Question

A single thread power screw is 36 mm in diameter with a pitch of 6 mm. A vertical load on the screw imposes a force of 9 kN. The coefficients of friction are 0.09 for the collar and 0.16 for the screw. The effective diameter of the collar is 52 mm. Find the overall efficiency and torque required to raise and lower this load.

Answer 1

Given

= 9000 N

Pitch , l = 6mm = 0.006 m

dm = 36 - (6/2) = 33 mm

mm

Total torque required to raise the load = Torque required to raise the load + Frictional torque at collar

Where = 0.16  and = 0.09 are thread friction and collar friction respectively

Upon substituion We will get the values as

Total Torque required to raise the load = 32.55 N.m + 21.06 N.m

Total Torque required to raise the load= 53.61 N.m

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Total torque required to lower the load = Torque required to lower the load + Frictional torque at collar

Upon Substitution

Total torque required = 14.97 N.m + 21.06 N.m = 36.03 N.m

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Efficiency

e = 0.264