Sunday, November 28, 2010

Greg Curnoe Bike Progress

While I have been too busy lately to do my work and work on bikes and maintain this blog regularly, I have had sufficient time to do items one and two. And so now, a belated report on some exciting progress on the Greg Curnoe bike.

I am actually now almost done. The rear triangle, as I am increasingly learning, is by far the hardest part of the bike. There are a million things to get right, and no fixture, however awesome, seems quite able to hold it all together. Then there are the specific challenges of the Curnoe rear triangle: mostly that weird and beautiful fastback attachment. This presented added challenges of fixturing, mitering, and brazing—and did in fact result in the rear wheel sitting very slightly off-centre between the seatstays. A half milimetre or so of dropout filing fixed that, however.

Now I'm in the midst of adding the braze-ons. It's always really hard to get bridges perfectly straight when you're doing everything by hand and checking straightness by eye—but they came out alright. The rear cable hanger was a bit tricky but come out pretty well. I'm now officially good at Mafac braze-ons, but I did end up putting one on backwards this time! I must say, though, it was pretty fun and easy to take it off and flip it over. Screwing up is always the best way of learning.

Now, the specifics...

Here is the bike with a faux-build. I'm afraid it's getting dark up here in Toronto, and I couldn't get any decent indoor lighting to take this photo. (This is also a big problem in the shop -- it's hard to see anything past about 3pm!)

Here is my pride and joy. Good Lord I love this seat lug and stay attachment! There's a lot going on: the old stamped Cinelli CS lugs have a reinforced binder, and the 11/14/11 double-tapered Deda seatstays are silver fillet brazed straight on to it. It doesn't look exactly like the one in the Curnoe painting, but it's pretty damned close—and even nicer, if I may say so myself. The cutout on the side of the seatlug (present in the Curnoe painting) is pretty cool too. You can't argue with a seatlug that looks like an angry bird mid-scream.

I'm also pretty fond of this whole aspect of the bike. With normal wrap-around stays, it can be tricky to place the Mafac bosses, since the brake requires 60-64mm pivot spacing, but with 130mm spacing and wrap-around attachment, you really have to miter the bosses to the extreme inside of the stays. With the fastback attachment, I was able to miter by bosses exactly to the centre of the stay. (And the stays are 14mm at the brake boss—nice and wide.) Since no brake is attached to the SS bridge, I was able to use a nice thin tube (9.5mm), which I think looks very nice. There's plenty of room for the 37mm fenders I'm going to use.

This picture tells a slightly more disappointing story. I went to the rather insane trouble of moving the derailleur hanger on this bike (normally it sits right at the "front" on the dropout slot)—all so that I could reduce chain gap and thus get good shifting performance from a Huret Jubilee derailleur. Well, let me tell you, the chain gap is very reduced: so much so that I won't be able to get the derailleur to shift on to the 21-tooth cog I had wanted to use. I could maybe get away with a 13-18... but since I actually want to ride this bike, it's a no go. I could just move the wheel back in the slot, but that would mess up my fender lines, and sort of defeat the whole purpose of getting really low chain gap. So I'm going to use this Chorus 10-speed derailleur. They shift better, anyway, aren't very heavy, and will allow me to use my preferred 13-24 rear setup. (Of course they don't look as cool as Jubilees.) Anyway, not quite a tragedy. (And I have a rear dropout that won't look like anyone else's!)

Here's the stop for the rear brake cable housing. It's offset a bit to the non-drive side and also pointed up, both of which should help the cable path to the brake. This little fellow also serves as a second SS bridge, which is nice since fastbacks are reputed to be weaker than wrap-around attachments. I'd think they're stronger than anything else in tension—there's nowhere to go!—and I'm sure my double-bridge setup will keep things from shifting around side-to-side. So should be very strong! I might even use this setup on my randonneur bike; I don't see any disadvantages... (Yes, there's still lots of clearance for 45mm fenders).

Brazing on the downtube bosses was an immense pain. I would get them centred (held in place with a c-clamp), but then during tacking one of them would slip—or I'd get them just about brazed and then the whole boss would shift slightly. Anyway, I finally got them just about right—and the shifters definitely look centred mounted.

So what's next? Well, I still need to add water bottle bosses (one set on the DT) and brake cable stops (I'm going to use single stops, placed at 12 o'clock on the TT) and a derailleur stop. Then I need to file the lugs some more... and then paint! I have (I think) decided to hand-paint the bike. Obviously this fits into the whole Curnoe theme. But I'm afraid it will look awful. I am obsessively trying to work out how to do it by hand and make it look really good...


RMHampel said...

Wonderful work here. I too love the seatstay cluster. Well done in all respects. This will be a fine bike.

OAP said...

That's too bad for the Jubilee. A victim of your success!

Parisian said...

love the Blog, I have just aquired a Routens and have noticed a few strange things , Care to coment or share some thoughts about the mafac spacing?
here is a link.

Parisian said...

I love the blog.
I have acquired a Routens and have noticed some mafac strangeness.
Check it out.

AH said...

Yep, looks to me like it was spec'd for Raids. What is the spacing centre-centre on the Mafac bosses? If it was made for Racers, the spacing should be about 62mm. If it's spec'd for Raids, it will be about 75mm. Let me know!