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Please note: The Web version of this article is different from the version that printed in the April issue of MA.

BOB ABERLE CONCEIVED the “From the Ground Up” article series to enable all new pilots to get the most from their RC modeling experience. As successful as his concept was, Bob was also so successful in the execution of the first two parts--radios and electric power--that it is a challenge to even try to continue the series. But try I will, and I hope to continue the spirit and detail of Bob’s series.

As Bob covered so well in his radio series, "From The Ground Up" will continue detailed coverage of all aspects of becoming a successful, experienced model pilot. Selecting and building that first airplane, learning to fly it, maintaining it, progressing beyond the solo, and those first steps after the trainer will be discussed.

However, gaining experience as a pilot first requires flying! For the pilot to get flying practice, the airplane has to leave the ground, and the most common way to make that happen is to drag it up there behind an engine. That makes engines the next step in this series.

Having the correct engine for the airplane, making it easy to start, and running it reliably and without excessive wear are some of the most important aspects of learning this hobby/sport. Learning to fly is challenging enough without having to worry about flights that end too quickly and far too quietly.

If you are flying with an instructor (always recommended), engine failure too far from the runway is almost the only way your trainer will be damaged during your flight instruction (if you follow Bob’s great radio advice). Having to repair your airplane may improve your building skills (covered later in the series), but it does little to speed your flight training.

So the goal here is to present engines, installation, mufflers, break-in and tuning techniques, fuel, fuel tanks and supply lines, propellers, support equipment, spinners, maintenance, minor repair, and, above all, safety practices in as much detail as possible to help you forget about your engine while you are learning to fly. Your engine is important but should not be the center of your attention during the early stages of becoming a model pilot.

The engine theory presented is intended solely to provide beginning RC pilots with enough knowledge of its workings to understand why choices regarding mixture settings, fuel selections, propellers, and other topics will be made.

There is no intent to fully detail an engine’s intricate workings. The new RC pilots are not going to be designing or disassembling (hopefully) their first few engines, but they will be setting high- and low-speed mixture settings.

All the theory presented will be strictly from an operations viewpoint. Proper engine operation is my only goal in this discussion. As with most things mechanical, a model-engine’s true operation is complicated.

Operations that are separately explained and appear to be independent actually overlap, and sometimes interfere with, other operations. But I will explain each operation as if it were the only action happening at that time, to simplify the theoretical presentation.

Click on photo to view large image with caption

What is this tool called a model “engine”? It is an air- and fuel-cooled, fuel-lubricated, venturi-fed, catalytically enhanced (the glow plug) combustion-ignition machine constructed from aluminum, with some steel in high-stress areas. It is designed to convert a fuel’s chemical energy into something that will turn a propeller.

Considering each aspect of that boring description helps you understand and avoid some of the most common model-engine problems. Having a machine convert fuel into mechanical energy releases heat. This heat has to be removed, or the machine will literally begin to melt and fuse its moving parts.

Our engines remove this heat by directing the propeller’s airflow over most of the engine; they are air-cooled. But airflow is a poor means of engine cooling. Unlike water or glycol (antifreeze), air is not the best “heat exchanger” and does not reach all parts of the engine equally. The parts in the propeller’s slipstream receive more airflow than parts that are not. Plus the air does not remain in contact with the engine for long and therefore does not have time to absorb much heat.

Unlike water-cooling, the cooling air cannot reach deep into the engine to cool the moving parts directly. Our engines use “fins” to increase the surface area contacted by the cooling air, but air-cooling remains a surface-contact process and is thus inherently inefficient.

To help remove heat the air can’t, our engines use fuel cooling as well. The lubricating oil in the fuel acts as a heat exchanger while the fuel’s methanol cools the lower internal engine parts by refrigeration.

Refrigeration, you ask? Methanol cools our engines' lower areas because it has a high heat of evaporation. During carburetor air intake, methanol in the fuel is transformed into a gas requiring a great deal of heat. The refrigeration process removes heat from the surrounding lower engine sections to have the energy to transform the methanol. But I don’t suggest you try using this “refrigerator” to keep your iced tea cold.

The fuel also helps cool the engine’s combustion chamber. Some of the fuel’s oil content is not burned during combustion but does absorb heat. As the heated oil is exhausted, it removes that absorbed heat. The important point to remember is that the fuel cools the engine as it powers it.

Equally important, our model fuel is the engine’s sole lubrication source. The fuel contains oil that keeps the moving parts separated from each other, reducing friction and lowering the engine’s temperature.

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