Class 4 (4th Engineer) MEKM 📅 Jul 2023

Exam Question

For 2-Stroke Main Engine of your ship, how are the following obtained

(a) Power card, showing vital point of diagram (4)

(b) Out of phase diagram indicating vital points (4)

(d) Compression diagram and its importance (4)

Reference Answer

### (a) Power Card (In-Phase Diagram)
**Method of Obtaining:**
1. **Instrument Setup**: A mechanical indicator (e.g., Dobbie-McInnes) or a modern electronic pressure transducer is connected to the indicator cock of the specific cylinder unit.
2. **Synchronization**: The indicator drum's rotational motion is mechanically synchronized to be perfectly *in-phase* with the engine piston's reciprocating motion. This is achieved via a cord and linkage driven by the engine's crosshead or a dedicated indicator drive mechanism.

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