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Best Quality DA Truss Rod?
- Thread starter Gilmourisgod
- Start date
First two letters is action (can it correct forward bow - SA - single action, or forward and back bow - DA - dual action) - second two letters are number of rod(s) (single - SR or dual DR).
So - SASR is single action single rod, and so on.
So - SASR is single action single rod, and so on.
There are four main types of truss rods available these days. There are single-rod and dual-rod designs, and either are available in single-acting or double acting. The single-rod single-acting and dual-rod double-acting are the most common, but the others do exist.
- Single-acting single-rod (SASR) is the classic "compression" rod used in almost all Fenders, Gibsons, and most guitars and basses up in to the 1980's. One rod in a curved channel, with an anchor on one end and a nut and washer on the other.
- Double-acting single-rod (DASR) truss rods are less common. I'm one of the few builders making and using them today. My DASR rods are used by about ten boutique builders around the LA area. They still have a single rod in a curved channel, but the adjustment end has a head assembly that can apply load in either direction.
- Single-acting double-rod (SADR) rods are also not as common. Rickenbackers are the classic example. Their truss rods are two flat strips right on top of each other. The nut at the end engages half threads on one strip and pushes a shoulder on the other. It pushes, but doesn't pull. However, they are symmetrical and removable. You can actually pull them out and flip them over if you need to correct a backbow. And of course, there are two of them in a Rick neck. I've also seen a few DRSA design rods on some old Japanese instruments from the '70's.
- Double-acting double-rod (DADR) truss rods are the most common rods used today. Basically everyone except for Fender, Gibson, Rickenbacker, and my handful of clients. Most boutique builders and even most cheapo imports use them these days. The reason is simple: they are the easiest and least labor to install. Cut a rectangular slot and drop it in. The drawbacks are that they are heavy and most of the common ones are limited in the bending power that they can apply.
Warwick uses DASR truss rods. I've used a couple of them. My only consern with them is 4mm rod which I think is a bit on the thin side.
I didn't realize that. Yeah, a 4mm rod is kind of thin, but it should be strong enough if they've done their engineering. A big advantage of an SR truss rod is that you can adjust the "droop" of the rod in the installation to provide more mechanical ratio and power. More force bending the neck, with less tension on the rod and load on the threads.
That's the big downside to the common DADR truss rods: Their design geometry limits their mechanical ratio. For the same force bending the neck, the metal threads and rods are under much higher stress.
If someone wants to buy a titanium truss rod produced by Hosco, DON'T DO IT! They are extremely soft, they do not have the necessary strength to lift a neck reinforced with carbon bars.
Ouch! Did that happen in or out of the bass? Been using the Bitteroot Guitars ones past couple builds, so far so good, but it's always possible to get a dud. They look just like all the other blue plastic wrapped ones, so it's hard tell the quality just by looking at them. Other than testing the full range of motion in a vise, I'm not sure how you'd confirm you got a "good one". Quality of the welds maybe? The LMI ones were excellent, but they are going out of business. @Bruce Johnson made some mention of considering making custom rods, but I don't know if he plans on producing more standardised lengths. Considering the consequences of a failed rod, I'd like to use the best available.
Can you take a decent picture of the fractured ends? It's an incredible long shot but I might be able to glean something about the failure mode.
Can you explain more?
Full titanium rod? Or hybrid steel/titanium? What length of rod?
What do you mean by "necessary strength to lift a neck reinforced with carbon bars"? Specifically what do you mean by 'lift'?
Thanks!
My assessment of the broken titanium truss rods:
I don't see any problems with the quality of construction of those two titanium truss rods. Unless the metallurgy of the titanium in the rod stock was seriously defective. Which I doubt. They sheared off at the threaded portion of the rod, and that's going to be the weakest spot. They didn't break at the welds, or the threads didn't strip in the blocks, or anything like that.
The only conclusion is that these truss rods were tightened beyond their capability. By their design and geometry, they can only exert a certain amount of load before they will snap at the weakest point. Which is twisting off of the threaded part of the rod.
These rods were put into a neck which was built very stiff and, I presume, had warped. The rods did what they could but couldn't handle the load and snapped. That's not the truss rod's fault if you exceed their design limits.
I want to remind everyone that truss rods are not designed or intended to straighten badly warped necks. And if the neck is built extra stiff, with carbon fiber bars or other reinforcements, it takes more load to bend the neck.
A warped neck is the result of poor construction method. Don't blame the poor truss rod.
I don't see any problems with the quality of construction of those two titanium truss rods. Unless the metallurgy of the titanium in the rod stock was seriously defective. Which I doubt. They sheared off at the threaded portion of the rod, and that's going to be the weakest spot. They didn't break at the welds, or the threads didn't strip in the blocks, or anything like that.
The only conclusion is that these truss rods were tightened beyond their capability. By their design and geometry, they can only exert a certain amount of load before they will snap at the weakest point. Which is twisting off of the threaded part of the rod.
These rods were put into a neck which was built very stiff and, I presume, had warped. The rods did what they could but couldn't handle the load and snapped. That's not the truss rod's fault if you exceed their design limits.
I want to remind everyone that truss rods are not designed or intended to straighten badly warped necks. And if the neck is built extra stiff, with carbon fiber bars or other reinforcements, it takes more load to bend the neck.
A warped neck is the result of poor construction method. Don't blame the poor truss rod.
I'm not planning on getting into manufacturing and selling DADR style truss rods. On that other thread, I'm showing everyone how to make their own.
I agree with Bruce on this. Checked Hosco’s website and they specify max torque the rod can withstand. Likely that was exceeded trying to bend the neck.
@Bruce Johnson
Sorry to miss-quote, I’ll have to re-read your post! Maybe wishful thinking on my part, I was hoping you were actually going to produce and sell rods. Seems like you have your hands full already! Do you have a favorite among the mass produced rods? I thought you had mentioned Bitteroot as being decent quality construction.
Sorry to miss-quote, I’ll have to re-read your post! Maybe wishful thinking on my part, I was hoping you were actually going to produce and sell rods. Seems like you have your hands full already! Do you have a favorite among the mass produced rods? I thought you had mentioned Bitteroot as being decent quality construction.
Well, I make my own truss rods for all the necks I build, so I rarely use the commercially available ones. Only once in a while in an unusual repair, where I can't use one of my own. And I don't do many repair jobs.
Most of my experience with commercial DADR rods is from watching over the shoulders of a few other Luthiers who've worked here in my shop. Jeremy, Keith, Mike Lipe, etc.
My overall assessment:
- Any of the commercial DADR truss rods will do the basic job of being a truss rod, adjusting the relief of a well made neck. As long as you don't overload them trying to straighten a warped neck. They all have their limits in strength and power.
- The strongest, most powerful DADR truss rods are the Stew-Mac Hot Rod, Bitterroot's top end brass block model, and others of that design. Two round rods spaced farther apart. That gives them better geometry.
- The compact models, with a flat bar tight against a round rod, like Bitterroot's low-priced Blue Wrap model, are not as strong or powerful as a Hot Rod design. But they are strong enough to work well in a not-warped neck.
- Bad welding between the blocks and the stationary rod. Short bead, poor penetration, overheating, etc.
- Bad welding of the nut onto the rotating rod. Particularly too hot, too deep.
- Overcut threads in the blocks. Too much slop movement between the rod and the blocks.
Hi all, new user here! I read all the thread, and it was very interesting. As some years passed from 2021 when most of the posts were made, I'd like to ask what's the best dual action that is currently available, for a ultra-thin neck. I'm building a 10mm carbon neck and the slot / truss rod channel depth could be 7 / 8mm / 8.5mm at most. There's "plenty of space" at the end/heel of the neck (15mm at the heel), so I'm considering DASR, but a straight channel would be much easier to work with.
I've seen the flexstrong ultralight that is 0.28 inches = 7.1mm, but I think the neck is probably too stiff for that to work. I'm thinking about the boston hybrid titanium and steel, in their website they say it's 8.5mm but I've met some people saying they are really 8mm, and not 8.5mm, and they seem much stronger.
Any help appreciated, thanks!
I've seen the flexstrong ultralight that is 0.28 inches = 7.1mm, but I think the neck is probably too stiff for that to work. I'm thinking about the boston hybrid titanium and steel, in their website they say it's 8.5mm but I've met some people saying they are really 8mm, and not 8.5mm, and they seem much stronger.
Any help appreciated, thanks!
Hello rbmusica;
Have you seen the thread I've been working on about making your own truss rods? There's a lot of engineering info in it about the design of truss rods, particularly about how the strength and power of a truss rod are related to the geometry and dimensions of the design.
https://www.talkbass.com/threads/building-your-own-custom-truss-rods.1640596/
With DADR style truss rods, the mechanical power and breaking strength of the rod is directly proportional the vertical height of the assembly, specifically center-to-center distance of the two rods. The weak point is generally the shearing off of the rod at the outboard threads. Assuming that the quality of welding is good.
So, I doubt that you'll see much difference in mechanical power or breaking strength between different brands that are the same vertical height/depth. It's mostly about the geometry. The choice of metals doesn't make that much difference.
For a super thin carbon fiber neck, I'd recommend a custom DASR rod. That can be made to have more power and strength within that limited space. And it will probably be lighter weight.
If you think you want to go that route, post over on the other thread, and I'll talk you through it.
Thanks Bruce, didn't see that thread, but I will read it and then post there, as building my own truss rods is one of the possible solutions. I wrote you an email with my current build status and some extra request, hope you received it.
Hi - I’m surprised there’s no mention of anti-seize lubricants in this thread.
The old truss rod designs used brass nuts on steel rods because brass is naturally slippery on other metals.
All of these dual action rods have stainless on stainless or titanium on titanium and those metal combos like to seize up under load.
I would expect that if luthiers applied anti seize compound to the threads before installing, we’d see fewer failures.
The old truss rod designs used brass nuts on steel rods because brass is naturally slippery on other metals.
All of these dual action rods have stainless on stainless or titanium on titanium and those metal combos like to seize up under load.
I would expect that if luthiers applied anti seize compound to the threads before installing, we’d see fewer failures.
Hello Maple;
I agree with you about using anti-seize compound in steel/stainless/titanium threads to prevent them from galling and seizing up. Good general metalworking practice. That's why I use brass on stainless for all the truss rods I make.
All of the decent quality commercial DADR truss rods I've seen have a dab of anti-seize compound in their threads. Or some kind of lubricant. I assume that they put it on while assembling the parts, before welding them. And then wipe off the excess after welding. So it's not real obvious, but it's in there. I haven't heard of many cases where DADR truss rods have failed from seizing up. They almost always fail from simply being over torqued. Usually the rod shears off right behind the adjusting head. Sometimes one of the welds breaks first, if they were done poorly.
I have seen some SASR Fender-style truss rods seize up and snap. But they are usually mild steel rods and nuts that rusted together.
