TM 5-1940-322-10
GENERAL INFORMATION
BRIDGE ERECTION BOAT (BEB)
MKII-S
NSN 1940-01-526-0770
P/N 12492423
THEORY OF OPERATION
GENERAL
This section explains how components of the BEB work. Functional descriptions of
components and their operation are covered in the following paragraphs.
FUNCTION OF THE PROPULSION SYSTEM
The propulsion system creates thrust by drawing in water through inlet grills on
the underside of the hull and expelling it through nozzles at the stern. Thrust is
generated by two hydrojet units mounted side-by-side on the transom. The hydrojet
contains a large impeller that functions as a high velocity water pump, and the force
with which the water is expelled depends on engine speed. Each hydrojet is powered
by a diesel engine in conjunction with a transmission. The transmission has a
neutral position, one forward and one reverse gear, and transmits power from the
engine to the hydrojet through a driveshaft. Thrust from both hydrojets is directed
by moving the position of the steering deflectors and reverse deflectors (scoops).
FUNCTION OF THE STEERING SYSTEM
The scoop is a moveable metal shield that deflects the flow of water from the
nozzles, and each scoop is controlled independently by a separate control lever. In
the neutral position, the scoops direct the thrust straight down. To propel the boat
forward the scoops are raised to allow thrust to the stern. To reverse the boat, the
scoops are lowered to deflect thrust towards the bow. At forward speeds, steering is
accomplished by controlling the position of the steering deflectors on each hydrojet
by way of the boat's steering wheel, or by use of both scoop controls. When stopped,
or at low speeds, steering is made possible by placing one scoop in the reverse
position, and the other in the forward position and by using the steering wheel. In
addition, steering is affected by the amount of thrust generated at a given engine
speed.
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