The Basic Engine


The primary engine type used by modelers today is a single cylinder, two (2) cycle, air cooled reciprocating engine that uses a glow plug ignition and a special fuel mixture of methanol, nitromethane, and castor oil. Most of the components of the engine are made of cast, forged, or machined aluminum. The power that can be achieved from these small engines is phenomenal and can vary greatly from one design to another. A typical inexpensive .40 size engine can produce 1.1 horsepower at 11,500 RPM. The same size racing engine can produce 2.4 horsepower at 20,000 RPM. All of these engines are the same in their basic components.

Typical Engine

Air bleed screw - Screw for adjusting the amount of air allowed to bleed into the carburetor during idle
Backplate - Cover over the rear of the crankcase
Carburetor - Device which mixes fuel and air and controls the amount of mixture entering the engine
Crankcase - Main body of the engine
Cylinder - The section of the crankcase where combustion takes place
Glow plug - Device which provides heat for ignition of the air/fuel mixture
Head - The component which forms the end of the compression chamber of the engine
Mounting lug - The section of the crankcase used to mount the engine to the airplane
Muffler - The device which reduces the noise level of the engine
Needle valve - The device used to adjust the air/fuel mixture
Prop shaft - The main crankshaft which transfers the power of the engine to the propeller
Throttle stop screw - Screw for setting the lower limit of the throttle movement

The design of the engine affects its power output, reliability, and longevity. The prop shaft is supported by bushings or bearings. Wear takes place between the piston and cylinder wall and the prop shaft and bushings or bearings. Most engines on the market today are classified as ABC meaning the they have an aluminum piston and chrome plated bronze cylinder sleeve. This combination normally produces an engine that yields many hours of trouble free operation if properly maintained. Those engines that have ball bearings for supporting the prop shaft normally produce about 25% more power and last much longer.

New .40 size engines can range from $55 to over $400. There are several that are accepted due to price, reliability, easy starting, and longevity.

BEST ENGINES
(In no particular order)
Click on the designation for additional information
MANUFACTURER DESIGNATION DESCRIPTION
OS 40 FP Inexpensive, easy to start, reliable, most widely accepted entry level engine
OS 40 LA Inexpensive, easy to start, reliable, newest entry level engine
OS 46 FX More expensive, easy to start, reliable, very powerful, sport and competition engine
Thunder Tiger GP40 Inexpensive, easy to start, reliable, fastest growing acceptance for entry level engine
Thunder Tiger Pro40 More expensive, easy to start, reliable, powerful, sport and competition engine
Magnum GP40 Least expensive, easy to start, reliable
Magnum Pro40 More expensive, easy to start, reliable, powerful, sport and competition engine
Super Tigre GS40 More expensive, reliable, powerful, sport and competitionengine
Enya 40TV More expensive, easy to start, reliable, powerful, sport and competition engine

These entry level engines are more than adequate for the average trainer and are a good investment. They will normally outlast several trainer airplanes if properly maintained.