Question 23 UFIV01 - Chief Engineer - UFIV

The Correct Answer is C **Explanation for Option C (Correct Answer):** Pneumatic Airflex clutches (often manufactured by companies like Eaton, Fawick, or their successors) used in marine propulsion systems for large vessels are typically of the drum type. In this configuration, the clutch mechanism consists of a flexible, toroidal rubber tube (the air bladder or tire) mounted externally to the driving or driven shaft component. When this tube is inflated with compressed air, it **constricts** (squeezes inwards) to grip the outer surface of a surrounding component, usually referred to as the **clutch drum** or friction rim. This action creates the friction necessary to transmit torque, thus engaging the clutch. Therefore, the clutch is a constricting type engaging the clutch drum when inflated. **Why the Other Options are Incorrect:** * **A) The clutch is an expanding type clutch and expands to engage against the clutch gland when inflated.** This is incorrect. While there are expanding pneumatic clutches (where the tube expands outwards to engage an inner drum surface), the standard, highly robust Airflex CB/VC/Wichita type clutches commonly used in marine propulsion applications are constricting. Furthermore, the term "clutch gland" is generally associated with seals and stuffing boxes, not the friction surface of the drum. * **B) The clutch is an expanding type clutch and expands to engage against the clutch drum when inflated.** This is incorrect because, as discussed, the widely used high-torque pneumatic clutches in marine propulsion (especially those described as "Airflex") are typically designed to constrict (squeeze inwards) onto the drum, not expand outwards. * **D) The clutch is a constricting type clutch and constricts to engage against the clutch gland when inflated.** This is incorrect. While the clutch is a constricting type, it engages the friction surface, which is the **clutch drum** (or friction rim), not the "clutch gland."