lesson5

What does an electric power system consist of? The basic components are the motor, the propeller
and any adapter that might be required to attach the propeller to the motor shaft, an Electronic
Speed Control (ESC) to control the motor throttling, the battery pack to supply the energy, and the
charger to charge that battery.

For an electric-powered model you must install the motor, ESC, and battery inside the aircraft and
integrate it into your onboard RC system. The radio essentially operates the ESC, which operates
the motor's speed in flight.

Your biggest concern at the start with electric power is understanding and correctly charging the
battery. A battery that is not fully charged is much like a fueled model with only a partial tank of fuel.

Motors: The electric motor itself is of primary importance. There are different types, such as simple
ferrite magnet motors; the more sophisticated cobalt (samarium cobalt) magnet motors; and the
highly efficient, long-lasting, expensive brushless motors.

After selecting the type of motor, your next concern is to size it so that it is capable of flying a model
aircraft of a particular weight. In this case the choice has been made for you. Another consideration
is running the motor direct drive (with the propeller attached directly to the motor shaft) or through a
gear-reduction drive that can add an advantage to the power output.

Since this is a beginners' article I've selected a basic ferrite motor known in the generic sense as a
Speed 400. These come in three different windings designated by voltage. This project will use the
6-volt winding. The motor can be obtained from many sources.

This size motor is capable of flying a model with a total flying weight of roughly 10-18 ounces. It can
accomplish this using a direct-drive propeller, so for this first try we will not use a gear-drive
assembly. Be advised for the future that a gear drive will allow you to fly heavier-weight models
and/or it can extend the flying time of a model flown on direct drive.

My choice of direct drive was to keep it simple and inexpensive. A Speed 400 motor costs
approximately $15. It is a sealed can. When you eventually burn out the brushes, you throw out the
motor and buy another!

The motor will have two terminals, and they are polarized (positive and negative). Most have a red
dot or mark indicating the positive terminal. For our beginner's package, a wire has already been
attached to each terminal. The connectors applied to the wire ends are the popular Anderson Power
Pole (APP) variety. There are many popular connectors available, but I felt that the APP were best
for this application. These connectors have already been attached for you.

Almost any brushed electric motor will generate some form of electrical noise which could
conceivably feed back into the RC system. To suppress this brush noise, one or more bypass
capacitors are added. Generally, one capacitor goes from each terminal to the case, which is like a
ground connection. In this case, the motor selected has the capacitors installed inside the motor
can, so nothing else is necessary.

When you start your motor the first time, the wind created by the propeller should blow toward the
rear of the model. If it blows forward, it means that the motor polarity has been reversed and the
propeller is turning in the wrong direction. That shouldn't happen in this instance since the work has
been done for you. Be advised for the future that if the propwash blows forward, reverse or swap the
motor terminal connections.

The motor shaft protrudes from the front of the motor. Some direct-drive propellers are simply
pressed onto the motor shaft. I'm not in favor of that approach, so I specified the use of a propeller
adapter. The adapter is slipped onto the motor shaft. A collet-type device essentially clamps to the
motor shaft as you tighten the adapter. I found the adapter already installed on my motor shaft; you
might find the same.

Once the adapter is in place, put the propeller on, followed by a propeller washer then the nut.
Tighten the nut, and you are set. The propeller of choice for this project is a Gunther 5 x 4 white
plastic. You will likely have to drill the center shaft hole somewhat to fit on the adapter shaft. Next
month I'll write about how to install this motor on your aircraft.




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		by Bob Aberle AT THIS POINT this series will begin to split off into the specialty areas of model aviation. Radio Control (RC), as noted in the past few months, takes up the major portion of interest. However, equally important to so many modelers are the non-RC aircraft, such as Free Flight, Control Line, Hand-Launched Gliders, rubber-powered models, and more! As the months go by, this series will "spin off" into all of these fascinating areas. From a primary power standpoint, the most popular for model aviation today involves the use of glow-fueled engines. To a lesser degree, but just as important, are the gasoline-fueled engines as employed in the larger models (quarter scale and the like). The third power category is electric, and this has become increasingly popular in recent years because of the many technological improvements in motors and batteries. Guest-author experts will soon be writing about glow- and gasoline-fueled models. Electric has been my specialty for some years; it is the only power source I use today. Read on in the next few months as I explain electric power and take you through the process of assembling, installing power in, and flying an electric-powered model. What is electric? Electric power uses the energy supplied from batteries to operate motors without the need for "wet" fuels. At the beginning of this series I pointed out that when you are referring to fuel, the power plant is an "engine." When you are referring to electric power, it is a "motor." Why would someone, especially a beginner, want to try electric power? The two primary advantages of electric power are that it is clean and quiet. It's clean in the sense that you will not end up with fuel residue on your model after each flight. It's also clean because there is no fuel to accidentally spill on the ground and get into the water table. There is a remote chance of that happening, but it is still a big concern in certain areas of our country. Electric power is quiet, as in no noise! Probably the loudest sound you will get from an electric motor is the propeller or air noise, and that isn't much. Quiet operation means that you have the ability to fly in urban areas without disturbing the public. Electric power is so quiet that you can fly at sunrise, in dead air or calm wind conditions, without the fear of waking up neighbors. There are more subtle advantages associated with electric power. Without a piston and connecting rod pounding away, there is little vibration. This makes it much easier on the radio-system components, which need little isolation or padding to survive. Electric motors are basically turned on by a switch or controller. You don't have to prime and flip a propeller, use a starter motor, or light a glow plug to get your model in flight. This easy starting feature is particularly nice when flying in colder weather. You can sit in your warm car while the battery recharges, then venture outside for the flight. There is never any waiting. When you are finished, you just put the aircraft in your vehicle; no cleaning is necessary. With the absence of fuel, you don't have to be concerned about the finish applied to your models. Anything will work! After hearing these advantages, could there be any disadvantages? Yes! When you apply electricity from the battery to the motor, it will start instantly. If you fail to realize this, you might accidentally connect a battery, have the motor start, and it might hit you or take off across your shop, wrecking everything in its path. Most modern speed controllers have safety features to help with this that I will discuss in a moment. Is electric power better than glow-fuel power? I've used both in the last 50 years (30 for electrics!). I think there will always be a place in our hobby for fueled engines. Modelers love the sound, and they like fueling, starting, and adjusting an engine. On the other hand, a beginner in modeling has much to learn in a short time. Sometimes the problems with starting and operating a fueled engine can consume most of the available time while attempting to learn to fly. And if not adjusted properly, the engine may stop in flight. With electric power, the motor always starts and will keep running as long as you have a charge in the battery. Yes, a wire could break or a fuse could blow, but that motor is usually going to keep running in a reliable fashion. As the charge wears down during a flight, the electric-powered aircraft will fly noticeably slower. This is your warning to set up for a landing. For these reasons, electric power is the perfect choice for the beginner in our hobby. There are many things you have to learn to use electric power. Since this is a beginners' series, my intention is to gradually bring you up to speed. Battery charging is important. Hooking up all of the necessary wiring could prove a problem for some. My first choice for an electric-powered ARF (Almost Ready-to-Fly) model will not require any soldering. Each power-system component will be what we call "plug and play"; that is, the radio and electric-power-system installations are totally handled with preassembled connectors. An entire electric-power-component package (which I will describe) will be available from Kirk Massey of New Creations R/C.

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