Suppose I have a rope that is capable of lifting 100 Kg without breaking. But I would like the rope to break if it is exposed to a sudden change in acceleration (jerk). So if the rope was lifting 10 Kg but was instantaneous exposed to 700 N impulse force, it must break. The numbers here are just examples. [that edit should make the physics clearer] So perhaps such ropes or similar exist? Or the rope could be divided in two with a hinge or something in between? Anything would work - just as long as it has these properties of breaking at some predefined change of acceleration...

Does something like this exist?


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    $\begingroup$ Try Yates' Screamers for climbers. Is that the sort of thing you are wanting? I have crap internet at the moment, else I would post a link. $\endgroup$ – Phil Sweet Apr 5 '18 at 19:59
  • $\begingroup$ Unless I am reading your question wrong you are misunderstanding acceleration. If a weight is hanging from a rope earths gravity is accelerating the weight towards just as fast as the rope is accelerating the weight away from the earth. Thus a rope that can withstand 100kg times the acceleration of gravity will always hold 80kg. Please revise to clarify your problem. $\endgroup$ – Drew_J Apr 5 '18 at 20:26
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    $\begingroup$ i think you need to elaborate on what you are actually trying to accomplish. $\endgroup$ – agentp Apr 5 '18 at 23:58
  • $\begingroup$ @Drew_J , you did misunderstand. I hope my rewrite makes it clearer. $\endgroup$ – Carl Witthoft Apr 6 '18 at 17:44

It is fairly common to put deliberate break points in rope or cable to ensure that they fail in a controlled and predictable manner when overloaded. Typically this is done in tings like fishing rigs or oil well wire-line winches to try to ensue that any overload condition results in a least bad scenario for example by preventing overload of expensive bits of kit or leaving making disconnected equipment potentially recoverable.

It is often preferred to put in a specific breakaway linkage rather than design it into the rope itself as this makes it simpler to engineer and manage as you can add it to an existing system and change to breakaway characteristic fairly easily and also gives you a predicable point of failure. Plus it potentially saves you from scrapping an expensive length of cable if it does fail as you can be reasonably sure that the cable itself wasn't overloaded.

As well as in-line linkages whcih can be placed anywhere in the system there are also various other systems such as torque limiting clutches and various types of tear failure linkages which are also good at absorbing and mitigating impact forces.

You could also use inertial and/or damping systems to engage or disengage clutches or couplings a bit like an inertial reel seat-belt in reverse.

Perhaps the simplest system is just a shear pin as part of a clevis type coupling . For failure under jerk conditions a brittle material with a notch might be a good option.

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  • $\begingroup$ I would be cautious about suggesting homebrew solutions when we don't know the ultimate application. I'd hate to be rock-climbing with a homemade breakpoint of unreliable strength :-) $\endgroup$ – Carl Witthoft Apr 6 '18 at 17:45

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