# How to measure stress/tension on a rope? - Page 2

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Re: How to measure stress/tension on a rope?

I didn't bother to read all of this post, but if the answer seems obvious,
it's likely that someone has already proposed what you did.  I guess we'll
never know.

Mitch

Re: How to measure stress/tension on a rope?

Exactly - The 3 sheave dynomometer. This method has been used in cranes
for years to measure the weight on the end of the hook.

Andy

Re: How to measure stress/tension on a rope?

Pendulum, yes.

But length only, not weight.  Therefore, probably no help here.

Perhaps if you knew the length and weight of the string, you
could calculate the center of mass by the period of the swing,
then from that the mass of the object.

But my last Physics class was about 30 years ago...

Rufus

Re: How to measure stress/tension on a rope?

Maybe you're trying to design the ultimate way to hang people? :D

Re: How to measure stress/tension on a rope?

I'm sure Gary Peek would know.  He's an
occasional poster on this group and has
used our controllers to measure tension
on parachute shrouds.

Re: How to measure stress/tension on a rope?

I dont know the maths (too long ago when I did this sort of thing) but surely
applying a force to the object that moves it a distance by a transducer then you
can calculate the weight of the object - eg m=force x distance or something -
then by measuring the period of the swing you can calculate the length of the
string.rope and by using a lazer 'device' measure the diam of the rope/wire etc
you can calculate it own weight (or close to it)  - then the stress etc becomes
the sum of the object plus the weight of the string

Or am I just rambling?

David - who loved physics but was hopeless at maths

Jim Stewart wrote:

Re: How to measure stress/tension on a rope?

My company makes these

http://www.dqplus.com/rlt.htm

Eric

Re: How to measure stress/tension on a rope?

snipped-for-privacy@abcde.com says...

Lots of people make load cells designed to measure tension on lines.
One compact version---albeit for higher loads, is shown at:

http://www.atairaerospace.com/das/sensors /

Mark Borgerson

Re: How to measure stress/tension on a rope?

a
string?

Piece of cake. Build a simulator, that is, an exact replica of the size or
wire or string, the length, and fix one end of the string to an anchor, and
the other end over a pulley with a weight on it. Now take a spring scale
such as those used by fishermen and hook your stretched string in the
middle. Have a piece of paper behind the line and mark the paper along the
straight line. Now hook onto the middle of the string and apply pressure.
Measure the distance in inches or centimeters, and write down the pull in
pounds or grams at different distances. Now change the weight on the string
and repeat the experiment. With this information in hand you can do a simple
proportional formula extrapolation for the unknown in your actual case.

Let us know what happens since this seems to be a very interesting thread.

Wayne
www.pueblaprotocol.com

Re: How to measure stress/tension on a rope?

The tighter the rope the higher resonant frequency becomes like stretching
an elastic band. It would require something to give it a twang and a microhone
to pick up the resulting ringing.

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Ashley Clarke
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