A torsional spring is to be located within the hub of the reel for raising the weight show...

A torsional spring is to be located within the hub of the reel for raising the weight shown in Fig. 1. The spring is wound from 5/16-in. square wire. The OD of helix is 6 1/2 in. Ignore the effect of curvature on stress. The number of active coils is 20.

(a) Find the initial angular deformation required by the spring in order to support the load in the upper position.

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(b) Find the additional force that must be applied to the weight in order to hold it in the lower position.

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(c) Using Eq. (31), compute the strain energy stored in the spring because of lowering the weight; check the result by totaling the work done by the external forces.

Figure 1