Bending moment in wire rope

[stephens248]

I am currently trying to determine the forces in a wire rope. I am trying to design a tension sensing device using a spring and piston. The wire rope enters the device, and is displaced via the piston, creating an "S" shape in the wire rope. Now I know this is not an accurate way to measure the tension, however I am using the design as a switch.

My simple problem thus far is: In the "S" shape of the wire rope, the first curve is caused by the reaction at the housing of the device. The other from the piston with a spring behind it. In theory the cable will be pulled on to a desired tension, at this tension the spring will be compressed a distance x. This will trigger a switch. I am having difficulty determining the force in the direction of the spring due to the wire rope tension (tangent force).

Any ideas? Thank you.

 

[Neilmo]

Hello Stevens248,

Im not sure if this helps or not, but here goes.
If you have a straight length of cable 'L' and you apply a point load 'F' to its mid length, at right angles to the cable, then, if you know the angle (theta) of the deflected cable, then -

T = F/2*sin(theta)

for small angles, this is -

T = F*L/4*(vertical deflection)

There are also some cable formula in 'Roarks Formula for Stress & Strain'

Regards,
Neilmo