Bob Mehew
Well-known member
I have been asked a question which is proving somewhat difficult to answer with confidence. So can people help with some references?
The background is in dynamic rope testing one usually drops a steel mass of 80 or 100kg and see what peak force is reached by a rope (semi static or dynamic) in arresting the mass's fall. Clearly steel is more ridged than a human body, so the question arises how much would the peak force be reduced by if it were a human body rather than a steel mass?
Years ago I was told 50% was a guide. But I have just come across https://m.petzl.com/GB/en/Sport/Fall-comparison-with-rigid-human-mass?ActivityName=Rock-climbing which (making a few assumptions over the probable poor translation) implies the reduction is between 50 & 70%.
I also found http://www.itrsonline.org/PapersFolder/2009/Holden-May-Farnham2009_ITRSPaper.pdf which suggests 80%.
I have found a You Tube video at https://www.youtube.com/watch?v=eqZQnCGl24A&feature=youtu.be but can't get any numerical value out of the commentary.
And most intriguingly a comment at https://www.mountainproject.com/edit/forum-message/0?replyToId=114310951"eId=114321524 which implies a value of 80%.
To put this in context, Crawford, see http://www.hse.gov.uk/research/hsl_pdf/2003/hsl03-09.pdf suggests that 6kN (as used in EN standards) as a maximum survivable force for the type of harnesses used in caving.
So has any one got any other data on the topic of relating the impact of falls between steel masses and human bodies?
The background is in dynamic rope testing one usually drops a steel mass of 80 or 100kg and see what peak force is reached by a rope (semi static or dynamic) in arresting the mass's fall. Clearly steel is more ridged than a human body, so the question arises how much would the peak force be reduced by if it were a human body rather than a steel mass?
Years ago I was told 50% was a guide. But I have just come across https://m.petzl.com/GB/en/Sport/Fall-comparison-with-rigid-human-mass?ActivityName=Rock-climbing which (making a few assumptions over the probable poor translation) implies the reduction is between 50 & 70%.
I also found http://www.itrsonline.org/PapersFolder/2009/Holden-May-Farnham2009_ITRSPaper.pdf which suggests 80%.
I have found a You Tube video at https://www.youtube.com/watch?v=eqZQnCGl24A&feature=youtu.be but can't get any numerical value out of the commentary.
And most intriguingly a comment at https://www.mountainproject.com/edit/forum-message/0?replyToId=114310951"eId=114321524 which implies a value of 80%.
To put this in context, Crawford, see http://www.hse.gov.uk/research/hsl_pdf/2003/hsl03-09.pdf suggests that 6kN (as used in EN standards) as a maximum survivable force for the type of harnesses used in caving.
So has any one got any other data on the topic of relating the impact of falls between steel masses and human bodies?