Pedal Car

The idea to build a pedal car came to me with the impending summer in between Junior and Senior year of high school (May 2024). I'd gotten a job running summer camp admin, but that wasn't enough to keep me occupied for three months. I wanted to continue building things with my best friends on my robotics team.

I organized a group of seven students and we met regularly on weekends throughout the summer, developing a human-powered vehicle. With no budget, I encouraged us to be resourceful; we used anything we could get our hands on: old rusty door hinges, ancient children's bikes, 2x4s from the woods, and screws from a bucket of random ones in someones garage.

Research and Development

The project began with disassembly of two bikes donated to the cause by my friend's parent. They were given under 1 condition: under no circumstances could they be returned. So, naturally we took them apart.

As we went about the demo job, we were gaining an understanding of how bikes worked mechanically, and what parts we could repurpose.

One of my proudest moments of this project was getting the bike shop owner to sell me two sprocket sets for five bucks!

We did design mainly with pen and paper, as most of us were just beginning to experiment with CAD. I was not quite confident enough to design in software yet.

Found some door hinges at my friends house and made angle brackets by hand from scrap metal.

Visualizing the chassis for the first time in real life.

Wheels from the old bikes are placed in position.

I now understand that our front steering system would be called a four-bar linkage, thanks to my engineering classes in college, but I had no idea what that meant back then. Instead, we were building what made sense in our heads, and seeing what happened. In addition, we'd done a fair bit of research to find examples of steering systems and people that had made Go Karts similar to our project.

Here you see us pedaling for the first time with the newly attached pedals and sprockets. We cut these off the old bike frames with a Sawzall and drilled holes to bolt them onto the wood. The car officially became a two-seater.

We were very lucky to have my friend's dad help us with the tools and supply the backyard as our workshop!

My favorite manufacturing moment from this project was when we welded the back wheel supports on to the rest of the frame. I'd never welded before and was thrilled to learn how.

For the frame we used some old wall mounts for shelves that we found. We also bent a scrap piece of metal for added support. Now, all four wheels were attached and inflated; we were surprised that all of them held pressure well!

Steering System 1:

For the first attempt, we attached twine to the piece of wood in the front that pivots along with the wheels.

The passengers would "steer" by crossing the rope and pulling on their side. It was very clunky and caused the front wheels to splay outwards after only a little bit of use.

I had plans for a permanent system, but was too excited to test ride it!

Steering System 2:

We wrapped the same piece of twine around a PVC pipe and bolted a frisbee as a steering wheel onto the top. It held the rope more securely and provided more turning leverage.

On the left you can see one of our first road tests in a parking lot with the new steering system!

After this road test, we unfortunately had to disband for the end of the summer. I had a wonderful time doing this as my first independent engineering project!

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