Abe's RC Airplanes
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RC Airplanes - Frequently Asked Questions and Information

RC Airplanes - Frequently Asked Questions 4 & 5

4. What are the elements of an electric power system of rc airplanes?

The power system of rc airplanes includes a battery, a motor, a control, and wiring. The battery is almost always made up of Sanyo NiCd cells in the appropriate number. Motors vary from the simple, cheap "can" type (otherwise known as "540" or "550" style), through more sophisticated styles adapted from RC car motors, up to the cobalt powerhouses.

Controls can be a simple on-off switch controlled by a servo, a directly controlled on-off switch, or a proportional electronic control.

If you are going to fly a glider or old-timer type rc airplane with less than a 500-watt motor, think seriously about getting battery packs made of Sanyo 900 SCR cells. They are significantly lighter than the more usual 1200 mAH (sub-C) cells and give excellent performance.

5. What do the various letters used to refer to NiCd cells mean?

SC is the basic cell. SC cells will take fast charging and have reasonably low internal resistance. SCR cells have lower internal resistance and a somewhat flatter discharge curve, that is, they put out nearly the same voltage from beginning to end of the discharge. SCRs are best for high current drain applications. SCE cells have somewhat more capacity for the same physical size, but also have higher internal resistance. They are best for low current drain use (less than about 10 Amps.) The higher capacity of SCE cells will not be realized at high current drains, and they will heat up more than SCR cells.

Many rc airplane kits nowadays come with a power system. In most cases, these systems are adequate for the application. It won't hurt to try what's there to start with; you can always experiment later. If the kit you choose doesn't come with a motor, of course, you'll have to choose one. If you are a beginner, go with the recommendations of the kit manufacturer. If you have experience flying rc airplanes, you probably don't need my help.

For a six- or seven-cell glider or old-timer with a cheap motor, an on-off switch is sufficient control. For anything else, you will have much greater enjoyment with a proportional throttle. Get a high-rate control, they are much more efficient at part throttle. There are several good brands out there; here is one of the better and more reputable supply houses on the web for all of these products.

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