TM 5-3895-360-13
Section Ill. TECHNICAL PRINCIPLES OF OPERATION
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1-9.
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-7
1-10.
Tamper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-7
1-11.
Engine Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-7
1-12.
Starter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ......
1-8
1-13.
Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-8
1-14.
Reed Valve Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-8
1-15.
Ignition System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-8
1-9. GENERAL.
a. The tamper is hand-operated and controlled and can
fuel and air mixture to enter the combustion chamber.
be operated by one operator.
When the piston approaches Top Dead Center (TDC), the
fuel and air mixture is compressed in the combustion
b. The tamper is driven by a 2-cycle, air-cooled,gaso-
.
chamber. A spark plug then ignites the fuel and air mix-
Iine engine.
ture.Theresulting explosion forces the piston down and
rotates the crankshaft. As the piston moves down, it un-
c. Compact frequency is 700 cycles per minute at an
impact force of 2200 lb (999 kg).
covers the exhaust ports. This allows the exhaust to es-
cape and the pressure in the combustion chamber to fall.
1-10. TAMPER.
A tamping shoe is mounted at the lower end of a cylindri-
cal spring housing. A piston, installed between large op-
posing springs inside the spring housing, is put into
action by a connecting rod and crank assembly through
a gear train and centrifugal clutch. The piston alternately
loads and unloads the springs resulting in a rapid lifting
and dropping action of the tamping shoe. This action
compacts the underlying material.
1-11. ENGINE ASSEMBLY
Afresh supply of fuel and air mixture is compressed In the
crankcase by the downstroke of the piston. As the piston
nears the bottom of this stroke, it uncovers the intake
ports. Thetiel and air mixture rushes into the combustion
chamber equalizing the pressure between the crankcase
and combustion chamber. The fuel and air mixture flows
up and around the baffles, then down and out the exhaust
ports. This pushes the burned exhaust gases from the
cylinder.
The compression stroke now begins with the intake ports
and exhaust ports covered by the rising piston. As pres-
sure increases in the combustion chamber, it decreases
in the crankcase allowing a new fuel and air mixture from
the carburetor to enter through the reed valve, preparing
for the next cylinder charge.
When the engine is started, the crankshaft turns and the
piston rises, uncovering the intake ports. This allows a
1-7
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