Electric “Radial” RC Aircraft Motor

For a long time radial aircraft engines, with their distinctive cylinder housings arranged in a circle, were a common sight on aircraft. As an experiment, [KendinYap], wanted to see if he could combine 3 small DC motors into a usable RC aircraft motor, effectively creating an electric radial engine.

The assembly consists of three “180” type brushed DC motors, mounted radially in a 3D printed casing. A 3D printed conical gear is attached to each motor shaft, which drives a single output gear and shaft mounted in the center with two bearings. The gear ratio is 3:1. A variety of propellers can be mounted using 3D printed adaptors. As a baseline, [KendinYap] tested a single motor on a scale with a 4.25-inch propeller on a scale, which produced 170 g of thrust at 21500 RPM. Once integrated into the engine housing, the three motors produced 490 g of thrust at 5700 RPM, with a larger propeller. Three independent motors and propellers should theoretically provide 510 g of thrust, so there are some mechanical losses when combining 3 of them in a single assembly. However, it should still be capable of powering a small RC plane. It’s also not impossible that a different propeller could yield better results.

While there is no doubt that it’s no match for a brushless RC motor, testing random ideas just to see if it’s possible is usually fun and an excellent learning experience. We’ve seen some crazy flyable RC power plants, including a cordless drill, a squirrel-cage blower, and a leaf blower.

23 thoughts on “Electric “Radial” RC Aircraft Motor

    1. Interesting to notice that several types of plastic have been used.

      I wonder that if the main gear can be made conical too, so the motors can be aligned with the propeller axis, instead of perpendicular.

    1. Don’t expect a reply. Its just someone who has something to say about everything. Wonder what kind of radial motors he has designed. Leave it to the arm-chair pro’s. Nothing constructive to say.

  1. In the end 3 of the single motored 4.25×6 blade seems to have more thrust than the 3 motor gear with 10×6 prop. With all the additional material, friction, etc, is it really worth it? We didn’t see power draw, so no word on efficiency. Anyway cool concept, just seems like a solution looking for a problem.

    1. I doubt it can win on any practical front until you really start pushing with really high power tiny motors that will need better cooling than being inline/direct drive can really provide.

      But damn does it look cool, and with a little refinement probably a nice motor to put in your RC piston engine warbird – it looks the part, and works.

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