In late 2014, two friends and I decided to begin building a bike based on the Strandbeest. The Strandbest is a walking machine created by Theo Jansen in the 1980s. Imagine this machine below, scaled down to the size of a bike, where the back wheels of a bike are replaced with legs. That is more or less what we set out to do. The process involved 3 people, took 6 months and 1000 man hours to complete.
As complicated as this machine may appear to be, it can be simple when broken down. The Strandbeest is a series of Jansen’s linkage’s. Each Jansen Linkage imitates the motion of a leg. A leg by itself is trivial but when they function together, you get something much more complicated.
Our idea was to leverage the concept of the Jansen Linkage to construct a bicycle that has rear legs instead of a rear wheel. In this blog I’m going to review the various work that was involved in order to make that idea a reality. By this point, most of the bike is done. There’s some painting and fine tuning to do. I’m pleasantly surprised with the results. We had a lot of confidence this bike would work and it wasn’t until maybe 70% through the project we we really able to unit test it.
First steps were to create a 3D model. This project was more or less the brainchild of JP and he created a miniature working prototype. Given the material in this 3D model does not lend itself to moving gracefully, with enough patience, the legs will function. The idea started with this toy model, JP presented it to Roy and myself then we began work on construction. Start to finish, it took about 6 months and 700 man hours. It includes ~450 metal pieces, ~120 plastic bushing, and half a bike.
Here is a summary of the initial materials list, required equipment and initial steps. The materials is not very exciting at this point. Most of the work in the first few months involved cutting, welding, sanding and bending 1/2 steel pipe. It wasn’t until we go to fabricating joints did the materials, equipment and work get creative.
- 160′ of 1/2″ steel pipe
- 3′ of 5/8″ cold rolled steel rod
- 10’x1″ of 1/8″ steel plate
- 120 bushings (part# MYI-05-05 from igus.com)
- Arc welder
- Drill press
- Pipe cutter
- Graduated drill bit for cutting 1/2 steel
Pre fabrication steps:
- Design the 3D model
- Print the 3D model
Initial fabrication steps:
- Create a full size leg prototype out of wood.
- Verify wooden leg linkage can function as expected.
- Define dimensions for metal fabrication, how many pieces of each length are needed.
- Cut steel pipe to specifications (very time consuming).
- Construct jigs for welding.
- Weld steel pipe pieces together.
- Research ability to have functioning joints.