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Spring constant of a rope
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jt512


Oct 8, 2008, 8:08 PM
Post #26 of 29 (689 views)
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Registered: Apr 11, 2001
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Re: [mtnrock] Spring constant of a rope [In reply to]
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mtnrock wrote:
...unless theres a way buy using the impact force of the rope to find the spring constant(also shows how streachy the rope is)

I already answered the question. Look back at my posts, and look at equation (11) in rgold's paper.

Jay


petsfed


Oct 8, 2008, 8:18 PM
Post #27 of 29 (684 views)
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Re: [mtnrock] Spring constant of a rope [In reply to]
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mtnrock wrote:
o got it. yea it was when i was finding an equation to find the force generated on the peace of equipment the one unknown i was missing was the spring constant but im just going to test for that on my rope unless theres a way buy using the impact force of the rope to find the spring constant(also shows how streachy the rope is)

Read Jay's post. Rinse and repeat.


petsfed


Oct 8, 2008, 8:37 PM
Post #28 of 29 (681 views)
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Re: [jt512] Spring constant of a rope [In reply to]
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jt512 wrote:
petsfed wrote:
jt512 wrote:
petsfed wrote:
rgold wrote:
Petsfed, there isn't a mathematical model in the world that incorporates every detail of the reality being modeled. If one did, it would in some sense be the reality and not a model of it. Perhaps the essential ingredient in every model is the fact that it ignores details, so your criticism is in fact a foregone conclusion. I'd love to see your model incorporating the mass of the rope, and I would be interested to see, after the mass is properly taken into account, how much effect it actually has on the results. Please do post up.

Its supposed to be too cold to climb this weekend, so I'll work on it. I'd expect that for a UIAA rope test, its pretty minor, but if you've got 100 feet of rope out, it might be pretty big (on the order of 5 or 10 percent difference). I'll try to work up some general equations and explanatory assumptions.

100 feet of rope weighs about 3 lb. I'm going to go out on a limb and say that rope mass can be ignored.

Jay

You're right, it is pretty negligible, but the more rope you have out, the more measurable an affect it will have on the overall system. If you have all 200 feet out, that's nearly 10% of the UIAA test mass.

Less than 5%, unless I made an arithmetic error.

Jay

Oh, duh. Its 2.2lbs to the kg, not the other way around. My bad. Yeah, around 2%.

Still, if I'm gonna be neurotic enough to actually develop the equations, I'm gonna toss in the little mitigating circumstances.


USnavy


Oct 9, 2008, 2:28 AM
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Re: [jt512] Spring constant of a rope [In reply to]
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jt512 wrote:
mtnrock wrote:
im trying to find what the maximum height you can climb above your protection before it will pop and i need to know the spring constant of a rope does any one know what it is

You can calculate the spring constant of a rope from the manufacturer's published impact force rating. See equation (11) in rgold's paper. The spring constant is k, which rgold refers to as "rope modulus."

I also know what punctuation is.

Jay

Note that the impact force does not give an absolute answer as to the elongation of the rope. I have seen ropes that have impact forces lower then a different rope with a lower elongation rating.

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