What To Choose When Converting RC Gas Engines To Electric Motors.

How To Choose Components For A RC Plane Gas Engine To Electric Conversion.

By Carl Baer

How To Convert RC Gas Engine To Electric Motor Easily.

Converting A Hangar 9 Arrow Gas Engine To An Electric Motor With Li-Po Battery.

What you should consider before converting your rc airplane gas engine to an electric motor system.

With the changes in rc electric motor technology it is possible to fly ANY size model using rc plane electric motors. The biggest leap in making this possible has been two fold. First we have model airplane electric engines that are powerful enough, not to mention much more efficient, that they rival or even surpass gas/slimers/smokers/nitro hogs, or whatever else you may call rc airplane gas engines.

In fact you can expect to see an increase in the performance of a model airplane in several areas. Your take-off is shorter, climb rate will increase and you can now fly in areas that have noise restrictions.

The debate between the benefits of rc plane electric and gas motors are as controversial as those between pc and Mac users. It will continue for as long as they are both in existence.

Some questions you might be asking before you convert your rc model airplane’s gas engine to an rc electric motor…

How long will the battery allow me to fly? With today’s Lithium Battery technology, you can easily expect 10 minute flights, even in bigger aircraft. The days of overheating the batteries and fire hazards are almost non-existent. There are many add on features that you can now purchase that all but eliminate battery hazards. Such as temperature monitors and voltage indicators.

Here are some questions to ask before you start buying any components. These questions will help determine what components to buy.

1. What is the radio control plane that you are wanting to convert? Is it a trainer, sport plane, 3D etc.. This is important because you will need to determine the electric motor based on your models capabilities, and what you want it to do.

Example: Hangar 9 Arrow with a .40 size gas engine.

Would require an electric rc motor equivalent to a AXI 2826/12 External Rotor Brushless.

This motor would allow this model to perform basic aerobatics with its semi-symmetrical wing.

Specs of the Hangar 9 Arrow

You will need these numbers to help determine the motor, battery, and prop requirements.

  • Wingspan: 63 in
  • Overall Length: 52.5 in
  • Wing Area: 710 sq in
  • Flying Weight: 5.7 lb (as a radio controlled gas plane)
  • Engine Size: converting a standard .40 size rc gas engine to an rc electric motor.

Now you need to determine what type of batteries you will need. This is based mostly on your budget and time till land variable. In other words, how long do you want to fly for and still get performance.

The most obvious choice is going to be a Lithium Polymer battery, this is the most advanced battery technology available for rc model airplanes. They are also the most expensive. Other older battery technologies are available, such as, lithium ion and nickel metal hydride. They can do the job, but at a weight cost and flying time consideration. So choose carefully.

In the Arrow Example: We will use a 4200 mAh 11.1V Li-Poly Pack. This was determined based on the flight performance we were after, some aerobatics, but mainly stable easy going flying. Nothing too extreme.

As with any gas rc plane conversion to electric (or any electric radio controlled airplane for that matter), you will have to consider an ESC (electronic speed control). This hooks up to the motor, battery, and receiver. You will need to pick one that can handle the required number of battery packs, servos and have programmable features. This will make life easier for you if you pick one that is feature rich. Of all the components, this is one to spend a little more on. You will be glad you did.

For this example, we used a 40 Amp Brushless Controller with Program features. There are lots of manufacturers of ESC’s so take the time to research them.

Prop Selection is an important consideration. You need to be aware that with an electric conversion there is a possibility that your model plane will not have enough clearance when using an electric motor prop. It may need modifications to the landing gear (making them longer) so that the prop has clearance.

For the Arrow example we used an APC 13×10 propeller. Most electric motors now have a table that you can find on their website that will recommend the propeller range to stay within.

One final consideration with rc gas planes converted to electric. You always need to factor in cooling of the battery pack and esc. In fact many modelers, including myself, put the ESC on the outside of the plane, usually I mount it under the engine on the firewall. You also need to make air vents to cool the battery inside the model. Without this, you run the risk of overheating batteries and ESC’s.

If you have any comments or need more help, I would be glad to answer any question you have.

Please post a question Below for the quickest response to your questions.  Or you can leave a comment about this article.  You can also write just to say hi:).   This is one big community and it’s great to get to know other electric radio controlled plane pilots.

Good Luck, and Happy Buying and Flying,

Carl Baer

About Carl Baer

I am a rc airplane guy, have been for almost 30 years and I grew up around rc airplanes. My dad built them and I used to watch him build, then we built together and then I built my own. I love to build rc planes and see what modifications I can make to create a real scale and functional look to the finished plane. This love, turned into this blog to share my experiences with model airplane building.

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