March 25, 2013

Electric Tricycle

So I built another electric vehicle.  This time around, I actually did some designing before I got any parts, so this was less of a "what do I do with this cool part" project than most of the things I build are.  However, the actual construction of the vehicle was started due to the acquisition of a cool part:  the "melon" sized brushless motor that drives the tricycle.  Getting the motor was a great excuse to implement a bunch of ideas for an electric vehicle I developed after building my electric scooter.

This was my first big project done with access to real machine tools (courtesy of MITERS), so this was both my learn how to machine things and learn how to Solidworks project.  Even with just a semester working with these tools, I was able to make this vehicle significantly more refined (while simultaneously even more ridiculous) than my scooter.

The design for the vehicle was inspired by the classic Radio Flyer tricycle.  That vehicle geometry is not exactly intended for the high speed go-kart like performance I wanted, so I tried to optimize the design while retaining the tiny kids-trike aesthetic.  

And now, a brief overview of the tricycle's specifications:

Motor: Turnigy C80100-130 brushless RC outrunner
Controller: Kelly KBS48121 120A peak BLDC controller
Batteries: 39.6V 7.5 Ah A123 Systems Lithium Nanophosphate pack
Drivetrain: Manual 8-Speed Shimano internal gear hub, custom spur gear differential
Chassis: Welded steel tubing and aluminum plate construction with side-to-side leaning
Top Speed: 45+ mph, if you're feeling brave

More pictures, videos, and build log can be found after the break.

The tricycle's build log can be found here (in reverse chronological order) or below:
The basic systems of the tricycle work as follows:
Hidden beneath the black cover near the back left wheel is 300 Watt-hour battery pack built from 36 A123 26650 cells.  This pack feeds a Kelly KBS48121 controller, capable of outputting over 4 kW peak, controlled by a twist-grip throttle. This in turn controls a Turnigy C80100-130 brushless DC motor.  The output from the motor (after a chain reduction) turns a  8-Speed Shimano internal gear hub, which can be shifted with a trigger-shifter on the handlebars   The output from the gearbox, after a second chain reduction, turns a spur gear differential, splitting the torque between the two rear wheels.  If you for some reason want to stop, a brake lever on the handlebars can actuate disk brakes on each rear wheel.  Steering is accomplished very similarly to a bicycle or motorcycle.  In addition to the handlebars turning the front wheel, the front half of the trike's frame also tilts side to side.  The tilting motion allows for fast, stable turns, which would not be possible if the frame were rigid.

Here you can see most of the inner workings of the drivetrain:

Action shot:

Large parking lots become excellent riding grounds at early hours of the morning:


  1. Awesome job!
    Where did you get that differential?

  2. What a sexy differential! I also loved seeing the rotary brakes on that baby. This build should be rated X for xcellent!

  3. He built the differential.

  4. Ouch, BLDC and a NEXUS... Thats the shizz.

    Congrats on some fine engineering.


  5. Brake as you enter the turn and accelerate at the apex! Driving 101

  6. Hey
    Yours is a cool project. I love it. You're not down in Cornwall are you? I have a project that I am trying to get up and running:
    I am using plastic as a frame but it won't take any massive weight. What would you use to build the frame please?

    1. No, I'm not. The curved portion of the frame was made from steel tubing, and the rest of it is aluminum plate.

  7. Could i ask what kind of range or how long the batteries would last on the trike with this setup. Would like to make something equivalant for commuting to work. Would not need such high peak power, but power non the less.