Frame progress
Administravia first: A couple of weeks ago I blogged about the Ibex Vim jacket. I actually raved mostly about the Dash Hybrid, which is an awesome jacket. I thought that the Vim would be very similar, but I’ve been using one for a couple of weeks (thanks to John Speare for loaning it to me) and I can report that it isn’t. The Vim is a much lighter jacket and nice in 50ish degree weather, but I don’t think I could wear it all winter long as I do with the Dash Hybrid. It also isn’t cut for cycling (the back doesn’t extend as far) and has no rear pocket.
Now onto the real news. I didn’t do much work on my bike frame this summer, deciding to spend weekends outside instead. I’m finally back at it, and got past what I expect is the most challenging part of the build. That was putting on the chainstays.
One minor note is that I fully rebuilt the front triangle for this bike early in the summer. I had some issues with the first one, but this new one has better brazing (thanks to a few key members of the framebuilders list who gave me good advice) and the geometry is right on.
This is what it looks like today:
I’d say it is starting to look a lot like a bicycle.
What follows is a photo essay of the chainstay work.
Checking the bends against BG101 to mark where I needed to cut the stays:
Using a slot cutting wheel on the milling machine to make slots for the rear dropouts:
Rear dropouts brazed:
Mitering the chainstay on the milling machine. This doesn’t look that sturdy, but the setup worked pretty well:
Testing the fit. It was critical that both chainstays were exactly the same length.
All brazed up. I used Fillet Pro from Freddy Parr to braze this. It is silver based (instead of brass), so the brazing took place at a lower temperature. This made it easier to use Alistair’s heat sink and resulted in less bottom bracket distortion.
A 50mm wide Pacenti Quasi-Moto tire fits with 6mm of clearance. I was hoping for a little more, but this is still pretty good. Most of the time this bike will run with ~40mm wide slick tires and fenders, but I wanted the option to fit 50mm knobbies for offroad riding.
I’ll do one thing differently with my next fillet brazed bottom bracket. Instead of fully brazing the dropouts into the chainstays first I’ll just tack them. Then I don’t need to worry about the chainstay length quite as much, because I could move one of the dropouts a little bit to tweak the alignment.
Remaining items before I have a bike:
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Fillet cleanup
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Seatstays
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Brazeons (canti bosses,cable routing,water bottle bosses, etc)
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Fork
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Rack
I’m hoping to push through in the next couple of months and wrap this one up by the holidays.
Nice to see some progress on this!
What Jimmy said!
This is one of your threads that I find fascinating. It’’s science and art, shaken up in the test tube that creates magic. Only not in some behemoth national (or corporate) laboratory but magic down in the basement.
Probably the funniest part is the “I”ll do one thing differently” next time comment: I don”t know anyone who has not said of their new bike at some point (off the shelf or custom) “If I had it to do over there is one thing I”d change”. It never occurred to me that
this thought might form even befor the bike pops out of the cake.
Thanks for the front row seat as we take a peek behind the curtain.
Yr Pal Dr C
how was the 50 mm decided for the cutoff for the tire size? i know there are some fatter ones out there, and i would think those could offer a little more cush on a full rigid frame…
Rory — It is a touring frame first, mountain bike second. 50mm was what seemed to fit easily on my drawings without making other compromises (like hindering the installation of fenders when I”m running 40mm tires).
I”ve had bikes designed for way larger tires than I normally ran, and never liked them.
Paul — Glad you enjoy it.
Alex, good stuff. Your C/S fillets look good. Seems like you”ve gotten the hang of the fillet pro. I hope to try some of it myself in the coming months.
. . . checking against your flat pattern layout on your monitor. That kills.
Hi Alex, just curious why you don”t crimp the chain stays for add”l tire clearance, like Alistair does on his frames?
I”ll do that after the fact if this doesn”t look good enough. Right now it seems okay, my 650B wheel is very out of true (some serious wobbles) and the tire never gets closer than 4mm from the chainstay.
Crimping straight stays wouldn”t have produced the necessary clearances, and crimping bent stays seemed like it shouldn”t necessary. These stays are also ovalized and already skinnier than Alistair’’s.
Looks like fabulously neat work