A power screw with a single-square-threaded, oiled, steel screw and steel nut needs to deal with a load of 1100 lb. The screw has a 1 in. major diameter with 5 threads per inch. Assume a friction coefficient for the threads is 0.12 and 0.09 for the cast iron collar with a frictional collar diameter of 1/4 inches.
a. Find the total torque required to raise the load.
b. Is the power screw self-locking?
c. Determine the overall efficiency, including collar losses.
A slow motor can turn the screw at 60 RPM. How many seconds will it take the nut to move 1 foot?