A Bicycle Built For One


[Bcmanucd] must have been vying for husband of the year when he set out to build his wife a custom time trials bicycle. We’re not just talking about bolting together a few parts either – he designed, cut, welded, and painted the entire frame from scratch. Time trial racing is a very specific form of bicycle racing. Bikes are built for speed, but drafting is not allowed, so aerodynamics of the bike and rider become key. Custom bikes cost many thousands of dollars, but as poor college students, neither [Bcmanucd] nor his wife could afford a proper bike. Thus the bicycle project was born.

[Bcmanucd] created the basic geometry on a fit assessment provided by his wife’s cycling coach. He designed the entire bike in Autodesk Inventor. Once the design was complete, it was time to order materials. 7005 aluminum alloy was chosen because it wouldn’t require solution heat treating, just a trip to the oven to relieve welding stresses. Every tube utilized a unique cross section to reduce drag, so [Bcmanucd] had to order his raw material from specialty bike suppliers.

Once all the material was in, [Bcmanucd] put his mechanical engineering degree aside and put on his work gloves. Like all students, he had access to the UC Davis machine shop. He used the shop’s CNC modified Bridgeport mill to cut the head tube and dropouts.

The most delicate part of the process is aligning all the parts and welding. Not a problem for [Bcmanucd], as  he used a laser table and his own jigs to keep everything lined up perfectly. Any welder will tell you that working with aluminum takes some experience. Since this was [Bcmanucd’s] first major aluminum project, he ran several tests on scrap metal to ensure he had the right setup on his TIG welder. The welds cleaned up nicely and proved to be strong.

The entire build took about 3 months, which was just in time for the first race of the season. In fact, during the first few races the bike wasn’t even painted yet. [Bcmanucd’s] wife didn’t seem to mind though, as she rode it to win the woman’s team time trial national championships that year. The bike went on to become a “rolling resume” for [Bcmanucd], and helped him land his dream job in the bicycle industry.

Echoing the top comment over on [Bcmanucd’s] Reddit thread, we’d like to say awesome job — but slow down, you’re making all us lazy spouses look bad!

16 thoughts on “A Bicycle Built For One

    1. Aluminum bikes are usually tig welded, there is no flux or splatter from welding so the table should be clean after. As long as he does not use the table as a ground there should be no marks from arcing either.

      1. You can MIG aluminum too and it is much easier to MIG it than TIG it for a beginner. While a decent welder *might* be able to keep most of the slag off, our weld tables are pretty slaggy after a few years of use. Yes, most of it cleans off but laser tables are generally regarded as nice, clean, aligned surfaces.

        1. Yes, I have both processes at home, tig and mig/pulse mig for aluminum with spool gun on my XMT304. When wire feeding aluminum you still should be in spray transfer and you still get some spatter but it is considerably less than steel mig. Also the dingleberries dont stick like steel one do and usually just wipe off.

    1. I was a weld inspector (x-ray and ultrasonic mostly) decades ago (summer job during university). This statement is not true. I’ve seen high-defect welds that cleaned up nice and awful looking welds that were perfect. The best welders most often produced quality with a clean finish.

  1. Fixed frame geometry, that’s….bold. I hope her pedal stack height, range of motion, or fitment changes. Because it can’t. A lot of time trial riders mistakenly get fit purely for aero, when they really need to be fit for both aero and being able to breathe.

  2. Building a bike is a great project, requiring a nice range of skills. CAD and CNC are one approach, but you can also do an fine job drawing the full-size layout on a piece of paper and using hand tools (hacksaw, file, vise, etc.).

    Getting a good fit before you start the design is great advice. I got fantastic results on my first attempt.

    One caveat here. Building a frame or two is definitely no way to save money. There was talk on the Framebuilders Google group recently of buying whole bikes and selling the carbon frame for cheap as one of the least expensive ways to obtain components. Just the tubeset itself costs way more than an inexpensively produced (e.g. Taiwanese) frame.

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