A screw jack having a 2 in double-thread Acme screw and a plain thrust collar having a 3.2 in mean diameter is being used to raise a load. Given the coefficient of static friction for the collar is 75% of the coefficient of static friction for the screw threads (μcs = 0.75 µs), determine the minimum allowable coefficient of static friction for the screw threads if the jack is to be "Self- Locking" (i.e. The handle of the jack should not "unwind" when it is released after raising the load.). Hint: Start with the "Load Lowering Screw Torque Equation" (i.e. The "TLL" equation which is essentially Eqtn. 10.5 Pg 380 (Textbook)), include collar friction (i.e. Collar Torque), use the "static" coefficients of friction, and solve the inequality TLL ≥0 for the screw thread coefficient of friction (Ms). Ans. = μsmin 0.03664

A screw jack having a 2 in double-thread Acme screw and a plain thrust collar having a 3.2 in mean diameter is being used to raise a load. Given the coefficient of static friction for the collar is 75% of the coefficient of static friction for the screw threads (μcs = 0.75 µs), determine the minimum allowable coefficient of static friction for the screw threads if the jack is to be "Self- Locking" (i.e. The handle of the jack should not "unwind" when it is released after raising the load.). Hint: Start with the "Load Lowering Screw Torque Equation" (i.e. The "TLL" equation which is essentially Eqtn. 10.5 Pg 380 (Textbook)), include collar friction (i.e. Collar Torque), use the "static" coefficients of friction, and solve the inequality TLL ≥0 for the screw thread coefficient of friction (Ms). Ans. = μsmin 0.03664

International Edition---engineering Mechanics: Statics, 4th Edition

4th Edition

ISBN:9781305501607

Author:Andrew Pytel And Jaan Kiusalaas

Publisher:Andrew Pytel And Jaan Kiusalaas

Chapter7: Dry Friction

Section: Chapter Questions

Problem 7.57P: The square-threaded screw with a pitch of 10 mm and a mean radius of 18 mm drives a gear that has a...

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