Tinkerer and bicycle lover Champx has created a transparent three-speed gearbox for his homemade “swinger” bike.

Constructed with cogs pulled from other internally geared hubs, the mechanical design is inspired by old tractors. The cranks drive a spindle with three different size cogs, and a brass slider engages keyed teeth inside the cogs one at a time to determine the gear. These turn a lower spindle, which is then connected back to a larger cog that turns an outer axle with the chainring attached on the outside. It’s all housed in a custom made plexiglass case and mounted to his own bike.

This is one of those projects that’s definitely better shown than told, so click on through to see how it all comes together. And see what a “swinger” bike is…

Here’s the almost finished gearbox. A single piece of orange plexiglass was used to get the spacing right, but it gives the impression that the whole thing glows orange.

A shifter slides the brass piece, which moves an internal axle to connect with an individual cog.

This bit actuates the slider, which is pulled by the shifter cable by way of a couple of rods and pivot.

A heavier duty return spring assembly was incorporated to pull the cable taut. You can see the first version in the photo above this one.

Here’s the bike in action, which is every bit as wild as the gearbox:

Want to create your own? See if you can follow along over on his Instructables page…where there’s also an Instructable on how to create a hubless bike, plus a few quick videos of the gearbox and tons more photos.