1-10-15 Roller Assemblies
Several roller assemblies are mounted on the launch frame to guide and assist the
passage of the launch beam through the launch frame. At the bottom rear of the launch frame is a
pinch roller, which ensures that the launch beam is in contact with the launch beam drive during
the early stages of the launch beam deployment and the latter stages of the launch beam
At the bottom front of the launch frame is a twin set of rollers mounted on a common pivot
which support the launch beam during deployment. The pivoted arrangement ensures that both
sets of rollers remain in contact with the launch beam during deployment.
Six vertical side rollers mounted on the launch frame ensure that the beam is guided
centrally through the launch frame.
A roller assembly mounted on the top of the launch frame ensures that the winch rope fleet
angle is kept within limitations.
1-10-16 Drum Winches
A drum winch is installed on the upper and lower surfaces of the launch frame. Attached to
the winches are the wire cables used to control and operate the forward and rear carriages. The
winches each weigh approximately 1180 lb. (535 kg) with no wire rope reeved onto the drum.
Each winch comprises hydraulic motor-driven planetary reduction gearboxes inside a cast
aluminum drum. Although the gearboxes and the drums are identical, the hydraulic motor for the
forward carriage winch is of variable displacement. This minimizes back-tension during drive-out,
when the winch has to allow its wire rope to reel out quickly under low tension. A solenoid valve
with pressure limitation control selects the variable displacement.
Two additional solenoid valves, each with a reducing valve for brake pressure limitation,
independently control the brakes on both winches.
A winch rope tension device is fitted to each winch. This device ensures that the winch
rope is recovered onto the winch with the correct amount of tension, it helps to prevent incorrect
winch rope layering on the winch drum.
1-10-17 Launch Beam Drive Unit
a. The launch beam drive unit is mounted on top of the launch frame and is controlled from the
launch chest pack. The launch beam drive unit is comprised of two hydraulic motors, which
incorporate disc brake assemblies, that drive two shafts each of which has two urethane tired
rollers. Drive to the shafts is achieved through a duplex chain and sprocket arrangement.
The hydraulic motor weighs approximately 44 lb. (20 kg) and the whole beam drive unit
weighs approximately 220 lb. (100 kg).
1-10-18 Launch Valve
The hydraulic control of the launch beam drive unit is provided by one `slice' of a three-
`slice' load-sensing valve controlled electrically from the chest pack. The valve, which weighs