Exam Question
With reference to the crankshaft and running gear of an engine, explain EACH of the following:
(a) Static balance
(b) Dynamic balance
(c) Torque reaction couple
(d) Critical speed
Class 2 (2nd Engineer)
MEKM
📅 Oct 2018
Reference Answer
(a) A crankshaft is statically balanced if its centre of gravity lies on the polar axis of its journal.
When the crankshaft is placed on knife edges (pivot supports), it should remain stationary in any position without rotating. If it rotates and settles in a particular position, it indicates that the centre of gravity is offset from the polar axis. A statically balanced crankshaft ensures that the centre of gravity aligns with the centre of rotation.
Achieving Static Balance :
The sum of all moments around the centre of rotation must be zero in any angular position.
When the crankshaft is placed on knife edges (pivot supports), it should remain stationary in any position without rotating. If it rotates and settles in a particular position, it indicates that the centre of gravity is offset from the polar axis. A statically balanced crankshaft ensures that the centre of gravity aligns with the centre of rotation.
Achieving Static Balance :
The sum of all moments around the centre of rotation must be zero in any angular position.
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