Question

Ordinary window shade rollers have long torsion springs that work on the same principle as the overhead garage door support of Problem 12.59. For a roller of 33-mm diameter, how many turns of 1.2-mm square steel wire with D = 19 mm would be required to give a shade pull force of 14 N with the spring wound up 14 turns? What would be the value of maximum bending stress in the spring? 33 mm dia. 33 mm dia. Cable Torsional springs 1.2 mm square steel wire D = 19 mm Cable

Answer 1

14 N wire diameter d 19mm 19.8.10 3 m will length M 1.2 mm 1.2 x 10-30 we know, E d 32 where bending stress o 32 F M od 3 32 x 14 x (1.2 x 10-3) T x 119 x 10-3) 3 0.0255 x 106 pa 25.5 kPa.

let I Number the twins of wive! Moment (M) Ed" T 10.8 ND FR Ed" T 10.8ND T = 10.8 x (EH) x (ND) Ed" 31.2 x 106 MPa 6 You steel E 14 33 mm 3 33 x 10 T = 2.06