Bike Forums

Bike Forums (http://www.bikeforums.net/forum.php)
-   Framebuilders (http://www.bikeforums.net/framebuilders/)
-   -   BB brazing (http://www.bikeforums.net/framebuilders/877264-bb-brazing.html)

calstar 03-11-13 10:31 AM

BB brazing
 
thought this was a good vid of lugged bb braze, and check out his other vids, lots of sequence and torch work shots. Brian

http://www.youtube.com/watch?feature...&v=0AMfK1OS_mc

tuz 03-11-13 11:40 AM

That guy is awesome. If you look the other videos or his website, you'll find has a peculiar building sequence where he does the HT-TT, TT-ST, DT-HT and hammers in and brazes the BB shell as the last step. I'm probably over-analyzing things but I thinks it's clever and I've copied the sequence. He also tacks the lower head lug first, this I don't get :)

unterhausen 03-11-13 12:42 PM

that is a weird sequence. I have always thought the traditional DT/HT; ST/BB; TT/HT; DT/BB; TT/ST sequence made the most sense if you aren't using a jig. I think the reason he tacks the DT/HT first is because that joint most often requires the most blacksmithing.

Using bronze results in more BB shell distortion, that's why he heats the bottom. For many years I was afraid to try using LFB for lugs, but I finally got over that and figured out how to do it. As usual, the secret was a bigger torch (OK, enough heat, but in this case it required me to get bigger tips for my torch). I am not sure if I will ever use this knowledge for anything other than seat tube reinforcements though.

tuz 03-11-13 01:00 PM

2 Attachment(s)
I think his idea is to isolate the BB alignment from the front triangle alignment. I think you are right for the tack, although I'm not sure how he puts the TT in the right plane afterwards.

Brazing lugs with brass is great. I don't use silver a lot but in my experience silver filler & flux is finicky compared to brass.

http://bikeforums.net/attachment.php...hmentid=303811http://bikeforums.net/attachment.php...hmentid=303812

e-RICHIE 03-11-13 01:51 PM

Quote:

Originally Posted by unterhausen (Post 15372785)
that is a weird sequence. I have always thought the traditional DT/HT; ST/BB; TT/HT; DT/BB; TT/ST sequence made the most sense if you aren't using a jig. I think the reason he tacks the DT/HT first is because that joint most often requires the most blacksmithing.

Re the sequence -
The three lugs are already finished brazed. Then, the bb shell is added onto the mitered ends of the down and seat tubes. Then, that joint is brazed last. Kalavinka's fixtures are sophisticated and well thought out. His procedures (and those like his...) allow for a minimum of stress to be put on, or added to, the main triangle before and during the heat cycles.

tuz 03-11-13 02:30 PM

here's the part preceding the OP's link, so cool.

http://www.youtube.com/watch?v=7FzsE8DqRzE


All times are GMT -6. The time now is 05:05 PM.