Cracked Chainstay: Best way to repair- Mtbr.com
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  1. #1
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    Cracked Chainstay: Best way to repair

    Hello,
    Unfortunately my first frame I have ridden/raced SS for about 2 years cracked on the drive-side chainstay.

    The crack is right at the vent hole (it is drilled underneath). I did crash on that side a couple weeks before...so maybe that added to the structural integrity.

    The tube is true temper (?) and at the crack is about 14.7 mm thick tapering up. The BB is lugged and dropout is a basic HJ track fork.

    What is the best way to repair this? (splitter, sleeve, new stay....(please say no!)

    How much powdercoat do I need to remove (1,2,3,4 inches each way?)

    I have my ideas on fixing it...but want the pro's recommendations before making it worse.

    Thanks
    Attached Thumbnails Attached Thumbnails Cracked Chainstay: Best way to repair-chainstay.jpg  


  2. #2
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    The best way to repair...cut out the stay, clean up the dropout and replace with a new stay that is NOT drilled on either of the vertical aspects. This will give you the greatest opportunity to learn.

    However, if you wish to preserve the stay or paint and want to repair it while increasing it's strength, you can do this...

    Groovy Cycleworks 330-988-0537: Behind the scenes...Chris's repair

    Good luck,

    rody
    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  3. #3
    Nemophilist
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    Hey;

    Whatever you do, I would strongly suggest that you make the surface of the break accessible for inspection. These types of failures usually occur over time and in one specific spot rather than breaking completely all at once. By carefully studying the mating surfaces of the break you should be able to see from what point on the surface the failure slowly began to work its way around until the tube was so compromised that the majority did fail completely "all at once." The older portion of the break will be darker and quite possibly rusted while the last portion will be cleaner/brighter. Also by studying the quality of the surface you can sometimes determine whether the material failed from brittleness or shear or whatever.

    There is most likely a lot of evidence in those two small surfaces. Taking the time and learning what to look for is the best way to refine your builds and avoid having it happen in the future.
    Last edited by TrailMaker; 03-19-2012 at 05:31 AM.
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  4. #4
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    Quote Originally Posted by Rody View Post
    The best way to repair...cut out the stay, clean up the dropout and replace with a new stay that is NOT drilled on either of the vertical aspects. This will give you the greatest opportunity to learn.

    However, if you wish to preserve the stay or paint and want to repair it while increasing it's strength, you can do this...

    Groovy Cycleworks 330-988-0537: Behind the scenes...Chris's repair

    Good luck,

    rody
    That was a great series of photos. Thanks!

  5. #5
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    Finally made the missing link...just a couple quick quesitons before brazing it in!

    Quote Originally Posted by Rody View Post
    The best way to repair...cut out the stay, clean up the dropout and replace with a new stay that is NOT drilled on either of the vertical aspects. This will give you the greatest opportunity to learn.

    However, if you wish to preserve the stay or paint and want to repair it while increasing it's strength, you can do this...

    Groovy Cycleworks 330-988-0537: Behind the scenes...Chris's repair

    Good luck,

    rody
    Rody,
    Thanks a ton for the guidance. I followed your directions/recommendations and was able to create the missing piece (and do some major clean up) that I am now ready to braze into the frame! *(ready to get my commuter back!) Please note the image was taken before the miter was complete...that is not how it will look.

    A couple quick questions.

    1) Vent hole: Can't I just drill a horizontal vent hole in the peice of 1018? It is much thicker walled than the chainstay.

    2) Silver or brass for the step: I am going to use brass on the dropout but what about where the piece slides into the chainstay? I was thinking silver but started to question that approach since the CS taper gets fatter towards the BB (all while the 1018 machined pieces stays constant)...and I am thinking the silver is too runny. I guess I would actually prefer silver since I get better flow/penetration with it but wanted your thoughts.

    Thanks again!
    I am currently rocking some LUV HANDLES on my MTB and wanted to say thanks for making a great product.
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  6. #6
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    Not sure if I "responded" correctly so that everyone gets the update.
    Just wanted to make sure everyone who subscribed sees this post (especially Rody.

  7. #7
    Randomhead
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    I probably would put a slug of 45% silver at the end of the plug and sweat it into the joint. When you fill the gap between the plug and the chainstay with silver, you know you are done.

    I don't know what a horizontal vent is. It needs to not be filled with filler, otherwise how you do it doesn't matter much as long as it vents the hot gas.

  8. #8
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    Ilcomm33,

    I typically drill 2 bullet holes in the existing stay near the terminus end of the insert, 180 degrees apart, to allow you to feed some 45% silver into and use gravity and drawing strokes with your torch to pull it through and down to the butt joint. This allows you to insure that you have even penetration and visual confirmation that the silver is where you want it.

    It appears that you drilled the new plug all the way through lengthwise...if so, I would not worry about a vent hole, as the expanding gases can escape at the dropout end. When you braze the dropout, good heat control and fill rate will allow you to close up the end without any expansion spit back.

    In the future, if you place your vent holes on the bottom bracket shell, inside the area where the stay connects, you will avoid the weakening of the stay and resultant fracture that you experienced.

    cheers,

    rody
    Last edited by Rody; 04-04-2012 at 05:35 PM. Reason: clarification
    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  9. #9
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    Up and running. Thank you for your help!

    Just wanted to follow up with a big thanks. Got my commuter back up and running which was pretty exciting since I couldn't take one more day on my old aolly hardtaiil 26er

    I did want to post some pictures as a way of paying it forward for the next person who might run into this situation. The pictures show everything from the 1018 solid rod all the way to the final spraypainted (yes..for now ridable product.

    Thanks again for everyone's guidance and feedback along the way.
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  10. #10
    nothing relevant to say
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    GREaT REPAlR !

  11. #11
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    i have a crack in the chainstay in the tube between the seat tube and chainstays that started on the side where the crank is and more than likely from stress pedaling and what is the best way to repair this type of set up. dont have a pic of the actual damage but here is a pic of the style.Name:  chainsty.jpg
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    pic of bike that i found exactly like mine on internet
    Attached Thumbnails Attached Thumbnails Cracked Chainstay: Best way to repair-img_7016_lg.jpg  

    Last edited by poconnell; 01-14-2016 at 09:47 PM.

  12. #12
    CS2
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    Quote Originally Posted by Rody View Post
    The best way to repair...cut out the stay, clean up the dropout and replace with a new stay that is NOT drilled on either of the vertical aspects. This will give you the greatest opportunity to learn.

    However, if you wish to preserve the stay or paint and want to repair it while increasing it's strength, you can do this...

    Groovy Cycleworks 330-988-0537: Behind the scenes...Chris's repair

    Good luck,

    rody
    Very nice repair.
    A garage full of steel frames means happiness.

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