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Thread: broken right crank arm- how unusual is this???

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    Default broken right crank arm- how unusual is this???

    Ok- I'm a little shell-shocked today.

    75 degrees, nice crisp ride up a steep ridge, just over it- then--- snap; I'm on my back & don't know why.

    My Rotor crank ( with QXL rings) snapped just above the pedal.

    They are shipping me a new one.asap-- but now I'll be freaking out about this.

    How unusual is this??

    Last time I did this was in 1982, on a Campy Crankset.
    Attached Images Attached Images
     

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    Default Re: broken right crank arm- how unusual is this???

    I've broken a good 1/2 dozen QUALITY crank arms. Stuff breaks.

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by Too Tall View Post
    I've broken a good 1/2 dozen QUALITY crank arms. Stuff breaks.
    and you've ended up on your back every time?

    I'm glad I tumbled into the grass this time- and not the road!!
     

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by tblairhug View Post
    and you've ended up on your back every time?

    I'm glad I tumbled into the grass this time- and not the road!!
    Never went down. I've got freaky good luck. The last one was a super high quality crank that T.K. and another VSalonista observed the full disaster. FWIIW Three were OG Campy cranks that were known to break in the same location.

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    Default Re: broken right crank arm- how unusual is this???

    A friend broke a nuovo record arm in the 80s and fell to the ground. I rode into him and did an over the bars slow motion face plant. I still have some scars on the bridge of my nose from that incident.
     

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    Default Re: broken right crank arm- how unusual is this???

    Look at the break and it will tell you a story.

    You should be able to see where the crack initiated and how quickly it grew. The older part of the crack will be dirty and oxidized. Maybe earlier than that there could be a smooth and polished area where the two surfaces moved relative to each other. And it might look like tree rings where it started to grow rapidly, and rough and matte where what was left finally broke.

    And please know that the current Campagnolo aluminum crank design, which uses a pressed-in conical washer at the pedal eye, is probably the best design ever for long-term durability and preventing this kind of failure.

    Cracking/Breaking Cranks by Jobst Brandt

    PS Glad you're OK.
    Last edited by thollandpe; 02-22-2018 at 02:12 PM.
    Tdd Hllnd

    Give a man a fish and feed him for a day. Teach a man to fish and feed him for a lifetime. Teach a man to cycle and he will realize fishing is stupid and boring. -- Desmond Tutu

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    Default Re: broken right crank arm- how unusual is this???

    there is a dirty & oxidized part!-

    next time around- would washers make any difference?

    ( i guess I will be inspecting these regularly too.)
     

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by thollandpe View Post
    Look at the break and it will tell you a story.

    You should be able to see where the crack initiated and how quickly it grew. The older part of the crack will be dirty and oxidized. Maybe earlier than that there could be a smooth and polished area where the two surfaces moved relative to each other. And it might look like tree rings where it started to grow rapidly, and rough and matte where what was left finally broke.

    And please know that the current Campagnolo aluminum crank design, which uses a pressed-in conical washer at the pedal eye, is probably the best design ever for long-term durability and preventing this kind of failure.

    Cracking/Breaking Cranks by Jobst Brandt

    PS Glad you're OK.
    Any opinion on the current Campagnolo carbon crank design?

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by Too Tall View Post
    Never went down. I've got freaky good luck. The last one was a super high quality crank that T.K. and another VSalonista observed the full disaster. FWIIW Three were OG Campy cranks that were known to break in the same location.
    Sorry, but what does "OG Campy cranks" stand for?
     

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by woodworker View Post
    Sorry, but what does "OG Campy cranks" stand for?
    In the vernacular it means Original Gangster. In this case 70's era cranks.

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by tblairhug View Post
    there is a dirty & oxidized part!-

    next time around- would washers make any difference?

    ( i guess I will be inspecting these regularly too.)
    Did the cracks initiate at 3:00 and 9:00 on the outside of the pedal eye? Washers certainly won't hurt. Also make sure the pedal eye is countersunk, that there's a chamfer or radius around the edge of that threaded hole.

    Quote Originally Posted by dogrange View Post
    Any opinion on the current Campagnolo carbon crank design?
    If the threaded insert is aluminum, and/or there's a steel washer around the pedal eye, then it's a good detail. No way to know if it's conical, but likely. You can also ask Campagnolo.

    The only way I know about this is by seeing a crank that someone ham-fisted and popped the washer loose.
    Tdd Hllnd

    Give a man a fish and feed him for a day. Teach a man to fish and feed him for a lifetime. Teach a man to cycle and he will realize fishing is stupid and boring. -- Desmond Tutu

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    Default Re: broken right crank arm- how unusual is this???

    Quote Originally Posted by Too Tall View Post
    In the vernacular it means Original Gangster. In this case 70's era cranks.
    Thanks.

    ...so aluminum.

    I know that the early versions of the carbon cranks had issues with the metal pedal thread coming loose from the carbon crank. But I wonder how the current crop of carbon cranks fare over the long haul.
     

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    Default Re: broken right crank arm- how unusual is this???

    Pic reminded me of this crank braking Left Leg Only | Steve Tilford
    The oxidation on the broken crank in the blog photo looks like it started near the pedal.
     

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