MrRecurve
ArboristSite Member
What is the minimum kN rating for climbing gear, for example, I have a pulley that is rated at 22kN, would it be considered safe to climb off? I ask because the lowest rating Ive seen on a carabiner is 26kN.
Minimum kN rating?
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BostonBull
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It is 22, I think.......
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One KiloNewton is equal to 225 Lbs....22 X 225 = 4950 Lbs.
Treeman587
ArboristSite Operative
While Rah's conversion is correct, You have to also remember that KiloNewtons are a measure of force. So just hanging, 4950 lbs is the limit. But swinging (adding a centrifugal force) and shock loading will have an effect on the load limit. Which is why we have a WLL, or Working Load Limit. For tree work it is said that a 10 to 1 factor is good. Therefore, You would not want more than 495 lbs on that carabiner to be considered safe.
kN is a unit of force; 1kN = 224.8+# of force
Rounded i use 225; this still puts 22kN slightly short of 5,000#
Rounded i use 225; this still puts 22kN slightly short of 5,000#
Treeman587
ArboristSite Operative
okietreedude1
ArboristSite Guru
Probably YES to actually answer your question. Now, according to ANSI standards - NO. That number is 5000# and as youve seen the above calculations, 22kn is not quite that.
maxburton
ArboristSite Operative
I agree. If I were you I'd spend a couple bucks and buy something that meets ANSI standards.
Ummmmmmmm sorry, i was doing a few things at once and Rah hadn't answered when i started...
A pulley on the support will lengthen the line taking the dynamics of the forces; so give more elastic response/ dampening; more line is better for this. A pulley(s) on Load; will divide the load between the legs of support, so each will have less tension/ so higher SWL/ so reciprocally less elastic shock absorbtion; So, contrary more line (used like this) to make more legs; is worse for dampening.
A pulley on the support will lengthen the line taking the dynamics of the forces; so give more elastic response/ dampening; more line is better for this. A pulley(s) on Load; will divide the load between the legs of support, so each will have less tension/ so higher SWL/ so reciprocally less elastic shock absorbtion; So, contrary more line (used like this) to make more legs; is worse for dampening.
This part I agree with. But it would perhaps be clearer if you said "the longer the line, the more the stretch." In the case of a falling load, this definitely affects the maximum force experienced by the line as you indicate.
Here you seem to say that more line has the opposite effect. But it is still true, as in the case above, that the more line the more stretch. I think you mean to say that more lines (not talking about length) will divide the load between them, and also divide the stretch between them.
In a pulley arrangement where the pulley is attached to the load and there are 2 equal-length supporting lines running to the support, the total stretch caused by a load will be 1/2 what it would be if only a single line of that length were supporting it, and 1/4 what it would be if we turned the whole picture upside down, attaching the pulley up above. A falling load will certainly experience more shock in this case, and so will the pulley, though the rope will not.
So it is possible to have a pulley on the support (your first example) where the shock load on the pulley from a falling load would be MORE than in the second configuration: you just need the distance from load to support in the second case to be at least 4 times longer than in the first case.
Finally, as Treeman587 pointed out, the WLL for this pulley is 495 lbs. It is not a variable. It does not go up or down depending on how you hook up the pulley. Your phrase "higher SWL" seems highly misleading to me. Someone might read this to mean you can somehow get more mileage out of a given piece of equipment by hooking it up differently. You can certainly alter the actual load experienced by the equipment (which is what you have discussed), but you cannot change the SWL. It never gets "higher."
John Paul Sanborn
Above average climber
Umm, Yeah, We said that.
Yeah, but you were 3 min apart on posting, so he was typing when you posted
Treeman587
ArboristSite Operative
Not my damn fault I can type faster. GEEEEZ it was just a little sarcasm.
Treeman587
ArboristSite Operative
While we are on this, Has anyone used that rigging software?
Seems it would be to time consuming, and a waste of labor. When most of the time experience and common sense will guide you to the correct path.
Seems it would be to time consuming, and a waste of labor. When most of the time experience and common sense will guide you to the correct path.
treevet
Addicted to ArboristSite
I ve climbed off a pulley or block and don t like it all. Too different/fast w out any friction. Don t mind climbing off crane hook tho.
What is kN rating of a tree you are about to climb? Use common sense, don't make an assumption that your tree is stronger than your shiny, rated, ANSI standards meeting gear! Unless you're climbing only rated trees, one day all those sophisticated calculations will go crushing to the ground together with your rated gear.
friction
Ah, but going UP is so easy and silky smooth.
Coming down you can really see the difference between different friction knots.
Ah, but going UP is so easy and silky smooth.
Coming down you can really see the difference between different friction knots.
i dont just access trees on rope. I access buildings, cliffs, canyons, caves, towers. I can rig off the biners, as well as ues them for life support. They are rated for 2 person loads (rescue) as well. Besides steel biners of this professional caliber (NFPA standards makes ANSI look like hacks), take more abuse and are more versitial than regular biners. (and really, who rates trees by a KN rating? WTF?)
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Tom Dunlap
Addicted to ArboristSite
NFPA standards are all based on two person loads in case a rescue needs to be done using what is worn. Using NFPA standards as a comparison doesn't have any standing since the two professions are very different.
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