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Cables and Lead Sheaves
Advance buffer

Aviation Boatswains Mate E 3 & 2 - Aviation theories and other practices
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Cable Equalizers RETRACTION SYSTEM The two cable equalizers, one for the advance cables and one for the retract cables, maintain equal tension on each cable. They also minimize whip in the cable system when the retraction system is operated. The cable equalizers also provide a means for adjusting the position of the grab in its battery position, thus setting the shuttle to its ideal BATTERY position. Each equalizer consists of a cylinder, a piston rod, and an adjusting shaft. The cylinder is bolted to the equalizer support structure of the retraction engine (fig. 4-39). The advance and retract cable equalizers operate hydraulically to keep the retraction engine cables tight. Hydraulic fluid under pressure flows directly into the cable equalizer, keeping tension on both sets of cables. When one set of cables is loaded, the other set becomes slack. Slack is taken out of the retraction-engine cables by motion of the equalizers. An orifice check valve in the hydraulic line back to the cable-equalizer reservoir slows the flow of the fluid and prevents fast motion of the piston when load is applied. This also permits rapid flow when removing slack. When one cable equalizer is working, the adjusting nut on the opposite equalizer is bottomed and acts as a cable anchor. The retraction engine, in figure 4-35, provides the power to retract the shuttle after the catapult has been fired. It is also used to maneuver the grab forward and aft. The retraction engine is a double-acting hydraulic cylinder unit, transferring its motion by means of a crosshead to the cable drive system. To advance the grab, pressurized fluid enters the advance chamber of the retraction-engine cylinder. This forces the piston and attached crosshead to move. The forward motion is stopped by the advance buffer. To retract the grab, pressurized fluid enters the retract chamber of the cylinder. This reverses the action of the piston and the crosshead. The retract motion is stopped by the retract buffer. Retraction Engine Cylinder and Piston The retraction engine cylinder and piston (fig. 4-40) are the main components of the retraction engine. When pressurized hydraulic fluid enters the advance chamber of the retraction engine cylinder, the piston moves into the cylinder. The motion of the piston is carried to the crosshead and the drive system cables, causing the grab to move forward. When pressurized hydraulic fluid enters the retract chamber, the piston is forced out of the cylinder. The motion of the crosshead and the drive system cables is reversed, causing the grab to move aft. Figure 4-40.—Linear retraction engine cylinder and piston. 4-31







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