The question is, if I weigh 140 pounds, what's my 6kn nut going to do for me if I shock load it, say in a fall of 2 feet, or 10 feet, or 20 feet? The only variables for a computation equation would be 1) weight of the climber, 2) distance of fall, and 3) kn rating of the piece. Am I wrong about this?

Thanks everybody for the input, but no one seems to know what kilonewton ratings mean in practical terms for the climber. . .
• the impact force calculator is useless, since I don't know what Fall Factor and Friction Factor are . . .
• and jt512 is right, the article could have stopped at the first line saying 1kn = 225 pounds . . .

The question is, if I weigh 140 pounds, what's my 6kn nut going to do for me if I shock load it, say in a fall of 2 feet, or 10 feet, or 20 feet? The only variables for a computation equation would be 1) weight of the climber, 2) distance of fall, and 3) kn rating of the piece. Am I wrong about this?

Yes, you're wrong about what the only variables are. The maximum impact force a climber feels in a fall is, in theory, a function of only the climber's weight, the elasticity of the fall, and the fall factor, defined as the distance of the fall divided by the amount of rope available to absorb the fall. Call this force T1. Then the force on the belayer is a fraction (1 – µ) of T1, where µ is the proportion of T1 that the belayer does not feel due to friction between the rope and the anchor. Call the force on the belayer T2. Then the force on the top anchor is T1 + T2. You can assume that µ, the friction factor, is 1/3. Now that you know what the fall factor is, go plug your numbers into the online calculator, and see whether the nut would be expected to hold.

Jay

Excuse me Jay!? Mass is integral to calculating impact force. You most definately need to know the MASS.


And while I cannot comment from my own knowlege wether a 'pound' is force or mass it seems that according to wiki a 'pound' is MASS. A 'pound-force' is a force and DEFINED in terms of a pound mass.
http://en.wikipedia.org/wiki/Pound

In other words "The kilonewton is a unit of force equal to 224.8 lb." IS NOT CORRECT.

Furthermore furthermore in industry or in home use, when something recommends maximum load of 220lb or 100kgs. They are talking about mass. The manufactures have made assumptions about the safe working loads of the product.

Putting 5000lbs on a carabiner would be highly misleading. People might assume that the carabiner is safe up to 5000lbs in mass. Which is clearly not the case!

It is much more sensible to use newtons because there is little room for misinterpretation.


To top it all off there is little doubt that SI units are far, far easier for calculatations. For example calculating the force required to contstrantly accelerate a car 0-160kph is trivial. Doing the same calculation for 0-100mph is significantly harder.

And while I cannot comment from my own knowlege wether a 'pound' is force or mass it seems that according to wiki a 'pound' is MASS. A 'pound-force' is a force and DEFINED in terms of a pound mass.
http://en.wikipedia.org/wiki/Pound

In other words "The kilonewton is a unit of force equal to 224.8 lb." IS NOT CORRECT.

Furthermore furthermore in industry or in home use, when something recommends maximum load of 220lb or 100kgs. They are talking about mass. The manufactures have made assumptions about the safe working loads of the product.

Putting 5000lbs on a carabiner would be highly misleading. People might assume that the carabiner is safe up to 5000lbs in mass. Which is clearly not the case!

It is much more sensible to use newtons because there is little room for misinterpretation.

To top it all off there is little doubt that SI units are far, far easier for calculatations. For example calculating the force required to contstrantly accelerate a car 0-160kph is trivial. Doing the same calculation for 0-100mph is significantly harder.

Thanks everybody for the input, but no one seems to know what kilonewton ratings mean in practical terms for the climber. . .
• the impact force calculator is useless, since I don't know what Fall Factor and Friction Factor are . . .
• and jt512 is right, the article could have stopped at the first line saying 1kn = 225 pounds . . .

The question is, if I weigh 140 pounds, what's my 6kn nut going to do for me if I shock load it, say in a fall of 2 feet, or 10 feet, or 20 feet? The only variables for a computation equation would be 1) weight of the climber, 2) distance of fall, and 3) kn rating of the piece. Am I wrong about this?

Or, to phrase it the other way around, how much would I have to weigh for my 6kn stopper to be useless? Last week my second told me I had placed an incorrect piece because it had only a 6kn rating.

~ beau

Thanks everybody for the input, but no one seems to know what kilonewton ratings mean in practical terms for the climber. . .

What a lame article thread. All you need to know is that the kilonewton is a unit of force equal to 224.8 lb.

Jay

I'm sorry, but here wikipedia is wrong. in the english system, a lb is a measurement of force and a slug is the measurement of mass. In order to make things easier they created the lbm (pound mass) to be used instead of the slug, lbf (pound force) is just to differentiate between the two.

Furthermore furthermore in industry or in home use, when something recommends maximum load of 220lb or 100kgs. They are talking about mass. The manufactures have made assumptions about the safe working loads of the product.

Once again, completely incorrect. when something recommends a maximum load, they are talking about the maximum force it can withstand. They have made the assumption that the device will be used here on earth under the acceleration due to the earths gravity.

A carabiner is safe up to 5000 lbs in mass as long as it is only under the acceleration due to gravity, why you may ask. because 5000 lbf and 5000 lbm exert the same force on the object as long as the only acceleration is that of the earths gravity (and we assume that g is constant everywhere on the earth which is a good enough assumption here).

As before safe working load is a long way away from the upper limit of breaking strain.

fixed.

Yes, you're wrong about what the only variables are. The maximum impact force a climber feels in a fall is, in theory, a function of only the climber's weight, the elasticity of the fall, and the fall factor, defined as the distance of the fall divided by the amount of rope available to absorb the fall. Call this force T1. Then the force on the belayer is a fraction (1 – µ) of T1, where µ is the proportion of T1 that the belayer does not feel due to friction between the rope and the anchor. Call the force on the belayer T2. Then the force on the top anchor is T1 + T2. You can assume that µ, the friction factor, is 1/3. Now that you know what the fall factor is, go plug your numbers into the online calculator, and see whether the nut would be expected to hold.

Jay

Once again, completely incorrect. when something recommends a maximum load, they are talking about the maximum force it can withstand. They have made the assumption that the device will be used here on earth under the acceleration due to the earths gravity.

Furthermore furthermore in industry or in home use, when something recommends maximum load of 220lb or 100kgs. They are talking about mass. The manufactures have made assumptions about the safe working loads of the product.

Care to show some evidence for that?
All my googling refers to pound as a measurment of mass. http://ts.nist.gov/...oad/h4402_appenc.pdf
http://ts.nist.gov/...blications/appxc.cfm
But who sets the official definitions of this bullshit system anyay!

If you can find me a more authorative source then go ahead.

Well perhaps then you can enlighten us as to what false inference was taken from your having said the following:


Seems pretty cut and dried to me.

BTW, still no word from you on the decimal tape measure thing... Does this mean you've conceded that it is in fact easier to do the calculations in meters?

BTW, still no word from you on the decimal tape measure thing... Does this mean you've conceded that it is in fact easier to do the calculations in meters?

Well perhaps then you can enlighten us as to what false inference was taken from your having said the following:


Seems pretty cut and dried to me.

So you're saying the impact force is independent of the mass of the falling object. Man, I hope I don't drop a biner in a FF 2 fall - it'll rip my anchor! OTOH, I guess it's OK to let my 150 kg partner whip onto that RP.