Exam Question

### (a) Describe what is Slipping of Crankweb and its effect on main engine. (4 Marks)
**1. Definition of Crankweb Slipping:**
Crankweb slipping is the catastrophic failure of the interference fit (shrink fit) between a crankweb and its associated journal or crankpin. In large, slow-speed marine diesel engines, the crankshaft is often of a semi-built or fully-built construction. This means the crankpins and journals are heated and expanded before being inserted into the precisely machined crankwebs, or the webs are heated to expand them over the journals/pins. Upon cooling, the components contract, creating an immense frictional grip.
Slipping occurs when an extreme torsional load overcomes this frictional grip, causing the web to rotate relative to the journal/pin. This permanently alters the angular position of that crank throw relative to the others, destroying the engine's designed timing and balance.