TM 5-5420-280-10
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THEORY OF OPERATION (Contd)
FUNCTION OF THE PALLET (Contd)
Palletized Load System Trailer (PLST). The pallet is transloaded from the CBT to
the PLST using the CBT LHS. The pallet can be maneuvered on the ground by its
own support wheels and steering system. The pallet has a self-contained hydraulic
and electrical system powered by a small diesel engine called the Launch Power
Unit (LPU).
FUNCTION OF THE PALLET LAUNCHER MECHANISM
The launcher mechanism is part of the pallet, and is made up of five major
components that work together to couple, extend, and emplace the bridge as follows:
(1) The launch boom functions to hold the bridge by its launch beam during
launch and retrieval. The launch boom contains a number of upper and lower
support rollers, a pin wheel drive unit, and a brake, which together support
and propel the bridge as it is extended and emplaced.
(2) The lower support boom functions to lift the launch boom under the weight of
the bridge as the bridge is coupled, extended, and emplaced. Two large
hydraulic cylinders connected to the lower support boom provide the necessary
force.
(3) The pin wheel drive units function to drive and retain the bridge, by means of
the bridge launch beam, during launch and retrieval. The gear on each pin
wheel drive unit is designed to engage with pins on the bridge launch beam to
move the bridge. A hydraulic cylinder, mounted adjacent to the rear pin wheel
drive unit, holds the bridge by means of end stop brackets mounted on the
bridge launch beam.
(4) The secondary boom functions to lower the upper bridge half during coupling
and lifts the upper bridge half during uncoupling. Two rollers on the
secondary boom keep the upper bridge half centered with the lower bridge half
for alignment during coupling.
(5) The winch functions to lower the ramp end of the upper bridge half by its
launch beam prior to coupling, and takes control of the bridge after coupling
by lowering the bridge to the ground.
HOW THE BRIDGE IS EMPLACED
In order to launch the bridge, the CBT is positioned on the shore, supporting
cylinders are lowered, and the LPU is started. A hand held remote control unit
(RCU) is used to operate the pallet launcher mechanism. Within the RCU is an
electronic Stored Program System (SPS) containing 22 functional steps required to
expand, couple, extend, and emplace the bridge. Each functional step is initiated by
the operator and is carried out either automatically by the SPS or manually by the
operator. Essentially, the two bridge halves are first expanded to roadway width.
Then the lower bridge half is driven out to the rear by the pallet's pinwheel drive
units. The upper bridge half is lowered and positioned so that the lower couplings of
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