Slight spoke bend

Discussion in 'Cycling Equipment' started by Jason, Jun 29, 2003.

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  1. Jason

    Jason Guest

    I have a rear wheel with a 28h cormia hub, velocity deepV, 2.0mm spokes, 2x on the drive side.

    As built the spokes have a slight bend in them around an inch from the hub flange (before the first
    cross) on the drive side and I have broken a spoke at this point.

    I am no wheelbuilding expert, but the corima hub appears to be "built" to be 3x. That is, the way
    the spoke elbow seats in the hub flange it aims towards a spoke hole in the rim that lays the spoke
    further over the hub.

    If you can understand my words and have an opinion I would appreciate your thoughts.

    Jason
     
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  2. Get Jobst Brandt's excellent book the Bicycle Wheel and learn all about it.
     
  3. Walter Mitty

    Walter Mitty Guest

    "Gearóid Ó Laoi/Garry Lee" <[email protected]> brightened my day with his incisive wit when
    in news:[email protected] he conjectured that:

    > Get Jobst Brandt's excellent book the Bicycle Wheel and learn all about it.
    >

    But buy a book on advanced material science first, and get a degree in "tensionology".

    While a great book it's hardly for the casual reader.

    --
    Walter Mitty.
     
  4. Dorn

    Dorn Guest

    Simply not true, a very easy read even for the mostly bike ignorant. Will explain the process and
    the premise. chris "Walter Mitty" <[email protected]> wrote in message
    news:[email protected]...
    > "Gearóid Ó Laoi/Garry Lee" <[email protected]> brightened my day with his incisive wit
    > when in news:[email protected] he conjectured that:
    >
    > > Get Jobst Brandt's excellent book the Bicycle Wheel and learn all about it.
    > >
    >
    > But buy a book on advanced material science first, and get a degree in "tensionology".
    >
    > While a great book it's hardly for the casual reader.
    >
    > --
    > Walter Mitty.
     
  5. S. Anderson

    S. Anderson Guest

    "jason" <[email protected]> wrote in message
    news:[email protected]...
    > I have a rear wheel with a 28h cormia hub, velocity deepV, 2.0mm spokes, 2x on the drive side.
    >
    > As built the spokes have a slight bend in them around an inch from the hub flange (before the
    > first cross) on the drive side and I have broken a spoke at this point.
    >
    > I am no wheelbuilding expert, but the corima hub appears to be "built" to be 3x. That is, the way
    > the spoke elbow seats in the hub flange it aims towards a spoke hole in the rim that lays the
    > spoke further over the hub.
    >
    > If you can understand my words and have an opinion I would appreciate your thoughts.
    >
    > Jason

    Your spokes are failing because of residual stress in the spoke from the time it was built. This
    stress could be worse if, as you say, your hubs have a groove or low spot designed to accept the
    outbound spoke in a 3x pattern. If, by doing a 2x pattern, you are not using this groove, you are
    increasing the stress on the spoke and increasing the chance for failure. I would suggest that you
    should rebuild the wheel as 3x using this built-in grooves if that is what you have. The differences
    between 2x and 3x are negligible, except perhaps 2x being marginally lighter and 3x being somewhat
    stronger. The key to stopping the spoke failures, regardless of which method you choose to use (you
    can probably still make the 2x work if you want..) is to remove all residual stress on the spoke.
    That is, don't have the spoke flexing when it's finally built. You want to manually bend the spoke
    during building to point in the direction of the whole, such that there is no lateral bending of the
    spoke. Normally, you would grasp spokes on opposing sides of the wheel and squeeze them together
    fairly hard until you're sure the spoke has no residual stress in a lateral direction. You would do
    this just before your final true when the wheel is almost fully tensioned. This will mitigate most
    stress-related failures. You can take that wheel to some other wheelbuilder as well and let him have
    a look at it to see if your suspicion about the spoke holes is correct as well.

    Good Luck,

    Scott..
     
  6. Dianne_1234

    Dianne_1234 Guest

    [email protected] (jason) wrote in message
    news:<[email protected]>...
    > I have a rear wheel with a 28h cormia hub, velocity deepV, 2.0mm spokes, 2x on the drive side.
    >
    > As built the spokes have a slight bend in them around an inch from the hub flange (before the
    > first cross) on the drive side and I have broken a spoke at this point.
    >
    > I am no wheelbuilding expert, but the corima hub appears to be "built" to be 3x. That is, the way
    > the spoke elbow seats in the hub flange it aims towards a spoke hole in the rim that lays the
    > spoke further over the hub.
    >
    > If you can understand my words and have an opinion I would appreciate your thoughts.
    >
    > Jason

    I think you've hit the nail on the head. Corima hubs have an unusual right flange:
    http://www.corima.com/corima/gb/produits/roues/aero.html Hard to see, but the spoke elbows are
    oriented 90 degreese from normal hubs.

    The bends in your spokes is the likely cause of the broken one. Chance of spokes breaking might be
    slightly reduced if you "custom bend" every elbow to correct the spoke line, but opening the elbow's
    angle is generally not as successfull as closing it.

    Rebuild with 3x, tension and stress relieve and all should be good.
     
  7. Walter Mitty

    Walter Mitty Guest

    "dorn" <[email protected]> brightened my day with his incisive wit when in
    news:[email protected] he conjectured that:

    > Simply not true, a very easy read even for the mostly bike ignorant. Will explain the process and
    > the premise. chris

    Sorry Chris I must disagree. It is fairly technical and not for those who are bike or
    physics ignorant.

    But maybe oim a bit tick

    --
    Walter Mitty.
     
  8. Jason

    Jason Guest

    "Gearóid Ó Laoi/Garry Lee" <[email protected]> wrote in message
    > Get Jobst Brandt's excellent book the Bicycle Wheel and learn all about it.

    Can you reference the page which deals with the unique flange on corima hubs?
     
  9. S. Anderson

    S. Anderson Guest

    "jason" <[email protected]> wrote in message
    news:[email protected]...
    > "Gearóid Ó Laoi/Garry Lee" <[email protected]> wrote in message
    > > Get Jobst Brandt's excellent book the Bicycle Wheel and learn all about
    it.
    >
    >
    > Can you reference the page which deals with the unique flange on corima
    hubs?

    There likely isn't a section dealing specifically with Corima hubs. However, you could look at this
    as if you are replacing spoke in a hub that has been laced before. Jobst suggests re-lacing in the
    same pattern as the wear in the hub, that is, where the indentations have already been made by the
    previous spokes. This pre-set indentation will reduce stress on the spokes by having an evenly
    distributed force on the spoke surface. You could think of this in the same way as the spoke grooves
    in your hubs.

    Cheers,

    Scott..
     
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