crilex

Hello everybody

I am new on this interesting site and I need an advice for my idea.

I recently bought a road bike and I was wondering if can I increase my speed using a plastic fan mounted in the front of my bike. I wanna mention that the fan will be powered by the motion of the front wheel at a ratio of 1 to 10-15 (I don't wanna use batteries or engines) . The diameter of the fan will be 2o".

I also wanna know if someone had tried this before and what were the results. Was it worth it? I ask this because I don't wanna waste my money.

I know that sounds crazy but my idea came while I was riding against the wind. I think everyone of as knows how hard is to pedal against the wind.

Thank you very much & I waiting for your advices.

bkaapcke

So you are proposing a fan set up to pull the bike forward, powered by the front wheel. This, in combination with the power of the back wheel, is to provide more forward speed than you would get from pedal powering the back wheel alone. So, where does the "free" energy come from? A headwind driving the fan which in turn drives the front wheel? Yup, You're right. This is crazy. bk

well biked

Yes, I've tried it. I went from my normal "just riding along" speed of 18-21mph to about 32-35mph. It was cheap, too; the whole setup only cost about $5. Was it worth it? Well, all the folks I rode with before I made the modifications refused to ride with me anymore because I was too fast. They resented the fact that I was so resourceful, and they hated the fact that they simply could not keep up with me any more. I lost a lot of friends over this. I would say it was definitely not "worth it." FWIW, I have removed the modifications I made to my bike and currently ride mostly alone......at my old JRA speed of 18-21 mph. Lesson learned....... BTW, I refuse to divulge the exact design of my front-mounted fan. I don't want others to go through what I did.

JanMM

Did your wife and children leave you, too?
Sad story.

kh6idf

I remember in college (engineering) we had this toy boat with a large propeller (above the water) at the front driving a smaller underwater propeller at the rear of the boat. You could turn on a fan and that boat would head straight for the fan, directly upwind!

BCRider

From my avatar it should be obvious that I like model airplanes as well as bicycles.

A fan, or rather a propeller, will never be as efficient as the direct mechanical link from your foot to the ground through the bicycles drive train. Adding a propeller at the front would slow you down by some amount rather than speed you up. You don't get energy for free. And what you have would be best used by just moving the pedals faster.

crilex

OK got it, but what about if I increase the size of the wheel diameter?...Or do you know any other methods to increase the speed of a bike, but without moving the pedals faster (just keep up a normal rhythm). I wanna know a method which allows me to increase the speed keeping a normal rhythm.

Thanks for your advice.

TerryH

That would be the same as using a higher gear. There's no free lunch, you'll go faster for a given speed of turning the pedals, but you'll have to work harder to turn them at the same speed.

Jeff Wills

The propeller bike has a long and fabled history:
https://blog.modernmechanix.com/mags/.../prop_bike.jpg

As Terry said, there's no free lunch. Since you're saying you don't want to increase the power you're putting into the bike, the only way to go faster is to reduce drag. Most of the resistance to forward motion at common riding speeds is aerodynamic drag, so you can go faster by:
1. changing your riding position to minimize drag by using "aero" bars or switching to a time-trial type bike:
https://www.roadbikeaction.com/imagef...bikeaction.jpg
2. switching to a laid-back recumbent bike:
https://www.bikeforest.com/zockra.jpg
2a. switching to a recumbent bike with a fairing:
https://home.comcast.net/~jeff_wills/jeff-big.jpg
2b. switching to a recumbent bike with a fairing and fabric "body-sock":
https://www.recumbents.com/wisil/recu...arl.Russel.jpg
3. Creating a recumbent bike with a full hard-shell fairing:
https://www.youtube.com/watch?v=jQwpGLCAMm4
https://www.youtube.com/watch?v=PMUNOLwW0io

None of this is free: you need to invest in equipment and/or increase your tolerance for appearing dorky and/or trade off other areas of performance (recumbents are known for not climbing hills well).

BCRider

And ride more often to get into better shape..... Your speed is only as good as the power of the engine.

iain.dalton

If you want to go faster for the same effort (on your part), you could put a motor on it.

wheelgrabber

If the fan idea worked we wouldn't have gear driven wheels. The chain would go to a fan and the wheels would simply be wheels. Fans are not known for efficiency. Fans that provide propulsion are typically powered by huge horsepower or watts. The limiting factor in your vehicle is your engine(ie you) not the transmission.

leweee 

This thread needs a few gallons of prop wash & a few yards of flight cord.

stevetone

do kids these days take any science in school? geez.

HillRider

That's flight line. What you are looking for is wing cord.

Mr IGH

I have an old JATO rocket mounted to my rear rack, I bet I hit 60mph!

Grand Bois

That's wing chord.

FBinNY 

I think that what your describing would fall into the class of perpetual motion machines. It takes energy to propel a vehicle, and in the case of a bicycle you're the main source of that energy. You can also "borrow" free energy on a short term basis riding down hill, but you'll have to replace it riding back up. You can also get energy from the wind, which is how sailboats work, but like a sailboat you can't use the wind to propel you directly into it.

HillRider

Yes, I know but spelling it correctly would have ruined the pun.

Bianchigirll 

didn't Wyle E Cyote have something like that? I do hope Well Biked is puling our collective leg.

wing Chord? are we going to start discussing the Arm and Moment of our bikes now too?


"This thread needs a few gallons of prop wash & a few yards of flight cord."

spoken like a true Airedale

BCRider

I was just listening to a string of whing chords last night. A very nice sounding effect it was too...

FBinNY, sailing directly into the wind IS possible with a prop as the power source. Much like the boat with two props mentioned above I've also seen reports of little cars using propellers as windmills to power wheels that can move the car directly against the wind.

The key in both the car's and boat's case is to set the blades to a very high angle. This acts like a reduction gear so the wind energy picked up does not come with the added cost of too much drag. Then the energy picked up is transferred to the water prop or wheels. The reason this "picking yourself up by your own bootstraps" contraption works is because there's little or no slip for the water prop and wheels and the effective "gearing reduction" by using the prop with a high pitch angle. If the prop were to use a very flat low pitch angle or if the driving medium (the water or floor) where more lossy or slippery in the same way that the air is then the story would be very different.

Mr IGH

how about a jet bike?

Bikewer

As the fellow said, "In Physics, there is no such thing as a free lunch." There were some folks marketing a motor-driven caged fan (or more properly,a propellor) that could be used to provide extra thrust for cyclists, roller-bladers, and so forth.
The whole thing mounted on a back-pack.

BCRider

IGH, do you know if they ever tried that thing? In model airplanes a class of speed flying used pulsejets like that one and they were both horrendously noisy and quite powerful for their size. The one on that bike should be strong enough to push the thing fast enough that the rider would certainly not be able to hold on. But maybe that's OK since they are also so thirsty that the fuel tanks shown would only be good for about a minute anyway. Either way I'd love to see a video of it and then to lay flowers of respect or condolence at the grave of the nutbar that they found to ride it....

Mr IGH

It runs: