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New Project - An Adjustable Bicycle

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New Project - An Adjustable Bicycle

Monday, June 29, 2020   |   Chris Blandford

Before I explain the Why, I’ll explain the What. (Nerdy bicycle stuff here--I apologize.) This is the second piece to a puzzle I’m slowly putting together. I’m building an adjustable geometry bicycle. I posted photos of the stem to Instagram few weeks ago, and the fork was next on the to-do list.

You’d think an adjustable rake fork would be easy enough to make. I wanted to accommodate variable headtube angles, however, and so... well... things got a little weird. The fork can be adjusted for use with a frame that has a 65-75 degree head angle. The rake is adjustable from ~20mm to ~90mm (rake is measured perpendicular to the steering axis, so the exact range varies with the head angle). The porteur-style rack was also made to pivot, so as to remain level regardless of head angle. The rack angle and the head angle can only adjust together (not independently), which locks the whole thing down nicely when torqued into place. No front brake. I’m trying to avoid a… umm... cat’s curiosity situation here... and thought braking forces on a sliding front wheel was probably not a great idea. I’m also planning on experimenting with multiple wheel sizes on this bike. It’ll clear up to a 700C x 43mm tire.

I designed the fork one day while my daughter and I were coloring out on our deck in the sunshine, back-of-the-napkin-style. From there I drew a full-scale drawing with pencil, paper, and a big-ass compass. Finally, I translated those drawings into the computer and sent off to the laser cutter for the component pieces. Building the fork took way less time than designing it and receiving the parts.

 


You can see a video of how this fork works, here on Instagram.

As for the Why? Well, that’s a little more complicated. While I’m mostly curious about front-end geometry and handling, I also have questions about the rear-end of bikes, center of gravity, load carrying, etc. My unwillingness to take others' words for things along with a rather relentless curiosity have gotten the best of me this time, I think. I’ll share more on that front soon.