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  1. #1
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    Need tips for bending chainstays

    I am looking to build a road frame to handle 50+mm tires. I want to use lugs so I will need to bend and crimp the chainstays to make clearance for the tire. The issue as I see it is the starting angle from which the stays exit the lugs at the BB so bending is a requirement.
    What is the best method to use since I need to make the bend in a very short distance?

    Plus, I need tips on crimping the interior and exterior of the tube for clearing the tire and chain ring. Thanks in advance.

  2. #2
    coprolite fietsbob's Avatar
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    You have a grasp on the Idea of Tubing benders in General?

    you might use a Die grinder and shape some steel Blocks like the shape
    you want the exterior wall to be..

    a very Hard wood may do as well. and be easier to make.

    squeeze them over the tube with a Heavy bench vise..
    Last edited by fietsbob; 12-26-12 at 03:54 PM.

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    Yes, I have used tubing benders for a different application, but the issue is the bends need to located so close to the BB. I don't want to apply heat, but may well need to. As for crimping the stays the last time I did it turned out very poorly. I shaped some blocks and squeezed them in the vise, but ended with a vertical crimp where the blocks ended. I may take them to a machine shop and seek their assistance.

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    I'd have a look at the available MTB lugged BB shells and commonly available single bend chainstays and see if there's something that may work first. Using 2" tires with a road BB (lugged especially) would either require some accurate bends and squashing, or some long chainstays.

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    coprolite fietsbob's Avatar
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    Maybe shaped blocks, like stamping dies, on the inside and out?

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    Thanks fietsbob. I have some vintage 531 tubing my brother gave me years ago and wanted to build up a "unique" road bike with it. Just thought someone would have a slick trick to making the quick bends near the BB. Guess some pre-bent stays are needed. Nuts!

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    coprolite fietsbob's Avatar
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    Sometimes making the jigs and tooling to make the parts is 90% of the job.

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    Randomhead
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    I would go with a fillet brazed bb if I wanted reasonable length stays and large tires. It will look fine. Nova has a MTB shell with wider angles, but it uses 1 1/4" downtube.

    Making a bend in a short distance is something that isn't easy and unlikely to come out the way you like. If you insist on a lugged bb, it may be better to modify the sockets and use oval s-bend stays

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    Quote Originally Posted by TiHabanero View Post
    I am looking to build a road frame to handle 50+mm tires. I want to use lugs so I will need to bend and crimp the chainstays to make clearance for the tire. The issue as I see it is the starting angle from which the stays exit the lugs at the BB so bending is a requirement. What is the best method to use since I need to make the bend in a very short distance? Plus, I need tips on crimping the interior and exterior of the tube for clearing the tire and chain ring. Thanks in advance.
    Check the framebuilter suppliers forum. Several of the suppliers sell the stays prebent/preformed for you separately or included within a tubing set. It would be far easier path and perhaps the end product would be better or at least quicker which would cut your cost if you are accounting for labor in your effort.

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    Oh, I forget to address the OP's q on indenting for the rings. Check the top of the list in this forum as one of the posters of the "show your work" or "show your builds" threads posted detailed pictures and description of this scratch built indenting jig.

    For my viewpoint; I don't like to indent on either side as I feel this ads a bit of flex. I will usually use ovalized stays or I will tend to use longer stays and then use a triple BB for a double crankset or a tandem BB for a triple crank. All the parts and lengths are interactive so you need to sort out all of it to make sure the chain line is still viable, etc., before following that path with a lighted torch. I have found that in most cases you can get it done without indenting. The original inspiration was a Motobecane Sprint Tour circa 1972 or so that had non-indented ovalized chain stays and was super stout in the rear triangle.

  11. #11
    tuz
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    I did one frame for 650x42 tires and fenders, lugged BB and oval stays. I did the math and it required a slight 2-3 deg bend. It should be about the same for 50 mm tires and no fenders.

    I took a piece of spruce, 1.5" thick, and carved a 2-3" radius on the band saw. I fashioned a basic clamp to hold the stay at the end of the curve. I then filled the stay with brazing rod and yanked on it. Results were okay: a slight bend with a wide indent. With a better "filler" (soapy frozen water?) it might be better but the indent was not really undesirable.
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  12. #12
    tuz
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    Oh and for the indends I use a basic aluminum form and squeeze it against the tube in a vise, with the stay in a tube block.
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
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    Tuz, you just gave me an idea! Thanks!

  14. #14
    tuz
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    I just bend some stays again, I thought I'd share some pics.

    I brazed a cap on the big end of the stays, filled it with sand and plugged the other end with a bolt (I cut 2 threads). I used the form of my blade bender (one end doesn't have the groove). It worked okay, the accompanying indent was smaller than when I used brazing rod as a filler. I needed a 3-4 degree bend for 45 mm tires, 443 mm chainstays.

    PICT1256.jpgPICT1259.jpg
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    What are you using 50 mm on a road bike for? Are you sure? Most all touring uses can be handled with 37mm. The rest is normally just a comfort bike for jelly bellies. Then there is mountain biking some of which certainly needs big tires, but that isn't road bike territory.

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    Quote Originally Posted by TiHabanero View Post
    I am looking to build a road frame to handle 50+mm tires. I want to use lugs so I will need to bend and crimp the chainstays to make clearance for the tire. The issue as I see it is the starting angle from which the stays exit the lugs at the BB so bending is a requirement. What is the best method to use since I need to make the bend in a very short distance? Plus, I need tips on crimping the interior and exterior of the tube for clearing the tire and chain ring. Thanks in advance.
    OP; Check the sources thread. Several of them sell the chain stays already "S bent" for just that purpose at basically the same range of price as un-bent ones. I have used them and they are very nice products. Clearly they are produced with hydraulic tooling that the average builder would be unlikely to have or to be able to put together at a reasonable cost.

  17. #17
    tuz
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    I'll try S-bend stays one of these days. However, a single and slight bend stay will work better and with more chainring clearance if you are using a lugged shell. Plus I beleive S-bends are hard to find in 22.2 ROR.
    Last edited by tuz; 04-15-13 at 06:49 PM.
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