Here are some terms and function that may
come across with various R/C engines.
A standard 2 stroke engine usually has one fuel inlet port on the
side of the cylinder opposite the exhaust outlet. On a Schnuerle ported
engine there are several fuel inlet ports on three sides of the cylinder
allowing more fuel to flow to the combustion chamber. This gives more
power than standard porting. A Schnuerle ported engine is usually a little
more expensive because of the higher manufacturing costs involved.
Long or Short Glow Plugs
There are two lengths of plugs available. The short plugs are used
on engines of .15 cu in displacement and smaller. The long plugs are used
on all engines greater than .15. It is best to follow the manufacturers
Idle Bar Glow Plugs
An Idle Bar Glow Plug has a metal bar across the bottom of the plug
which prevents raw fuel from dousing heat from the element during idle.
Idle Bar plugs have long been a topic of discussion at the flying field.
Many flyers swear by them while others question their usefulness.
The stroke of an engine refers to the distance the piston travels
from top to bottom. In a Long Stroke engine this distance is a bit longer
than on the standard engine making the engine stronger in torque and operation
at lower RPM. Quite often an engine is "Long Stroke" if the stroke distance
is greater than the diameter of the piston.
The size of an aircraft propeller is described by two numbers; the diameter
times the pitch in inches. For example, a 10 x 6 propeller is a propellor
of 10" in diameter with 6" of pitch. The diameter is simply the length
of the prop. The pitch is described as the distance the propeller will
travel forward in a perfect or solid medium at 100% efficiency in one
revolution. That is to say, if you were to rotate your 10 x 6 propeller
exactly once, your plane would move ahead 6", assuming this could be done
with 100% efficiency.
Different sizes of engines require
different size propellers to keep their operating RPM's within the optimum
range. But it is useful to know, that the same size prop made by two different
manufacturers could well perform differently. Experimentation is the best
way to come up with the best performing propeller fro your particular
engine and aircraft combination. As a guide to the right propellor to
use on your engine see 'Choosing
The Right Propellor'. Again, it's best to follow the manufacturers
Thread & Shaft Sizes
It is important in knowing the shaft size of your engine when ordering
spinners, spinner adapter nuts, safety spinners and prop nuts.