Bi-Oval Downtube- Mtbr.com
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  1. #1
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    Bi-Oval Downtube

    I have been looking everywhere for a bi-oval DT and can't find any in stock! Does anyone know where I can find one (or 6)?

  2. #2
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    Has anyone had any luck making their own? I wasn't sure how precise the orientation of the axes would be but maybe I was overthinking. It seems feasible to get an accurate phasing, I think I'll give it a whack....thanks guys!

  3. #3
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    Quote Originally Posted by FullTiltBoogie View Post
    Has anyone had any luck making their own? I wasn't sure how precise the orientation of the axes would be but maybe I was overthinking. It seems feasible to get an accurate phasing, I think I'll give it a whack....thanks guys!
    I don't think i've made a frame without at least a couple ovalizations. I miter it, ovalize with a soft jawed vice, and miter it again to take the ears down. It doesn't much matter how precise your ovalizing is because it's the miters that fit up to the other tube.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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    I have some that were made by true temper. I'm not sure on the specs, but I think they're pretty light (like 8/5/8), and I know they're S3 tubing. Other than that I don't remember much about them. If you might be interested, I can measure them.

    I've been curious about the best way to hold them for mitering. Seems like a tricky thing. Any tips?

  5. #5
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    Quote Originally Posted by Bpotts View Post

    I've been curious about the best way to hold them for mitering. Seems like a tricky thing. Any tips?
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    Tube blocks are the nice way to do it. Stick them in a vice and go nuts. You can buy them or just make some with a hole saw.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  6. #6
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    Quote Originally Posted by Bpotts View Post
    I have some that were made by true temper. I'm not sure on the specs, but I think they're pretty light (like 8/5/8), and I know they're S3 tubing.
    38.1 OD, ovalized to 31x45, and .61\.41\.51

  7. #7
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    There was a time ago, a common use of squeezing tube ends, some seat tubes were done this way onto the BB Shell. Handlebar stems were another with opposite set at 90 degrees.
    I do mine as suggested above in a soft jaw vice and gently squeeze, remove, check and squeeze again. The steel we use in bike frames is very springy and memory prone, so expect to have to repeat. If you try too much in one go, thin walled tube can suddenly crush and you've lost a tube.

    Eric
    If I don't make an attempt, how will I know if it will work?

  8. #8
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    Full Tilt, head over to bikefabsupply.com we have plenty of the 35mm bioval trutemper tubes , .7/.5/.7 x 680 and some other shaped tubes as well. None are over 680mm in length though so not sure if that fits you build requirements or not.
    Andrew Cooper
    Bicycle Fabrication Supply - Let's Build More Bikes
    bikefabsupply.com

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