Question

An open-coiled helical spring of wire diameter 12 mm, mean coil radius 84 mm, helix angle 60° carries an axial load of 480 N. What is the twisting moment ?
1. 10.22 Nm
2. 20.16 Nm
3. 14.24 Nm
4. 24.11 Nm

Answer 1

Correct Answer - Option 2 : 20.16 Nm

Explanation:

Given Data

Wire diameter(d) = 12 mm

Mean coil radius(R) = 84 mm

Angle of helix (\(\alpha\)) = 60⁰

Axial Load (W) = 480 N

Now the twisting moment(T) due to the axial load acting on an open-coiled helical spring is given by

 \(T = WR \cos\alpha\)

\(T = 480 \times 84 \times \cos60\)  N-mm

 T= 20.16 N-m

 The axial load acting on an open-coiled helical spring, bending moment(M) is given by

  \(M = WR \sin\alpha\)

The Strain energy in open-coiled helical spring due to axial load given by

 Strain energy = Strain energy due to bending + Strain energy due to torsion