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Name: Patricia
Status: Educator
Grade: 12+
Location: NY
Country: United States
Date: Winter 2009-2010


Question:
Is the strength of a rope made up of 3 optimally twisted strands, stronger than the sum total of the strengths of the individual strands? I have searched long and hard and I cannot find an authoritative answer, backed by experimental evidence that proves this to be the case. Mr Vince Calder and Mr James Przewoznik (in your list of Expert scientists) have answered "yes" to this question. I have also conducted a crude, kitchen-table experiment myself and the result seems to confirm this. But when I Googled on the subject, I cannot find any authoritative reference that confirms this conclusion. In fact, the only writings that I found on the subject indicate that the opposite is true. Can someone help?



Replies:
I stand by our original response. There is an electrical analogy. Split an incoming current into "n" parts, and each part only has to carry 1/"n" th of the total current. Quantitatively, 1/N = SUM (1/n). The same distribution also applies to simple fluids. I know that this is a bit off your question but remarkably, the same principles apply! Things get a bit more complicated with 'twisted' chords, but unless you want to make this a research project, ignore that factor.

So the calculation you would need to carry out is the SUM of 1/n's, which you have apparently done.

As a frequent "Google" user myself -- you have to realize that they are not always correct. You need to use them as a resource, but not as an absolute truth.

Vince Calder



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