to L1 and L2 to L2), as above. With most
equipment with which the AC unit may
be used, and with all ordinary lighting,
the relationship is unimportant.
4-3. Equipment Conversion (AC Unit)
Position the voltage change switch, S2, either
for 120 volt or 240 volt operation, as required.
Refer to figure 2-3, View A.
4-4. Procedures for Constructing Revetment
a. General. This equipment is designed to oper-
ate in the open with unrestricted ventilation. In
some situations it may be necessary to operate
the equipment from the protection of a revetment.
This paragraph provides information on the con-
struction of a revetment to protect the equipment
should it become necessary.
b. Dimensions. The
minimum allowable inside
dimensions are shown in figures 4-1 and 4-2. The
entrance to the revetment is shown in figure 4-3.
These minimum dimensions are based solely on
consideration of engine cooling and ventilation
allowing a minimum practical amount of space for
service and maintenance.
c. Foundation and Drainage.
If the generator
set is attached to a shipping platform, this will
provide an adequate foundation. Otherwise, use
planks, timbers, logs, ammunition boxes, or other
available material to prevent the skids from sink-
ing into soft earth or sand. In no case should the
foundation exceed a height of six inches; the
generator set should be situated on a level plane
not to exceed a tilt of 15° in any direction. Drain-
age must be provided to insure run-off of water
away from the generator set and out of the
revetment through drain holes at inside ground
level. Where there is no natural slope for the
water to run away from the revetment, a sump
and drainage trench must be provided outside of
the revetment for each required drain hole.
d. Wall Constructwn. The walls of the revetment
may be constructed with sandbags, ammunition
boxes filled with sand or dirt, or any other mate-
rial available. The wall height should not exceed 3
feet (0.91 meters) and should be constructed as
shown in figures 43 and 44.
e. Roof Construction. The
roof can be supported
by any means possible, but should be 1 foot (0.31
meters) above the wall of the revetment and
provide as much open space around the top as
possible. Refer to figures 4-2,4-3,4-4,4-5, and 4-6.
The materials used in the roof construction con-
sist of two pieces of lumber (4 inches by inches) or
logs (4 inches in diameter) about 10 feet (3.1
meters) long and the necessary cross pieces of
lumber, logs, or steel planking to cover the entire
roof as shown in figure 4-6. These cross pieces
should be about 8 feet (2.44 meters) long. If the
above materials are not readily available, any
available material of a like nature may be used.
The thickness of the roof (figs. 4-3 and 4-5) will
depend upon the amount and type of protection
desired. Caution should be taken when adding
protection to the roof to insure that the roof is
supported properly to carry the additional weight.
f. Miscellaneous Construction.
should be constructed for fuel storage outside of
the revetment as shown in figure 4-1. The size of
the fuel storage area will depend upon the size of
the fuel container being used. Since air tempera-
tures within the revetment will build up consider-
ably above the outside ambient when the genera-
tor set is operating, always locate. the fuel supply
outside the revetment to minimize safety hazards
associated with gasoline at high temperatures.
For the same reason, it is recommended that the
integral fuel tanks, with which some generator
sets are equipped, not be used. The exhaust from
the generator set is to be ducted out of the
revetment. The installation should be similar to
that shown in figure 4-7. If flexible pipe is not
available to use for an exhaust extension, a piece
of exhaust pipe or any other similar material may
be utilized. The point at which the exhaust dis-
charges goes through the revetment wall depends
entirely upon the equipment that is available. The
exhaust may be discharged into an external ex-
haust chimney constructed as shown in figure 4-1.
This chimney will aid in ducting the exhaust
gases away from the revetment and will reduce
the noise level. A revetment doorway shield must
be constructed as shown in figures 4-1, 4-2, and 4
6. This shield is a wall 3 feet (0.91 meters) high
and 7.5 feet (2.26 meters) long, constructed in a
manner similar to the revetment walls to prevent
direct entrance of projectiles or fragments
through the doorway into the revetment.
g. Alignment Instructions.
the revetment, the orientation of the revetment
will be such that its entrance is facing into the
direction of the prevailing wind (fig. 4-1). Each
generator set will be located within the revetmen
so that its long axis is parallel to the long axis of
the revetment and is centered within the revet-