Over hauling in power screws
Mechanical Engineering (MCQ) questions and answers
Design of Machine Elements - 1
Q. In power screws, if friction angle Φ is less than lead angle λ, then the screw undergoes _______
- Published on 14 Sep 15
both a. and b.
none of the above
ANSWER: over hauling
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-Posted on 04 Nov 15
1) Over-hauling screws:
- If Φ ≤ λ in the equation T = (Wd
/ 2) x tan ( Φ - λ), then torque required to lower the load is negative or zero.
- Hence no torque is required for the load to move downwards which rotates the screw. This screw is called as over hauling screw.
- These screws have friction angle less than or equal to lead angle.
2) Self locking screws:
- These types of screws are used in screw jacks and C-clamps
- Self locking screws have friction angle greater than lead angle and the torque required is positive.
- tan Φ > tan λ or μ > l / πd
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