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What tubing are you testing on there? Seems to be a lot of blackening, so maybe a more concentrated flame needed by feeding a bit oxygen.
sensom-
It’s just whatever that red frame is made from. Columbus SL seat tube if the decal is to be believed.
I’ll try a concentrated approach. I’m going to do a few more tests and I think even get some practise lugs as suggested above -
I think he said he burned the paint off a donor frame which might explain it
PhilDAS
atz
This gave me some material for practise brazing.
I don't have a work surface or table so I'm using the kitchen table which as you can see, is pretty tatty anyway and its a rented flat so not mine. With this in mind though, I don't have anywhere to put a proper vice so I bought this little clamp on variable angle Stanley number which whilst small, is actually pretty sweet, clamps tight, is pretty fucking rigid considering.
I also don't have any tube blocks so I'm holding tubes straight in it whilst not clamped particularly tight. It works ok, moves a little bit when rigorous filing but I'd rather that than crushing a tube.
Anyway, hand filed two sections of tube together
Whacked out the flames and burnt the paint off
After checking the mitre is still tight I smothered it all up in flux (not enough as I later learned) and cracked on with the fire
Handsome devil
End result is that where there once was two tubes, there is now one T shape piece. They are indeed stuck together and I am moderately happy with it.
Lessons learnt are:
Use more Flux. By the time I flipped the joint over to do the back, there was very little flux on the joint and when the brass melted it just blobbed on rather than pooling and flowing so the back is rougher.
Use more heat. I was scared of over heating it and as a consequence, I was hovering around the temperature of the brass melting so it was barely doing so and I was getting quite frustrated. I think I need to use a slightly bigger flame, more oxygen, get the whole area a bit hotter.