Question 28 MODE01 - Chief MODU Engineer

The Correct Answer is A. ### Explanation for Option A (Correct Answer) The pinion of a starting motor (whether for an auxiliary diesel engine or a standard gasoline engine) must engage the flywheel ring gear to crank the engine, and then **immediately disengage** once the engine starts, to prevent the fast-spinning engine from overspeeding and destroying the starter motor's armature. The **Bendix drive** (or an overrunning clutch/solenoid shift mechanism, which is covered by "or similar mechanism") is specifically designed for this purpose. The Bendix drive uses inertia to automatically throw the pinion forward to engage the ring gear when the starter motor begins to spin and then retracts it once the engine achieves self-sustaining speed, protecting the starter. ### Explanations for Incorrect Options **B) automatic follow-up:** This term is not a standard mechanical device used for engaging and disengaging starter motor pinions. It is too vague and does not describe the specific mechanism (like the Bendix or solenoid shift) required for starter protection. **C) magnetic type coupling:** While starting motors utilize a solenoid (an electromagnetic switch) to engage the power and sometimes to physically shift the pinion gear, the actual mechanical connection and crucial automatic disengagement relies on a physical gear drive and an overrunning clutch mechanism (like the Bendix drive). A purely magnetic coupling would not provide the necessary torque capacity for cranking a diesel engine or the critical mechanism for preventing starter damage upon engine start. **D) muff coupling and release:** A muff coupling (or sleeve coupling) is a simple, rigid device used for permanently connecting two shafts end-to-end. It is not designed to engage and release dynamically, especially not at high speed under load, and therefore cannot be used for the momentary engagement required by a starter motor.