Full and sudden failure of a fork
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  1. #1
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    Default Full and sudden failure of a fork

    Ok, this was abuse. We were moving bundles of steel beams hanging from straps up a narrow steep path. A telehandler holding up the rear and a rough terrain forklift the front (going backwards).
    Telehandler had a single FEM3 size (full size in my book) 2 meter fork with the strap hanging at about 1,80m out and about 2 tons of load.
    The fork was bending but not deforming, but then it suddenly broke at the root and the load fell about a foot.
    No biggy, but impressive failure mode.
    Picture taken the day after, slight rust from rain.
    Last pic shows mud on parts of the break of the vertical fork part..
    win_20210511_16_54_03_pro.jpgwin_20210511_16_53_52_pro.jpgwin_20210511_16_54_22_pro.jpg

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    Sounds like you got lucky, that had been waiting to fail for a while...

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    Quote Originally Posted by Martin P View Post
    Ok, this was abuse. We were moving bundles of steel beams hanging from straps up a narrow steep path. A telehandler holding up the rear and a rough terrain forklift the front (going backwards).
    Telehandler had a single FEM3 size (full size in my book) 2 meter fork with the strap hanging at about 1,80m out and about 2 tons of load.
    The fork was bending but not deforming, but then it suddenly broke at the root and the load fell about a foot.
    No biggy, but impressive failure mode.
    Picture taken the day after, slight rust from rain.
    Last pic shows mud on parts of the break of the vertical fork part..
    win_20210511_16_54_03_pro.jpgwin_20210511_16_53_52_pro.jpgwin_20210511_16_54_22_pro.jpg
    They doo that. You were thinking maybe they would simply bend ?

    Don't work them hard like that.

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    Yes I expected plastic deformation and have seen that some.
    I saw a rental recently where the forks were bent about 5 degrees down.

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    On a side note, that fork is repairable, I've done it. A properly re-welded fork is just as strong as a virgin fork when the repair procedure is followed to a 'T'.


    Stuart

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    The top of the break suggests a previous overload stress crack that propagated into the total failure.

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    go magnaflux your forks folks!

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    Some years ago ,I got the job of reassembling two Hyster 520s at an auction yard...I had to make some of the pins for the masts that were "too costly to buy off Hyster"......anyhoo,the giant forks on both had been crack tested with dyecheck,and the bends were full of small cracks......the auctioneer came out with a wire brush and removed the white coating.....Both forklifts were from Queensland Railways....who used to maintain their equipment better before they were privatised.

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    Quote Originally Posted by Martin P View Post
    Yes I expected plastic deformation and have seen that some.
    I saw a rental recently where the forks were bent about 5 degrees down.
    Well, Chinese steel strikes again.
    There are no standards anymore.

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    Quote Originally Posted by digger doug View Post
    Well, Chinese steel strikes again.
    There are no standards anymore.
    you sure? How do you know that?
    and that's the only reason? No chance overloading, and previous damage?

    just curious how you know it's chineese metal... I don't doubt it, but I don't know.

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    "On a side note, that fork is repairable, I've done it. A properly re-welded fork is just as strong as a virgin fork when the repair procedure is followed to a 'T'."
    Stuart


    You are out of your mind, no way will OSHA allow a welded fork, and how would you put the heat treat back into it? Forks are forged and heat treated for a reason, and next time it breaks you might kill someone. Both forks should changed out with new ones and the old one cut up for scrap. Just like a airplane wing so many flex,s and they will snap...Phil

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    Quote Originally Posted by atomarc View Post
    On a side note, that fork is repairable, I've done it. A properly re-welded fork is just as strong as a virgin fork when the repair procedure is followed to a 'T'.


    Stuart
    Is there a standards organization that established this repair procedure?

    These fork failures are likely related to cyclic loading(bouncing load), which is why it broke in a brittle manner at a load below the yield or tensile strength. It is basically accumulated damage that can result in cracks that cause a brittle failure. Damage to the surface of the forks can cause a stress concentration that further exacerbates this process.

    I can't imagine any repair that would fix the accumulated fatigue damage in the adjacent areas and would cost less than just getting a new fork. That, along with fatigue challenges related to welds makes a repair extremely suspect. Static load capacity is far from the only design requirement for a fork. You need to accommodate fatigue because have to be thin, and therefore flexible, which causes a lot of fatigue.

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    Well fellas...you have to be smarter than the fork and know how to follow a welding procedure. When I did the deed, there was no such thing as OSHA, you had to use your brains. It's much different today...but as Phil noted, I'm probably out of my mind.


    Welder-Stu

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    I wouldn’t weld that and I’ve done some SKETCHY shit with a welder and that’s no something I would do.

    The internal stresses in the weld/filler would be pretty bad if not tempered back I would think.

    I also get the vibe if the welded fork snapped at the weld you’ll possibly get some “energetic fragmentation”.

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    Well Mr. Blob...that's why you preheat, peen, post heat and use a filler that's compatible with the original metallurgy of the fork. It a recipe, just like making brownies...if you forget to put in the weed, the brownies will just plain..suck!


    Ganja-Stu

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    Quote Originally Posted by Homebrewblob View Post
    I also get the vibe if the welded fork snapped at the weld you’ll possibly get some “energetic fragmentation”.
    From the owner or user of the fork lift, if nothing else.

    I'm going with "replace both tines", and with a known-good US maker. I have a pair of cheapass CN tines that will be used at a very derated level for an inhouse purpose, but otherwise would only use US, CA, or a good EU brand.

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    Quote Originally Posted by atomarc View Post
    Well Mr. Blob...that's why you preheat, peen, post heat and use a filler that's compatible with the original metallurgy of the fork. It a recipe, just like making brownies...if you forget to put in the weed, the brownies will just plain..suck!


    Ganja-Stu
    Well heck, might as well forge you some new pokies at that point.

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    Quote Originally Posted by Milland View Post
    From the owner or user of the fork lift, if nothing else.

    I'm going with "replace both tines", and with a known-good US maker. I have a pair of cheapass CN tines that will be used at a very derated level for an inhouse purpose, but otherwise would only use US, CA, or a good EU brand.
    Can’t argue with that

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    Been around forklifts for many a moon and not once..until post #16 have I heard them referred to as 'tines', must be a New Hampshire 'thang'!


    Tine-less Stu

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    Quote Originally Posted by atomarc View Post
    Been around forklifts for many a moon and not once..until post #16 have I heard them referred to as 'tines', must be a New Hampshire 'thang'!


    Tine-less Stu
    Get with the tines, young man. We in the Great Northeast are hep, mod, and with-it, so know all the nomenclature...

    Forklift Forks and Tines Guide | Learn Before You Buy | Tontio


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