Fan Bicycle

[Countach LP400]

A while ago, I read a thread about a motorbicycle powered by an R/C airplane propeller hooked to a weedwacker. Inspired, and very curious about how it would work and how well it would work, I built one myself.

First, the build. It was fairly easy to engineer, and all I used was a drill, a dremel tool, and a jig saw. The motor mount is aluminum, and it mounts to the luggage rack on the back of my bicycle. It cost about 4 days of work, and $150. Notably, it required a reverse propeller, which had to be special ordered. The most difficult thing was mounting the propeller to the shaft. I used the dremel tool to sand the end of a bolt into a square key which fit into the shaft, then I installed a X shaped piece of metal and cinched it down with a hose clamp, so that it was tightly secured. The clamp did not affect prop balance.

It has some very interesting riding dynamics. First and foremost, it does not like hills (but it does make them easier to pedal up!). Secondly, it has no low end power, meaning acceleration is abysmal, third, it has a good top speed, provided you can find ideal conditions. I had it going 25 around the hangers at my local airport, and on a shallow downhill, 40 would not surprise me. Higher speed means more airflow, so it really begins to come into it's own just as a regular chinabike runs out of breath. I rode about 20 miles on 2 pints of gas. It does not so much power the bike as assist it, and allows me to ride farther and faster. It adds about 12 pounds to the weight of the bike. It is designed such that the entire assembly can be attached and removed in about 10 minutes, aiding convienence.

Please know that it is not practical, nor will it be without much more work. It is pleasantly reliable, and good on gas, but not fun for long rides, or bumpy terrain. I built it as a proof of concept vehicle, as well as a challenge to myself, and am happy with the results.

I took these pictures before I finished it, and as such, it is missing the throttle linkage, prop shroud (from an old fan), and the butt-saving exhaust deflector plate, which was made from a thin piece of steel rather than aluminum.

Everyone I come across is facinated by it, people pull over to look, and pilots absolutely love it.

If you are going to make one of these, please, for the love of God, put a shroud on it before you ride it in public.

[Dave31]

That is really cool Countach!

[FileStyle]

very cool! "it slices, it dices"

[Vistaman73]

It would probably produce more thrust if you wrapped a cylinder around it. It would channel the air and make it more powerful. I don't know what to call it but picture slipping a opened ended trash can over it and mounting it. I hope it makes sense. This would also be kind of cheap to make. But, not easy. Apparently you like a challange. Hope you try it out.

[Xiodinc]

looks harmful, but awesome, what is the estimated speed on that?

[Countach LP400]

Originally Posted by Vistaman73

It would probably produce more thrust if you wrapped a cylinder around it. It would channel the air and make it more powerful. I don't know what to call it but picture slipping a opened ended trash can over it and mounting it. I hope it makes sense. This would also be kind of cheap to make. But, not easy. Apparently you like a challange. Hope you try it out.

Interesting that you mention that, a friend of mine who used to be an aircraft engineer in the navy said the same thing. He said it would be that it would be the best way to increase power without adding accidental finger removal risks.

The biggest problem is the tendancy of the rig to bounce, meaning that the propeller bumps against the shroud if I'm not carefull. It becomes very irritating on anything but the flattest terrain. I guess I should improve the bicycle shelf mounting point. Unfortunately, it is far more difficult to mount the shroud stiffly, and it would be very difficult to safely mount a duct tube with a tight enough clearance to have any positive effect.

I wonder if I could simply attach a metal cylinder to the end of the propeller; as that would do away with mounting difficulties. Do you think that would have the same effect, or would it destroy potentially good vorticies and have other undesirable effects?

[Vistaman73]

do you mean attach metal directly to the prop if so, than i wouldn't it would put a huge load on the engine and it would need very precise balancing, might even have a flywheel effect. And i don't know if it would have the same thrust effect or not. it seems that it would though. never thought of that i will ask around. but still until i find out more, i wouldn't.

[Nadogail]

On a ship the tube around the propeler is known as a Kort Nozzle. Google Kort Nozzle for more information.

You could insert struts from the interior of the nozzle tube to a bearing on the propellor shaft. This would keep the tube in alignment with the propeler.

[craisin]

i like it.
I wonder how it compares to an electric assist

[RusticoRay]

I found this a couple of years ago before the motored bike addition. ThrustPac - Empower Yourself