Brazing the front triangle together
It's probably fair to say that I'd rather have attended a meet and greet with the arachnids that inhabit our loft and out buildings rather than take the torch to my frame this morning but needs must!
I need to get more confident with brazing thin steel tubing together as it's all a bit nerve wracking and in the heat of the moment it seems there's a lot to remember - melt, move, rod.. it's just a knack but I'm annoyed that I was brazing perfectly well at the end of yesterday and this morning it fell apart rather.
Still it wasn't only me - we all found it a bit tricky when it came to tackling our carefully mitred tubes. We were determined not to burn any holes through them and we all ended up with brazed frames and no holes. Phew!
The first step was to take all the tubes out of the jig apart from the bottom bracket and seat tube and then tack-braze those two together. Here's Nick working on his bottom bracket:
Once that was attached we could set the frame back up in the jig and tack the rest of the tubes together - for tacks per joint.
For some reason it was the tacking that I found the most difficult - I couldn't get both tubes heated to the correct temperature and then melt the rod to them... Well, it was tricky but I got it in the end!
After lunch we got on with fillet brazing, basically joining the tacks up with braze. For some reason this was easier than the tacking and after an hour or so the four main joints were complete:
Here's the frame tacked in its entirety, off the jig
Here is the bottom bracket joint prior to cleaning up:
And the head tube joints (they're a bit messy so I'll be spending a long time filing them!)
My final brazing task was the most difficult bit yet - attaching the seat clamp sleeve to the seat tube. Under Brian's expert direction, I heated both tubes to the correct temperature and began adding brass rod into the top to get it to drop down between the two bits of metal. It seemed to take ages but in reality it was all over in about 15 minutes. It was a case of over-brazing is better than under-brazing so we added quite a lot of rod to the edges and cutout circles on the sleeve, meaning that there was quite a lot of cleaning up for me to do with the file:
That's looking pretty tidy now even if I do say so myself, mind you that's the product of about 10 hours of work (cutting, filing and drilling the sleeve, mitering, tacking and fillet brazing the top tube to the sleeve and then brazing the sleeve to the seat tube and filing it all clean again. The top of the sleeve will be the top of my frame when it's finished so I'll be trimming off that untidy brassy bit above it - no need to file it down.
One great thing is that the frames so far are so light! The lack of lugs and Reynolds 631 tubing means that they're not far off being as light as a steel frame can get.
Tomorrow the frame goes back into the jig so that I can begin to set up the rear triangle and rear dropouts. Really looking forward to it.
No comments:
Post a Comment