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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 08-30-08, 12:20 AM   #1
cassette
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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
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Old 08-30-08, 08:53 AM   #2
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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.
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Old 08-31-08, 07:06 PM   #3
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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.
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Old 08-31-08, 08:57 PM   #4
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It may be bent like that to get the proper angle for the lug... It looks kinda cool
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Old 09-01-08, 09:08 PM   #5
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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.
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Old 09-02-08, 09:45 AM   #6
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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.
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Old 09-02-08, 11:25 AM   #7
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The mid-seventies Schwinn Paramounts were available with a "Sprint-style frame" that had a bent seat tube. It was an extra cost option.
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Old 09-02-08, 05:51 PM   #8
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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.
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Old 09-03-08, 08:48 AM   #9
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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?
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Old 09-07-08, 09:47 AM   #10
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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.
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Old 09-08-08, 09:16 PM   #11
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Old 09-09-08, 11:24 AM   #12
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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.
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Old 10-14-08, 10:58 AM   #13
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Hi is that Clark-Kent a ax-1? I have one of those frames, cool bike
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Old 10-14-08, 06:53 PM   #14
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Hey, isn't that Crit geometry?






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