I'm back with another fun electric bike build. I recently junked an old trike frame from a previous project and since the rear part of the trike was still in reasonably good condition i wanted to make something new.
You can check out all of my previous builds here on instructables.com or on my YouTube channel
Step 1: Tools and Parts Required
An old wheelchair motor with gearbox. These can easily be found online or at thrift stores. I like to use these motors because the gear reduction is perfect for adapting them to bicycle gears. The one i am using makes about 150rpm at full speed and is powered by a 24 volt 350 watt motor.
Two 12 volt batteries. The bigger the batteries the longer the range but balancing weight of the batteries with range is tricky. The batteries i am running are 72 amp hour wheelchair batteries which weigh about 35lbs each. Since the motor is a 24 volt motor the 12 volt batteries will be hooked in series making 24 volts. The batteries i will use in this instructable are 12 volt 72 amp hour electric wheelchair batteries that are about 7 years old and well maintained.
Hooking the two 72 amp hour batteries in series gives you 24 volts with 72 amp hours of capacity. I know from previous experience with two of these motors on the same gearing will go 10 miles on these old batteries. (see Electric Trike On The Cheap)
Motor speed controller. I used a PWM DC Motor Speed Controller with Adjustable Variable Speed purchased on Amazon for about $21. If you check out Friction drive electric bike controller in my YouTube series it will show you more about the controller.
About 20 feet of thick copper wire. Enough to carry the amperage of your motor. This will be used to run the power from the batteries to the speed controller and to the motor. Too small of wire and it can melt causing your system to short out.
30 amp automotive fuse with holder.
Bucket of random nuts and bolts. Use what u have. keep it cheap
16in length of 1x1in box steel for the motor brace.
An old bicycle tube.
a 8in long bolt with nut or a length of allthread. For chain tensioner.
Zip ties. Always have them. Always carry extra.
Some cardboard to make a template of the motor mounting points.
Electrical connectors. For connecting wires or you can tin them together.
A board or metal plate to make the base out of
some random brackets or bits of metal for motor mounts.
Drill and drill bits.
Bicycle chain tool or another way of taking apart bike chain.
A basic socket set
Step 2: The Frame.
I purchased a BMX bike at the thrift store for 7 dollars to use as the front of the bike. The trike rear end was from an old project.
After bolting the trike together and fiddling with the connections to make the bike as straight as possible i tightened the bolts. This connection may not be strong enough for all the weight it is holding so i may weld it together later if required.
Step 3: The Base for the Motor and Batteries
After finding a board or piece of steel for the base mark it out and cut holes for the chain and sprocket. The motor I used had a flat mounting point with two raised spots. Drill one hole for the raised spot on the motor and one larger hole for the neutral/drive switch on the gearbox.
Using a bit of cardboard make a template of the 6 possible mounting holes on the motor and transfer them to the board.
Step 4: Mounting the Motor. the Sprocket.
The cardboard template is used to drill holes in a small metal plate to make a bracket. The bracket is placed under the board to clamp the motor to the board and make it more sturdy.
Using 1x1in box steel i made a brace for the middle of the board to keep the base more rigid and prevent warping/breaking of the board. This piece will also double as the front mount and chain tensioner.
Step 5: Keeping the Chain Tight.
To keep the chain tight the front mount is drilled and a 6in long 5/8in bolt is used to connect it to a metal plate connected to the old rear brake mounts on the BMX frame.
By twisting the nut clockwise it raises the motor deck height and tensions the chain. This also allows an easy way to remove the chain to repair any issues with the drive system or service the parts.
Step 6: Speed Controller and Throttle.
I got the Speed Controller online. See the Parts required section at the beginning of this instructable for more info.
The throttle is mounted to the bracket that once held the rear brake handle. The handlebar grip was trimmed up slightly to allow the throttle to be mounted in a comfortable position to use.
Step 7: The Box
This box was a great find. High enough to fit the batteries and big enough to fit the batteries and motor in, The box had to be mounted slightly to the left of the center but that gives room to put something else on the side.
To keep the batteries from moving around i used bits of PVC pipe and 1x1 box steel. before installing they were wrapped with 4 strips of a bike tube. This keeps anything from rubbing against the batteries.
Step 8: A Little Decoration.
A red blinking light is placed on the back for safety and some old stickers were placed onto the battery box.
Step 9: Test Ride and Video of the Build.
Here are the test ride and build videos.
Don't forget to vote for me in the Bicycle contest!