Question 28 OSE01 - Chief Engineer - OSV

The Correct Answer is C ### 2. Explanation of why option C is correct The operation of an Airflex pneumatic friction clutch relies on controlled air pressure to determine the force (clamping load) exerted between the friction surfaces and the drum. Torque capacity is directly proportional to the applied air pressure. * **If the operating clutch supply air pressure is higher than recommended:** The clamping force is excessive. This results in a very sudden and harsh engagement when the clutch is applied, leading to a tendency to **grab**. Grabbing puts undue stress on the gear train, reduces operational smoothness, and potentially causes premature failure of associated components (though it minimizes slip, it maximizes mechanical stress). * **If the operating clutch supply air pressure is lower than recommended:** The clamping force is insufficient to transmit the required torque load fully. When the load is applied, the friction surfaces cannot lock up completely and will rub against each other, leading to a tendency to **slip**. Slipping is the primary cause of heat generation and rapid wear in friction clutches, drastically reducing efficiency and lifespan. Therefore, maintaining the recommended pressure is critical: too much pressure leads to mechanical shock (grabbing); too little pressure leads to frictional wear (slipping). ### 3. Explanation of why each of the other options is incorrect **A) If the operating clutch supply air pressure is higher than recommended, the clutch will have a tendency to slip. If the operating clutch supply air pressure is lower than recommended, the clutch will have a tendency to grab.** * **Incorrect:** This option reverses the physical outcomes. Higher pressure increases the clamping force, preventing slip (causing grab). Lower pressure decreases the clamping force, causing slip (not grab). **B) If the operating clutch supply air pressure is maintained either above or below the recommended pressure, the clutch will have a tendency to grab.** * **Incorrect:** Only excessive pressure (above recommended) causes the clutch to grab or engage harshly. Pressure maintained below the recommended level causes the clutch to slip, not grab. **D) If the operating clutch supply air pressure is maintained either above or below the recommended pressure, the clutch will have a tendency to slip.** * **Incorrect:** While pressure below recommended causes slipping, pressure above recommended causes excessive clamping force, leading to grabbing or harsh engagement, not slipping. Excessive clamping force ensures maximum grip.