Wednesday, 13 November 2013

Day 11: Tuesday

Finishing the Frame Off

Apologies to those people who have been in contact to ask whatever happened to my bike frame - I know I didn't finish the blog and now my mental scars have cleared up a little, I can finally lay it to rest for now!

I had a very stressful final day on the course, which started with brazing the seat stays between the rear dropouts and the seat tube/top tube junction.  That wasn't too much of a drama, however once they were brazed in place, the rear wheel wasn't straight in the frame.  BIG PROBLEM:

I don't know how it happened and neither did the course tutors but the upshot was that something had to give - the rear triangle couldn't be bent now that the final side of it was in place, the dropouts weren't going to help and seeing as the wheel lined ok up on the chainstays, they weren't going to help either.  To cut a long story short, the only solution was to put a wheel in the dropouts, unbraze the top of the seat stays and then move them until the wheel lined up, before re-attaching them.  Oh, while also not burning a hole in any of the parts.

I was mighty annoyed because I'd followed all the instructions, measured it all very carefully a lot of times, set it all up in the jig and it still wasn't right.  What gives?! I think the problem is actually caused by a weakness in the jig design because it's impossible to be sure that the dropouts are lined up in the same direction and even a small rotation of one of them would result in the sort of problem I was experiencing.

It was a tense few minutes while I stood and watched one of the tutors heating and adjusting the seatstays but after a lot of fluxing, brazing and tweaking, the frame was straight.

Just the braze-ons and a few other bits to do but it was already lunchtime and I had to be back in Cambridge, 2 hours away, in enough time to clear our kitchen out (including a large fridge, dishwasher and washing machine) because we were having a new vinyl floor fitted. The remaining jobs included: filing and fitting the rear brake bridge, creating a small bridge between the two chain stays, various cable stops, trimming off the seat tube, fitting the seat post clamp, sawing out the slit in the seat tube so that the clamp would work, and reaming out the seat & head tubes.

It all ended up being a bit of a rush to complete the frame - the braze-ons were relatively trouble-free, although getting the head tube ones lined up was fun and games necessitating pains-taking measurement, lining up and then re-lining up as the clamps weren't very good at holding them in place.

 Holding the gear braze-on in place so it can be silver-soldered.

 Here's my hand-made chain-stay bridge with complicated but shallow mitres

Cutting the slot in the seat tube (actually two parallel cuts about 2mm apart, about 25mm down from the top) was a lot easier than I thought it would be (maybe I was getting better at working with metal by now!) and in not much time at all everything was in place and it was just a case of tidying up the brazes by - you guessed it - filing!

There was also just about time to ream out the seat tube and head tube:

It became clear that I was going to run out of time -it was getting around to about 6pm and I had to put my tools down and admit temporal defeat.  I paid for the frame materials, said my goodbyes packed the car up and headed for Cambridge.

Here's how the frame ended up (with chintzy new wheel added for good measure):

Due to a mix up about timings, I'm going to have to re-book and make the forks after Christmas - good news in some ways because it'll mean I can pick up one if the jigs that they're selling so I can make a mk. 2 frame ;-)

I'll be writing more when that takes place...

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