Introduction: Free Propeller Bike Mod Update
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.
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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
- 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.
- Try to run the motor at 16 volts. I can use sets of 4 lithium ion cells in series instead of 3 cells.
- Add cooling fins to motor
- Add larger capacitor to motor, the capacitor reduces the start up current spike which can damage the batteries and motor
- Larger motor, I was thinking of using a starter motor to get really high power
- 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.
- 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
- 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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