Class 2 (2nd Engineer) MEKM 📅 Jan 2024

Exam Question

With reference to crankshafts, explain EACH of the following.

(a) The cause and effects of torsional vibration (4)

(b) The term critical speed indicating why it can be a problem (4)

(c) The term fatigue cracking and state, with reasons, TWO factors of crankshaft operation which have greatest influence on the likelihood of fatigue cracking (4)

(d) How a torsional vibration damper can reduce the effects of torsional vibration (4)

Reference Answer

(a) Cause and Effect of Torsional Vibration
Causes of Torsional Vibration
Torsional vibration in a multicylinder engine arises from the dynamic behaviour of the elastic shaft system when acted upon by periodic varying torque. This vibratory motion is caused by the following:
The fluctuating torque imposed by the gas pressure in the cylinders and the inertia forces of reciprocating masses contributes significantly to torsional vibration.

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