Session 3 - more progress

Pretending to be a single parent this weekend, so I haven't had much time. I did sneak a couple of hours after the boy went to bed though...



Uncut head tube. Measuring and marking before...



Cutting it to length on the bandsaw.



Marking the centreline, so I can make sure that the upper and lower head lugs are in the same plane. Easiest way to do this is to lay the tube in some aluminium angle and run a marker or a scriber along the edge of the angle.



Drilling pin holes in the head lugs. I use a system of removable pins to keep various parts in alignment during the build. There are other ways of doing it, but once you get the hang of this it's a pretty handy way of doing it. First, I drill a 2.4mm hole in the lug. Then position the lug in the correct spot and drill through the tube. Then a 2.5mm nail is ground to a slight taper and gently hammered in the hole. The pins stay in place throughout the brazing and are cut flush and filed down afterwards.



Pinned head tube.



And at the other end of the bike, seat stays and seat stay end caps. There are a million ways of attaching seat stays to the seat cluster, and this is one of them. A cap is brazed to the seat stay and then the whole assembly is brazed to the lug. I would normally braze the seat stays to the back of the seat binder bolt, but this bike is going to be running mudguards so I thought some extra clearance wouldn't go amiss. You can't see it, but the other side of the end cap is profiled to exactly the same curve as the seat lug, which will give the final braze a huge surface area to work with, making for a very strong joint.



Trial fit then...



Ready to braze. You can't see it here, but inside the seatstay is a coil of brass. I'll heat the whole assembly up to temperature and then hopefully the brass will all melt at once and the join between the tubes will be a neat little golden ring, with 100% penetration inside the join. More pics when I've soaked the flux off and have some time...

Edit:
Next morning, the flux was soaked off and after some work with a file and some emery cloth... If you look closely you can see the ring of brass that marks the join between the tube and the top cap.