An Acme thread in a power screw jack for an automobile is made of cold-rolled 1045...

 

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An Acme thread in a power screw jack for an automobile is made of cold-rolled 1045 steel having a diameter of 1 1/8" x 8. The thread is cut for general purpose used to raise an automobile, the base of the screw is supported by a steel collar having a mean diameter of 1.5 in. The nut that does the lifting is made of the same material as the screw. Assume fs = fc = 0.33 for starting the screw in motion, and fs = f = 0.25 for keeping the screw in motion. [a]. To raise a 5000 lbf car to change a tire, what would be the required torque and the screw efficiency? Consider both static and dynamic (in motion) friction cases. [b]. Will the screw overhaul (i.e., spin by itself to lower the load) after the load has been raised? An Acme thread in a power screw jack for an automobile is made of cold-rolled 1045 steel having a diameter of 1 1/8" x 8. The thread is cut for general purpose used to raise an automobile, the base of the screw is supported by a steel collar having a mean diameter of 1.5 in. The nut that does the lifting is made of the same material as the screw. Assume fs = fc = 0.33 for starting the screw in motion, and fs = f = 0.25 for keeping the screw in motion. [a]. To raise a 5000 lbf car to change a tire, what would be the required torque and the screw efficiency? Consider both static and dynamic (in motion) friction cases. [b]. Will the screw overhaul (i.e., spin by itself to lower the load) after the load has been raised?

Answer rating: 100% (QA)

a Torque calculation First lets calculate the torque required to raise the car We can use the following formula T Load x Distance Efficiency x Thread ... View the full answer