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Stranded wire torsion springs

Stranded wire torsion springs

(OP)
I am trying to design a stranded wire torsion spring.  Is there any information available that can be used to calculate forces and safe operating stress levels for a spring of this type?

RE: Stranded wire torsion springs

Do you mean helical torsion spring or a helical compression spring or straight torsion bar/wire made of few strands of wire?

RE: Stranded wire torsion springs

(OP)
I'm refering to a helical torsion spring made from many strands of wire.

Jackpot

RE: Stranded wire torsion springs

The commom use for starnded wire springs is for helical springs. Where the springs are designed where the helix of the strand is in the opposite direction of the helix of the spring. When the spring is compressed the strand is subjected to a twisting moment which causes the wires in the strand to forcefully stick to each other thereby creating a friction effect that adds a damping property to the spring. This is why it is popular where high velocity displacements are required such as in the return mechanism of fire arms.

However, when you use a strand for a helical torsion spring the strand is subjected to bending moment only therefore, I do not see the reason for using a straned wire for helical torsion spring.

Anyway, you just treat it torsion springs in patallel. For example if the strand contains 3 wires of 0.040" wire diameter. You actually have three torsion springs of 0.040" wire diameter working in parallel. So you can calculate one of them and multiply the moment by three. Just remember to use the mean (outside) diameter of the strand in the calculations.

RE: Stranded wire torsion springs

(OP)
The issue for the design of this torsion spring is predicated by a lack of available space (and a high stress level) for a single wire spring. Does this make good engineering sense to you?

RE: Stranded wire torsion springs

Using few smaller diameter wire in parallel instead one larger diameter wire may make sense. Ususlly smaller diameter wires have higher tensile strength for cold drawn wire (such as music wire or austenitic stainless steel wires) however, other high strength spring wire available where the tensile strength does not change much with wire diameter.

Can you provide more info for your design problem such as available space (maximum spring diameter, maximum spring length), torque, deflection angle, type of use (static, cyclic), etc.

RE: Stranded wire torsion springs

(OP)
We are still trying to decide what the torques will be.

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