Flying Planes With Squirrel Cages

Fixed wing remote control planes are ridiculously overpowered. Whereas normal, manned fixed wing aircraft need to take into account things like density altitude, angle of attack, and weight limits, most RC aircraft can hover. This insane amount of power means there’s a lot of room for experimentation, especially in new and novel power plants. [Samm Sheperd] had an old squirrel cage fan taken from an electric wall heater and figured one man’s trash was an integral part of another man’s hobby and built a plane around this very unusual fan.

squirrel-cage-fan-wideThe only part of the squirrel cage fan [Samm] reused was the impeller. Every other part of this power plant was either constructed out of foam board, plywood, or in the case of the brushless motor turning the fan, stolen from the ubiquitous box of junk on every modeller’s workbench.

The design of the plane puts the blower fan directly under the wings, blasting the air backwards underneath the empennage. During testing, [Samm] found this blower pulled around 350W from the battery – exactly what it should draw if a properly sized propeller were attached to the motor. The thrust produced isn’t that great — only about 400g of thrust from an airframe that weights 863g. That’s very underpowered for an RC aircraft, but absurdly powerful for any manned flying machine.

Does the plane work? Of course it does. [Samm] took his plane for a few laps around the neighborhood and found the plane flies excellently. It is horrifically loud, but it is a great example of how much anyone can do with cheap RC planes constructed out of foam.

42 thoughts on “Flying Planes With Squirrel Cages

  1. How does the precession feel on that? I imagine it having wicked different turn coordination at high throttle vs low.

    Madly cool project! So much nicer a way to build than the balsa and dope of my dad’s generation.

    1. Bit more practical, don’t have to worry about weight. Though I might actually recommend a 110V brushed motor, from a blender or something, so you don’t pull from your power supply.

    1. Next up use Dyson centrifugal vortex style fan.
      I wonder how those jet blowers McDonald’s have been using for a while would fair in this sort of design. [The ones that try to take the skin off your hands with the water.]

        1. Yes, “bladeless” (stupid auto correct)
          Not truly without a fan, more a different ducting design but perhaps if it were spun as it exited the side of the ring and the ring was tapered, it could pull through and concentrate more air.

  2. I think there very well may be a superb use for this power plant: high speed flight. I do not believe it’s thrust would fall off with airspeed as does a normal propeller driven aircraft, allowing high-speed flight on modest power consumption. That’s why jets fly so fast.

    1. Nope. Centrifugal compressors were on the first jet engines to take flight, but quickly proved inferior in performance to axial compressors, the only benefit radial compressors have against axial is cost (usually you need just one stage, an axial one needs many) and size…

      1. I thought that centrifugal and axial compressors were relatively comparable but that axial won in jet engines basically because they’re long and skinny as compared to centrifugal being short and fat?

  3. So you have this rather big flywheel turning (the squirrel cage) … and it probably acts like a gyroscope. So how does the plane handle when you try to turn perpendicular to the spinning cage? Do you have to compensate for that somehow? I would think it would resist the turn and pitch up or down radically.

  4. What I find most cool is the point where he comments on the handling, and ten seconds later he’s got a 3-axis gyro on it to fix it, like that’s an everyday thing to do… What’s cool about it it that it IS an everyday thing to do, these days. These are great times when stuff like that is quick, easy and cheap.

  5. I know he had only one fan but, what about two in the wings with the inlet facing up and servo controlled thrust nozzles, all running off belts on a single motor mounted in the body with the shaft vertical?

  6. Now imagine if he’d done it the even better way, and had the exhaust air blowing out over the top of the fuselage, and not the bottom? The Coanda force would be lifting up, instead of pressing down.

  7. If one oriented the fan to exhaust over the upper surface of wing and fuselage, the airflow would increase the venturi effect, and add to the total lift of the wing; example, Ekranoplan. With two fans side-by-side, one exhausting over each wing root, the total lift could be increased considerably.

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