Question

3. Problem 3: Consider a power screw design for a vertical force of 15 kN. The coefficient of friction for the threads is 0.1. If the screw is a single square threaded with 20 mm in diameter and 5 mm pitch. 3.1. What is the required torques to raise and lower this power screw? (2.5 points) 3.2. Suggest a modification for the current design of the power screw that leads to a lowering torque of 10.65 N.m (2.5 points)

Answer 1

15A10 N Given w 15 KN d dia of screw 20mm P 5 mm gingle square thieaded Torque requi ved to vaise the load, w.dm tanc t Trase Wheve o 1 tan 6-71 Pitch for single start tbedd -Re ad ton 5 mm TT dm dm: d- P/h = 20-5 17-5 mm. Tx 17-5 oc 5-196 15x103 x 17-5 x tan (5-71+5 196 Traise 25-289 N-m. 25-289 x 103 N-mm tarld- tan(5.71-5-196 Tiowe 15 x)03x 17-5 2 1-177 N-m If we wont to hove lowering torque to be 10-65 Nm o3x 15x30 17-5 tan C 10-65 x103 tan Cp-)e o-08114 4-4-6389 if we incease the coefficlent of frichon 4-5.396 4.G3 89 9.8349 ltan : 0'1784