Calculating Torsional Force - Compression Springs

AI Thread Summary
To calculate the torsional force required to twist a helical compression spring, one must consider the relationship between linear and angular forces, utilizing Hooke's law as a foundation. The formula for angular deflection involves parameters such as the applied moment (torque), mean coil diameter, number of active coils, Young's modulus, and the second moment of area of the wire. The design involves a rod with a handle that compresses the spring, and the goal is to determine the force needed to release the spring from a locked position. Consistent units are crucial for accurate calculations. Understanding these principles will aid in effectively designing the spring mechanism for the intended application.
apt403
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Let's say I've got a helical compression spring of a known length and strength, and I want to know how much force it would take to twist the spring around the axis of its coils, effectively making the diameter of each coil smaller, so it acts a bit like a torsion spring.

I know Hooke's law is probably relevant, just not sure how to go from data on a linear force to that of angular force.

I'm working on a doohickey that compresses a spring fixed around a rod with a 90 degree handle on one end - The rod is inside a tube with a channel cut down its length, with a notch at the end of the channel so the rod can be locked into place and hold the spring compressed. I'd like to calculate (roughly) the amount of force I'll have to apply to the handle in order to move it out of the notch and subsequently let the spring/rod assembly fly forward (ignoring drag from the air, friction of the parts against each other, etc).

- Apt
 
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angular deflection = (M*pi*D*N)/(E*I)

where M = applied moment, or torque
D = mean coil diameter
N = number of active coils
E = young's modulua
I = second moment of area of wire

Use consistent units.

Cheers,
Terry
 
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