Calculate the bearing life if expected life for 90% bearings is 9000h and shaft is rotating at 1500rpm.

Mechanical Engineering : Machine Design - Quiz(MCQ)

810 h

850h

850 million rev

810 million rev

Correct Answer : Option (D) : 810 million rev

Explanation : L=60x1500x9000/10â¶ million rev.

Recently Updated in Machine Design Questions

Which type of rope drum is preferred?

Drums with helical grooves

Plain cylindrical drums

Both are equally preferred

None of the above

Correct Answer : Drums with helical grooves

Explanation : They have more bearing surface of the drum and prevent friction between adjacent turns of the rope.

Small sheaves are preferred over large sheaves on what parameters?

Higher cost of small sheaves

Increasingly centrifugal force in large sheaves

Preferring centrifugal force reduction even for more money

None of the above

Correct Answer : Increasingly centrifugal force in large sheaves

Explanation : Larger sheaves have higher centrifugal forces and higher cost because more material is used in their construction.

The wire rope is subjected to

Tensile Stress

Bending Stress

Both bending and tensile stress

None of the above

Correct Answer : Both bending and tensile stress

Explanation : There is direct tensile stress due to load being raised as well as bending stress.