Cutting ropes under tension

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As part of the work I’ve been playing around with on Tyroleans the question of how tolerant a rope is to abrasion when under tension has repeatedly been raised. 

As an attempt to have a little look at this I set about some back yard testing! I took 2 Type A Semi Static ropes, one over 10 years old and another unused. Both ropes were cut using a knife, gently, when under tension of around 2kN and 4kN. 

As a general observation I didn’t see anything I wasn’t expecting, in that the greater the tension the easier it was to cut the rope. There didn’t appear to be much difference in performance between the old and new rope; if anything the sheath of the older rope may have been a little more robust, but this may be down to design type (the older rope being a DMM Worksafe and the newer one Beal).

The rope under greater tension cut far more dynamically (with all the gear clattering into the fence the rope was anchored to!) than the lower tensioned rope. Also worth noting was how the rope tensioned to around 2kN held when down to just a single core strand (or less) where as the rope tensioned to 4kN failed when several core strands were still intact. 

Clearly the greater the tension in a rope the easier it is to cut, so the less resistant the rope will be to abrasion; supporting the argument for greater diligence when rigging a Tyrolean to edge protections. 



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