single vs. dual action truss rods

Discussion in 'Other T-Types and Partscasters' started by chucker, Jul 21, 2021.

  1. chucker

    chucker Tele-Meister

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    what would you say to some pearls of wisdom on this matter.
     
  2. RodeoTex

    RodeoTex Doctor of Teleocity

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    There's a lot of double acting trussrods being sold on the innermess that actually aren't.
    It's pretty much just a catch phrase now
     
  3. NoTeleBob

    NoTeleBob Tele-Afflicted

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    A little odd to adjust, based on having dealt with one recently that needed to be just out of the neutral zone. Took more experimentation to find the sweet spot. But, it's nice to know that I could pull it the other way if needed.
     
  4. SbS

    SbS Tele-Holic Silver Supporter

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    I got two necks with double action truss rod, just in case. Agree with NoTeleBob. Mine was pretty good too even without tension, but it should have at least some.

    Necks are little heavier, that's a downside.
     
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  5. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    They work on entirely different principals. A Fender single acting rod is a curved rod placed below the neutral axis of the neck anchored at one end and with a nut and washer that pushes against the length direction at the other end. Tightening the nut pulls the ends together putting the rod in tension and compressing the neck. String tension is pulling the head towards the heel, the rod is doing the same thing behind the neutral axis.

    A true double acting rod consists of two rods or bars, one fixed length with threaded pieces at each end. One piece has a standard thread, the other a reversed thread like a turn buckle. Turning the rod moves the ends towards or away from each other which flexes the fixed rod.

    Here is a double acting rod that was adjusted to its neutral position, then given one half turn clockwise (tighter), you can see how the rod is deflecting. It assembly is inserted into the neck with the adjustable rod down, the fixed rod is against the bottom of the fretboard. You can see how it will be applying an upward force in the center of the neck and down at the heel and nut end

    IMG_1045.JPG

    Both styles of rods work very well to control relief. A double acting rod does allow you to add relief but I have never found it necessary. I happen to use double acting rods in all of the guitars that I build - I have never bothered to build the somewhat complicated jig to route the curved channel for a Fender style single acting rod.

    There was a pretty good study on different truss rods in an older issue of American Lutherie magazine. I believe the conclusion was that double acting rods require slightly less torque on the adjuster for a given amount of flexing of the neck but that both worked equally well.
     
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  6. LutherBurger

    LutherBurger Poster Extraordinaire

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    I have two necks with double-action truss rods, but string tension alone has been sufficient for adding relief to every neck I've ever owned, so I haven't really needed them.
     
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  7. chucker

    chucker Tele-Meister

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    i was wondering about the subject. i'm getting my next neck with a single action to save the weight.
     
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  8. Ron C

    Ron C Tele-Holic

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    That’s where I’ve landed. Single action rod, vintage tuners and no exotic (dense) woods help a light guitar avoid neck dive.
     
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  9. EsquireOK

    EsquireOK Poster Extraordinaire

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    The only large advantage of a double acting rod is for the builder. You can just rout a straight channel, instead of needing to engineer and build a way to install the rod with a curve in it.

    I have no problem with them, but as a buyer, I would never pay extra for one. Single acting rods work just fine, and in literally thousands of adjustments, I have never busted a rod or had any other mishaps worth noting.
     
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