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Cushioning Piston - 14001_93
Operation - 14001_95

Aviation Boatswains Mate E 3 & 2 - Aviation theories and other practices
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SHEAVE DAMPER Because of the high engaging velocities of modern carrier-based aircraft, cable tension and vibration would be excessive unless eased by the shock absorption provided by the sheave damper. The sheave damper reduces peak cable tension and lessens cable vibration. In figure 3-20, a sheave damper assembly is mounted to the ship’s structure below each port and starboard retractable or fixed horizontal deck sheave. The port and starboard assemblies are identical; therefore, only one will be discussed. Description Each sheave damper assembly consists of a movable crosshead assembly, damper cylinder assembly, damper piston, damper accumulator and fluid piping, buffer assembly, and charging panel. The system is also equipped with a common fluid stowage tank, which provides a stowage space for fluid in the sheave damper assembly while maintenance is being performed. The tank is capable of stowing all the fluid in one sheave damper installation. The crosshead assembly consists of one roller bearing sheave mounted between a steel base plate and a side plate that are bolted together. A sheave shaft, mounted through the bottom of the base plate, is secured to the side plate by a cap and setscrew. A yoke is bolted between the side plate and the base plate and provides a means of connecting the crosshead to a clevis that is screwed onto the end of a piston rod. The crosshead rides in a track mounted in a horizontal position on the bulkhead. Phcnolic slippers, at all four corners of the base plate, provide a bearing surface between the crosshead and the track. Attached to the crosshead is a cam that actuates a limit switch when the crosshead is fully retracted and causes a green light to light at the deckedge control station. This indicates to the deckedge operator that the sheave damper is in its BATTERY position. The damper cylinder assembly is secured to the ship’s structure by brackets, which are welded to the bulkhead and bolted to the cylinder. A cylinder cap Figure 3-20.—Sheave damper installation. 3-24







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