The Air Hogs Sky Shark was a free-flying model airplane powered by compressed air. When it was released in the late ’90s, it was a fairly innovative toy featuring a strikingly novel compressed air engine made entirely out of injection molded plastic. Sales of these model planes took off, and landed on the neighbor’s roof, never to be seen again.
A few weeks ago, [Tom Stanton] revisited this novel little air-powered motor by creating his own 3D printed copy. Yes, it worked, and yes, it’s a very impressive 3D print. That build was just on a workbench, though, and to really test this air motor out, [Tom] used it to propel a remote-controlled plane through the air.
The motor used for this experiment is slightly modified from [Tom]’s original air-powered motor. The original motor used a standard 3-blade quadcopter prop, but the flightworthy build is using a much larger prop that swings a lot more air. This, with the addition of a new spring in the motor and a much larger air tank constructed out of plastic bottles results in a motor that’s not very heavy but can still swing a prop for tens of seconds. It’s not much, but it’s something.
The airframe for this experiment was constructed using [Tom]’s 3D printed wing ribs, a carbon fiber boom for the tail, and only rudder and elevator controls. After figuring out some CG issues — the motor doesn’t weigh much, and planes usually have big batteries in the nose — the plane flew remarkably well, albeit for a short amount of time.
37 thoughts on “A Remote Controlled Air-Plane”
This sort of propulsion would be nice to have to use with R/C gliders. Give a little boost to reach the next thermal.
And eject the air tank when the boost is done
Or fill the tank with liquid Nitrogen!
how about some dry ice i.c.m. with a pressure valve (to prevent the “air tank” from exploding if pressure build up to fast).
oops, some people already mentioned this (a few comments down)
It needs a remote start / stop for that and that is a non-trivial problem for sure.
I wonder how long it could fly on a couple of chunks of dry ice (in a smaller reservoir)…
I’d like to see that. It would could go quite far if it didn’t explode first.
Have a weather balloon take up up a way first. Add a couple of rockets as a third stage too for good measure. Maybe you get to low earth orbit.
Just have a pressure release and no explosions.
Get a lanyard and hand that radio around your neck.
Hmm. Which is more efficient: an air engine swinging a big prop or an air “rocket” engine? At first glance, the fewer moving parts, and less friction, of the rocket engine would tip the balance in favor of the rocket engine. But maybe controlling the rocket engine is so hard that it’s impractical?
But an interesting idea none the less!
Rockets are pretty much always less efficient, because they only push on their propellant, whereas propellers can push against a much larger mass of air.
More efficient to move a lot of air a little bit than to move a little air a lot. That’s why modern jets have large fan sections in front that handle most of the air.
All that motion left in the air is wasted energy, and energy goes up as the square of velocity.
So the air engine is converting the high pressure of the propellant into high torque, low velocity to turn the prop efficiently. OK, I’ll buy that. Thanks!
Isn’t this a consequence of conservation of momentum vs kinetic energy? While momentum is just v*m, KE is (1/2)mv^2. That means that one can impart the same change in momentum onto a plane by pushing 1kg of air back and 1 m/s or by pushing 1/2 kg of air back at 2 m/s. This will provide the same change of momentum for the plane itself, which translates into identical changes in velocity assuming that both plane types have the same mass. The only difference is that the latter method will require twice as much energy because KE is proportional to the square of velocity, not velocity itself. I was thinking about this type of thing the other day and would be appreciative if someone a little bit more knowledgeable could correct me if I am wrong.
That’s genius! It also explains why adding water to a bottle rocket improves efficiency over just compressed air.
And the most efficient propeller is large and slow turning.
The engine may not do well at low rpm however.
A heavier valve might be an interesting test
and a flywheel on the larger prop or weight the prop tips?
For that battery-nose weight, CO2 cartridge on a bleed-release?
Noone say vinegar and baking soda, ok? hahaha
CO2 cartridge is a good shout, though I don’t know how you’d control the pressure without a heavy regulator. I’d love to see it running on liquid nitrogen but that’s hard to get hold of in the UK unless you’ve got a contact in a university lab or a business that deals with it.
Try to add Diet Coke and Mentos to boost
I had an AirHog, and could never get it to go anywhere. Finally, I realized it was really difficult to get the prop to go in the forward direction, negative thrust will limit flight times. The first time I got it to work, it was a real surprise. Fortunately, we have some really tall trees between us and the neighbors or the crash might have been a lot more spectacular.
Wondering how the higher pressure pumps with carbon fiber tanks say for high powered air rifles would work? Those get up to 4000psi I want to say, though not sure about duty cycle.
Quick look online was what I was thinking… kind of pricey though the tank only spec’in out to 410gms and 3625psi capabilities costs $149.
This is a better deal and weighs in about half the weight and not quite that in cost.
Can a rubber band or surgical tubing launch start the engine and also help with gaining initial altitude?
Way neat build, design and creative idea Tom and thanks for sharing Brian. I have some carbon fiber golf clubs I was testing for electric conductivity and resistivity where two are not conductive… so was thinking for an aircraft since the conductive ones can be used for the larger telescoping antenna I am playing with and the ground to use less wires on a drone build I am pondering.
Wondering also if the wing is sealed… would hydrogen help with making the craft lighter? I’ve been wondering about hybrid duragable, drone, balloon and aircraft design. What Tore noted above with liquid nitrogen (seems would require a engine design testing phase and potential mods)… got me thinking just plain hydrogen in the body of the craft to lighten the weight.
The real question comes down to how much weight someone could save by replacing air with some lighter gas. Given that has a density of about 1.285 g/L, even replacing the air with a total vacuum while somehow avoiding implosion would yield minimal results. With this plane, you *might* save a gram or two by using hydrogen. That is before it leaks out of the airfoil, of course. Probably not worth the effort. If that type of thing where worth the effort I would imagine that space agencies would be filling the cargo areas in rockets with helium, which would be close to the weight reduction of hydrogen without adding even more explosive potential to the rocket. That being said, best of luck with any attempts at hybrid drone/blimp aircraft.
Right, I totally didn’t do the math for the mass balance. More a brain storming unedited thought. Maybe a balloon launch is more feasible. :-) Helium costs more. Hydrogen can be made with some scrap zinc castings and battery acid that can be salvageable. Maybe add a scrubbing bottle to clean the gas. I think I recall seeing a youtube video that I didn’t watch regarding some sort of remote controlled airplane that was gas filled and like you note a different design that lead the vision on.
I’ve seen models of airliners, done in large scale, that were hybrid dirigible and electric powered. The fuselage and wings were filled with helium, and this got them to almost neutral buoyancy, so not much airspeed (walking pace) was necessary to maintain level flight. This might be a good application for pressurized air, but the motor(s) would probably need to be sized down to get decent flight times. With hydrogen, you could do this with somewhat smaller models, but with all lighter-than-air craft, bigger is easier.
Looks like just the fuselage is full of helium, and I probably underestimated the airspeed – looks more like about 10 mph. https://www.youtube.com/watch?v=2Kk5EGpYuck
I’m so not moving forward with this project and will eventually. The latest vision is rocket launch from a kitoon or dirigible drone kite. Seems like a neat project to use the kitoon or dirigible drone kite as a repeater also… even if passive. Thanks for the link.
I want to be able to use for RDF also.
Sounds like a lot of fun. The main drawback of balloons of any kind, though, is that they don’t tolerate wind of any kind very well.
Yeah… I was thinking that and why I need a hard line and maybe even wire coming down with the kite string or strings. With at least two strings making the system more stable. The wire makes the whole thing even more dangerous and exciting to plan and the kite helps stabilize the craft with the drone style system having even more controls and potentially solar panels to stay charged and help power the rest of the system(s) as well as make the abort recover/impact more programmable. Reading into the wire coming down the string(s) seems more dangerous than I expected and even can double as an antenna and not just a digital pipeline. Now days I’m thinking we’ll have to get a license to fly a kite with all the liberal attorneys that like to make up paperwork to charge people money and create law suites as a hobby as Elon Musk mentioned recently.
CO2 engines have been used for years in free flight models. A good read of the history can be found here: http://www.craftsmanshipmuseum.com/BrownJr.htm
I liked this a lot. I really enjoyed the other video that detailed the engine build.
Just awesomeness, like most of his vids!
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