Free Propeller Bike Mod Update




About: I am an engineer focused on recycled batteries, electric vehicles and renewable energy. I am always working on engineering projects I can’t stop.

This instructable covers some improvements in the propeller bike mod and a video of the test ride with some more info and how the bike performed.

Please find the first instructable at the link below.


Step 1: Test Ride

Using a 10A door bell switch, some 14 gauge wires, 100 Watt Hour lithium battery (2 laptop batteries) and the new mount I was able to go for a nice test ride.

The batteries would last about 30 minutes at full power. This was enough for a test ride but I will be getting more laptop batteries for longer trips.

The Prop (20 inch diameter and 6 inch pitch) was designed to work best around 20 to 30km for nice bike cruising. At these speeds the forward wind speed result in the best angle of attach which gives the highest thrust to drag for the prop (highest thrust to motor power). Moving forward reduces the drag on the prop and allows the motor to spin faster where it is more efficient.

In this test I pedaled with the prop on and it took very little force on the petals to accelerate quickly. Around 20km/h the prop really sped up and pushed the bike really hard. I had to stop pedaling because I was going too fast.

The bike works great. It is so easy just to pedal when you want and use the prop when you want or use both together. You can just use an on off switch and control your speed by turning the prop on and off for longer or shorter times.

The motor got a little warm so I might want to build some cooling fins for it.

Step 2: Improvements From First Design

For the first design the motor was only duct taped on. This was super dangerous as the motor could just take off. I used two large hose clamps to pull the motor down onto the mount. I also have a wood stop behind the motor. This prop pushes so the motor want to go backwards and is stopped by this piece of wood.

I improved the mount to the bike. Now I attached 2 2x1s to the vertical carrier supports. I used hose clamps to secure it to the mounts so it can be removed easily from the bike. I installed a block of wood at the end so that the motor and prop can be screwed to it.

The motor and prop have their own 3/8 inch plywood mount. This piece can be easily screwed onto the block on the bike mount. I used a sharpy to help line up the screw holes. This way the motor and prop can be easily removed and installed to the bike.

Step 3: Future Improvements

  1. Use more batteries, now I have 12 cells (2 laptop batteries), 24 cells (4 laptop batteries) would give me about an hour of full power and reduce the fast discharge rate of the batteries which can damage them.
  2. Try to run the motor at 16 volts. I can use sets of 4 lithium ion cells in series instead of 3 cells.
  3. Add cooling fins to motor
  4. Add larger capacitor to motor, the capacitor reduces the start up current spike which can damage the batteries and motor
  5. Larger motor, I was thinking of using a starter motor to get really high power
  6. Variable speed, I could use a double pole double throw switch to flip between 2 voltages. I could do 12 volts low speed and 16 volts high speed.
  7. I might add a duct or some kind of protection. This will be big and heavy and will reduce thrust. My theory is that with a prop the is not as wide as me if I only use it when I am already moving (used pedals to start) then the prop shouldn't hit anything. Something would have to jump between me and the prop to hit it or hit me from behind
  8. Safety switch, I want to add an extra switch that is only on while I am moving. This way there will be 2 switches disconnected when I am stationary. This will reduce the risk of accidentally hitting the switch when the bike is not moving.



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    10 Discussions


    4 years ago

    Good point mp,

    The problem is I only have the tools and money to work with wood. Everything I build is very cheap because I use scrap wood I already have.

    I don't want to modify the bike (I use this bike everyday to go to work and don't want to destroy it. Also it is very easy to use the pedals, prop or both.

    Also I am an aerospace engineer so messing around with propellors is lots of fun. One day I hope to build my own full sized plane from scratch.

    1 reply

    Reply 3 years ago

    you are doing good work. don't let the unimaginative discourage you.

    have you done any experiments with the nylon cooling fans run enshrouded?

    i would be most interested in finding out just how much thrust they could provide with the electric motor. btw regular alkaline cells ARE rechargeable if you construct a proper charger( check out wiki, the specs are there) rayovac fusion ,"D" cells have a capacity of 26 amp hours at 1.64 volts, with the good charging system they are said to last indefinitly) and dead batteries can be scrounged. this is high technology hiding in plane sight.


    4 years ago on Introduction

    If you add a tight fitting shroud it will not only increase your thrust but add a level of safety


    4 years ago

    it seems like with all this work on a propeller, you're not getting much useable energy from your batteries and motor. air propulsion is nice, but typically only very effective for vehicles designed to move relative to the air around them rather than the earth. perhaps instead of going to the trouble of building, balancing, and mounting a propeller that could potentially hurt someone, you could use the motor as an electric assist, driving the rear tire to provide much more efficient propulsion.


    4 years ago on Introduction

    Use this on long rides and you can use the prop as a salad shooter, or a Bass-O-Matic!


    4 years ago

    Very ingenious, I like it!

    Just fall and/or hit something sideways (e.g. the floor) and you will have high speed wood shrapnel spewing out like crazy. Also, you can hit someone and still the person can be in the path of your propeller.


    4 years ago on Introduction

    Excellent project. I think point 7 will be very good idea, the thrust will not be reduced, it will be augmented due to the reduced turbulence.

    Point 8, maybe you could add a micro-switch under the seat, activated by your weigth.


    4 years ago on Introduction

    Nice mod, but EXTREMELY DANGEROUS to you and to others around, unless you have a very good cage around the propeller. Only use it when there is nobody around, please.