I’m making progress on the cross frame. The front triangle is all welded up with a 1st pass and today i got the dropouts all brazed up and welded the chainstays to the BB.
I learned to braze by watching the Tim Paterek DVD’s and reading his book, along with watching some YouTube’s from random builders that were so kind to post them doing their thing. It’s not easy to teach yourself brazing, never knowing when you’re really f’ing things up or not…but trial and error is one of the best teachers around.
The method I use for slotting the chainstays is pretty easy if not completely foolproof (more accurate and repeatable ways involve more machinery that I don’t have):
After I crimp the stays for increased tire clearance (if you need to) and make your rough-cut of the chainstay length (from your drawing or just eying in in the fixture), I line up the chainstays with the BB and dropouts, draw a rough outline of where the slot will go with a thin sharpie, then take a hacksaw to it (32t blade, not a 12t) and cut about 8-12mm down from your rough cut of the chainstay end – depends on the length of the dropout tabs. This, for me, comes before I put the chainstays in my Sputnik fixture to cope the tubes for the BB. I like this method because it keeps everything in phase so you don’t have to figure out what is vertical after you miter the stays for the BB. [I’m not sure that the Anvil does this so the process is probably a little different.] Anyways, after I make two cuts vertically down the end of the chainstays with the hacksaw, I pry the resultant tabs off the ends of the chainstays with needle-nose pliers by rocking them back and forth until they tear off). Getting these perfectly in phase with the bend of the chainstays has not been easy for me but with using the flat file I can get it pretty close.
Then, I take a 10″ round file and ‘scallop’ the ends of the newly slotted chainstays at 90 degrees from the slot. Totally aesthetic choice, not purposeful at all as far as I can tell. Once the slots are all perfect, I miter the stays for the BB by hand or with the fixture. I’ve done both and I’m really not sure I save any time with the fixture at this point in my framebuilding ‘career’. It’s funner than filing though.
Ok, so once that’s all done, I load up everything in the frame fixture and tack the dropouts to the chainstays with the tig welder so it stays in place while I braze. I’m not sure how others do this…but this just makes sense to me since otherwise, I’d have to do some bending (er…cold-setting) afterwards to get it to fit in the frame fixture. After brazed (this was my best brazing so far!), there is some cleanup with the files and emery cloth so that no brass is on the outside of the chainstay or dropouts – clean margins or shorelines or something like that. I think it’s shorelines for lugs and margins for cancer surgery…hmm…not sure what they call cleaning up brass brazing…
Next post will be about mitering seat stays. I did them without a fixture and…well…it was rough! Took me way longer than i thought it should. I have done these twice before but this was my first run at not bending them and mitering to fit on the side of the seat tube…more later…