Camshaft, Crankshaft & Vibration Damper MCQs with Detailed Explanation

Correct Answer: B. Uniform wear of lifter

• The slight offset gives a small rotary motion to the lifter when it moves up and down.
• Because of this rotation, the same portion of the lifter bottom does not continuously rub against the cam.
• So, the bottom face of the lifter wears uniformly and its service life increases.
• This offset is mainly related to lifter wear, not camshaft bush wear or valve opening.

Correct Answer: A. Gear drive

• Gear drive is suitable when the camshaft and crankshaft are placed very close to each other.
• In this mechanism, power is transmitted directly through meshing gears.
• Chain drive or belt drive is generally used when the distance between shafts is comparatively more.
• In a four-stroke engine, the camshaft speed is half of the crankshaft speed.

Correct Answer: D. All of these

• The timing gear is mounted to drive the camshaft in proper timing with the crankshaft.
• The fan pulley helps drive accessories such as water pump, engine fan and generator/alternator through a fan belt.
• The vibration damper is also mounted at the front end to reduce crankshaft torsional vibration.
• Therefore, all the listed components can be mounted at the front end of the crankshaft.

Correct Answer: C. Torsional vibrations

• The crankshaft is subjected to twisting vibration due to repeated power impulses from the engine cylinders.
• This twisting vibration is called torsional vibration.
• The vibration damper absorbs or reduces these torsional vibrations and stress in the crankshaft.
• It helps to increase crankshaft life and smooth engine operation.

Correct Answer: C. Twice as many teeth as crankshaft gear

• In a four-stroke engine, the camshaft completes one revolution for every two revolutions of the crankshaft.
• So, the camshaft must rotate at half the speed of the crankshaft.
• For this speed reduction in gear drive, the camshaft gear is made larger.
• Therefore, the camshaft gear has twice as many teeth as the crankshaft gear.

Correct Answer: C. Both A and B

• Commonly mentioned vibration damper types include rubber floating type and clutch & rubber bush damper.
• Both are used to reduce torsional vibration effects in the crankshaft.
• Timing belt is a camshaft drive component, not a type of vibration damper.
• Hence, both option A and option B are correct.