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Thread: Potential for failure in rod end adjuster nuts

  1. #11
    Electron Karl's Avatar
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    Quote Originally Posted by bolus View Post
    I need a way to inexpensively test breaking on these when I get one. I am not going to pay $300 to get an independent lab to break test them. My physics is rusty, how would one test one with a long lever until breaking an calculate the force it takes to break one?
    Fatigue cracking cannot be tested with an ultimate strength rig; you need to build a device that simulates the cyclic load that the part experiences in its normal application. So, you'd need the outer sleeve, the mid sleeve, and the rod end, and you'd need to know what loads it experiences (not a lot of bending (save for shock loads), lots of tension/compression). Then, you build a machine with an actuator that loads and unloads the assembly until crack propagation causes failure, and you do that a few times. It's going to be very difficult to completely eliminate the risk of fatigue cracking from this part because the thread cuts make for gnarly stress risers. It would be easier to replace them on a regular basis.
    Last edited by Karl; November 8, 2011 at 10:49 AM.
    300hp K20A | "It'll never go, my dears! Not if he's had anything to do with it."

  2. #12
    Proton Terry Kennedy's Avatar
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    Quote Originally Posted by MadMaxAtom View Post
    Another thought I had..what if the rod ends threaded stock diameter was reduced to 1/2" (I believe they are 5/8" currently) and correspondingly machined thimbles were made,so the wall thickness of the new thimbles would be greater? 1/2" rod stock would still be an overkill for strength in the Atoms application. If you were making new thimbles anyway,and the 1/2" shank rod ends were available,this should be adequate insurance against a weak link.
    I think it depends on what the costs will be. PRB-10T (the stock 5/8" size) is $87.99 each at Hoerr; PRB-8T (the 1/2" size) is $64.99 each. Thimbles are somewhere between $22 and $150 each. At some point it is probably cheaper just to use custom rod ends.

  3. #13
    Neutrino MadMaxAtom's Avatar
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    If the new thimbles could be made for the 1/2" rod stock,I would buy new rod ends and the custom 4130 thimbles, as my rear rod ends are showing some play.As the rest of my rod ends wear and need replacement, they could then be upgraded to the sturdier setup.Hmm...
    The power of an Atom is a terrible thing to waste! Atom owner/operator since 2007. The more you chase perfection,the faster it becomes. John Force for President! (I asked him once in person...he laughed)

  4. #14
    Neutron
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    One problem is what to do next time. Either we have a custom rod end to try and reorder or a custom thimble to try and reorder. And Im not going to stock any of these if a new owner needs a set down the line. This is an annoying problem

  5. #15
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    My order was finished and is on the way. Should have them here in a few days.

  6. #16
    Proton Terry Kennedy's Avatar
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    Quote Originally Posted by bolus View Post
    One problem is what to do next time. Either we have a custom rod end to try and reorder or a custom thimble to try and reorder. And Im not going to stock any of these if a new owner needs a set down the line. This is an annoying problem
    Presumably what you do with any other unique Atom part. Either stock up ahead of time, scavenge, see if anybody has any leftovers, or have some more made.

    I really don't see this as a massive problem. I must have over 12,000 miles on my current set of AM/AB rod ends, and inspection 3000 miles ago showed no wear and no magnetic imperfections. I'd buy 2 sets of extended rod ends (12 pieces) and probably only do the tops of the uprights (I agree with Max - the rear bottom thimbles are under a fair amount of compression, are not stressed in the axis of failure, and would be non-catastrophic if they did fail). That leaves me with 8 rod ends to replace based on wear, which I'd guess would be after 20,000 more miles.

    Street use is probably more stressful than track use for this particular part, at least if your streets have more potholes than your tracks.

  7. #17
    Neutrino MadMaxAtom's Avatar
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    I'm thinking I buy a set of custom 1/2" thread 4130 thimbles, and as my rod ends wear,replace them with 1/2" off the shelf units.The rod ends being a standard item that would need regular replacement anyway makes this direction a no-brainer for me. Once you replace the "old" thimbles with 4130 1/2" units,they should never need replacement.
    The power of an Atom is a terrible thing to waste! Atom owner/operator since 2007. The more you chase perfection,the faster it becomes. John Force for President! (I asked him once in person...he laughed)

  8. #18
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    Just annoying. Spoke to like 8 different places to just get a set of thimbles made. Prior to that I looked though umpteen sites trying to find an off the shelf part not realizing that Brammo made them on their lathe. The paid more than I really wanted to (though my car isnt going to sell, I accept that now, might as well start pumping more money into it ) to get 22 of these that I hope will fit and hope someone will by some of them from me. If they dont fit though, Im making them into salt and pepper shakers and giving them away for Christmas

    Just cant be easy can it

  9. #19
    Lepton Positron's Avatar
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    Quote Originally Posted by bolus View Post
    Just cant be easy can it
    ... and what fun would that be?..

    Thanks for spearheading another project.
    AtomII #73 for sale, PM for details.

    Turning money into smoke and noise since 2006.
    Member "I drove the Brammo mule with Tom S." club.


  10. #20
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    Quote Originally Posted by Positron View Post
    ... and what fun would that be?..

    Thanks for spearheading another project.
    Not me, Terry has done all the work up until this point. He gets all the credit

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