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  1. #1
    The Brave Descender High Fist Shin's Avatar
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    Crank set needs stress relief

    Saw this in the For Sale forum:

    "Campy SR 170mm 53/42 rings. MUST BE STRESS RELIEVED. If you dont know what 'needs to be stress relieved' means do not buy and do not ask."

    Ok, I'll admit I don't know what "stress relieved" means. Can someone kindly enlighten me?

    Dan
    In life there are no mistakes, only lessons. -Shin

  2. #2
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    This makes my "BS" meter read rather high.

  3. #3
    Senior Member embankmentlb's Avatar
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    I think it means " If you are looking for a usable crank then don't buy these".

  4. #4
    The Brave Descender High Fist Shin's Avatar
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    Ok, "BS" or not, what does it mean? I've never heard of stress relieving a crank or rings or whatever.
    Last edited by High Fist Shin; 12-20-08 at 03:53 PM.
    In life there are no mistakes, only lessons. -Shin

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    Real Men Ride Ordinaries fuzz2050's Avatar
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    I don't think it means anything. You can stress relieve wheels, but thats because they have different parts held together under tension. Cranks don't. Obviously that the post is really some sort of covert spy transaction.

  6. #6
    Let your bike be the tool cranky old road's Avatar
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    Campy cranks of that era are known to develop micro cracks where the crank attaches to the spider, a "stress crack". Folks keep the crack from running by grinding away the cracked area. I've never had to do this to my NR cranks so my description might be inaccurate. So the seller is sayin' the crankset has a crack in it...
    Last edited by cranky old road; 12-20-08 at 05:13 PM.
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    The Brave Descender High Fist Shin's Avatar
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    Quote Originally Posted by cranky old road View Post
    Campy cranks of that era are known to develop micro cracks where the crank attaches to the spider, a "stress crack". Folks keep the crack from running by grinding away the cracked area. I've never had to do this to my NR cranks so my description might be inaccurate. So the seller is sayin' the crankset has a crack in it...
    Thank you. I wasn't aware of this as I've never had Campy cranks on my vintage bikes.
    In life there are no mistakes, only lessons. -Shin

  8. #8
    Small Member maddmaxx's Avatar
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    Quote Originally Posted by cranky old road View Post
    Campy cranks of that era are known to develop micro cracks where the crank attaches to the spider, a "stress crack". Folks keep the crack from running by grinding away the cracked area. I've never had to do this to my NR cranks so my description might be inaccurate. So the seller is sayin' the crankset has a crack in it...
    Good information................thanks.

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    All of my NR cranks had that little crank, back in the 70's. Get a 3/16 inch small rat-tail file and radius the little web aluminum where the arm joins the spider, then use emery paper on the file and polish up what you file, you will likely file that the crack is very shallow and disappears after the filing... FYI i never heard of the cranks breaking at this spot

  10. #10
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    Generally in metal working stress relieved means bead blasting the to relieve stresses that could lead to cracks in the metal. Roger

  11. #11
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    Quote Originally Posted by rhenning View Post
    Generally in metal working stress relieved means bead blasting the to relieve stresses that could lead to cracks in the metal. Roger
    I often also means heat-treating the part after cold working or forging to relieve the internal stresses.

  12. #12
    i ride a bicycle
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    Quote Originally Posted by rhenning View Post
    Generally in metal working stress relieved means bead blasting the to relieve stresses that could lead to cracks in the metal. Roger
    Bead blasting actually imposes a stress, not relieves it.

    Mac

  13. #13
    Rumblefish jtarver's Avatar
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    Why didn't you just ask the OP of the cranks, he seemed more than happy to explain.
    1973 Crescent Pepita FG, 1987 Panasonic DX-4000, 1991 Trek 1400 FG, 1990's Gary Fisher Hoo-Koo-e-Koo SS, 1990's Denti Road Tech Five, 2009 Surly Long Haul Trucker

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    There are lots of ways to remove stress.It can be done with temperature,sound waves,shot peening,vibration.Depends on what kind of stress your trying to get rid of.If your trying to eliminate stress cracks,the best way is to shot peen.That will compact the metal and spread the stress over a larger area.
    Everything should be as simple as possible...But not more so.---Albert Einstein

  15. #15
    Sometimes knows stuff. rmfnla's Avatar
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    Quote Originally Posted by sac02 View Post
    Bead blasting actually imposes a stress, not relieves it.

    Mac
    It doesn't do either; it peens the surface to eliminate small voids that could become stress risers.

    It also work-hardens the surface slightly.
    Today, I believe my jurisdiction ends here...

  16. #16
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    Quote Originally Posted by jtarver View Post
    Why didn't you just ask the OP of the cranks, he seemed more than happy to explain.
    Well he wrote:"If you dont know what 'needs to be stress relieved' means do not buy and do not ask."

    To me that means he doesn't know either and doesn't want to have to admit it.

  17. #17
    slowest! dsellinger's Avatar
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    I think he just wants to be an elite prick.

  18. #18
    Member kenja's Avatar
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    The difference between bead blasting and shot peening needs to be clarified in this thread.
    http://www.speedwaymotors.com/METAL-...INET,2606.html
    http://www.metalimprovement.com/shot_peening.php

    OT, but a new one for me is laser peening:
    http://www.metalimprovement.com/laserpeening.php
    Last edited by kenja; 12-22-08 at 07:35 PM.

  19. #19
    Sometimes knows stuff. rmfnla's Avatar
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    Quote Originally Posted by kenja View Post
    The difference between bead blasting and shot peening needs to be clarified in this thread.


    OT, but a new one for me is laser peening:
    http://www.metalimprovement.com/laserpeening.php
    Really just a difference in the blasting media being used; the techniques and the results are pretty similar.

    The laser technology is interesting; with the temperture component there might be a slight surface tempering effect as well as the mechanical effects.
    Today, I believe my jurisdiction ends here...

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