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 ships structure below each port and
starboard retractable or fixed horizontal deck
The port and starboard assemblies are
identical; therefore, only one will be discussed.
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
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
ships structure by brackets, which are welded to the
bulkhead and bolted to the cylinder. A cylinder cap
Figure 3-20.Sheave damper installation.