Choosing The Right Engine

As might be expected, there are a wide variety of engine types and models to choose from.  PARMA HOBBY can help you make the right engine and fuel choice for your model R/C project.  The basic types of model engines are discussed next.

The Typical Nitro (Glow) Engine

RC engines work by burning a fuel.  The burnt gases expand and move a piston, which moves a rotating crankshaft, which in turn drives the airplane's propeller.

The fuel for most model airplane engines is something called "glow" fuel.  It is actually mostly a type of alcohol (methanol, please do not drink), plus nitromethane to help burning, plus some oil to help keep the metal parts lubricated.

It's called "glow" because the engine uses a glow plug instead of the spark plug found in regular gasoline engines.  In the glow plug, a heated element causes the fuel to burn.  The plug has a steady glow instead of an intermittent spark.  To start the engine, a battery is used to create the initial glow; after that, the heat of burning keeps the plug glowing, and the battery is removed (saving weight).

The typical glow model airplane engine is a "two-stroke".  The engine burns fuel (produces power) on every second stroke of the piston.

"Four-stroke" engines are also available, that produce power on every fourth stroke of the piston.  The four strokes are more complex and expensive, but quieter as well as more fuel efficient.

The Typical Diesel Engine

Diesel engines work the same as 2-stroke glow engines in that they are crankcase-charged.  Air and a kerosene-based fuel mixture are inducted into the crankcase (below the piston) through a carburetor or venturi.  The combustible mixture is then moved through cylinder transfer ports into the combustion chamber above the piston.  There it's compressed and heated to ignition.  The high compression of the air/fuel mixture causes ignition.  Thus, a glow plug or spark plug is not required.

The major difference between nitro and diesel engines is basically that the diesel has a low-rpm torque advantage while the nitro engine has the overall power advantage.   Summing it up, if you don't mind the kerosene fuel mixture smell, they offer a quiet, low-rpm, big-prop combination.

The Typical Gas Ignition Engine

Many large scale flyers opt for gas ignition engines.  These engines are cheaper to operate as they use common gasoline for fuel.  The gas ignition engine can be of either the two or four-stroke variety.  similar to a car engine, an "ignition system" is used to supply a spark, properly timed, to detonate the gas.

The Typical Jet Turbine Engine

All model jet engines work on the same principle.  At the front of the engine is a spinning compressor, similar to a automotive supercharger.  This draws the airflow into the chamber, slowing the air down and cooling it at the same time.

The fuel is normally kerosene.  It is introduced into the chamber as a very fine spray so as to mix with the air easily.  The air/fuel mixture is then ignited by a small glow plug, much the same as the common nitro glow engine.

The air/fuel mixture ignites and explodes within the chamber causing the temperature to rise quickly and the air to expand in volume.  This hot air moves out of the rear of the combustion chamber at a very high speed which generates the thrust to power your model.

A turbine is used at the rear of the jet turbine engine.  It is connected to the front compressor with a shaft that runs through the center of the combustion chamber.  The hot air exiting the engine causes the turbine to spin at a very high speed which, in turn, causes the front compressor to spin.  This results in even more air being forced into the engine and allows the whole process to continue.

A jet turbine engine is started by introducing compressed air to initially power-up the turbine.  Once the proper RPM is reached, the fuel is introduced into the combustion chamber bringing the engine to life.