Question

1. An electrically driven screw-press is shown. The "load-bar" is raised or lowered via two threaded screws supported via collar-bearings. Each screw is a 20mm diameter and 4mm in pitch with single square threaded. The collars each have an effective diameter of 30mm. The thread coefficients of friction is 0.075 and 0.095 for the screw and collar respectively. Each screw supports a load of 6kN. a) Find the torque required (per screw) to raise or lowerthe bar b) Determine if the threads are "self-locking Motor Spur gears Worm What is the power required to raise or lower the bar if the screws turn at a rate of 1rev/sec. Ans. Raise, 207Watts How far is the bar raised or lowered per-minute? Ans. 0.24m d) Bronze bushings CI Collar bearing 2I's Foot H

Answer 1