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trenchdigger
Feb 10, 2007, 6:43 AM
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Registered: Mar 9, 2003
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In short, force is not the same as energy. Energy is force applied over a distance. On top of that, your units are all F'd up in your calculations. Pay attention to that.
Ropes stretch to absorb energy similar to the way a spring does. Therefore the max force (tension) in the rope is also based on the length of rope in the system and the spring constant of the rope (which may not acually be constant).
Before you waste more time trying to calculate what you won't be able to figure out, do a search about "fall factor" and study up. Fall factor is far more important than the length of the fall in terms of max force in a fall.
(This post was edited by trenchdigger on Feb 10, 2007, 6:46 AM)
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bbentley77
Feb 10, 2007, 7:34 AM
Post #5 of 14
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Registered: Jan 1, 2007
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that works. thanks.
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rocknice2
Feb 10, 2007, 12:59 PM
Post #7 of 14
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Registered: Jul 13, 2006
Posts: 1221
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This site calculaator doesn't work. No matter what variables are entered the impact force is the same.
The previous link worked much better
http://www.myoan.net/...t/climbforcecal.html
Thanks
(This post was edited by rocknice2 on Feb 10, 2007, 1:03 PM)
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sbaclimber
Feb 10, 2007, 9:28 PM
Post #8 of 14
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Registered: Jan 22, 2004
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Can someone tell me why I can't get a fall factor of less than one using that calculator?
I entered 70kg(my weight w/ gear) + 60m(rope length) + 0.25m(barely above last piece) + dynamic rope, and the stupid calculator still says I am creating a fall factor of 1.0041666666666667..........
Doesn't compute!
Edit to add: ...and a shock force of almost 4kN!!! I don't think so....
Edit x2: figured it out I think. The formulas being used are:
lanch=distance from last piece
lrope=rope length
shock=weight/80*((lanch+lrope)/lrope)*4.5
fall factor=(lanch+lrope)/lrope
The formula for fall factor looks a little too simple to me, but I may be wrong.... (it can definitely never be less than 1)
(This post was edited by sbaclimber on Feb 10, 2007, 9:49 PM)
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wrbill
Feb 10, 2007, 10:10 PM
Post #9 of 14
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Registered: Dec 5, 2002
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Yes is does work. You need to see that there are three calculators on that page. One for Impact Force Calculations and two for Rope Calculations. Use the first one and the bottom two are for calculating your rope modulus for the rope that you are using.
Hey sbaclimber,
I used the one on the site that I posted and it came up as 0.0041666666666667.
Bill
(This post was edited by wrbill on Feb 10, 2007, 10:16 PM)
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rocknice2
Feb 11, 2007, 2:50 AM
Post #10 of 14
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Registered: Jul 13, 2006
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Sorry guy's your abslutely correct, I just saw that the other site was easier to use but upon closer examination it does not compute properly.
Once I used the site above properly[calculated rope modulus] it was a cream puff.
IceClimbers can't count 'cause ower fingers are frozen
(This post was edited by rocknice2 on Feb 11, 2007, 2:51 AM)
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rgold
Feb 11, 2007, 5:35 AM
Post #11 of 14
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Registered: Dec 3, 2002
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Maybe just do it yourself? I wrote up the formula and two different approaches to deriving it and posted on this site here
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rocknice2
Feb 11, 2007, 7:50 AM
Post #12 of 14
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Registered: Jul 13, 2006
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Ice Climbers can't count 'cause our fingers are frozen
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kaesar
Feb 13, 2007, 9:23 PM
Post #14 of 14
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Registered: Aug 12, 2002
Posts: 16
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For the moment I have no time to look all the links you have posted, but one impotant thing to be taking into account is that ropes are made of plastic. This means that they does not behave like a spring. When strain of the rope is over a determinate value stress remain, more or less, constant. This means that maximum force a rope can deliver has a limit. In Spain it is called shock force, and it is written in your rope label.
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