A Simple Tension Meter

[Curbie]

This guy outlines a simple tension meter you can build it yourself for
about $5.00
http://www1.foragebeef.ca/$foragebeef/frgebeef.nsf/all/frg35/$FILE/fencetension.pdf

It's for wire and not cable in which I'm interested in but the idea is
pretty simple:

Two wire guides 40" apart, deflect the wire with a spring scale ½
inch, multiply the scale reading by 20 to determine the amount of
tension on the wire.

I know this has no direct value with cables with 1000's of pounds of
tension (like guys), but I was wondering if anyone knows or can point
me to the math behind the idea?

Thanks,

Curbie

 

[Curbie]

Jim,

Here's a commercial one. Click on the Tension Meter (long URL):
http://www.dillon-force.com/

Thanks, they have a large image of their device showing mechanical
details here:
http://www.dillon-force.com/compone.../product/abdb983a1fa6ad01da4c05c327dcb7d5.jpg

The device seems to use the same principles (math) for cables that the
device I posted uses for wire, and I'm still interested in the math
behind it.

Any idea on terms for keywords I should use to search for the math?

Thanks,

Curbie

 

[amdx]

Jim,

Thanks, they have a large image of their device showing mechanical
details here:
http://www.dillon-force.com/compone.../product/abdb983a1fa6ad01da4c05c327dcb7d5.jpg

The device seems to use the same principles (math) for cables that the
device I posted uses for wire, and I'm still interested in the math
behind it.

Any idea on terms for keywords I should use to search for the math?

Thanks,

Curbie

Hi Curbie,
I can't help you with the math, but you might ask on sci.physics.
Mike

 

[Martin Riddle]

Hi Curbie,
I can't help you with the math, but you might ask on sci.physics.
Mike

Cantenary Curve Effect

<http://www.spaceagecontrol.com/calccabl.htm>

Cheers

 

[Curbie]

Mike,

I can't help you with the math, but you might ask on sci.physics.

Thanks, I give it a try.

Curbie

 

[Curbie]

Martin,

Cantenary Curve Effect
<http://www.spaceagecontrol.com/calccabl.htm>

Looks like what I am looking for, Thanks.

Spread-sheet time.

Curbie

 

[daestrom]

Jim,

Thanks, they have a large image of their device showing mechanical
details here:
http://www.dillon-force.com/compone.../product/abdb983a1fa6ad01da4c05c327dcb7d5.jpg

The device seems to use the same principles (math) for cables that the
device I posted uses for wire, and I'm still interested in the math
behind it.

Any idea on terms for keywords I should use to search for the math?

Thanks,

Curbie

Well the 'math' goes along these lines (pun intended.

Looking at the straight line where the wire is originally and the wire
position after it's deflected, and draw a line perpendicular from the
mid-point over to the original line of the wire. We have a right
triangle with one leg's length 1/2 inch and the other leg's length 20
inches and the hypotenuse is the wire. With such a long narrow
triangle, we can approximate the length of the hypotenuse as also being
20 inches. And the sin of that narrow angle is the opposite over
hypotenuse so we have (0.5)/20 = 1/40.

The tension in the wire is pulling at a very shallow angle, trying to
straighten out. So the sideways force created by the tension in the
wire is X*sin(angle) = X/40.

Looking at the whole thing you can see that it is symmetrical and there
is a second triangle formed on the other side of the point where the
scale attaches. The tension in *that* segment of wire is also 'X' and
it also is creating a side force of X/40.

So these two sections of wire are creating a side force of X/40 + X/40
or X/20. And that side force is exactly countered by the pull on the scale.

So working it the other way around, the pull on the scale times 20
equals the tension in the wire.

daestrom

 

[daestrom]

Curbie,

Let me teach you something, Motor and Generator use Permanent magnet are
the same. That's what they use blocking diode to control the current flow.
Don't be picky, learn the core of science and stop fooling around with the
two dead animals in this group or you will be infected like them.

Ah, you've proven that you can't read the original poster's message. (or
you can't figure out how to use your news reader)

daestrom

 

[Curbie]

Well the 'math' goes along these lines (pun intended.

Looking at the straight line where the wire is originally and the wire
position after it's deflected, and draw a line perpendicular from the
mid-point over to the original line of the wire. We have a right
triangle with one leg's length 1/2 inch and the other leg's length 20
inches and the hypotenuse is the wire. With such a long narrow
triangle, we can approximate the length of the hypotenuse as also being
20 inches. And the sin of that narrow angle is the opposite over
hypotenuse so we have (0.5)/20 = 1/40.

The tension in the wire is pulling at a very shallow angle, trying to
straighten out. So the sideways force created by the tension in the
wire is X*sin(angle) = X/40.

Looking at the whole thing you can see that it is symmetrical and there
is a second triangle formed on the other side of the point where the
scale attaches. The tension in *that* segment of wire is also 'X' and
it also is creating a side force of X/40.

So these two sections of wire are creating a side force of X/40 + X/40
or X/20. And that side force is exactly countered by the pull on the scale.

So working it the other way around, the pull on the scale times 20
equals the tension in the wire.

daestrom

daestrom,

Thanks for the easy to understand explaination; it's going to save me
a lot of time!

Mike & Tim had me headed down the right track, thank you two also.

Curbie