i would first like to say i absolutely love the instructables.com garage projects at their best!
i have made myself an electric bike for under 150 bucks. the range on it is about 7 miles or if u use it on the hills as an assist and coast down you can double that.
bike goes about 18mph and tops out around 25 on flat land
but it has pedals!!! so when the batteries run down you can ride old school.
so lets get started.
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Step 1: Parts!!! SAVE YOUR MONEY HERE!!!!
ok. lets check out the parts we need.
a bicycle. i was lucky and found one for free.
scooter motor, controller, throttle <--- get a razor scooter off of craigs site. i got one with dead batteries for $40 and came with the charger.
Batteries. Now this is where your money goes. you always want to start with fresh batteries.
I bought 4 of these --> UPG Sealed Lead-Acid Battery - AGM-type, 12V, 7 Amps, Model# UB1270 off of amazon. got them for about $22 each.
you will need some wire but if you carefully remove the electrics out of the CL scooter you should have everything you need.
couple of extra thing you will need.
a door hinge <-- stronger the better.
1x6in board. about 5 ft.
misc nuts bolts and screws
a 3.75in rubber caster wheel
Step 2: Design and Biulding the Motor Mount and Arm.
ok. this part will take a few cups of coffee and some staring at the bike. you need to ask yourself.
-where can i put the controller and electrics.
-where the heck am i going to fit the batteries.
how do i make this motor go on the back of here.
when you mount the motor arm you need to make sure that it is well constructed since all the force from the motor will be pushing against it.. the arm need to move up and down on the hinge so u can get tension but there should be no left to right movement on the arm. it will cause the wheel to slip off the bike tire.
Step 3: The Motor!!!
for this i am using a 250 Watt 24 volt motor i got out of the scooter.
you will need to take this motor to the hardware store and find a coupler that screw onto the end of it and some bolts that will also screw into the other side of the coupler.
Step 4: The Hinge Arm and Why.
i made the hinge arm for my motor so i can have a cable run up to my handlebars and lift the drive wheel off the tire. i used a bike shifter lever and cabling to make mine.
if you can remove the friction off of the motor while going down hills and when not using the motor it makes it way easier to ride and coast farther.
also without the motor spinning it has time to cool down while not in use.
Step 5: Control Box and Throttle.
run the throttle cable up to the handlebar. make the wire coming back to the control box longer or shorter if needed.
stash the control box in a place that is dry and out of the way. give it area to vent it generates a good amount of heat.
on my bike i have a bike rack over the hinge arm. the control box and wiring is mounted under the bike rack out of the way of the motor arm.
Step 6: Tensioning the Friction Drive Arm and Riding Instrustions
now this is kinda tricky. too much tension and u burn up your bearings, too little and u go nowhere.
you will have to play with the tension on the arm. use a bungee cored or spring to tension the drive arm to the tire. i drilled some small holes in my rubber caster wheel to give it better traction. what also helps a bunch is to go out and get a road bike tire (a 26in road bike tire will fit your 26in mountain bike wheel) it will be a smooth flat surface to run the wheel on instead of mountain bike treds.
now since this is a tensioned system you DONT WANT TO HIT ANY LARGE BUMPS OR SWEET JUMPS!! this setup is made for flat land. when i bump the bike the drive arm will pop up and come back down on the wheel very hard. can possibly break the mount, motor, wheel, or you.
also. WILL NOT WORK WELL WHEN ROADS ARE WET.
thats the problem with friction drive. when the wheel gets wet it causes the drive wheel to slip.