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Modifying the bottom bracket.
Beginning steps - deciding what you want to build.
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The bottom bracket proved to be something of a challenge. When I measured the angles on my drawing, the angle between the chain stays and the seat tube was 67 degrees, whereas that on the lug was 62.5 degrees. This difference was due to my high bottom bracket. The bottom bracket was designed for a road bike rather than a track bike, so I would have to modify it to fit. I asked a bunch of questions on the framebuilders list, and was advised that I could reseat the lug sockets by simply putting a heavy wall tube in them and bending them to the correct angle. I found some tube that would fit the seat tube and down tube sockets, but it was impossible to find tubes to fit the chain stay sockets, as they were oval. Instead, I used the chain stays themselves, packing nails in at the ends to ensure the tube walls wouldn't collapse when I bent the sockets. I figured that when I tried to set the chain stay - seat tube angle, the seat tube - down tube angle would also change. To avoid this, I did the chain stay - down tube angle first. I put both (packed) chain stays in place, with the bottom bracket sitting on a concrete floor. I stood on the end of the chain stays (wearing sneakers). I then put the down tube replacement bar in the down tube socket, and pushed it away from me (with considerable force on a 3 foot bar). After some mucking around, the down tube and chain stays could be inserted at the same time, and laid down on the diagram at the right angles. However, the sockets now had considerable slop, so the tubes could be moved around considerably. I then set the seat tube angle. This tightened up the down tube joint considerably, but the seat tube could now flop around. Once the tubes could fit at the right angles, I used a brass drift to close the sockets up to lock the tubes in place. I did this by tapping from the base of the socket on the open side, and working my way from side to side. After an hour or two of persuasion, tapping, and checking on the drawing, the bottom bracket was pretty much right, with the angles I needed. As I'd put so much work in to the bottom bracket, I thought it would be nice to really customise it. I drew my initials in a stylised way in AutoCAD, and printed them on some label paper. I then stuck this to the bottom bracket, and drilled and filed out my initials in the bottom bracket, to match my drawing. The result can be seen below. I'm awfully proud of it, and gained a fairly impressive blister to boot.
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