Class 2 (2nd Engineer) MEKM 📅 Mar 2018

Exam Question

(a) State the reasons for the progressive slackness of an engine camshaft drive chain in service.

(b) State the effect chain stretch has on engine timing and performance.

Reference Answer

(a) Cause of chain elongation in service:
The primary cause of chain elongation is wear-down between the pins and bushes in the roller chain. Over time, this wear effectively increases the pitch of the chain (the distance between the centres of adjacent pins), causing the chain to elongate.
As the chain's pitch increases, it no longer matches the pitch of the sprocket teeth, leading to:
Excessive wear on the teeth of the sprockets.

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