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rope wrap on object and friction
2

rope wrap on object and friction

rope wrap on object and friction

(OP)
The concept that I'm looking at is very simple but I'm want to put the numbers to it. If you wrap a rope around a pipe to hold a weight is there a formula to calculate the number of wraps resulting in the required holding force. I know I've use this many times in life but now it's time to put some numbers to it.

RE: rope wrap on object and friction

Tout/Tin = eμθ

Relates the in and out tension where

μ is the coefficient of friction between the rope and pipe and θ is wrap angle in radians.

RE: rope wrap on object and friction

I do testing in my own garage since Any believable formula for rope friction would have been derived from empirical data anyhow.  Wet nylon can be pretty slippery.  

Note satchmo's formula requires T in.  After a few wraps the load can be stopped pretty easy with slight drag on the free end of the rope.  5 wraps of a rope with
? = 0.1 solves to more than 20>1 retarding ratio

RE: rope wrap on object and friction

Interesting thread from a marine point of view as we deal with this problem all the time. I do not know any technical data but here are a few practical things that I thought might affect your answer.

Some ropes are manufactured to maximise friction others to minimise it. Also the weave of the rope would come into play (3-strand, 5-strand, platt, etc).

Another problem is the diameter of the pipe versus the diameter of the rope. Also are you assuming the rope is always perpindicular to the pipe axis

RE: rope wrap on object and friction

(OP)
I'm assuming that the rope is always perpindicular to the pull. The problems is actually a bit more involved but this part of it is based on the rope concept. You input has been very helpful. Thank you all.

RE: rope wrap on object and friction

When this posting appeared I happened to read it and did not appreciate much. However on the same day or the next there was an accident and 5 lives were lost and many injured as the wrap around rope gave way and the scaffolding collapsed. This happened in infosys campus at Bangalore.

RE: rope wrap on object and friction

arunmrao

can you supply link to article?

RE: rope wrap on object and friction

Tie a clove hitch & don't worry winky smile

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