Model engine
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For the band (previously known as Black Eyed Sceva), see Model Engine.
In radio-controlled modeling, a model engine is an internal combustion engine used to power a radio-controlled aircraft, radio-controlled car, or radio-controlled boat; the fully-functional, albeit small, engines vary from the most common single cylinder two-stroke to the exotic multiple cylinder four-stroke, the latter taking shape in both the v-twin and radial form. Most model engines run on a blend of methanol, nitromethane, and lubricant (either castor or synthetic oil). They range in typical size from .12 cubic inches (2 cubic centimeters) to .5 ci (8 cc) and generate between .5 horsepower (370 watts) to 3 hp (2.2 kw). While the methanol and nitromethane blend engines are the most common, it should be noted that new generation models are coming out with gasoline engines. This article concerns itself with the methanol engines; gasoline powered model engines are similar to those built for use in string trimmers, chainsaws, and other yard equipment.
[edit] The role of the glowplug
Glow plugs are used for starting as well as continuing the power cycle. The glow plug consists of a durable, mostly platinum, helically wound wire filament, within a cylindrical pocket in the plug body, exposed to the combustion chamber. A small direct current voltage (around 1.5 volts) is applied to the glow plug, the engine is then started, and the voltage is removed. The burning of the fuel/air mixture in a glow-plug model engine, which requires methanol for the glow plug to work in the first place, and sometimes with the use of nitromethane for greater power output, occurs due to the catalytic reaction of the methanol vapor to the presence of the platinum in the filament, thus causing the ignition. This keeps the plug's filament glowing hot, and allows it to ignite the next charge. Since the ignition timing is not controlled electrically, as in a spark ignition engine or by fuel injection, as in an ordinary diesel, it must be adjusted by the richness of the mixture, the ratio of nitromethane to methanol, the compression ratio, the cooling of the cylinder head, the type of glow plug, etc. A richer mixture will tend to cool the filiment and so retard ignition, slowing the engine, and a rich mixture also eases starting. After starting the engine can easily be leaned (by adjusting a needle valve in the spraybar) to obtain maximum power.
