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Aluminum-Brass-Chrome. The components used in the production of non-ringed engines. These engines use an aluminum piston, and a chrome or nickel plated brass sleeve. The engine is harder to turn over and start due to the tight fit between the piston and cylinder. This tight fit is what makes the engine more efficient, and powerful. ABC engines must be run in for best performance.

After Run Oil
A lubricant designed to displace unburned fuel in the engine after running. The fuel can accelerate corrosion on some engine parts. By using an after run oil, the fuel is displaced, and a protective coating lines sensitive engine parts. This is an inexpensive engine insurance, and promotes long engine life. There are several good after run oils on the market.

Brake horsepower. A measurement standard used by manufacturers to help consumers compare engines. NOTE: BHP is measured at the maximum operating RPMof the engine, which may not be the RPM level at which your engine will provide maximum life and consistent performance.

Term used to describe the weighted end of the fuel pickup line in the fuel tank. The purpose of this is to ensure that the fuel pickup is always in the fuel supply, even when inverted

This effect is the bending of the rotor or propeller blades when stressed.

Dead Stick
Slang term for a landing without engine power.

Term describing the shape of the rotary wing or propeller formed by the spinning blades.

The methanol or gasoline fueled power plant used in a model. Two or four-stroke gasoline and glow engines are very popular in aircraft. Four-stroke engines tend to turn higher diameter lower pitch props, and therefore tend to be used in applications requiring more torque and less speed response.

The methanol/nitromethane/lubricant mix used to fuel model engines. A helicopter fuel mix has a higher concentration of lubricant to counter the lack of sufficient airflow over the engine in a hover.

Slang for a model using a gasoline engine as a power plant.

Glow Fuel
A Methanol based fuel, with a lubricating agent, used in most model engines. Most model fuels also use a percentage of nitromethane.

Glow Heater
This is used to heat the element in a glow plug, and is used when starting the model engine. AKA Ni-Starter.

Glow Plug
This is the plug that is used to help ignite the fuel in a model engine. The combustion of the fuel in the engine keeps the element hot between cycles, thus the glow plug does not need to be regulated or powered while the engine is running.

Header Tank
This is a small fuel tank used in line between the main tank and the carburetor. The purpose of the header tank is to ensure that the fuel fed to the carb is free of bubbles, which can be caused by foaming, or by the clunk falling away from fuel during complex maneuvers. Also, lets the pilot see the fuel level for helicopters which have a hidden fuel tank.

Helicopter Fuel
A fuel mix using a higher concentration of lubricant, to aid in the cooling of the engine in helicopter models.

Hot Start
An engine which has been running will tend to remain hot for a short time. During this period, it is possible to restart the engine by turning the crankshaft without the glow plug being plugged in to a glow starter. This is something to be aware of, as it could possibly create an unsafe condition.

Hydraulic Lock
Hydraulic lock happens when the engine becomes flooded with fuel, to the point where the piston cannot compress it in the combustion chamber. This can result in engine damage if the crankshaft is forced through a rotation without relieving the pressure. To cure, remove the glow plug, and pour out the excess fuel.

Refers to carburetor setting. When an engine is run too lean it will overheat, causing damage, and likely an in flight engine failure. Tuning a carburetor is best accomplished by starting rich, and working gradually to the condition which produces maximum power, while allowing a small amount of unburned fuel mixture to lubricate and cool the engine.

Lean Run
This happens when an engine develops a lean condition. Possible causes are improper tuning, improper fuel choice, fuel foaming due to excessive vibration, or a leak developing in the fuel delivery system. The air in the fuel line will cause the engine to run lean.

The agent used to aid in the reduction of friction between two parts. This term is used for many substances, which in turn are used in many different ways. They are all, however, used to reach the same objective, that being the reduction of wear between parts. In the case of engine fuel, the lubricant is added to the fuel at the factory in many cases. This might be castor, a synthetic, or a blend. The percentage of lubricant required in the fuel will depend on the type of fuel, the engine, and the model requirement. For helicopters, a higher percentage of lubricant is required, as the engine is not in a position to receive as much airflow. Thus the lubricant is also used as a coolant. Bearing grease, and oils for moving parts are other examples of lubricants.

The power band of an engine between idle and full throttle. The helicopter engine specifically requires more careful tuning for optimum performance in the midrange, as that is where the helicopter will hover.

Fuel to air mixture is determined by the needle valve on the engine carburetor.

Needle Valve
This is used to tune the fuel to air mixture on the engine carburetor. On most engines, the needle is turned clockwise to lean the mixture, and counterclockwise to richen.

Abbreviation for nitromethane. The addition of nitromethane in fuel provides more power, and a smoother idle, thus making the engine easier to tune. The nitro also makes an engine require more careful tuning, therefore, the amount of nitro added to a fuel results in a tradeoff. Common nitro mixes vary from 0% to 30% and beyond.

The addition of nitromethane in fuel provides more power, and a smoother idle, thus making the engine easier to tune. The nitro also makes an engine require more careful tuning, however, to avoid overheating. Common nitro mixes range from 0% (FAI fuel) to 30%.

Prop Balancer
Device designed to aid in the balancing of model airplane propellers.

This is the vibration frequency of a rotating or moving object. When the resonance of many parts of a machine are in synch, the whole machine will vibrate at a greater rate. This can cause vibration damage. Resonance can cause difficulties in an aircraft, particularly when using a vibration mount with an improperly balanced propeller/spinner wherein the engine is vibrating at one frequency and the propeller at another.

An engine which uses a piston with a piston ring. Compare to ABC or ABN. Best used in dusty environments, a ringed engine is less susceptible to damage from contaminants in the fuel/air mixture, but does not provide the higher compression ratio of the ABC/ABN engines.

The force which tends to cause rotation.

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