Free Electric Propeller Bike Mod

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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.

Update Instructable with test ride video at link below.

https://www.instructables.com/id/Free-Propeller-Bike-Mod-Update/

Video of Bike and Propeller test.



I wanted to put an electric motor on my bike. I didn't want to mess with a chain and sprockets so I build an electric propeller bike. It is easy to install and remove. It sounds cool and its easy to use the pedals, the prop or both.

I used a free car electric motor that I fixed, free laptop batteries that people threw out and a home carved propellor.

Step 1: Parts Needed

Parts needed
Electric motor (car rad fan, AC compressor)
Battery 100Wh + (laptop batteries work best)
Switch (door bell switch over 10A works)
Wires (I used 14 gauge)
Some wood (to build the mount and prop)




Step 2: Carving the Prop

First I used excel to calculated the angles needed at the different prop stations.

I choose a diameter of 20 inches because thats about how wide I am. I don't want the prop sticking out and hitting stuff as I ride my bike.

I just want the propeller to push me around 20 to 30 km/h. So I want a pitch that work well at these speeds. I started with a 6 inch pitch. From my excel sheet a 6 inch pitch is about 27km/h at 3,000 rpm. Most large motors operate around 5,000 to 10,000 rpm. The prop will operate most efficiently at an angle of attach of about 3 degrees. The air will also accelerate as it is sucked onto the prop. So I am thinking that it might be more like 5000 rpm when the bike is doing 27km/h.

I used pine 4x1 boards to carve the prop. I decided to have a 2 inch tip width and 3.5 inch root width. I used the excel sheet to Calculate the drop every inch along the radius. I marked the drop with a marker. I then started carving using a box cutter and homemade draw knife. The motor side of the blade is curved and the other side is flat. I used 80 grit sand paper to get a very aerodynamic blade shape.

Step 3: Attaching to Motor

Every motor shaft is different. I found with the motor I used it was easiest to JB weld a wood mount to the shaft.

I cut 2 circles using the hole saw. I glued the shaft in the center and glued a 3.5x3.5 inch square of 3/8 plywood to it. I then used 4 screws at the corners to attach the prop to the motor.

Step 4: Batteries

If you use laptop batteries like I did you will need over 6 cells (one laptop battery).

Best would be 3 batteries or more (over 18 cells).

You can see how to build the battery pack below.

https://www.instructables.com/id/Free-lithium-Ion-Battery-Pack


Step 5: Motor Mount

You can make a sturdy mount out of wood for most motors.

I had to use a 3 inch hole saw to cut 2 half circles to hold the motor.

Step 6: Balancing and Testing

It is important to balance the propellor very well. The propeller is rotating very quickly so a small imbalance will cause a lot of vibration.

Vibration will damage the motor and steal a lot of power.

To balance, mount the prop to a shaft. Place the shaft on two objects of the same height. The heavy blade will rotate down. Remove some wood and balance it again. Also balance the hub.

Test run the motor/prop and made sure it pushes.

Step 7: Control Switch

For the control switch I used a 10 A doorbell switch.

I like this switch because it switches off when you stop pressing it (much safer).

I used 14 gauge wire to wire the positive to the handlebars and through the switch. The negative was directly wired to the motor.

A larger switch may be required as the motor can pull more than 10 A.

Step 8: Mounting to the Bike

In my first test I mounted the motor and propeller to my cargo crate. This was not strong enough.

I made a mount that uses hose clamps to fasten to my rear carrier vertical tubes. I drilled holes in 2 2x1s to put the hose clamps through. The motor mount was then screwed into the ends of the 2x1s. This was very secure.

I only mounted the motor here because I wanted to keep my cargo crate attached. The motor should be mounted so that the prop sees clean air if possible.

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    40 Discussions

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    Physicsman5000

    Question 6 weeks ago

    I know it's a weird question but I have to ask because I am really curious. What if we attach propellars to both the wheels. Won't the bicycle run at much better speed? Also considering the propellars are light weight with piezoelectric batteries attached to it.
    My apologies if I am not making any sense. I am really curious.

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    GeorgeP70

    2 years ago

    I'm doing something similar but on an old ATV. Its just a rolling chassis. No motor or plastics . Mounting a v-twin on the back sideways with an aluminum prop. The V-twin motor is a Yamaha 1100 cc. will put an instructable on here when completed and tested

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    jaspreetzz

    3 years ago

    Great invention bro. At first u pedal and than use the power of propeller. Great idea buddy and i think u must use a dc table fan which is complete and just fix and go..

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    Undead_Engineering

    4 years ago

    I do appreciate the advice and I don't think its fair to drive by and hit someone with the tip of a propellor that doing 200km/h.

    I am still improving the design and am now working with a larger battery and radiator fan motor.

    Once my testing is complete and I have a perfected design I will try to build a large plywood duct. I am just worried it will be difficult to make it light and strong enough. If I am moving and I drop the bike I think the prop is hitting something regardless of how much protection I have.

    Allow me to explain the irony of my comment. CARS are dangerous. PEOPLE are dangerous... propellors are VERY dangerous... but you have the choice to stay away from the danger if you wish. This person obviously does not wish to. Me? I stay away from HIS danger. I create my own dangers. The dangerous comments are somewhat humorous here, it is pretty clear that this is VERY dangerous. I didn't mean otherwise. Sorry if I ruffled feathers. It IS a pretty cool toy, though.

    2 replies
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    stringstretcher

    Reply 4 years ago on Introduction

    You can get hurt by shutting your finger in a car door, too. Stop whining and live dangerously. Life is dangerous. Cool Propellor, be careful :P

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    agis68stringstretcher

    Reply 4 years ago on Introduction

    life is dangerous some times but stupidity is dangerous all the times!!!....that's a simple stupidity! call 911 and paramedics!

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    Undead_Engineering

    4 years ago

    Abinc

    Thanks for the great questions.

    This bike has 55psi in the tires so friction is low. Going up hill you need to pedal to assist the prop. No gyroscopic effect.
    Range with 2 laptop batteries maybe 15km.



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    Undead_Engineering

    4 years ago

    Motor is now held on with hose clamps. It was too powerful for duct tape.

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    Undead_Engineering

    4 years ago

    About using RC plane motor. Yes they are small and efficient but also expensive. I like using broken car 12 volt motors I get for free. I think the one I am using is about 300 watts. The magnet was broken and I just glued it with JB kwik so I am worried about vibration and the motor getting hot.

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    Undead_Engineering

    4 years ago

    With 12 cells (2 laptop batteries) its about 30 minutes at 30km/h (15km). But I am adding more batteries.

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    Undead_Engineering

    4 years ago

    Update instructable with test ride video.

    https://www.instructables.com/id/Free-Propeller-Bike-Mod-Update

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    r_e_l_a_x

    4 years ago on Introduction

    por que no, mejor usas el motor con una serie de engranajes o poleas, para mover tu bicicleta, esto se me hace peligroso para quien pasa a tu costado y para ti por si llegas a caerte, pero si tu idea es usar una hélice, pues te recomiendo que uses una ya fabricada, las venden en tiendas de aviones a radiocontrol, las hay de madena y nilon, búscate una con un buen paso de avance y que sea para empuje, para que puedas impulsarte (lo dudo), te recomiendo esto por que las fabricadas estan pensadas para que sean flexibles, no se desprendan en movimiento, esta balanceadas. Pero antes de tomar esta idea piensa un poco más en seguridad...

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    Wingloader

    4 years ago on Step 8

    How far can you go on that batter pack?

    PLEASE REMOVE THAT from your Bike before you hurt yourself or someone else!

    other than that its a great instructable on how NOT to propel a bike!

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    Tanzer26

    4 years ago

    I'll echo the safety concerns. Just a brush with the blade tip would cause severe injury. I would go with building a ducted shroud. It would add safety and efficiency.

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    imperio

    4 years ago on Introduction

    utilizzando quelle piccole batterie, che è la gamma [km] di tua moto?

    Imperio da Firenze


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    steveofthenw

    4 years ago on Introduction

    A fast-spinning blade on the back of a bicycle. What could possibly go wrong???