TM 55-4920-384-13&P
GENERAL INFORMATION
AND DESIGN
R.P.M.
HORSEPOWER
1400
24.5
Wisconsin engines are of the four cycle type, in
1600
27.6
which each of the four operations of suction, com-
pression, expansion and exhaust requires a complete
1800
30.2
stroke. This gives one power stroke per cylinder for
2000
32.4
each two revolutions of the crankshaft.
2200
34.5
COOLING
2400
36.0
Cooling is accomplished by a flow of air, circulated
The horsepower given in the chart is for an atmos-
over the cylinders and heads of the engine, by a
pheric temperature of 60 Fahrenheit, at sea level,
combination fan-flywheel encased in a sheet metal
a n d at a Barometric pressure of 29.92 inches of
shroud. The air is divided and directed by ducts and
mercury.
baffle plates to insure uniform cooling of all parts.
For each inch lower Barometer reading deduct 3%
Never operate an engine with any part of the
from above horsepower.
this will retard
shrouding removed, because
the air cooling.
For each 10 higher temperature there will be a re-
duction in horsepower of 1%.
CARBURETOR
For each 1000 ft. altitude above sea level there will
The proper combustible mixture of gasoline and air
be a reduction in horsepower of 3%.
is furnished by a balanced carburetor, giving correct
The friction in new engines cannot be reduced to the
fuel to air ratios for all speeds and loads.
ultimate minimum during the regular block test, but
engines are guaranteed to develop at least 85 per
IGNITION
cent of maximum power when shipped from the fac-
The spark for ignition of the fuel mixture is furnish-
tory. The power will increase, as friction is reduced,
ed by a high tension radio shielded magneto driven
during a few days of operation. The engine will
off the timing gears at crankshaft speed. The mag-
develop at least 95% of power shown on chart when
neto distributor rotor turns at half-engine speed. T h e
friction is reduced to a minimum.
magneto is fitted with an impulse coupling, which
For continuous operation allow 25% of horsepower
makes possible a powerful spark for easy starting.
shown, as a safety factor.
Also, the impulse coupling automatically retards the
timing of the spark for starting, thus eliminating dan-
INSTRUCTIONS FOR
ger of a kick-back from the engine when cranking.
STARTING AND OPERATING
LUBRICATION SYSTEM
Some of these engines are covered with a sheet metal
house, as shown in Fig. 2, and are called p o w e r
A gear type pump supplies oil to four nozzles which
units. Others are furnished without a house, as shown
direct oil streams against fins on the connecting rod
in Fig. 1, and are called open engines.
caps. Part of the oil enters the rod bearing through
holes in the rods, and the balance of the oil forms a
On engines with a house, the side doors must
spray or mist which lubricates the cylinders and all
always be removed when operating, so that
other internal parts of the engine. An external oil
cooling air will circulate properly.
line from the oil header tube in the crankcase lubri-
cates the governor and gear train, see Fig. 4.
LUBRICATION
Before starting a new engine, fill the oil base with
GOVERNOR
the correct grade of lubricating oil, as specified in
A governor of the centrifugal flyball type controls
the "Grade of Oil" chart. Fill through the breather
the engine speed by varying the throttle opening to
tube shown in Fig, 5, with 6 quarts of oil; 5 quarts
suit the load imposed upon the engine. All engines
for the crankcase and an additional 1 quart is re-
are equipped with either fixed speed governors, a
quired if engine has a Military type oil filter.
variable speed regulator to control the governed
After the engine has been run-in, as per instructions
speed of the engine, or an idle control.
on inside of front cover, the oil lines and oil filter
will have been filled with oil. Shut off the engine and
ROTATION
check the oil level by means of the oil gauge saber,
The rotation of the crankshaft is clockwise when
as shown in Fig. 6. If necessary, add enough oil to
viewing the flywheel or cranking end of the engine.
bring the level up to the fu// mark. An oil saber is
This gives counter-clockwise rotation when viewing
located on the left hand side of the engine below
the power take-off end of the crankshaft. The flywheel
the oil filler and breather tube, and if specified a
end of the engine is designated the front end, and the
saber can be furnished on the opposite side as shown
in Fig. 6.
power take-off end, the rear end of the engine.
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