Framebuilders - bending the seat tube

what is the process of curving/bending the seat tube, like on the older pursuit frames. here's an example:
http://www.arttusdesign.com/mino-denti/index.htm

Chromo bends nicely. To do that well you would need a JD squared type bender with a 1.125 die. There are ways of bending other than that, but in this case you have a short tube, a tight linked bend. There are lots of online plans for this kind of bender. There is a lot going on with the seat tube, so you don't want to add to the stress by doing something like a hot bend.

That seems unnecessary to have a double-bend in the seat-tube. It would appear that having a single-bend to tuck the rear-wheel up close is all you need. The angle of the seat-tube at the seatpost may then be aiming back more, but that's find if you want to maintain similar position over the BB anyway.

It may be bent like that to get the proper angle for the lug... It looks kinda cool

The tube was made that way by the manufacturer, probably when it was drawn. Columbus made a few tubesets with curved tubes, as did True Temper, and probably others.

I have an old custom steel frame, a Clark Kent, that has a bent seat tube, but I don't know how it was done. that was kind of their claim to fame, gets you a steeper seat angle (78 deg.) but it still has sharp road bike geometry in the front, not like a tri bike. I like it.

The mid-seventies Schwinn Paramounts were available with a "Sprint-style frame" (http://www.geocities.com/sldbxtralite2/1975/75xlite02b.jpg) that had a bent seat tube. It was an extra cost option.

true temper still has a s curves seat tube. its not round though, its aero in the bend section and was designed by Yamaguchi a while back.

true temper still has a s curves seat tube. its not round though, its aero in the bend section and was designed by Yamaguchi a while back.

Where can you buy them?

Where can you buy them?

henry james. they are listed under aero tubing. there are two versions. one is round at the bottom and the other is ovalized. they are a bit tougher to use than a regular tube but it doesn't take too much figuring to get it right. One thing to watch out for is that it stays aero pretty high up, so when building a small frame you usually have to extend the ST so that there is enough room for a seatpost before it gets aero.

http://i130.photobucket.com/albums/p260/BillyGoat71/100_2179.jpg
http://i130.photobucket.com/albums/p260/BillyGoat71/Moser84a.jpg
http://i130.photobucket.com/albums/p260/BillyGoat71/moser84.jpg

henry james. they are listed under aero tubing. there are two versions. one is round at the bottom and the other is ovalized. .
Thanks.
I asked because the last time I spoke to Monika about them (last year) they were out and she didn't think TT was making more.
I'll have to call when they get back in town.

Hi is that Clark-Kent a ax-1? I have one of those frames, cool bike

http://i130.photobucket.com/albums/p260/BillyGoat71/100_2179.jpg
http://i130.photobucket.com/albums/p260/BillyGoat71/Moser84a.jpg
http://i130.photobucket.com/albums/p260/BillyGoat71/moser84.jpg

Hey, isn't that Crit geometry?






:D