Smoke Signals From The Bench
Engine Basics
The two stroke model engine is usually referred to by its size in terms of its swept volume.
This is known as the area of the top of the piston times the distance the piston travels up
and down.
Trainer aircraft models typically use engine sizes 20, 40 or 60. The decimal is left out of
the number but it represents the engine capacity as .20, .40, and .60 cubic inches of
volume respectively. This is equivalent to (Cubic inches x 16.39 = Cubic centimeters) 3.278,
6.556, and 9.834 cubic centimeters (CC’s) respectively.
Gas engines for giant scale aircraft models are also identified in terms of their capacity.
A Quadra 42 CC gasoline model engine is equivalent to approx. 2.56 cubic inches of
capacity. (42 CC’s divided by 16.39).
The most prevalent model aircraft engines are the two stroke glow type engines. They
have a small coil that is heated using a battery to start the engine. Once the engine is
started the battery is removed as the energy within the engine cylinder maintains the coil
at the proper temperature.
The two stroke or two cycle principle is quite simple, fuel is burnt and power is produced
each time the engine piston reaches the top position within the engine cylinder. The fuel
most commonly used is alcohol based with a percentage of lubricant, typically 5 to 15
percent.
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