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Why Double Action Rods Are A Good Idea
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=49872
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Author:  meddlingfool [ Sat Dec 09, 2017 3:44 pm ]
Post subject:  Re: Why Double Action Rods Are A Good Idea

Good tips, thanks! I've just been using Rona kitchen/bathroom stuff but maybe I should switch.

Author:  Arnt Rian [ Thu Dec 14, 2017 6:43 am ]
Post subject:  Re: Why Double Action Rods Are A Good Idea

Eric Reid wrote:
And Why They're Not:
#1: neck buzzing--I saw hundreds of these. To be fair, most of these didn't buzz when played. (They rattled like the devil when you rapped on the back of the neck with your knuckles.) Some that buzzed when playing were cured with a little tension on the truss-rod (and a little loss of playablity because now the neck relief wasn't optimum). Some of those that didn't buzz initially would buzz at random moments of humidity change--lots of fun for the repairman.

#2: Weld-fouled threads--I came into guitar building from a background in racing bicycle manufacture. All of the welded truss-rods I've seen have had amateurish welds. Let me say that again: ALL OF THE WELDED TRUSS RODS I'VE SEEN HAVE BAD WELDS. I'm not as much in the loop as I used to be, but every time I see a discussion here with pictures of a welded truss-rod, it takes me back. Fouled threads will limit adjustment.

#3 Cracked welds--ALL OF THE WELDED TRUSS RODS I'VE SEEN HAVE BAD WELDS. I would say that at least 70% of the welds I looked at had substantial cracks. In a very small percentage of the welds, the crack had propagated far enough to render the rod useless. Cracks propagate over time.


#8: Weight. For some playing styles (flamenco), neck weight is critical. Maybe Stuart's designs would solve that problem, but most truss-rods are a good deal heavier than Spanish cedar.


I haven't read the whole thread, but this matches some of my observations as well. I usually do use a DA rod in my guitars, the only one I trust is the newer Martin design, it seems fairly reliable, but the SA compression usually works as well or better. They both have problems though, so pick your poison.

Buzzing: From my experience, DA rods are more likely to buzz than SA rods, probably due to more moving parts. A tighter fit, some (non silicone) caulk, tightening the rod etc will usually fix it, but still more trouble than SA rods.

Bad welds: Certainly. Not just the old LMI rods, the early Blanchard style rods from Allied were pretty bad too. I had failures, rattles, freezing and all kinds of trouble with those. I hear the new ones are better, but...

Weight: I like a light neck, and I select woods, tuners and some times use a SA truss rod to keep the weight down. E.g. a double action bass rod adds a noticeable amount of weight.

Deeper slot: The SM Hot Rod requires a very deep slot, some neck designs may not permit it. I find it hard to operate, but I have not had failures with this rod, but there are enough reports of trouble out there to be apprehensive.

I like a SA compression rod with a heat shrink tubing to avoid buzzing, a right angle to a anchor it at the heel end, a small nut that requires minimal wood removal at the headstock, and backstrapping of the headstock to make up for the loss of strength. If you put some tension on it before you level the FB, you get some dual action adjust-ability. This is a good, lightweight and reliable design.

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