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Thread: Original oil cooler brackets keep breaking

  1. #1
    smcnutt's Avatar
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    Default Original oil cooler brackets keep breaking

    We have the original oil cooler and hard lines mounted in the chin and the brackets keep breaking. Not sure exactly what's wrong and why they keep breaking. This has got to be the 5th or 6th time a part of the bracket has broken. We've had both the left and right side break at different times and different places. Currently the left side one with 3-legs has broken where the leg attaches to the generator. Basically the flattened part of the tube broke. It's getting kind of frustrating as it's a nuisance taking the prop, nose bowl off to get to it, repair it and put it all back together and pray you don't have a oil leak when you are all done.

    I know it's a big hunk of metal hanging there but why do the mounts keep breaking? I really don't want to buy a new lighter oil cooler because we have no issues with oil temp with the existing one. We had the engine dynamically balanced a couple of years ago so there isn't any unreasonable vibrations. We're wondering if maybe we should/could switch from the hard lines to flexible lines and possibly remove a point of tension -i.e. the hard lines pushing one way while the mounts push a different way? Would it help/hurt and can it be done without an STC of some sort?

    I was also looking at Univair and their replacement mounts MAN oh man are they proud of the ones they are selling -$225 for one and $450 for the other. I guess we will keep repairing ours.

    Any suggestions on how to keep them from breaking again? The repaired sections are not re-breaking (so far) but I think with every repair we're just moving the weak link to another spot on the bracket. There's got to be an underlying reason why it's under abnormal (at least I think it's abnormal) stress.
    “Common sense is in spite of, not the result of, education.”
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  2. #2
    Pacerfgoe's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    I wonder if it's work hardened itself to the point of being brittle?.... the only thing that will fix that is a new one.
    Good Judgement comes from Experience --and Experience- well, that comes from Poor Judgement

  3. #3
    Steve Pierce's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    From my experience it is not uncommon to find them broken but sounds like you might have something in a bind or work hardened like Forrest posted. Only thing I know to do is to make sure everything is relaxed when you start tightening things up. Not sure the hard lines are stiff enough to cause a problem. I replace them with -8 Stratoflex with fire sleeve via a log book entry, common hardware and practices.

  4. #4

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    Default Re: Original oil cooler brackets keep breaking

    Try getting a dynamic balance on your prop. I find most airframe cracks like this are prop vibration induced- low cycle fatigue.


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  5. #5
    smcnutt's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    Quote Originally Posted by dgapilot View Post
    Try getting a dynamic balance on your prop. I find most airframe cracks like this are prop vibration induced- low cycle fatigue.


    Sent from my iPhone using Tapatalk
    We've done that a couple of years ago partly because of problems like this. They did reduce some vibration but it wasn't that far off before either.
    “Common sense is in spite of, not the result of, education.”
    ― Victor Hugo

  6. #6
    PeterL's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    I have some extra brackets that I can send to you at no charge, just let me know if you would like them.

    Peter Lubig

  7. #7
    smcnutt's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    That would be awesome even if to make sure ours have not been tweaked from previous repairs. I'll send you a PM.
    “Common sense is in spite of, not the result of, education.”
    ― Victor Hugo

  8. #8
    Gilbert Pierce's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    I had a generator bracket welded by a "Pro". As soon as the bead was completed he threw it in a bucket of water.
    I thought well it will break again very shortly which it did. It should have been allowed to air cool slowly.

  9. #9
    mmoyle's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    [QUOTE=It should have been allowed to air cool slowly.[/QUOTE]

    I'll second Gilbert. Vermiculite is a wonderful media for slow cooling to prevent formation of martinsite crystals. Heat above and below stress effected areas....Dull red.....Tempi sticks are great tools for insuring you reach annealing temperature...say 1600 degrees https://www.amazon.com/Tempil-Surfac.../dp/B01HQ3L7IC


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  10. #10
    PeterL's Avatar
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    Default Re: Original oil cooler brackets keep breaking

    Quote Originally Posted by smcnutt View Post
    That would be awesome even if to make sure ours have not been tweaked from previous repairs. I'll send you a PM.
    How do these look?

    Peter
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