps, ok?

[skrovi 0]

I just have a hard time looking at jumpers pulling on chest
straps while doing freefly or in formation or jumpers hanging on to other jumper's chest straps. I'm just curious being a newbie, won't it come undone? or if you have routed the chest strap correctly, merely pulling on it to stay with other jumpers will not undo it? I'm ok with pulling or tagging on to my leg straps, you can pull as hard as you want on the leg straps, it probably won't come undone.
(PS: sorry about this silly post, but figured, I'll ask anyways)

[CSpenceFLY 1]

A chest strap and a leg strap have the same kind of hardware.Why would it be ok to pull on one and not the other.I'm not saying either is a good or bad idea.


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[skrovi 0]

sorry, I probably didn't state it right, I didn't mean intentional pulling, what I meant was hanging on in freefall using chest strap. I'm sure you have seen some pics. where a jumper is "hanging" on to other using the chest strap. Now I do realize that both the bodies are in free fall in the same direction so on hanging as it may seem, the chest strap is not being loaded, maybe?

[packerboy 3]

The chest strap is designed in such a way (if routed properly) that if you are putting a force on it, the hardware cinches even tighter. They are designed to keep you in your harness when you open your parachute. Someone hanging on puts a load in the same spot your opening would, but not as much of a load. So as long as you stay away from the emergency handles it can be done safely.

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In matters of style, swim with the current; in matters of principle, stand like a rock. ~ Thomas Jefferson

[CSpenceFLY 1]

I understood your intended meaning.I still don't see why you would think one is ok and the other is not.I guess my question would be do you understand how you gear works?

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[karenmeal 0]

Next time you put on your rig, give your chest strap a good tug. If it slips, something is wrong.

"Life is a temporary victory over the causes which induce death." - Sylvester Graham

[waltappel 1]

Quote

A chest strap and a leg strap have the same kind of hardware.Why would it be ok to pull on one and not the other.I'm not saying either is a good or bad idea.


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Theoretically because the chest strap is not a load-bearing component and, as such, is not as strong.

Realistically, I don't think it's a problem.

Walt

[JerryBaumchen 1,050]

Hi Walt,

This is not a knock on you, OK?

Because the chest strap is of lighter webbing and uses lighter hardware, many people seem to think that it is 'non-load bearing.'

IMO, it is load bearing; just not the same loads as the MLW's get during opening. Otherwise:

1. We would never see chest straps that fail on opening; this has happened.

2. We would not really need chest straps.

Chest straps take a load during the opening sequence, just not as much as other portions of the harness.

HTH,

Jerry

[billvon 2,404]

>A chest strap and a leg strap have the same kind of hardware.

Not really. Legstraps used forged metal friction adapters, good for thousands of pounds of force. Chest straps use stamped metal friction adapters that are considerably weaker. If you have a Para-Gear catalog go in back and compare H335 (used on legstraps) to H337 (used on chest straps.)

An additional factor is that legstraps are designed to be loaded downwards. Chest straps are not designed to be loaded by being pulled outwards or downwards; the harness stitching is not that strong in that direction.

[pchapman 262]

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Chest straps are not designed to be loaded by being pulled outwards or downwards

However, it may help jumpers that the main lift webs and chest strap aren't rigid beams, but are flexible and can in some cases move in order to better accommodate unusual loads.

E.g., yanking the chest strap outwards in a 'V' shape doesn't just try to peel the strap away from the MLWs. The MLWs will twist, so that the forces along the chest strap feed (as perhaps intended) nearly straight along the plane of the MLWs. And if one has chest rings there's even more flexibility to allow good load paths.

(Actually, isn't the load of someone pulling outward a little like the force of a jumper's torso pushing out on the chest strap while being pulled upright on opening, if the MLWs over the shoulder aren't taking all the load? So the pulling isn't entirely unlike something the rig might be designed for. Pulling downward along the direction of the MLW, however, is something I don't expect the chest strap to be designed for.)

I wonder what rig designers actually have chest strap load information, rather than just designing by precedent, using designs at least as strong as what everyone else has done in the past! The issue of what types of loads chest straps are actually designed to handle, is unclear to me.

[Orange1 0]

Does anyone know if there have been any incidents where using a chest strap as a grip was a factor?

Skydiving: wasting fossil fuels just for fun.

[JerryBaumchen 1,050]

Hi pchapmen,

Re: 'The issue of what types of loads chest straps are actually designed to handle, is unclear to me.'

I've been a Mechanical Engineer for 35 yrs and it is unclear to me also. As you mentioned, it is not a rigid beam so a simple static analysis of the joint will not work. It would give us some information but not the actual loads or percentage of load that is imposed to the chest strap.

One could (with some difficulty) put a load cell/load transmitter onto the chest strap hardware and then get some loading info. It just takes more $$$$ than I want to spend.

However, if you folks that really want to know will start contributing to a fund, I will be glad to do this test when there is sufficient money there. :)

Good post,

Jerry

[billvon 2,404]

>The MLWs will twist, so that the forces along the chest strap feed
>(as perhaps intended) nearly straight along the plane of the MLWs.

Do the experiment yourself. Put a rig on and have someone hang from it. See where the load happens and whether the stiching is loaded evenly, or whether one (or a few) stitches are loaded more heavily than others.

Chest rings do help if the rig has enough slack for them to comply, since the stitching will be oriented in the direction it is designed to load in.