Electric Bike (Assisted - Not Full Electric) Step One




Introduction: Electric Bike (Assisted - Not Full Electric) Step One

How to turn an average bike into an electric assisted one. Step one.

Step 1: Get a Second Back Wheel - Geared Axle.

To start this project you need to get a second back wheel. This backwheel that has a gear on it will become your new front wheel.

The image here of a geared back wheel does not have a freewheel. The freewheel is the part with five or six gears on it that can only apply force in one direction.

Step 2: Problem Solving

If you happen to try to put the back wheel into the front wheel spot , you will find it doesn't fit.
The back wheel is typically around six inches, the front is five.

To solve this problem, you need a bolt or an axle from the rear wheel.

And you need some luck and the correct front axle fork.

The correct axle fork is one that can be stretched, not all can be stretched outwards to accommodate a wider axle..

1)Bolt one side of the axle to the side of the front fork. Two lock nuts.

2)On the other side "loosen" a third nut outwards towards the other side. This will stretch the metal frame of the fork.

I don't have a picture of these steps , I will add them later when I have time.

DANGER When you are putting pressure on the fork, it will try to push out of the slot. It may pop out suddenly so watch your fingers and eyes.

The turning will take so time be patient, and you might have to do it a few times as the third bolt you are turning outwards tends to slip out.

When to stop
With a measuring tape, check on the distance between the front fork from time to time.

Its static distance size can be stretched a bit (about a half inch) so when measuring it does NOT have to be the exact size wide of the rear axle.

Step 3: Bolt the Wheel in Place

Bolt the wheel in place.

Step 4: Other

This works in the sense the wheel spins, but the ratio is totally wrong.
The motor is a high RPM one and has low torque.
And it is very heavy so makes it too dangerous to steer, for the general public to use.

Step 5: Other 2

Steel frame too heavy , but witha gear reduction ratio for the high RPM motor.

Works well but is too heavy.

Step 6: Other 3

Last build.
I mounted the batteries in the frame. There is a voltmeter on the handelbars. The steel frame is held by steel bars (black) now. And a rear derailer spring-slack absorber was added.

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    12 Discussions


    9 years ago on Step 6

    First what type and model batteries did you use second how did you put the gear on the motor you found?

    I have a motor with a 3/8 inch X 1.25 inch shaft and a 10mm inner shaft?
    What does inner shaft mean also could normal bike freewheel be put on it how would that work



    Reply 9 years ago on Step 6

    I used six 12 volt lead-acid batteries. They were relatively cheap.
    I had a two stage switch. The first switch stage was 36 volts (or three batteries in series), when the bike got moving to a decent speed I then went to the full power of all six batteries. 72 volts total. Had to stop when the batteries got too low, if you drain the batteries too low, they might not recharge or be damaged. Then you flushed your money down the toilet.

    This is only a for fun project, reliability is very low. I can not depend on it for regular travel.

    RE how did you put the gear on the motor shaft?
    It was very difficult.
    There is a freewheel removing tool.

    I mounted it to the axle of the motor, and used a bolt and large washer to hold the freewheel on. The bolt fit inside the shaft on the motor.

    To glue I used this epoxy designed for metal.

    If the fit is the tiniest bit off, the freewheel will wobble, and you cant have any wobble if you want the chain to stay on.

    Motors can be very different.
    You can have a high amperage 24 volt motor, or like I had a high voltage motor with lower current. Both add up to high wattage.
    24 volts times 15 amps = 360
    72 volts times 5 amps =360
    You need a minimum of 300 watts to push the average person.


    12 years ago on Introduction

    I like the simplicity of using a "back wheel" for the freewheel, but this feels a little unfinished even for a "step one". If you've finished the project I suggest you write it all up as one Instructable, if you haven't then it is probably wiser to hold off on publishing until you have enough for a substantial Instructable.


    Reply 12 years ago on Introduction

    I have made a complete electric bike, but it broke after every run. It broke due to its complexity-too many moving parts. I decided to go simple here, as in KISS. The next step in this project will be finding an electric motor and attaching a freewheel to it.


    Reply 10 years ago on Introduction

    Hi mark !, do yo write the next step yet? thanks


    Reply 10 years ago on Introduction

    I must make one! You need four (4) things for an electric assisted bike. 1) motor including gears that propel the front or back wheel 2)battery package 3)electric control circuits 4) bike The front wheel project (here-step one) is part of the motor project. I made a battery package that fits inthe triangle frame of the bike. The battery package will be the next instructable.


    Reply 11 years ago on Introduction

    sorry about not having a write up yet. I will do soon as possible.


    Reply 12 years ago on Introduction

    That's more like it :) Are you going to write up the rest of the project for an Instructable? I'm quite taken with this design, if my current junker bike didn't have suspension forks I would look into doing it.


    Reply 12 years ago on Introduction

    I have several DC motors from the last bike, "find" is the instruction.