beam passes the safety stop without hitting it. If no new beam is attached, and the launch beam
is boomed forward the stop block would foul the safety stop and restrain the launch beam.
1-10-24 Forward and Rear Carriages
The forward and rear carriages are similar assemblies manufactured from aluminum alloy
232B. They consist of upper frames and lower bridge lifting beam assemblies pinned together by
shoot bolts. They are operated and moved by the drum winches on the launch frame.
Two roller assemblies are mounted on the top of each upper frame assembly and support
the carriages on the launch beam. The roller assemblies consist of two rollers which roll on the
launch beam and a free running central roller which allows the winch rope to run under the
carriage rollers. Grooved pulleys are installed on both the upper assembly and on the lower
assembly to allow separation of the two halves to lower the bridge.
The lower bridge lifting beams also incorporate attachment points for the bridge lifting
slings. The upper and lower assemblies are fitted with attachment lugs to enable the assemblies
to be manually pinned together. When the pins are removed from the upper and lower
assemblies, the lower drum winch can be operated to raise or lower the bridge.
Steel wire ropes from the drum winches on the launch frame are routed around the launch
beam modules to the forward and rear carriages. When the rope from the upper drum winch is
tensioned and the rope from the lower drum winch is paid out, the forward carriage is moved
along the launch beam.
Fig 1.8 Forward and Rear Carriages
When the bridge is attached to both forward and rear carriages, this action moves both
carriages along the launch beam. Hydraulic control of the drum winches is achieved through the