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Thread: So I'm thinking about brazing a fork...

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    Default So I'm thinking about brazing a fork...

    Other than buying/making an appropriate jig, any specific issues I need to think about? I know I need a crown that's relatively wide (cross tire), will probably go for a straight blade design with 45-50mm of rake and a length of about 380. Any tips on the brazing sequence? Steerer first and then blades or whole thing in one shot? Favorite crowns? Ya know, stuff like that...

    Part of my reasons for asking is that I've come across comments about how it's harder to braze a fork crown than say chainstays to BB shells and that one's first fork should probably just be a decorative piece. I welcome any scary fork stories to get me pumped up...

    Thanks,
    Hansen
     

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    For safety's sake I'd buy some crowns, blades and steerers and braze one and then cut it up in section so you can be sure your brazing material has filled all the voids. Learn from what you see on the first one and change your tact on the second, third, 4th....etc until you consistently have 100% fill.

    I know it goes without saying but when a chainstay comes loose you get a ride from from your wife. When the fork blade comes loose you get a ride to the big brick building in the panel van with the spinning light on top.

    Better safe than sorry.

    dave
    D. Kirk
    Kirk Frameworks Co.
    www.kirkframeworks.com


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    Quote Originally Posted by Dave Kirk View Post
    I know it goes without saying but when a chainstay comes loose you get a ride from from your wife. When the fork blade comes loose you get a ride to the big brick building in the panel van with the spinning light on top.

    Better safe than sorry.

    dave
    Yeah, I've had many vivid images go through my head since I started looking at fork crowns lately. Makes me wonder, what's the most common type of fork failure that you guys have seen through the years? I also wonder how that failure rate compares to the carbon ones...

    -Hansen
     

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    other than hipsters doing tricks on their fixed gears, I've never seen a failed steel fork. There was a listing on Ebay for a failed Cinelli fork. The steerer apparently was brazed with no penetration, and the fork had been held together for years with the brake bolt. The old guys used to drive a hardwood dowel into their steerers, so apparently at one time failed steerers was a concern.
     

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    Quote Originally Posted by EricKeller View Post
    other than hipsters doing tricks on their fixed gears, I've never seen a failed steel fork. There was a listing on Ebay for a failed Cinelli fork. The steerer apparently was brazed with no penetration, and the fork had been held together for years with the brake bolt. The old guys used to drive a hardwood dowel into their steerers, so apparently at one time failed steerers was a concern.
    Wow... good to know that a brake bolt might save my life in more ways than one!
     

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    Quote Originally Posted by suhacycles View Post
    Wow... good to know that a brake bolt might save my life in more ways than one!
    there are no brake bolts on that 'cross frame you're making atmo.

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    Quote Originally Posted by suhacycles View Post
    Wow... good to know that a brake bolt might save my life in more ways than one!
    i had a steel fork seperate crown from steerer, then the crown split at the brake hole and i still ate shit. me and about 45 other guys in the field behind me.
    Nick Crumpton
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    Quote Originally Posted by e-RICHIE View Post
    there are no brake bolts on that 'cross frame you're making atmo.
    No, not a 'brake' bolt but let me clarify:
    Attached Images Attached Images
     

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    Quote Originally Posted by suhacycles View Post
    No, not a 'brake' bolt but let me clarify:

    you are joking, no atmo?

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    Quote Originally Posted by crumpton View Post
    i had a steel fork seperate crown from steerer, then the crown split at the brake hole and i still ate shit. me and about 45 other guys in the field behind me.
    you must have been well-regarded at that point. I hope your injuries weren't too serious. What brand of bike?

    I guess this just proves the superiority of those old sand-cast Cinelli crowns.

    This is one failure that I can only barely understand. Pulling the braze through from one side to the other just seems like the most natural way of brazing in a steerer. I can't imagine there even needs to be all that much penetration to avoid a failure. The fact that there couldn't have been much penetration means that the braze was barely hot enough. An experienced person would have realized they didn't get enough penetration and discarded the part. So my interpretation is that there was a newbie building forks. That makes sense.
     

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    Default Steerers should never part with the crown if.............

    Make sure the steerer to crown fit is easy, meaning the crown will slide along the steerer when pushed lightly with very little pressure.
    This is important, because even if you get all to correct flow temp the braze will need clearance to flow.
    Most steerer to crown failures are from the steerer being tight in the crown, and the braze flowed along the edge and maybe even found it's way to the bottom of the crown along a small path, but not all the way around the joint.
    Thus fooling the builder into thinking the joint is correct. {seeing braze at both ends of the crown
    Many times in the factory the chap brazing was not doing the fit up of the parts.
    Make sure your fit ups are correct
    Clean mechanically the inside of the crown and the outside of the steerer
    I pin the crown to the steerer to ensure it does not move when brazing
    then flux and braze within minutes
    Use a big flame, not small hot intense flames {common mistake I see is the small hot fast flame}
    I use a five jet small rose bud for the crown {and LPG/Oxy torch}
    Feed from one end and witness it coming out the other end
    I feed from the crown race seat and flow to the bottom of the crown, the excess is filed/cleaned off from the underside of the crown.
    Some builders flow from the bottom to the crown race {with the crown steerer assembly upside down }
    this is cool.

    Fork blades is the same, make sure they are not too tight!
    Cheers Dazza
    The rock star is dying. And it's a small tragedy. Rock stars have blogs now. I have no use for that kind of rock star.
    Nick Cave

    www.llewellynbikes.com
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    Darrell Llewellyn McCulloch

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    Quote Originally Posted by e-RICHIE View Post
    you are joking, no atmo?
    I plan on getting the air-hardened version of that brake hanger bolt and really cook the sucker... then market it as the fork 'lawyer bolt' to complement my lawyer tabs...
     

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    Quote Originally Posted by crumpton View Post
    i had a steel fork seperate crown from steerer, then the crown split at the brake hole and i still ate shit. me and about 45 other guys in the field behind me.
    That wasn't your fork, was it? I hope that wasn't in a road race...
     

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    Quote Originally Posted by Dazza View Post
    Make sure the steerer to crown fit is easy, meaning the crown will slide along the steerer when pushed lightly with very little pressure.
    This is important, because even if you get all to correct flow temp the braze will need clearance to flow.
    Most steerer to crown failures are from the steerer being tight in the crown, and the braze flowed along the edge and maybe even found it's way to the bottom of the crown along a small path, but not all the way around the joint.
    Thus fooling the builder into thinking the joint is correct. {seeing braze at both ends of the crown
    Many times in the factory the chap brazing was not doing the fit up of the parts.
    Make sure your fit ups are correct
    Clean mechanically the inside of the crown and the outside of the steerer
    I pin the crown to the steerer to ensure it does not move when brazing
    then flux and braze within minutes
    Use a big flame, not small hot intense flames {common mistake I see is the small hot fast flame}
    I use a five jet small rose bud for the crown {and LPG/Oxy torch}
    Feed from one end and witness it coming out the other end
    I feed from the crown race seat and flow to the bottom of the crown, the excess is filed/cleaned off from the underside of the crown.
    Some buildesr flow from the bottom to the crown race {with the crown steerer assembly upside down }
    this is cool.

    Fork blades is the same, make sure they are not too tight!
    Dazza, you rule... thanks! BTW, do you guys recommend drilling holes in the steerer leading to each fork blade to facilitate venting and soaking the flux out?

    -Hansen
     

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    Quote Originally Posted by suhacycles View Post
    I plan on getting the air-hardened version of that brake hanger bolt and really cook the sucker... then market it as the fork 'lawyer bolt' to complement my lawyer tabs...
    you are kinda scary at this point.........
    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com

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    Quote Originally Posted by suhacycles View Post
    Dazza, you rule... thanks! BTW, do you guys recommend drilling holes in the steerer leading to each fork blade to facilitate venting and soaking the flux out?

    -Hansen
    Not me
    Water and sand and toad guts end up in the blades
    My front dropous are vented on the inside and face down wards and the blade stays vented
    and I also drill the blade midway
    do all the washing soaking and then pin the holes in the blade.
    I am working on a crown design that the fork blade will be open to the steerer but the bottom of the crown is covered, like the LS 32 {but with out the 5mm hole underneath} so flushing is very good and simple and the fork will stay dry inside and be sexy in shape and have lots of simple features to make fork life simple and effective
    but that project is year or two away.
    Cheers Dazza
    The rock star is dying. And it's a small tragedy. Rock stars have blogs now. I have no use for that kind of rock star.
    Nick Cave

    www.llewellynbikes.com
    The usual Facebook page
    https://www.flickr.com/photos/llewellyncustombicycles/
    Darrell Llewellyn McCulloch

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    Quote Originally Posted by Dazza View Post
    Not me
    Water and sand and toad guts end up in the blades
    My front dropous are vented on the inside and face down wards and the blade stays vented
    and I also drill the blade midway
    do all the washing soaking and then pin the holes in the blade.
    I am working on a crown design that the fork blade will be open to the steerer but the bottom of the crown is covered, like the LS 32 {but with out the 5mm hole underneath} so flushing is very good and simple and the fork will stay dry inside and be sexy in shape and have lots of simple features to make fork life simple and effective
    but that project is year or two away.
    Cool - except for the toad guts stuff... doesn't taste good with flux...

    That LS 32 crown looks like it has lots of space for water to flow through the steerer and fork blades and your idea sounds like the end of gunk collecting under the crown. Looking forward to it!

    Thanks,
    Hansen
     

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    Quote Originally Posted by suhacycles View Post
    That wasn't your fork, was it? I hope that wasn't in a road race...
    no, i didnt build the fork. yes, a race. everybody lived.
    Nick Crumpton
    crumptoncycles.com
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    "Tradition is a guide, not a jailer" óJustin Robinson

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    Hey whataya'll think of this 3rensho fork, recently auctioned on the 'bay. Crown coming loose off the steerer?
    http://picasaweb.google.com/norbikes/3RenshoBlue#
    http://picasaweb.google.com/norbikes...96119043170898

    I think "maybe".

    I told the seller as much and he replied something to the effect of "naw it's fine" and sold it anyway. I'd wanna do some reefing on it before riding, if'n it was mine.
     

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    Quote Originally Posted by bulgier View Post
    Hey whataya'll think of this 3rensho fork, recently auctioned on the 'bay. Crown coming loose off the steerer?
    http://picasaweb.google.com/norbikes/3RenshoBlue#
    http://picasaweb.google.com/norbikes...96119043170898

    I think "maybe".

    I told the seller as much and he replied something to the effect of "naw it's fine" and sold it anyway. I'd wanna do some reefing on it before riding, if'n it was mine.
    Great! Perfect for the brake hanger lawyer bolt... working on a Ti version for 2011...
     

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