Sunday, June 27, 2010

Greg Curnoe Bike

Since Toronto has been effectively shut down over the last few days by the G20 meeting, I gave myself a working holiday at the shop. My goal was to see if I would build a front triangle in two days, working 10 hours a day. The bike I was working on was the Greg Curnoe bike.

This bike is going to based on the above print, by Canadian artist Greg Curnoe, of a Mariposa time trial bike. I'm not trying to build a replica, since I don't really want a time trial bike. But I will use some of the same components: Huret Jubilee rear derailleur, TA cranks (doubles, though), Super Record brake levers (with clear hoods to replicate the hoodless look of Curnoe's bike), a radially laced front wheel (but with my Mavic SSC rims). I'll differ in using brazed-on Mafac Competitions, a front derailleur, a different saddle, etc. I'll also build it around fenders, though I'm not sure I'll always leave them on. And I'll use a fastback attachment.

The main thing—strangely given that I'm the one building the frame, not painting it—will be the paint job. Curnoe's print was of a green Mariposa, and he added the yellow, red, rainbow, orange, etc., parts, constrained only by his imagination. I'm going to have Noah of Velocolour do a "literal rendering" of Curnoe's print; the bike will have yellow on the top of the tubes and green underneath, for example. This can only be taken so far: the lugs will probably all be green with yellow lining, and I'm not sure what to do about the rear triangle. I think I'll paint the fenders orange. I don't think I particularly want a red chain.

Why this particular painting/print? I owe my love of bicycles to it. Growing up in London, Ontario—where Curnoe was from—I saw it constantly, and it is directly responsible for my aesthetic appreciation of bikes. I love also that it's a painting of a Mariposa, my favourite real-life marque. (Here are two links about Curnoe/Mariposa).

"Mariposa T.T." is a painting of a bicycle. I'm going to make a bicycle of a painting!

I've already assembled all the components (see here and here). I have also moved the derailleur tab on some Campagnolo 1010 dropouts to give me more options with my Jubilee rear derailleur. This weekend I took it from here and built the front triangle.

I decided to use some original Cinelli CS stamped lugs for this bike—the ones used on the Cinelli Supercorsa. They don't much resemble the short-point lugs in the print, but I like them better! I decided to leave the shape more or less as-is, since the paint job will be sufficiently busy without added curls in the lugs. I did make a cutout in the side of the seatlug, though, to match the painting and create some visual interest in the absence of wrap-around stays.

I did subject these lugs to my "investment stamping" process—which was slightly less time-consuming this time around, but not much—but I forgot to take any pictures. Rest assured that the rounded transitions are filled with sharply pointed fillets of brass!

I spent Friday doing that and mitering the tubes. Yesterday I finished reaming out all the tubes, cleaning them, etc., and then started brazing around 2pm. Here is the first joint, the seat tube to bottom bracket, which went fine:

The flux had to be soaked off that and the excess tube filed off. Then came facing. The cool, oldish Roto shell needed quite a bit of material taken off.

Then I needed to slightly adjust the downtube/BB angle, which was quite a bit of work. Unfortunately I mitered the downtube to the "unadjusted angle," and so it pulled in a few milimetres in the proper position. Probably not a big deal—I added a silver fillet at the bottom just in case.

Here we are tacked and ready to go (with all levers depressed) at about 4pm:

Here's the bike with three of five joints completed, viewed from proper Curnoe-ian non-driveside:

And a particularly picturesque flux gob on the completed seat lug, photographed after I'd arrived home at 6:30.

My brazing was pretty perfect this time, with nice tight shorelines and only one tiny gap to go in and fix. This was mostly because I did a better job of making sure all the points sat flush against the tubes before sticking them in the fixture. 

After messing up the front end clearance, I was particularly careful this time around, and completely changed the way I used the fixture. I also made a paper drawing just to be sure. Happily it seems to have come out as intended. 

It also came out absolutely straight to the milimetre. This is a sign of good miters, which is good to see, since I did these quickly and by hand.

I now have another fork to make (for this bike) and some rear triangles to complete (for this and for Monty). I'll be busy with teaching for the next few months, so I fear it may take a while...

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