Electric Trike With Bmx Front End.




Introduction: Electric Trike With Bmx Front End.

About: Check out ThriftStore Hacker on YouTube! Where junk makes neat stuff! Follow me on TikTok @ThriftStoreHacker

Hello Everyone!

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

ThriftStore Hacker on YouTube

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.

Electrical Tape.

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.


Tape Measure


Drill and drill bits.

Bicycle chain tool or another way of taking apart bike chain.

A basic socket set


adjustable wrench.

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!

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    LaMar Solarcabin
    LaMar Solarcabin

    6 years ago

    You leave rude comments and attack other designs in contests. Not very mature or sporting and certainly not in the interest of Instructables. Have a good day!


    6 years ago

    If it helps you (or anyone else building one), I built a similar one a few years ago, but in semi-recumbent style with pedals/chain on front wheel:


    which was decommissioned last year to make a new one that has been much more useful to me:


    ThriftStore Hacker
    ThriftStore Hacker

    Reply 6 years ago

    Lots of good ideas in your post! i am thinking of making the trike a recumbent if i can find a front end that is lower.


    Reply 6 years ago

    If you're gonna do any welding on it anyway, you can just build a front end; it doesn't have to be lower--look at the SB Cruiser:  I've attached an image of it with just the basic front frame shape put together, made out of the headtube, toptube, and downtube still assembled as original, off an old ten-speed bike.  The downtube is inserted into 2" square tubing which is the new downtube.  The new "toptube" is 1" square tubing a few inches above that, and a BB shell and cranks off a bike go between them at the angle change point.

    This whole thing then gets welded to whatever backend you have at whatever length puts the seat wherever it's comfy for you.  I just used the entire backend off Delta Tripper to simplify things as it was already how I wanted it, I just hated the frontend of DT.   

    The pic shows the approximate longitudinal position of the rear wheels; I think mine ended up a bit longer wheelbase, by a few inches, can't remember for sure.  

    This makes the trike much longer, and also MUCH more stable in turns at speeds above a slow walk. ;-)    With the 20" rear and 26" front, and no load in the back, with the rear hubmotors, I can make a right turn at 16-18MPH depending on the road conditions.  I can make a left turn at 18-20MPH, as it's always a wider turn.   This means I don't get runover by car drivers too impatient to wait that extra tenth of a second for me to be past wherever it is they think they need to be, when I'm still in the turn lane.  ;-)

    I"m actually getting ready to move the seat forward a few inches, and move the BB/cranks to in front of the downtube, so I can get the dog crate forward just a bit, by custom building a cage-style one with fold-down cover-sides for shade and rain protection, with insulation in them/etc., cuz the new dog Teddy is a bit longer than Tiny was, and Yogi is longer than either one, so to fit comfortably in there they need more space.  Can't extend it in back cuz then their weight will be behind the axle and the trike will rear up like a scared horse.  ;-)

    ThriftStore Hacker
    ThriftStore Hacker

    Reply 6 years ago

    This is the 3rd build for that trike rear end.

    first one is here: https://www.instructables.com/id/Electric-Trike-on-...

    That was a great design but the frame could not hold the weight and broke off near the front.

    I cut the end off of the bike, welded on an extension , and put a 1990's style kick scooter front end on it. It served me very well until i build my new recumbent. The BMX frame is cool looking but i agree that the trike needs to have a lower center of gravity. I may go back to a lower slung design on the next build. Maybe even 4 wheels to make a sweet gokart.


    Reply 6 years ago

    I wish we could have four-wheelers here, but AZ law says to be a bicycle it cant' have more than 3 wheels in contact with the ground. :-( Since I'd rather not ever have to deal with the legal issues involved should someone decide to not like my vehicles, I stick to the legal versions of them so they can't pick on me for that, at least. :)

    ThriftStore Hacker
    ThriftStore Hacker

    Reply 6 years ago

    California law says i cannot have a 4 wheeler here as well. I am thinking of making a caged 4 wheel cart just to run around on a friends property with.

    ThriftStore Hacker
    ThriftStore Hacker

    Reply 6 years ago

    Oh. Also. I really like the design you are working on. You should look into a 500 watt wheelchair motor with gearbox to power it. With the wheelchair gearbox already doing a 20 to 1 reduction you would be able to hook a freewheel sprocket on it and power it with the bike's chain.


    Reply 6 years ago

    If you check out my CrazyBIke2 thread over on Endless Sphere, you'll see where I used a couple of different kinds of those to power it that way, with varying results (lots of destroyed bike parts from the torque!). If the frame hadn't been so flexy at the time, I would probably not have had those problems and would've stayed with those motors. I still have them in the shed. The frame is a lot stiffer now after several generations of mods, and would probably work fine if I ever had to try it...but it uses two hubmotors now, and gets 0-20MPH acceleration of about 4 seconds, quick enough to avoid being run over from behind by cars at traffic lights when I get stuck as first in line, even with a bunch of heavy cargo on it.

    For the SB Cruiser Trike, the two rear hubmotors are fine right now, as they provide plenty of power to accelerate and haul even two Saint Bernards (one on the trike and one in the trailer) plus cargo and me, right up to the 20MPH speed limit here in AZ. :)

    But I do have eventual plans to add a third motor to the front wheel, for 3WD, though it will probably be a geared hubmotor I already have in the right size wheel, since I have to build a suspension fork that's better than what I have anyway.

    Someday I may revisit the powerchair motors via chaindrive, though, once I have to rebuild the trike or make a new one anyway, and can add a transmission to the rear end to drive both rear wheels (something better than a double-freewheel jackshaft, which while easy doesnt' work very well for my purposes).

    I do plan on doing a powerchair-motor-driven version of the flatbed trailer, though, so it has one on each side, primarily for power boost during startup or hills or slopes with heavy cargo or one of the dogs in the trailer.