So, your girlfriend is a competitive cyclist who needs a new time trial bike, but you’re both broke college students? Well, if you just happen to have just finished your master’s thesis and have full access to the universities machine shop, you simply make her one! Sounds easy right? Well, it isn’t, but the following gallery almost makes it look that way.
Bike engineer Brendan Connors took a lot of time to take fantastic pictures and document every step of the process. You can see the incredible amount of work that he had to put into not only designing the bike, but even having to make some custom tools to get the job done.
Designing And Building A Bike For Time Trials
02 - KlyBPn6
The model in Inventor was crucial to the development of the design, as it allowed me to analyze clearance issues (i.e., crank and chainring clearance with the chainstays). I was also able to use the tubing profiles to create NC programs for tube mitering and milling of the dropouts and head tube, for example.
03 - iQX2ZMX
I chose to use 7005 aluminum alloy, as it would not require solution heat treatment. My suppliers were Nova Cycles of Rocklin, CA and Fairing Industrial of Chino, CA. Each tube had a unique cross section, so I used a Mitutoyo coordinate measuring machine (CMM) to measure tube shapes. This is the down tube. The CMM recorded x and y coordinates for the surface at every millimeter, and I was able to import this data into Inventor.
05 - Ja304J2
I wanted the head tube to be both short (for the fit) and narrow (to reduce frontal area). I designed the head tube to accept an integrated headset and a 1" steer tube. This got the diameter down to 42 mm on the ends. with some intricate surface milling I reduced the width to 35 mm in the middle.
14 - 3oBC4ZU
The dropouts with set screws installed. This allows a convenient way to adjust the spacing of the rear wheel behind the seat tube. Note the knurling impressions on the right dropout - I clamped the dropouts in a rear wheel to do a frame mockup to check clearance on the rear brake and cable routing.
21 - TPSELMT
This chainstay bridge plate also served as the mounting point for the rear brake. I replaced the mounting stud on the Oval Concepts aero brake with a bolt, and threaded the hole in the plate. I rotated the seat tube out of the way for this photo to illustrate the upper side of the plate - note the rib reinforcing the bolt hole.
23 - QF6MvEO
The head tube junction. I filed off the contour lines on the head tube later, which helped with the fit. Notice the hole in the top tube near the trailing edge of the down tube. I cut holes in the top tube to route the cables through the frame, entering behind the stem. I inserted an unused portion of the seatstay in the top tube to reinforce these holes.
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The ultimate happy ending can be witnessed here. He successfully made what appears to be a really nice bike and to top it all off, she won the women’s championship that year with it.