Question About Truss Rod 'Styles,Types'

[LHawes]

I've ordered a StewMac 'U-Channel' truss rod as my LMI's have run out and was wondering about the intended adjustment location of this rod and whether it makes any difference or not.

The product description says it's "Designed as a sound hole accessible truss rod" but I would like to use it as a peghead adjustable rod. Is there any inherent problems using a truss rod designed as a 'sound hole accessible' rod as a peg head adjustable rod? If so, what might those problems be?

Thank You

[Rudy4]

A couple of things to consider.

Are you OK with a one way adjustable rod?

There aren't a lot of length choices for the SM U channel rod, so that might be a consideration.

The U channel adjustment nut is longish, so make sure you have enough clearance so it doesn't bind. It should be fine to adjust from either end.

My last couple rods I ordered from Bitterroot and I was happy with them. I ordered the 2 way rods and they were identical to the ones I had been ordering from LMI but they were about a third of the price that I was paying from LMI.

[Fathand]

If Martin would ship to Canada, I'd be using these, only $8, low profile and 2 way adjustable, remove a minimal amount of wood from your neck.

https://www.martinguitar.com/13BAR0001.html

Since they won't, I buy similar styled ones from Amazon, etc. I have used adjusting from both ends. I also shorten them if needed, requires a welder.

One issue adjusting at headstock is the pocket reduces heastock strength. I find the soundhole set up easier to manage so only use the headstock style if replicating a guitar that uses it.

[LHawes]

Originally Posted by Rudy4

A couple of things to consider.

Are you OK with a one way adjustable rod?

There aren't a lot of length choices for the SM U channel rod, so that might be a consideration.

The U channel adjustment nut is longish, so make sure you have enough clearance so it doesn't bind. It should be fine to adjust from either end.

My last couple rods I ordered from Bitterroot and I was happy with them. I ordered the 2 way rods and they were identical to the ones I had been ordering from LMI but they were about a third of the price that I was paying from LMI.

Thank You. Don't need a 2 way truss rod as back bow is never an issue, so OK with one way adjustable rod. Thanks for the idea re: bitterroot, not familiar with them. Is there a source you're familiar with for a one way rod?

The thing I'm not so thrilled about with the SM u-channel truss rod is the width of 12 mm, whereas the 1/4" width of the LMI rod is so easy with my 1/4" spiral bit on the router table. The SM rod should arrive shortly and I'll evaluate.

thank You Again.

[LHawes]

Originally Posted by Fathand

If Martin would ship to Canada, I'd be using these, only $8, low profile and 2 way adjustable, remove a minimal amount of wood from your neck.

https://www.martinguitar.com/13BAR0001.html

Since they won't, I buy similar styled ones from Amazon, etc. I have used adjusting from both ends. I also shorten them if needed, requires a welder.

One issue adjusting at headstock is the pocket reduces heastock strength. I find the soundhole set up easier to manage so only use the headstock style if replicating a guitar that uses it.

Wow $8 dollars? ordered a couple THANKS

[Rudy4]

Originally Posted by LHawes

Thank You. Don't need a 2 way truss rod as back bow is never an issue, so OK with one way adjustable rod. Thanks for the idea re: bitterroot, not familiar with them. Is there a source you're familiar with for a one way rod?

The thing I'm not so thrilled about with the SM u-channel truss rod is the width of 12 mm, whereas the 1/4" width of the LMI rod is so easy with my 1/4" spiral bit on the router table. The SM rod should arrive shortly and I'll evaluate.

thank You Again.

Bitterroot has been around for quite a while and is used by many builders.

I switched to LMI, and now Bitterroot, so I could use a uniform depth 1/4" channel and not have to use a specialty router bit.

I quit using single truss rods long ago for a few different reasons. First, actual "truss rods" by definition require a curved channel, as the rod creates upward pressure against the apex of the bend by bearing against the "truss" portion of the curved insert. The whole process of installing them just makes it a lot more complicated than it really needs to be. The two way rod slips into a uniform height channel and can be removed easily at any time should the rod no longer function. They also don't require a "pocket" at the head stock for a larger adjusting wrench. I digress on all that, though.

If you like single rods they are quite easy to make, so that might appeal to you. The ease of making a single rod might be why they aren't as commonly seen for sale by suppliers.

[John Arnold]

I have always favored the U channel, but I adjust through the soundhole. IMHO, the large rout is too much of a reduction in strength if it extends through the peghead.
I have settled on making my own U channels from a very hard wood, rather than aluminum. That resolves the issue that can arise with the simple rod, where the anchor compresses relatively soft mahogany. It also adds some stiffness, though not as much as the aluminum.

[LHawes]

Received truss rods from both Bitterroot and Martin (StewMac forgot to ship their version) and both seem very serviceable. The Martin truss rod is identical to the LMI version I was previously using and the Bitterroot a very similar design. For $8 the Martin will be my go to TR.

[Howard Klepper]

Originally Posted by Rudy4

I quit using single truss rods long ago for a few different reasons. First, actual "truss rods" by definition require a curved channel, as the rod creates upward pressure against the apex of the bend by bearing against the "truss" portion of the curved insert. The whole process of installing them just makes it a lot more complicated than it really needs to be.

Actually, the opposite is the case re trusses. A truss is composed only of "two force" members. That means each component is either only in tension or only in compression, in a straight line parallel to the component's longitudinal axis. The sideways pressure that a curved rod puts on the middle of the neck is what makes it not entirely a truss.

A single rod will actually work pretty well without any curve, so long as it is set below the neck's neutral axis. Then it is only in tension, and works like a cable truss to counter the tension of the strings on the other side of the neutral axis (think, for example, of the guy cables on a radio tower). The curvature adds a second way of action to force a curve into the neck, but in that way it is not acting as a truss. And no double rod acts as a truss.

But so what if the name is not in keeping with the definition, as long as it works? That's not much of a reason for switching neck rods.

I've always used single rods, and always made them myself. What I like about them is they do act as a truss insofar as they oppose the tension of the strings as a cable truss, which seems to me to be addressing the issue more directly and less likely to cause odd "S" curves near the body end of the neck. They also are less likely to rattle than double rods, and need less wood removed. If you have never used a die to thread a rod, ask around among your friends, or find a YouTube video. It's easy. It's also easy to make a simple jig for guiding your router to make a curved channel, to find a roundnose 3/16" bit, and to shape a fillet to glue in above the rod.