Figure 4-36.—Linear retraction engine drive system,
system to advance the grab up to the shuttle after
launching, and retract the grab and shuttle to
BATTERY position.
Grab
When driven by the retraction engine, the grab
advances the length of the shuttle track, automatically
engages with the shuttle, withdraws the shuttle to the
BATTERY position, and secures it until the grab
unlocking mechanism is actuated by the bridle
tensioner.
The grab (fig. 4-37) is a spring-loaded latch,
mounted on a wheel frame and installed within the
shuttle track behind the shuttle. The two retract cables
are fastened to the aft end of the grab, and the two
advance cables to the forward end. After a launching,
the grab is pulled forward the length of the shuttle track
by the drive system, and automatically latches to the
shuttle with a positive-locking device. Diagram A of
figure 4-38 shows the grab in the UNLOCKED
position, approaching the shuttle. When the grab latch
(5) comes in contact with the shuttle clevis pin (6), the
latch rotates and the latch cam follower (8) moves out
of the cam detent (7) in the lock block (9) and
continues upward until it reaches the top surface of the
lock block. The spring-loaded lock block then moves
under the cam follower, trapping the latch and locking
the grab to the shuttle clevis pin, as shown in diagram
B. The grab will not release the shuttle until both have
been returned to the BATTERY position and the grab
unlocking mechanism
is actuated by the bridle
tensioner. When the bridle-tensioner piston rod moves
forward, the bridle-tensioner buffer cap (11) pushes the
grab pushrod (1) inward until the buffer cap contacts
the grab block (2). When the pushrod is pushed inward,
the lock block (9) is pulled from under the latch cam
follower and the latch is free to rotate and release the
shuttle, as shown in diagram C. When the shuttle and
bridle tensioner move away from the grab, the grab
remains in the UNLOCKED position, as shown in
diagram A. During no-load tests, the grab and shuttle
must be unlatched. The grab is manually released from
the shuttle, as shown in diagram D. A manual-release
disengaging lever (12) is placed over the manual-release
arm (3), which is accessible through the track slot,
lifted up and pushed forward. This motion pulls the
4-28
