Electric Bike (v1)

System Architecture

I built this bike when I was 13. I didn't have a lot of money, so I used a "friction drive" system. This means the motor sits directly on the tire and spins it using a piece of sandpaper tape.

Sandpaper tape on the motor provides grip against the rubber tire.

Mechanical Design & Fabrication

It wasn't very efficient and the tape wore out quickly, but it was the easiest way to make the bike move without a chain or gears.

Electrical & Firmware Implementation

Hand-Soldered Battery

The battery was my first big electronics challenge. I used 48 individual 18650 cells that I bought from the Facebook Marketplace. Since I didn't have a spot welder, I soldered thick copper wires directly to the cells.

I used thick copper wires from an old extension cord to connect the cells.

This was a dangerous way to build a battery because the heat from the soldering iron can damage the cells. I wrapped the whole thing in foam and blue duct tape to keep it together.

Validation & Failure Analysis (Post-Mortem)

The bike worked for a few weeks, reaching about 20km/h. Eventually, the cheap motor controller (ESC) burned out because it wasn't meant to handle the high current needed to start the bike from a stop.

Throttle

The ESC needed a PWM signal in the standard RC range. A potentiometer outputs analog voltage. I could not find a ready-made adapter, so I wired a cheap pot into an Arduino Nano and wrote a short sketch to read the ADC and output a mapped PWM signal on a servo pin. The Nano ran off the ESC's BEC.

Arduino Nano reading the pot and outputting PWM — powered from the ESC's built-in 5V BEC

The throttle body itself was 3D printed, with a small lever sized for one finger.

Lessons Learned

After the ESC died, my dad got me a VESC 6.7 Pro. That became v2 — a much more reliable build that I actually rode for a full year and took on longer trips.

The CAD files for the printed parts are probably gone. The machine I was printing on at the time had no remote backup and no Klipper, so nothing was saved. I have not been able to find them.