What I learned in school this year
Or, how I built a recumbent bike in six months
by Nolan Chase, age 16
Building a bike, frame and all, is a long, difficult process, unless you are set up for production work. With two, three-hour classes a week in which I’ve been able to work on my bike, I’ve been working on it for 6 months now. The frame started as a frameset of cut, bent, and mitered tubes, ready to be put together. We got the frame parts from Burley, which, late last year, stopped making bicycles, and donated all their leftover framesets to us. The frameset is true temper 4130 double-butted cro-moly tubing, so the bike shouldn’t be lacking in strength.
The bike I’m building was a short wheelbase recumbent, branded Hepcat, for the spendy high-end model, or Django for the more affordable bike. Since we didn’t have a fabrication jig for this frame, we started the hard way, by tacking parts together, then checking the alignment. After I had the frame tacked together, minus the chain stays, we started building a jig based on the frame. This took several weeks. Once we got the jig put together, I was able to tack the chain stays on and be sure they would be on straight.
Once I confirmed that all the parts were aligned well, I began TIG welding the bike together. When you’re welding a bike together, you have to weld parts of the frame in a pattern, or the shrinking of the weld can pull the bike out of alignment. This makes the welding process take a bit longer than one might think. After the welding, I needed to braze on the cable mounts, as well as brake bosses, in case I ever needed them.
After that, I built the wheels for the bike, a 26” on the back, and a 20” on the front. The next step after that was the seat. Almost every recumbent manufacturer uses their own proprietary seat design, Burley being no exception. The original seat had a rail that was pop-riveted to the frame, and the seat slid for and aft on that. Being that we had no such rail, or even the right seat, we had to make a compatible design using the Human Powered Machines seat. I continued to think about it while I built the seat. The seat is made of bent and mitered aluminum tubing, with a mesh seat cover over it.
The tube that the rail mounts on was round; meaning that putting the rail on evenly would prove a challenge. Over the course of the next month or two, we had co me up with a design with an aluminum rail sitting on several arched pieces of hard plastic, then riveted to the frame. This design would help ensure that the rail sat straight.
With the problem of the seat rail solved, I was free to continue putting the bike together. Instead of using a front derailleur, I built the back wheel using an SRAM Dual Drive hub. This hub combines a 3 speed internal shifting hub with a 9-speed derailleur and cassette. I decided to do this for many reasons. Without a front derailleur, I had no need to attach a tube to mount it on, like Burley had to. Also, you can shift down while not moving the pedals, which can be handy on a recumbent, as they tend to have trouble going up hills. And finally, I used it because Satan, Lord of all Lies, spawned front derailleurs exclusively to piss me off.
For a recumbent with above seat steering, it’s important to have an adjustable stem. For my stem, I ordered a GlideFlex stem from Terracycle, in Portland. The GlideFlex is the only stem of its kind that has no metal on metal contact in the pivot, so it adjusts much more smoothly than others, and it lasts much longer.
At this point, the bike is very close to completion. I need to put the mounts for the seat support rods, add fender and rack mounts and machine the seat rail clamps. After I put all the parts on and test it, I will then disassemble it for sandblasting and powder coating. I plan to paint it a dark, metal flake green, called metallic mossy green. With any luck, by the time you read this, I’ll already be blissfully riding my awesome new bike.
Possibly Related
- May 2008: Collecting oddball bikes
- April 2007: Filmed by Bike is back in town
- January 2008: My bike is reverse-engineered
- January 2007: ActiveTunes iRide stereo system
- March 2008: BMX racing: a rider's perspective
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