Question 21 CEL01 - Chief Engineer - Limited

The Correct Answer is C 1. **Explanation for Option C (Correct Answer):** Option C describes a below-deck drive arrangement where the main drive components (motor, brake, gear reducer) are situated on a lower deck, and the capstan head itself penetrates the weather deck to be accessible. In this configuration, the reduction gear output shaft must transmit torque vertically through the deck penetration to the capstan head input shaft. Because the foundation supporting the gear reducer on the lower deck is structurally separate and distinct from the foundation supporting the capstan head/housing on the weather deck, there is a high probability of relative movement, misalignment, or vibration between the two shafts, particularly as the ship loads, unloads, or encounters heavy seas. To accommodate this inevitable shifting and potential misalignment without damaging the bearings, shafts, or seals, a **flexible coupling** must be installed between the gear reducer output and the capstan head input shaft. 2. **Why Option A is Incorrect:** Option A describes an arrangement where all components (motor, gear reducer, and capstan head) are co-located on the weather deck, likely mounted on a common, rigid base or foundation. When all components share a common foundation, precise alignment is easier to achieve and maintain. While a coupling is required, a highly rigid or slightly flexible coupling is typically sufficient, and the necessity for a coupling specifically designed to handle large degrees of misalignment (which is the primary reason for needing flexibility in C) is minimized. 3. **Why Option B is Incorrect:** Option B describes an arrangement where the drive components are "hung from the underside of the weather deck." In this design, the drive components and the capstan head are typically mounted directly to the same large structural member (the weather deck plating). This common structural mounting minimizes relative movement between the gear reducer and the capstan head, as they move together as a single unit with the deck. Therefore, while a standard coupling is used, a highly flexible coupling to accommodate significant inter-foundation misalignment is usually not required. 4. **Why Option D is Incorrect:** Option D is incorrect because, as explained above, while all drive systems require some form of coupling to connect shafts, the critical requirement for a **highly flexible coupling** specifically designed to accommodate large, unavoidable misalignment between two separate foundations only applies definitively to the below-deck arrangement described in Option C. Arrangements A and B, due to their common or proximate foundation mounting, do not mandate the use of a flexible coupling for the same reasons as C.