ShortHopper head tube – down tube gets fillet brazed

July 12, 2010 · 2 comments

The ShortHopper project continues. Assembly of the front triangle is progressing.

ShortHopper began as a drawing based on the rear triangle of a donor frame. After the frame was chopped the reconstruction to the new geometry could begin. In the previous ShortHopper post you can see the chopped front triangle of the 26” bike.

The first step in reconstruction was to miter the down tube to fit the head tube and then fillet braze them together. The fitting of the miter and fillet braze can be seen in the photos.

The mitering of the down tube had to match the drawing so I used a bevel gauge to help with mitering to get the fit to the head tube precise. This joint is one of the most critical on a bicycle so it has to be a perfect fit.

Once the miter was done the joint was fillet brazed. To hold the joint together at the precise angle, tube blocks were used and clamped to the welding table. The joint was tacked and then removed for final brazing in a bike stand. I’m working on the video of this so you can see.

The next step in the build is to figure out how to align the rear triangle with the front triangle. Once I can check the alignment I’ll fit the down tube to the bottom bracket which is the first joint to connect the front and back triangles.

So far I have figured out how to create the frame without using an expensive frame fixture. It is more time consuming but is teaching me how to think about frame alignment that I might not have learned if I had a fixture.

Keep watching as this build progresses. I’ll be finishing up the frame and then building it up with an electric motor kit.

{ 2 comments… read them below or add one }

1 Jocke Selin July 13, 2010 at 3:35 am

I’ll be following this with high interest. Thanks for posting!

2 Dan July 14, 2010 at 7:33 am

Thanks for the kind words. If there is anything specific you would like me to expand on, let me know.

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