Solved: Help with LMI double action truss rod install (wood plug for end) ?

Discussion in 'Luthier's Corner' started by rwkeating, Sep 12, 2016.


  1. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Edit: I solved this problem. See post #17 for more information

    On my first build I used and LMI double action truss rod (Truss Rod, double action welded nut) After dropping the rod into the channel, I made a "plug" for the adjustment end (in my case that was at the head stock end of the neck.) Everything is okay except the rod is extremely hard to adjust.

    In the bottom right of this picture you can see the plug and where I was about to install it.

    full?lightbox=1&last_edit_date=1456844370.jpg

    On my current build, I am doing the same thing and as soon as I put the plug in, the truss rod becomes hard to turn and that is even before the fingerboard is installed!

    What am I doing wrong? Thanks in advance.
     
    Last edited: Sep 14, 2016
  2. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Why do you need a plug?
     
    Dadagoboi likes this.
  3. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
  4. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    If the rod is a snug fit in the channel, you'd have to try pretty deliberately to pull the rod out. Once it's installed and under tension, even a little bit of tension, it will stay put by itself.
     
    Dadagoboi, RBS_Johnson and Deep Cat like this.
  5. michaelwayneharwood

    michaelwayneharwood Builder of the Wastelands Commercial User

    May 1, 2014
    Colorado
    Owner Melodious Resonance Constructs
    What I have found in the AllParts rods I use is that the adjustment "nut" is a slightly wider diameter than the rest of the rod. I use a 1/4" slot for the main rod, and widen the area of the adjustment nut to 5/16" to provide enough clearance.

    How snugly does the rod fit in the slot in general, and does the nut have enough clearance?
     
    kaoskater08 likes this.
  6. HaMMerHeD

    HaMMerHeD

    May 20, 2005
    I prefer truss rods to be removable. I'd hate to have to rebuild a neck because of a failed truss rod.
     
    kaoskater08 likes this.
  7. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Michael, the rod fits in the channel very securely. There is no nut on this rod. It is 2 rods connected to each other that work against each other.
     
  8. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    HaMMerHed. Do you know if this LMI rod is designed to be removable? They don't say anything about that on the web page and I'd think it would be a good additional selling point if it was removable.
     
  9. kaoskater08

    kaoskater08

    Apr 1, 2011
    I've used the LMI rod before and it fits snug in the channel without a plug. If you don't put the plug on the end just release any tension (rod and strings) and use a pair of needle-nose pliers to pull it out. That's what I've done before when I had one break where it was welded together.
     
    rwkeating likes this.
  10. michaelwayneharwood

    michaelwayneharwood Builder of the Wastelands Commercial User

    May 1, 2014
    Colorado
    Owner Melodious Resonance Constructs
    The rods I use are double action rods as well. The "nut" I am referring to is the round adjustment "screw" assembly that is welded to the rod.
     
  11. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Got it. The "nut" has plenty of clearance.
     
  12. michaelwayneharwood

    michaelwayneharwood Builder of the Wastelands Commercial User

    May 1, 2014
    Colorado
    Owner Melodious Resonance Constructs
    Based on your initial post the rod turns fine prior to installing the plug, post plug installation the rod becomes difficult to turn. My first guess is that the plug is pressing down on the nut in some way and causing the issue. What I would do is install the plug half way verifying that the wood is nowhere near the rod and test. If the rod turns fine slowly tap the plug into place in very small increments and test each iteration to see what effects, if any, it is having on the issue at hand.
     
  13. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Just to be clear, here is how the plug is installed. The red lines are the only points touching the rod, so you may be correct. On the other hand, the plug is flat and the "nut" is round. I am surprised that could cause so much more tension especially since the tension increases the more the rod is turned. I would think it would be consistent.

    Since the plug is already installed, I may do some experimenting prior to chiseling the plug out. Hmmmm.


    PlugDiag.jpg
     
  14. michaelwayneharwood

    michaelwayneharwood Builder of the Wastelands Commercial User

    May 1, 2014
    Colorado
    Owner Melodious Resonance Constructs
    Did you test the rod in the channel prior to installing the plug? I have made it a habit to test all my rods prior to putting them in a channel, testing during a "dry run" test fit, and once again after I install the rod over the bead of silicone caulk I use to eliminate rattling. It only took one incident requiring me to pull off a fingerboard to institute a rigid and paranoid regimen of tests. ;)
     
  15. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Yes, I tested the rod alone (without the plug) and it adjusted fine. I put the plug in place and tested it and there was no change. I glued the plug in place (not clamped) and adjusted the rod with no problem (the glue was still wet.). It was only the next day that the rod started to become difficult to turn.
     
  16. michaelwayneharwood

    michaelwayneharwood Builder of the Wastelands Commercial User

    May 1, 2014
    Colorado
    Owner Melodious Resonance Constructs
    My working theory is that the plug is glued in tightly enough that it's pressing down on the nut enough to cause the issue. I'm just a hack, so I am more than likely wrong.
     
  17. rwkeating

    rwkeating

    Oct 1, 2014
    Chicago
    none
    Solved! Make sure the adjustment end of the rod has room to move up and down.

    I figured it out. The part where the wrench goes (call it the nut) needs to be able move up and down (actually pivot) as the truss rod is adjusted. By having a plug in there this movement couldn't happen.


    I chiseled out that part of the plug. I left part in because I talked to a guy at LMI and he said they recommend the plug.


    Here I am trying to show the movement of the nut between loose and tightening the rod. The wood is for reference. You can see how the angle changes as you tighten the rod. The opposite happens in the other direction


    Now I have to go back on fix this (somehow) on my 1st build.
     
    83_Silberpfeil likes this.
  18. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Well, that makes sense!! :)
     
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    Primary TB Assistant

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