Designing a Bike

I love bikes, want to be able to use them more often than I do, and have been looking for something to do as a hands on project that doesn’t use the computer so much. Building my own bike seems like a neat and unique project.

When thinking about what I would want in a bike there are a couple things that I would put as the most important design constraints.

1. the frame should be as simple as possible, ideally something that has very few parts and could be manufactured entirely by robot.
2. It should be hackable and extendable for easily adding trailers, baskets, etc.
3. should allow for electric motor version with a mid-mounted motor.
4. should should theoretically possible to make it very inexpensive to build.

While thinking about and researching a lot of the existing products on the market I thought there was some opportunity to create something better and unique. It started with an electric motor and transmission design.

I designed a motor integrated with the crank and isolated sprocket so that the pedals and motor can independently power the belt drive. This is housed in a single small unit and will allow for a simpler fixie style rear wheel hub while still allowing the pedals to idle. By moving most of the mechanical complexity into a single component which can be enclosed and made water tight it can be made maintenance free and high reliability.

For the bike frame itself I want to think about something that requires no, or very little welding, ideally it would be made from as few parts as possible. Car unibody design gave me the idea of doing something with stamped metal sheets. I wondered if there was a way to build a bike frame from a single piece of metal with only a couple of mount points for the seat post, stem, rear wheel, and crank to attach to it. A key thing was to have a rear wheel mounted on only one side (like some motorcycles do). This allows the frame to be stamped out of a nearly rectangular piece of metal which reduces wasted scrap and eliminates many steps from traditional bike manufacturing.

What’s next? There are two things I need to solve. Firstly, there’s a lot of engineering to refine the design enough to validate it. Secondly, I need to build a prototype. The steps and knowledge required to get to a testable bike is well outside my expertise so any realistic future where this gets built will need a team working on it. There are two ways that I could get this done. Either open source the bike design and try to attract a community to continue working on it or hire people. In either case one of the logical conclusions for this kind of project would be to do a kickstarter to fund production after the prototype is validated.