Section VII. UNDERWATER VENTILATING SYSTEMS
a. Combat and transport vehicles, if expected to
compound. In addition, special gun shield covers are
used to prevent entrance of water around the shield.
ford deep water or operate in surf landings, must be
Special air intake and air exhaust stacks (fig. 36-20)
specially prepared or equipped to go through such an
must be installed, and sealing boots placed on
operation and be used immediately. This means that the
machinegun ports in the hull.
vehicle must be able to go through fording or landing
operations and continue to operate in a normal condition;
that is, the special preparations must not reduce the
operative effectiveness of the vehicle.
a. Operation of a transport vehicle under water
b. Late-type ordnance transport vehicles are
is made possible by the sealing, at time of manufacture,
specially designed and built for fording and landing
of all parts or assemblies that are affected immediately
operations without modifications. Necessary
by the entrance of water. Watertight housings are
waterproofing and engine-accessory ventilating
provided for such parts as the instruments, switches,
systems are already installed on such vehicles. All
starter, generator, regulator, and distributor.
breathing mechanisms on the vehicles are connected to
the carburetor air cleaner and secure air through it. Most
b. A series of ventilating tubes (fig. 36-21) are
important is the engine, which requires large amounts of
required to provide venting of various accessories, as
air for operation. But in addition, the carburetor float
chamber, brake master cylinder, fuel tank, transmission
and transfer, ignition distributor, and the crankcase
(1) The carburetor float chamber is vented
ventilator are all vented through the air cleaner. For
to the air horn by an internal passage and is extended to
normal fording operations where a specified depth will
the air cleaner tube by an external tube (6).
not be exceeded (for example, 30 inches on the 1/4-ton
4x4 utility truck M151), no special preparations are
(2) The brake master cylinder is vented
required. For deepwater fording, special air intake and
through the tube (5) that extends up between the foot
exhaust extension tubes must be installed. These raise
pedals to the dash elbow (4), mounted on the dash, and
the height of the intake and exhaust so that deeper water
the dash elbow to the dash tee tube (3) to the dash tee
can be forded. All instruments, switches, starter,
(15), and the air cleaner to the dash tee tube (14) to the
generator, regulator, battery vents, ignition filter,
distributor, and ignition cables are waterproofed,
because they will be immersed during fording operations.
(3) The fuel tank is vented through the
gasoline tank to the air cleaner vent tube (2) which
c. With tanks and tanklike vehicles, the
connects to the air cleaner.
problems of waterproofing and engine ventilation are
different from transport vehicles. With tanks, the hull
(4) The transmission and transfer are
itself must be made waterproof so the individual engine
vented through the transfer to the dash tee vent tube
components do not require special treatment or venting.
(13) connected to the top of the transfer to the air cleaner
On this type of vehicle, all normal or abnormal openings
through the dash tee (15) and the air cleaner to the dash
(cracks, seams, and holes) must be sealed tightly so that
tee tube (14).
no water can enter when the tank is immersed.
Examples of normal openings that must be sealed
(5) Positive circulation of air through the
include filled caps, machinegun mounts, and hull
distributor housing is ensured by connecting the
ventilators. These generally are sealed by use of
distributor to the vacuum line tube (11) and the
nonhygroscopic tape and sealing compounds. Examples
distributor to the air cleaner tube (12). One tube (11)
of abnormal openings that must be sealed include holes
from the air cleaner provides an air intake for
(missing bolts, etc) and cracks or seams in the hull.
These can be sealed by first caulking the larger holes
with rags, and then covering all openings with sealing