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His Girlfriend Needed A Racing Bike. What He Built Is Incredible.

tt_bike_7_scaled Via imgur

When they were in college, Reddit user bcmanucd‘s girlfriend was on the college cycling team. Her team made it to the national championship. She needed a custom-fitted time trial bicycle to compete at the national time trial. However as a struggling college student with tuition and bills to pay, she didn’t have  the thousands of dollars needed for a custom bike

Bcmanucd wanted his girlfriend to have this opportunity of a lifetime. So even though he was already busy writing his master’s thesis, he spent every spare minute in the college machine shop designing and building a bike for her. And when you see the final photos and read the surprising ending, I think you’ll agree that what he built is more than just a bicycle–it was a labor of love.  Enjoy the slideshow in the words of the builder himself.

Click “Next” to see how he designed the bike…


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I designed the geometry based on a fit assessment from her coach. The position is very aggressive, and necessitated a head tube length of 85 mm including headset.

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Building a 3D model of the bicycle frame in Inventor was crucial to the development of the design, as it allowed me to analyze clearance issues.

Click next to see the hard work he put in to make the design come true…

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I did most of my machining on a Bridgeport vertical mill with hybrid CNC controls.

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The head tube after surface milling. I clamped the head tube in the welding fixture, and kept it there through the welding process to maintain orientation.

Don’t miss out on the action shots of his girlfriend riding the bike in the later slides…

tt_bike_9_scaled Via imgur

No one makes horizontal dropouts with derailleur hangers in 7005, so I machined these as well.

tt_bike_12_scaled Via imgur

The completed dropouts.

Don’t miss out on the surprise ending

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Mitering the top tube. I used FeatureCAM to write NC programs for the tube miters based on imported Inventor parts files. The clamps holding the thin-wall tubes were also cut from FeatureCAM programs based on the tube profiles from the CMM.

tt_bike_18_scaled Via imgur

The tube clamps used for mitering also doubled as welding fixtures.

Click next to see the frame of the bike starting to take shape

tt_bike_16_scaled Via imgur

The Welding fixture. I machined several blocks to hold the dropouts, bottom bracket shell, head tube, and main tubes, and clamped them all to an optical table.

tt_bike_17_scaled Via imgur

I also had the frame sketch printed out in 1:1 scale. This was very helpful in laying out the fixture on the table.

tt_bike_20_scaled Via imgur

The bottom bracket joint, coming together. I had to do a mockup of the rear wheel, frame, and rear brake to determine the optimum shape for the opening in the down tube for cables to exit. This required several iterative cuts of the down tube’s bottom joint.

Click next to see the welding process

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The welding setup: clamps, vise, file, wire brush, wire cutters, 5356 weld rod, leather gloves, auto-darkening hood, and jacket. I was spoiled with a Miller Synchrowave 350LX.

tt_bike_25_scaled Via imgur

Here is one of my welding test pieces. The welds weren’t always pretty (right), but I proved to myself that they were strong, and they cleaned up nicely (left).

tt_bike_26_scaled Via imgur

I spent as many days practicing welding aluminum as I did actually welding the bike.

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After completion of the welding (and the day in the oven), I started a lengthy process of sanding down the joints and building them up with Bondo body filler. It was meant as an aero bike, not a light bike, but the total frame weight before paint was 2.75 lb. Not too shabby.

tt_bike_28_scaled Via imgur

It took many applications of Bondo to get acceptable fillets.

tt_bike_31_scaled Via imgur

The fillets still aren’t perfect, but that’s where high-fill primer came in later.

tt_bike_32_scaled Via imgur

Here’s a shot of the bottom bracket area. you can see the placement of the rear brake a bit better. Adjustment of the pads isn’t easy with the cranks installed, but this was never a bike of convenience.

tt_bike_29_scaled Via imgur

The bike, fully assembled (minus wheels). After Bondo came a layer of self-etching primer, but the painting process was interrupted on the weekends. By that time she needed it for races!

tt_bike_30_scaled Via imgur

The bike from behind. Note the rear brake, the wedge-style seatpost clamp, and clean cable routing.

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The builder contemplates his creation.

Click next to see his girlfriend’s reaction seeing the bike

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Look at that smile. I think she likes it!

Click next to see her riding the bike

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Modeling the bike. Here’s that aggressive position I was talking about.

Click next to see the custom paint job for the bike

tt_bike_36_scaled Via imgur

Back to painting. I resumed with several layers of high-fill primer (with delicate sanding in between), a white top coat, a blue fade done with an airbrush, and a few layers of clear coat to get things glossy. We then cut masks from Contac paper (a lovely wood-grain pattern).

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The final step was a few layers of flat black enamel for a durable finish. I used Dupli-Color automotive paints throughout, as I’ve been dissatisfied with common hardware store rattle cans in the long run.

tt_bike_38_scaled Via imgur

Notice the homemade masks under the paint. The goal was glossy white-blue-faded letters on a flat black backdrop.

Click the next button for the first surprising ending

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All in all, I’m quite pleased with the results.

My wife was pleased too (Yes, she married me!)  

Click the next button for the FINAL surprise


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Using the bike I built for her, she won the national championship.

My wife is the smiling one on the far right.

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