Solution to Problem 348 | Helical Springs

Problem 348
A rigid bar, pinned at O, is supported by two identical springs as shown in Fig. P-348. Each spring consists of 20 turns of 3/4-in-diameter wire having a mean diameter of 6 in. Determine the maximum load W that may be supported if the shearing stress in the springs is limited to 20 ksi. Use Eq. (3-9).

Bar attched to springs


Solution 348


Why is the light spring equation used here instead of the heavy spring equation? d/4R = 0.0625 (d/4R >= 0.05, hence heavy spring). If heavy spring equation is used m=8, P2 = 466.41lb and W = 333.15 lb. Is this not the safer load also?