Category: Bicycle Frame Building

Next step in the frame building process is to figure out the rear triangle (I know, don’t have the main triangle quite done yet). This will be a track bike as you can see and will use a vintage style seat stay attachment flute.

I had a piece of 1 inch plate hanging around and jury rigged a bottom bracket holder. It worked pretty well. Need to work on the bottom bracket holder some more to get rid of the washers as they are not strong enough. But like I said it seemed to work well enough for now.

Close up view of the bottom bracket holder. Had some old machined tractor parts hanging around that worked out quite well. Drilled out the plate and attached the fixture and was able to cold set my first seat tube / bottom bracket assembly.

Main triangle is all setup and triple checked for proper length. Next steps will be to get jig all set in place, remove pieces and add all the flux and reassemble in jig. Tack all the joints (maybe complete in jig, not sure yet) and check for alignment before finishing all the joints.

My first brazed lug! I bit more brass than I probably needed so the cleanup was a bit much. I do think that the penetration of the joint was good though. I did some cold setting on it and it did not flinch. Overall I am pleased with the newbie attempt.

Going to find a source for “blemished” lugs so that I can practice a whole lot without breaking the bank.

With the bottom bracket / seat tube down I can pull the down tube length from the drawing. Carefully aligning the frame over the drawing with the help of a machinist square and v-blocks I can now scribe the lines where the down tube intersects the bottom bracket. Also note, only the lug is only attached to the head tube at this point.

With the frame aligned about the drawing I can scribe the lines where the bottom bracket and down tube intersect. Notch out the lines and the down tube length is done.

The seat tube is brazed in the bottom bracket shell. I can start pulling off the rest of the dimensions from the drawing. I am using a reasonably flat surface from and old cast iron table saw.

The brazing is not cleaned up yet. Will work on that soon. Also, it is a pretty messy joint but seems to be solid which is what I am most worried about for now.

Drawing out the first frame. Pretty much completed the drawing so I can get my final tube lengths and cut the final miters.

Head tube – small frame so lugs are pretty close to one another.

Bottom bracket shell will dictate the angle of the down tube. I am struggling with final alignment of lugs/tubing but I think a lot of cold setting and lug prep will do the trick.

Good notch will allow BB to fit without a problem.