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majid_sabet
Apr 26, 2010, 6:17 PM
Post #26 of 41
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is there away to have this program so i could install it on my laptop ?
do not want to do it via exl or calculator
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shu2kill
Apr 26, 2010, 6:18 PM
Post #27 of 41
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qtm wrote: shu2kill wrote: qtm wrote: No, there's no need since they ask for the "Length of rope" and "distance from last anchor", fall factor is easily calculated as ("Distance from last anchor" x 2) / "length of rope" However, this is the incorrect formula they are using. ("Distance from last anchor" + "Length of rope")/ "Length of rope" That ends up calculating FF higher than it should be. how do you know they are using that formula instead of the first and correct one you mention?? Put in some numbers and then worked backwards to figure out what would give the same result.
haha, ok. so thats why you say that the formula only works when distance to last anchor = lenght of rope...
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jt512
Apr 26, 2010, 6:25 PM
Post #28 of 41
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shu2kill wrote: jt512 wrote: shu2kill wrote: jt512 wrote: shu2kill wrote: qtm wrote: shu2kill wrote: thanx. i did the force calculations for a fall some time ago, considering fall factor, lenght of rope used, weight of climber, and elongation of rope. i think those are the variables needed. or do you need something else?? i wanted to see if my math was correct... Well, that's all you need according to the formula in RG's "The Standard Equation for Impact Force" http://www.rockclimbing.com/...ent;postatt_id=2957; Of course there are a lot of variables when it comes to the actual numbers in an actual fall... but that's the basic formula FWIW. thanx. unfortunately at work i cannot open .pdfs but ill try it at home. and im glad to know i included the variables needed. when i can look at the formula i will see if i used them correctly... If you included both the fall factor and the length of rope in your calculation, then your formula is either wrong or very advanced. Jay well, it was not just one formula. i used the lenght of the rope to calculate the fall factor, and also to calculate the elongation (i assumed 30% of all the rope used). this was to account for the fact that, if i have a factor 2 fall on 1 meter of rope, i will start at 1 meter above the anchor but i will end 1.3 meters below it, because of the elongation. i know its just an approximation that does not takes into account several things, such as the desacceleration during those 30 cm.... because the body would be accelerating for 2 meters and then the acceleration would decrease until it reaches 0 and the rope suffers maximum elongation. but i think taking all that into account would be really difficult, as most probably the desacceleration wouldnt be at a constant rate... So, are you treating elongation as a constant 30%, regardless of the fall factor? Jay yes, i assumed it would be the same 30%.
Unfortunately, then, I do not see how your approach can come up with reasonable impact force estimates, except for high fall-factor falls, since elongation depends on the fall factor, and force depends on elongation. When you're able, take a look at the pdf that was linked up-thread. It shows two ways to derive the standard model for impact force.
Jay
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shu2kill
Apr 26, 2010, 6:26 PM
Post #29 of 41
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qtm wrote: shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken. if i simulate a fall with a 80 kg climber, that falls 1.5 meters for a factor 2 fall with dinamic rope, i get a shock of 9 kN on the climber. then i change the 1.5 meters for 15 meters and i get the same 9 kN. this doesnt sounds right, since obviously if the lenght of the fall increases, the speed increases, right?? so does anyone knows of a good, accurate calculator?? thanx!! You're right, that one doesn't work right. I couldn't find any other, so I wrote one myself but it's not online. Jay wrote one that was much prettier than mine, don't know if he put it online. It's relatively easy to do with an excel spreadsheet. I'll look around to see if I can find it. OK, here's the formula. COL A = Rope KN COL B = Fall Factor COL C = Weight in LB COL D = KN on climber =(C2 * 0.4536 * 0.0098) + SQRT((C2 * 0.4536 * 0.0098)^2 + (((A2*(A2-1.568))/1.396)*(C2 * 0.4536 * 0.0098)*B2)) You have to manually calculate the FF.
i just noticed you posted the formula...
whats column A "rope kN" ??
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qtm
Apr 26, 2010, 6:31 PM
Post #30 of 41
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Registered: Apr 8, 2004
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That's the UIAA Impact Force for the Rope.
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shu2kill
Apr 26, 2010, 6:35 PM
Post #31 of 41
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jt512 wrote: shu2kill wrote: jt512 wrote: shu2kill wrote: jt512 wrote: shu2kill wrote: qtm wrote: shu2kill wrote: thanx. i did the force calculations for a fall some time ago, considering fall factor, lenght of rope used, weight of climber, and elongation of rope. i think those are the variables needed. or do you need something else?? i wanted to see if my math was correct... Well, that's all you need according to the formula in RG's "The Standard Equation for Impact Force" http://www.rockclimbing.com/...ent;postatt_id=2957; Of course there are a lot of variables when it comes to the actual numbers in an actual fall... but that's the basic formula FWIW. thanx. unfortunately at work i cannot open .pdfs but ill try it at home. and im glad to know i included the variables needed. when i can look at the formula i will see if i used them correctly... If you included both the fall factor and the length of rope in your calculation, then your formula is either wrong or very advanced. Jay well, it was not just one formula. i used the lenght of the rope to calculate the fall factor, and also to calculate the elongation (i assumed 30% of all the rope used). this was to account for the fact that, if i have a factor 2 fall on 1 meter of rope, i will start at 1 meter above the anchor but i will end 1.3 meters below it, because of the elongation. i know its just an approximation that does not takes into account several things, such as the desacceleration during those 30 cm.... because the body would be accelerating for 2 meters and then the acceleration would decrease until it reaches 0 and the rope suffers maximum elongation. but i think taking all that into account would be really difficult, as most probably the desacceleration wouldnt be at a constant rate... So, are you treating elongation as a constant 30%, regardless of the fall factor? Jay yes, i assumed it would be the same 30%. Unfortunately, then, I do not see how your approach can come up with reasonable impact force estimates, except for high fall-factor falls, since elongation depends on the fall factor, and force depends on elongation. When you're able, take a look at the pdf that was linked up-thread. It shows two ways to derive the standard model for impact force. Jay
yes, my approximations only "work" for high fall factors, that would be the critical points. why would i want to calculate the kN on a top rope setup?? however i see what you say, my calculations are not universal, the formulas used work only in certain setups and give rough estimates, and i knew that when i made them...
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JimTitt
Apr 26, 2010, 6:38 PM
Post #32 of 41
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The one you linked to is worthless.
The Petzl one was better, in fact quite good as they banged in a fair few fudge factors to move from the theoretical models to nearer real life results, as mentioned it seems to hsave gone from their site along with some other interesting stuff.
The Beal one is sort-of o.k and the best one out there at the moment but you still want to be looking at numbers 30% either side of the values you derive using it. (It is based on a computer model of a lot of test drops, not a theoretical basis so when you move away from the drop test parameters it goes a bit haywire!, generally overestimating the forces on the gear and faller and underestimating those on the belayer if I remember right).
Fall calculators donīt change what happens when you fall off!
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jt512
Apr 26, 2010, 6:47 PM
Post #33 of 41
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Registered: Apr 12, 2001
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shu2kill wrote: jt512 wrote: shu2kill wrote: yes, i assumed it would be the same 30%. Unfortunately, then, I do not see how your approach can come up with reasonable impact force estimates, except for high fall-factor falls, since elongation depends on the fall factor, and force depends on elongation. When you're able, take a look at the pdf that was linked up-thread. It shows two ways to derive the standard model for impact force. Jay yes, my approximations only "work" for high fall factors, that would be the critical points. why would i want to calculate the kN on a top rope setup?? however i see what you say, my calculations are not universal, the formulas used work only in certain setups and give rough estimates, and i knew that when i made them...
Well, here is one reason.
Jay
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hafilax
Apr 26, 2010, 6:48 PM
Post #34 of 41
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Registered: Dec 12, 2007
Posts: 3025
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Somebody write an iPhone App so I can use it while I'm leading.
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jt512
Apr 26, 2010, 7:00 PM
Post #35 of 41
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qtm wrote: shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken. if i simulate a fall with a 80 kg climber, that falls 1.5 meters for a factor 2 fall with dinamic rope, i get a shock of 9 kN on the climber. then i change the 1.5 meters for 15 meters and i get the same 9 kN. this doesnt sounds right, since obviously if the lenght of the fall increases, the speed increases, right?? so does anyone knows of a good, accurate calculator?? thanx!! You're right, that one doesn't work right. I couldn't find any other, so I wrote one myself but it's not online. Jay wrote one that was much prettier than mine, don't know if he put it online.
Here's what my aesthetically pleasing impact force calculator looks like on my computer.
Currently, it only exists as a Linux application. If anyone who is running Linux wants a copy, PM me. Also, if anyone wants to recompile it for Windows or Mac, let me know, and I'll send you the source code. It's written in Haskell and uses gtk2hs for the GUI. I don't have it online, but I probably should do something about that. It would be a good excuse to learn a little PHP.
Jay
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impact2-OB.jpg
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shu2kill
Apr 26, 2010, 7:38 PM
Post #36 of 41
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jt512 wrote: qtm wrote: shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken. if i simulate a fall with a 80 kg climber, that falls 1.5 meters for a factor 2 fall with dinamic rope, i get a shock of 9 kN on the climber. then i change the 1.5 meters for 15 meters and i get the same 9 kN. this doesnt sounds right, since obviously if the lenght of the fall increases, the speed increases, right?? so does anyone knows of a good, accurate calculator?? thanx!! You're right, that one doesn't work right. I couldn't find any other, so I wrote one myself but it's not online. Jay wrote one that was much prettier than mine, don't know if he put it online. Here's what my aesthetically pleasing impact force calculator looks like on my computer. Currently, it only exists as a Linux application. If anyone who is running Linux wants a copy, PM me. Also, if anyone wants to recompile it for Windows or Mac, let me know, and I'll send you the source code. It's written in Haskell and uses gtk2hs for the GUI. I don't have it online, but I probably should do something about that. It would be a good excuse to learn a little PHP. Jay
that one looks nice. i will try to convince a cousin who is a programmer to compile it for windows. if he accepts, could you send me the source code??
thanx!!
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jt512
Apr 26, 2010, 7:45 PM
Post #37 of 41
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Posts: 21904
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shu2kill wrote: jt512 wrote: qtm wrote: shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken. if i simulate a fall with a 80 kg climber, that falls 1.5 meters for a factor 2 fall with dinamic rope, i get a shock of 9 kN on the climber. then i change the 1.5 meters for 15 meters and i get the same 9 kN. this doesnt sounds right, since obviously if the lenght of the fall increases, the speed increases, right?? so does anyone knows of a good, accurate calculator?? thanx!! You're right, that one doesn't work right. I couldn't find any other, so I wrote one myself but it's not online. Jay wrote one that was much prettier than mine, don't know if he put it online. Here's what my aesthetically pleasing impact force calculator looks like on my computer. Currently, it only exists as a Linux application. If anyone who is running Linux wants a copy, PM me. Also, if anyone wants to recompile it for Windows or Mac, let me know, and I'll send you the source code. It's written in Haskell and uses gtk2hs for the GUI. I don't have it online, but I probably should do something about that. It would be a good excuse to learn a little PHP. Jay that one looks nice. i will try to convince a cousin who is a programmer to compile it for windows. if he accepts, could you send me the source code?? thanx!!
Well, I'd be a lot more comfortable knowing that the person I sent it to was the one who was compiling it, rather than a third party.
Jay
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shu2kill
Apr 26, 2010, 7:48 PM
Post #38 of 41
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jt512 wrote: shu2kill wrote: jt512 wrote: qtm wrote: shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken. if i simulate a fall with a 80 kg climber, that falls 1.5 meters for a factor 2 fall with dinamic rope, i get a shock of 9 kN on the climber. then i change the 1.5 meters for 15 meters and i get the same 9 kN. this doesnt sounds right, since obviously if the lenght of the fall increases, the speed increases, right?? so does anyone knows of a good, accurate calculator?? thanx!! You're right, that one doesn't work right. I couldn't find any other, so I wrote one myself but it's not online. Jay wrote one that was much prettier than mine, don't know if he put it online. Here's what my aesthetically pleasing impact force calculator looks like on my computer. Currently, it only exists as a Linux application. If anyone who is running Linux wants a copy, PM me. Also, if anyone wants to recompile it for Windows or Mac, let me know, and I'll send you the source code. It's written in Haskell and uses gtk2hs for the GUI. I don't have it online, but I probably should do something about that. It would be a good excuse to learn a little PHP. Jay that one looks nice. i will try to convince a cousin who is a programmer to compile it for windows. if he accepts, could you send me the source code?? thanx!! Well, I'd be a lot more comfortable knowing that the person I sent it to was the one who was compiling it, rather than a third party. Jay
ok, maybe i can put you in contact with him?? he is also a climber, but he is not a member of this forum...
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rgold
Apr 27, 2010, 5:21 AM
Post #39 of 41
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shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken...
Oh god, not that pile of junk again. It's been up forever and wrong forever. A little experimentation reveals that it thinks the fall factor is 1 + F/2, where F is the real fall factor, so that, for example, it calculates a fall factor of 1 when the fall height is zero. (Of course, if and only if the real fall factor is F=2, then the myoan mess gets it right, but who know what, in general, it does next; I never tried checking that.)
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jt512
Sep 7, 2010, 8:00 PM
Post #40 of 41
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rgold wrote: shu2kill wrote: hey. i found this online calculator http://www.myoan.net/climbart/climbforcecal.html but i think its mistaken... Oh god, not that pile of junk again. It's been up forever and wrong forever. A little experimentation reveals that it thinks the fall factor is 1 + F/2, where F is the real fall factor, so that, for example, it calculates a fall factor of 1 when the fall height is zero. (Of course, if and only if the real fall factor is F=2, then the myoan mess gets it right, but who know what, in general, it does next...)
It does the following. If w is the climber's weight (kg-f), f is the mis-calculated fall factor, and WTF_d and WTF_s are the "impact forces" (kN) for a dynamic rope and a static rope, respectively, then
WTF_d = (9/160)wf
and
WTF_s = 2WTF_d .
I'm not kidding.
Jay
(This post was edited by jt512 on Sep 7, 2010, 8:45 PM)
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bill413
Sep 7, 2010, 8:41 PM
Post #41 of 41
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Well, at the least, it indicates that a static WTF is greater than a dynamic WTF.
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