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Frets.com shows Collings Guitars method and type of truss rod they use. Does anyone know the diameter of the rod? Most important to me is the channel slot. Is it straight or does it have a downward curve to it? If so how drastic would the curve be?

With a resounding silence of zero answers I'm wondering if I didn't make since or was it a stupid question. I'm realtively new to all of this.

Most major manufactures use a single acting rod. I toured Collings and they mentioned the dip in the channel. Over adjusting the rod and then leveling the fretboard allows the rod to act in the form of a dual acting rod. The rod is slimmer allowing less wood to be taken away leaving more strength in the neck. A single rod covered with heat shrink is less likely to cause any rattling or fail because there are no welds to break.

Thoughts? I've been lurking here for a good while and know that there are plenty of differing opinions on most every topic.

I think most luthiers these days are using double truss rods such as the "Hot rod" on Stewmac or LMI's version. I use Stew Macs. they require a 7/32 wide 7/16 deep channel and can be accessed either from the body or the head stock. A curved channel for these is not necessary.
http://www.stewmac.com/shop/Truss_rods/ ... t_Rod.html

I have seen those but am wondering why use them if the alternative seems to hold the same ability to adjust as well as being lighter and having less potential for failure or rattle. It would make sense from an economic point of view to put in a dual action rod making the set up of the instrument possibly having less chance of error. Just trying to figure out the pros and cons.

Because you can adjust them both ways. A little silicone will prevent any rattling.

Orion,
I know another "Orion", a guy in the band "Brown Chicken Brown Cow"

I used to know Bill Collings pretty well in the far past, and he has very strongly held preferences of the best way to do something, along with the drive to do it. He has a great reputation for a good reason. If you like Bills reason for preferring a single acting rod, you should study how it works, and how he does it, and you'll be a long way toward doing a good job with it.

As in most things "guitar building" there is no one "best way" but many different ways to do something.
There are several very well made and good working double acting rods on the market, some are pretty small in cross section.

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I mean no disrespect to Collings whatsoever, but I've installed hundreds of double rods and never had a single one fail, or break a weld on me, nor have they run out of adjustment room. The nuts welded onto them seem hard enough to outlast any hex key. Early on I got some rattles but have since learned how to correct the problem, without the damping effects of silicone, which may or may not be real. The double rod systems are also a lot more sensitive than the single rods. A little turn has more affect than with a single rod, and so double rods have a LOT more adjustment range than singles
I've seen hundreds of guitar necks with single rods that have had one or more of the following:
Stripped threads, loose anchors causing spinning, uncorrecteable back bow even under string tension, uncorrecteable underbow due to lack of threads (nut tightened all the way), unknown failure characterized by the ability to straighten the neck to a certain point but no more and the nut keeps tightening (I think it's caused by the rod being straightened in the neck so that the rod is being tightened like a string) without further straightening of the neck.
I don't believe that if a builder made two guitars with the same quality workmanship, wood selection, and electronics that you could record the two, and tell which one has the single rod. If you took a sampling of opinions over which one sounded better, it would be split 50/50.
Finally, tensioning the neck, leveling the fretboard and then radiusing the neck doesn't cause the single rod to act like a double rod. A single rod cannot force a backbowed neck to relieve, once the neck has warped backwards sufficiently to necessitate that. It does, however, cause the neck to develop relief when the truss rod is loosened all the way without string tension, thus ensuring the neck will most likely always be able to be relieved, assuming the neck doesn't warp backwards sufficiently to cause a problem. Doing that also limits the adjustment range of the system, by pre-using some straightening range to create the artificial neck relief.
Personally I think well selected timbers will stay true for the life of the instrument, but you never really know, we're dealing with wood here.

I use the LMI syle double rod with the rectangular top bar, and I install the rod into a round bottom slot, I use a file to round the bottom of the square ends, and I glue a thin spline over the rod to take up the spacein the middle of the rod..

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Old growth, shmold growth!

I got a few of the Allied Luthiers ones that are stainless steel, and have finer threads (I think) for finer adjustment, after a design from esteemed luthier Mark Blanchard. Before that I tried one from Martin guitars, which was reasonably priced and of excellent quality. No problems so far. I think a beginning builder has many other skills to perfect before worrying too much about truss rod design. The KISS principle comes to mind here.

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

Thanks for the responses. The KISS principle is exactly what I am after. I'm new here and new to Luthery although I have many years experience building furniture, working in the architectural millworking trade and a small but complete shop. There is a lot of good information to be mined on this forum. I have been lurking here for a good while just reading as well as reading everything I can on the topic of steel string guitar construction. I'm to the point that I need to start making sawdust.

Many questions to follow I'm sure. I just hope I don't too glaringly show my ignorance although why ask a question if you think you know the answer!

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Christopher Morley

I make my own single action truss rods. I like them because they are lighter. I install them in a semi-curved slot in the neck. The slot is flat in the upper part of the neck. From the 5th fret to the nut, the slot curves up about 1/16". Lately, I have been using Fender style bullet truss rod nuts which don't require a cover.

The way I address the single action versus double action issue is I tighten the truss rod before I do the final leveling. This gives me some minor double action adjustment room in case I need it further down the line.

All of the double action rods I have seen from Allied, LMI and Stew Mac are 3/16" rods which makes cutting a #10 thread easy. They use heat shrink tubing, to prevent rattling, which makes the rod a larger diameter. I have heard of a weld failing 1 time and that was at the nut on the rod. On a stress test on the ones I have made, the rod has broken before the weld, and if one were to ever get to that point, something else is wrong. Once you have the neck on the guitar your total range of use should be less than a full turn. (Actually the Blanchard ones from Allied use a different pitch thread on each end and require more turns to achieve the same action). The slot should be well below the center line of the neck.

Tim

Single action rods can fail also, and relying on curved slots and pre tightening is not fair to your customers. I have been using the Martin 2 way rods and love how they work. I figure a company like Martin can demand a good part and has certainly tested them out. I have some one way rods I was given from Timeless instruments and I would not chance putting one in a neck they look rough. I think he makes them himself.

Fred

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Fred Tellier
http://www.fetellierguitars.com
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Fred, that is a little harsh.

Sorry just my opinion which I think is still allowed. The players I know want the necks adjusted to suit their playing style and want carbon rods so they can change tunings without a lot of fooling around thus the need to adjust either way.


Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

I have used many different rods but settled on the Martin 2 way . I have had a non martin 2 way fail and switched to the Martin design. I also make and use Tee bars for true pre war applications. I agree 2 ways are overkill and never had a issue with the Martin 1 way .
As a toolmaker I think the weak link is that the steel properties change if they overheat the metal on the barrel nut. This will make that area brittle and that is what happened to the rod failure . On the older 1 way they didn't need to weld anything so that wasn't a problem.
Many older 1 way rods were long bolts . Wayne Henderson uses a similar set up in his guitars . Simple and reliable. I don't see the advantage to a curved slot , the action on some oneways is the compression of the neck . In the older Martin is was a back flex of the rod that made the neck reverse the effect of string tension . I will also say that I can't speak of the design collins is using.

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John Hall
blues creek guitars
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You Don't know what you don't know until you know it

Just to clarify things a bit......

The rod Allied Lutherie is selling is a double acting rod. It uses two different thread pitches to achieve less rod movement per turn of the adjuster nut. This makes the rod much easier to turn and makes fine adjustment easier. Other than that difference, it looks and fits in the neck the same as the rod LMI sells.

Also, the rod is not entirely stainless steel. Only the round rod is stainless, but that helps considerably to prevent the rod from "sticking" over time.

If anyone is interested in a "premium" version of the Allied rod, all stainless and brass with a slightly different adjuster mechanism, I am now making and selling them directly to luthiers. Contact me at mark@blanchardguitars.com for details.

Thanks,
Mark

Single action rods work fine, as already mentioned they need to be pre-tensioned before levelling the fretboard. The main advantage I see is weight (less of it). I installed quite a few of those and never had an issue.
The nut weld breaking or thread being damaged has nothing to do with single or double rods, but either with a cold weld or lesser quality metals. A brass nut is a good idea: it can easily be replaced, re-threading a rod is sometimes an impossible proposition.
The lightest double action rod I know is the Allied one, it is also the one that requires the least wood removed and is the one I use.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/