O.S. engine GT120THU, Instruction Manual

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the set voltage. For example, at the situation setting output voltage is 12V, the generator speedup ratio
of GT120THU is 3.94:1/ the counter electromotive force is 1.43 mV/ conversion efficiency is around
85%)
≒ 2,500rpm.
So when it drops lower than 2,500rpm, the output voltage will decrease proportionately.
8. COOLING SYSTEM
The engine cylinder block has to be cooled down while running since it is air-cooled. Since the propeller,
cooling fan and shroud are not provided with this engine. Prepare your own.
In case of making your own cooling system, the system is supposed to cool down the cylinder head
temperature (CHT fig. 4) lower than 180
℃
to make the engine work properly.
Fig. 4 shows the temperature measuring point.
Fig.4
9. INSTALLATION
(1) Engine
Bolts for mounting it on the aircraft are not provided as accessories. Purchase 6 pieces by yourself.
The strength level of the screws should be higher than 12.9, which can be used as cap screws. Also, the
screws for meshing part with the engine are suggested to around 7-8mm (tightening torque 5.4 N
･
m).
(2) Silencer
Mount the silencer which is included in the accessories with M5X25 cap screw and nord-lock washer
(tightening torque 7.2 N
･
m). Apply the liquid gasket which is gasoline resistant, on the joint surface to
prevent oil leakage from it (ThreeBond TB1212).
(3) Air cleaner
Mount the air cleaner on the carburetor with the attached hose band (tightening torque 1.0 N
･
m).
10. FUEL TANK
(1) Fuel consumption of the engine is
“100cc/min/7,000rpm (full load)” in this manual.
Decide a fuel tank capacity according to it.
(2) Choose a gasoline resistant fuel tank. Do not
use a fuel tank for glow engines because tank cap is
not gasoline resistant.
(3) Wash a fuel tank with gasoline before the first use
to wash off remaining plastic pieces and dusts.
Fig.5
(4) Do not use muffler pressure from a fuel tank.
Make sure to have an air vent pipe for ventilation.
(5) Use the following tube for piping: Tygon® F-4040A, Fluoro rubber or Nitrile rubber (I.D. φ3.0
～
3.2mm,