Question 30 1AE01 - First Assistant Engineer

The Correct Answer is A **Explanation of why Option A is correct:** Option A describes a **below-deck drive arrangement** (also known as a vertical drive or anchor windlass configuration). In this setup: * The primary machinery (motor, brake, gear reducer) is rigidly mounted to a lower, structural deck (e.g., the machinery deck or below-deck foundation). * The capstan head itself is mounted on the weather deck, often resting on a bearing housing that passes through the deck penetration. * The shaft connecting the gearbox output (below deck) to the capstan head input (on the weather deck) must pass through the weather deck. This configuration necessitates a **flexible coupling** for two primary reasons: 1. **Alignment Compensation:** It is extremely difficult (if not impossible) to ensure perfect, rigid alignment between the machinery foundation on the lower deck and the support structure/bearings for the capstan head on the weather deck. A flexible coupling compensates for inevitable minor static misalignment. 2. **Deck Flexure and Movement:** The weather deck is subject to dynamic loads, bending (flexure), and movement (especially under heavy towing or anchoring loads), which can change the relative position and angle between the two shaft ends (the gearbox output and the capstan head input). The flexible coupling absorbs this dynamic movement and prevents high bending stresses on the gearbox output shaft and potential damage to the gearbox bearings. **Explanation of why the other options are incorrect:** * **B) The drive arrangement where the drive motor, electric brake, gear reducer, and capstan head are all located on the weather deck:** This is a **unitized or packaged drive arrangement**. Since all components (motor, gearbox, and capstan head) are typically mounted on a common, rigid base plate or foundation that sits directly on the weather deck, they can be aligned precisely and rigidly. A standard, rigid connection or a simple flange connection is usually sufficient, as the base plate moves as a single unit with deck flexure. A flexible coupling is not strictly required for alignment compensation in this unified package. * **C) The drive arrangement where the drive motor, electric brake, gear reducer are hung from the underside of the weather deck, and only the capstan head is located on the weather deck:** Although the components are separated by the deck, the entire drive unit (motor/gearbox) is mounted directly to the *underside* of the same weather deck structure that supports the capstan head. Since both the driving and driven elements share the same structural mounting surface (the weather deck), they will move and flex together, maintaining relative alignment. Thus, a rigid connection is often employed, and a flexible coupling is generally not required for this specific configuration. * **D) A flexible coupling is required on all three drive arrangements listed above:** This is incorrect because, as explained above, arrangements B and C, where the driving and driven components share the same structural mounting deck (either via a common skid or by mounting to the same deck plate), do not inherently require a flexible coupling for alignment or movement compensation.