rear triangle lessons

it's 11:30 and i finished brazing the rear triangle just a few minutes ago. generally it went well, although i don't have a true rear wheel to see just how well.

i only want to make a few notes so i can wake up for class tomorrow.

i was able to built a larger fillet than i had expected at the seat cluster, using 56% Ag. the seat stay caps were maybe 1/16" or a mm away from the surface of the seat lug at some spots, and filling that took some serious pre-heating of the lug, especially around the ears, but presented no real problem. i had done the seat lug brazing with 45% Ag Cadmium-brearing; there was some leakage at the sides and bottom, but i didn't see any gaps open up in the seat tube top so i left well enough alone. there's probably some holes in the brazing inside the seat lug, but i reckon not enough to cause any concern.
i ended up building too much of a fillet along the seat stays, and that means lots of filing for me. thankfully it's silver, not brass.

i had previously thinned and flattened out the seat lug sides to better mate with the seat stays...i got a little carried away and filed into the silver. so that melted when i did the most recent brazing, leaving a rather unsightly area of missing seat lug. i think i'll solve that by filing it away a little on both sides for a wavy look.

pinning was not working so well tonight, except at the BB shell. maybe i had my drill bits mixed up. i ended up doing the following braze sequence:
set up jig, pin everything
braze seatstays->seatlug (shoulda saved this for last, it was hardest)
tack dropouts->seatstays
remove jig
braze chainstays->BB shell
braze dropouts->seatstays

i got a couple mm of contraction in rear spacing due to brazing...i.e. i started with 136 mm spacing and ended up with a slightly tricky fit for a 135 mm hub, meaning around 133mm i think.

when i braze the bridges, i was thinking to put my dummy axle in place to prevent any further contraction. maybe i'll turn it a couple mm narrower so the stays aren't under any stress when i do the brazes.

photo dump

i finally uploaded a bunch of photos to my flickr account, including a few of the rear triangle jig mk II.