lock block from under the latch cam follower and frees
the latch so that the grab and shuttle can be separated.
Cables and Lead Sheaves
The cable system (fig. 4-36) transmits energy from
the retraction engine to the grab. The cables are reeved
around the sheaves in the retraction system. The cables
are made of 9/16-inch-diameter wire rope. Each of the
two main lengths is fitted at one end with a swaged
cable fitting bolted to the grab. The opposite ends are
reeved around the cable equalizer sheaves and clamped
together with five cable clamps for each set of cables.
The cables stretch with use. To compensate for the
stretch, it may become necessary to retension the cables
and readjust the cable clamps.
The sheaves guide and support the cables between
the shuttle track and the retraction engine. Numerous
lead sheaves are used to guide the cables from the grab
to the retraction engine and change the cable direction
as required by the ship’s installation.
Two fixed-idler sheaves are mounted on the
cylinder and two on the fixed sheave installation at the
buffer end of the retraction engine. These sheaves lead
the cables to the cable equalizers.
The two fixed-lead sheaves mounted near the
cylinder extension on the retraction engine turn the
retrieving cable 90° as it enters the retraction engine.
Crosshead and Fixed-Sheave Assembly
The crosshead and fixed-sheave assembly (fig.
4-35) converts the longitudinal motion generated in the
retraction engine cylinder into motion of the cables that
operate the grab. The crosshead is essentially a frame
bearing four nests of sheaves with eight sheaves in each
nest. The crosshead is installed on the external end of
the retraction-engine piston and is fastened with a
piston-rod cap, nut, and nut lock. Rollers are mounted
on both ends of the shafts, and travel on crosshead
guides in the support assembly, which keep the
crosshead and sheaves level during operation.
The fixed-sheave assembly consists of two nests of
fixed sheaves mounted on the cylinder extension of the
retraction engine cylinder and two nests on the
retraction engine buffer cylinder. These nests are similar
to those mounted on the crosshead, except the guide
rollers are not provided.
Figure 4-39.—Cable equalizer.
4-30
