Over the last year - I've toyed with the notion of making an EDF fan bike.
EDF is short for Electric Ducted Fan. They are basically enclosed propellers for model airplanes - they look kind of like little jets!
I finally got around to putting one together - here's some test footage:
The hope would be it could boost my top speed when peddling - and mitigate going up hills. It also has the advantage of not messing with the current drivetrain mechanicals - and being easy to add / remove.
Although in reality - this project is just about having fun. This is probably the least efficient way to move a person imaginable.
The 3 EDF's I got are rated for about 2 lbs thrust each when run at 12v (so maybe 6lbs thrust total). The specs say 20-40 amps (no - nothing more specific than that).
I got them on ebay for about $40 each including brushless motor and motor controller.
Normally the motor controllers are connected to a receiver - but I wanted something a little less cumbersome. So - I rigged up an Arduino to generate a PWM signal - and tossed together a little control panel.
The battery is a big sealed lead acid (SLA) 12v. It's good for 18 amp hours - but that's assuming the energy is consumed over a 20 hour period. When SLA's are drained quickly - they only provide a fraction of their total capacity. I'll make up a number - and say I'm getting maybe 5 amp hours.
Using almost any other kind of battery (NiCD, Lithium, etc.) - would have given me more capacity per the weight - but for $30 it was the cheapest way I could come up with to supply the 60-120 amps for a moderate duration.
Also - 18lbs really isn't that much when you think about me + bike being more like 250lbs.
The fans + electronics are only about 2lbs - for a total weight around 20lbs.
I laser cut the base plate out of 1/4" MDF on my new Laser Cutter - which is proving to be a fairly well spent $2500.
Testing proved a real challenge - finding a truly flat street to test on with little to no wind proved very difficult.
The solution to this was to test on the same street going both directions.
It was hard to concentrate on the speedometer - but I saw 8.5mph just as I was turning around - and then slowed to about 6.5mph returning (assuming there was some wind / slight slant in the road).
I had made some rough guestimates - suggesting a top speed around 10mph. This seems reasonable.
It also seems to give about a 5-6mph boost in top speed when peddling (this is really hard to be objective about though - can I really say I didn't peddle harder?).
I probably get about 6 minutes useful runtime - then the power starts dying off quickly.
I'd say the current setup is a little shy of being really useful - but it proves that it works.
Pretty happy considering I only spent about $180.
This project could really rock with 2-3x the thrust (maybe 15lbs) - and about 6x the battery capacity (say an actual 30ah at 12v - or equivalent at higher voltage).
Adding another 3-4 fans wouldn't be that hard /expensive (there's probably better / larger options) - but adding that much battery capacity would probably get pretty expensive (weight would like dictate going to Lithium / NiMH).
If you'd like to help fund this effort - please buy some Uranium or Thorium from me.