The goal of this project was to create a comfortable and fun means of transportation that is able to be carried up stairs and stored inside. The result was a mix of the practicality from the electric bikes and fun of the Little Tikes Go-kart, with a level of portability far beyond all the previous vehicles.
Building this project using the shared framework of batteries, motors, brakes and electronics used by the Little Tikes Go-kart and E-Bikes allowed for it to be built quickly and efficiently using proven parts, resulting in a vehicle that is reliable and doesn't require many unique spare parts or maintenance as the majority of the powertrain is standardized.
Time: Dec 2023 - present, V1 early 2024, V2 early 2025
Skills:
Fabrication: TIG Welding, Mill, Lathe, 3D Printing, Soldering
Software: Fusion 360 (design and FEA), Inkscape
Motor: 6000w+ capable modified MY1020
Battery: 60v 30Ah, 16s6p Tesla Model 3 cells
Controller: Fardriver 72300, set to 5000w
Speed: 45mph
Range: 35+ miles
Weight: 80lbs
One of the main modifications done to the frame was to cut apart, lengthen and TIG weld the swingarm back together to fit the larger motor
The longer swingarm and larger motor meant that the rear suspension had to be relocated, so I fabricated new mounts on the frame and swingarm
I modified the front wheels to fit laser cut adapters for larger brake rotors, and added brackets to mount larger calipers, both of which I ran extensive FEA on
I designed in Fusion 360 and 3D printed front and rear fenders, seat mounts, headlight pod, electronics enclosure, and controller mount, among others
Using a diffused addressable LED strip and a 12,000 lumen pod light, I created a very bright headlight with built in blinkers and other effects
This compact assembly takes in 60v, and has 12v and 5v buck converters, a relay, and uses an Arduino and handlebar mounted switches to control all the lights
I created a wiring harness and battery enclosure to mount and protect the 16s6p battery pack made from Tesla Model 3 cells
To make the bike more visible I added underglow, which also double as blinkers as each side is attached to seperate relays in the electronics housing
To handle the higher current from the upgraded controller, the old phase wires were replaced with 10 AWG, which is 50% larger
The holes in the endplates of the motor were drilled out larger, and screen was glued into the holes to stop dirt and dust from entering
To increase airflow further, an external fan was attached to the motor using a 3D printed mount I designed in Fusion 360
A heat sink was added to the outside of the motor, which has proven to be very effective in previous projects
I picked up a Burromax tt250r second hand because it is small minibike with full suspension, which from my research will hopefully result in a smoother ride despite the small wheel size.
Next placed the dead 24v lead-acid batteries for 33.6v of LiPo packs wired in series, which was able to go about 15 mph. I knew I was going to replace the entire powertrain but I wanted to test the current motor so if weight becomes an issue later, I could return back to the original motor.
I disassembled both the Burromax as well as a second minibike I bought at the same time for a later project and more parts, and experimented with different wheel sizes on the Burromax frame.
I also test fit the new motor which supported my existing plan to extend the rear swingarm both for more space and to make the bike more stable and less prone to wheelies from the added torque.
Next I created multiple initial sketches of various ways I could go about modifying the rear swingarm to fit the newer motor.
From the test fit and these sketches I realized I would have to relocate the rear suspension as well, so I drew up some initial sketches for how I might go about that as well.
I milled down the front wheel hub on a rotary table to be able to mount a brake rotor. First I took 140 thou off the top of the hub, while keeping the center a friction fit with the inside of the rotor for ease of centering and mounting later. Next I drilled and tapped the mounting holes for M6x1 threads.
I also created a CAD model of rear swingarm in Fusion 360 to start figuring out dimensions and experimenting with various motor placements.
Once the mounting location for the motor and suspension was determined I cut the old swingarm apart with a portable band saw, and found some scrap pieces of metal for the longer side rails and crosspiece.
I also cut the previous lower suspension mount off and used a belt sander to get it to the correct angle. I also cut in half and ground down a piece of the same stock used for the longer side rails for the upper shock mount.
Next I TIG welded the rear swingarm back together, and my friend welded the upper shock mount onto the frame so I could continue working on other parts as it was getting late.
Once the frame was together I moved onto modifying the motor. I removed the stock 14 AWG phase wires and soldered 50% larger 10 AWG wires on instead. I had to Dremel the access hole larger to fit the larger phase wires.
I drilled the holes on the end plates out for more airflow, and cut down and glued screen into the holes to stop dirt from entering.
Then I designed and 3D printed a mount for an 80mm computer fan to mount to the rear of the motor to increase airflow, and mounted a screen to the outside of it too.
I also mounted a heat sink to the motor which I have found to be very helpful in the past.
Next I cut down a piece of 3/16" thick Aluminum plate to the correct width and drilled holes to mount the motor into both it and the swingarm. As this was the first time the motor was placed into the assembled frame, there was a lot of test fitting to make sure it was in the best location to not hit the suspension and still have the chain properly tensioned.
I also cut out a notch for the chain as it was hitting the motor mount plate when I mounted it.
First test ride! I replaced the cable actuated front brakes with 4 piston hydraulic mountain bike calipers which will be necessary for safety at the speeds this will be going. For the first ride I left the old rear brakes as I didn't have any other hydraulic brakes that were bled.
Modifying the throttle.
3D printing, electronics, soldering, and more