Solved: Help with LMI double action truss rod install (wood plug for end) ?

rwkeating

rwkeating

Oct 1, 2014
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#1
Edit: I solved this problem. See post #17 for more information

On my first build I used and LMI double action truss rod (Truss Rod, double action welded nut) After dropping the rod into the channel, I made a "plug" for the adjustment end (in my case that was at the head stock end of the neck.) Everything is okay except the rod is extremely hard to adjust.

In the bottom right of this picture you can see the plug and where I was about to install it.

full?lightbox=1&last_edit_date=1456844370.jpg


On my current build, I am doing the same thing and as soon as I put the plug in, the truss rod becomes hard to turn and that is even before the fingerboard is installed!

What am I doing wrong? Thanks in advance.
 
Last edited:
#5
What I have found in the AllParts rods I use is that the adjustment "nut" is a slightly wider diameter than the rest of the rod. I use a 1/4" slot for the main rod, and widen the area of the adjustment nut to 5/16" to provide enough clearance.

How snugly does the rod fit in the slot in general, and does the nut have enough clearance?
 
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#9
rwkeating said:
HaMMerHed. Do you know if this LMI rod is designed to be removable? They don't say anything about that on the web page and I'd think it would be a good additional selling point if it was removable.
Click to expand...

I've used the LMI rod before and it fits snug in the channel without a plug. If you don't put the plug on the end just release any tension (rod and strings) and use a pair of needle-nose pliers to pull it out. That's what I've done before when I had one break where it was welded together.
 
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#10
rwkeating said:
Michael, the rod fits in the channel very securely. There is no nut on this rod. It is 2 rods connected to each other that work against each other.
Click to expand...
The rods I use are double action rods as well. The "nut" I am referring to is the round adjustment "screw" assembly that is welded to the rod.
 
#12
rwkeating said:
Got it. The "nut" has plenty of clearance.
Click to expand...
Based on your initial post the rod turns fine prior to installing the plug, post plug installation the rod becomes difficult to turn. My first guess is that the plug is pressing down on the nut in some way and causing the issue. What I would do is install the plug half way verifying that the wood is nowhere near the rod and test. If the rod turns fine slowly tap the plug into place in very small increments and test each iteration to see what effects, if any, it is having on the issue at hand.
 
#13
Just to be clear, here is how the plug is installed. The red lines are the only points touching the rod, so you may be correct. On the other hand, the plug is flat and the "nut" is round. I am surprised that could cause so much more tension especially since the tension increases the more the rod is turned. I would think it would be consistent.

Since the plug is already installed, I may do some experimenting prior to chiseling the plug out. Hmmmm.


PlugDiag.jpg
 
#14
rwkeating said:
Just to be clear, here is how the plug is installed. The red lines are the only points touching the rod, so you may be correct. On the other hand, the plug is flat and the "nut" is round. I am surprised that could cause so much more tension especially since the tension increases the more the rod is turned. I would think it would be consistent.

Since the plug is already installed, I may do some experimenting prior to chiseling the plug out. Hmmmm.


View attachment 949136
Click to expand...

Did you test the rod in the channel prior to installing the plug? I have made it a habit to test all my rods prior to putting them in a channel, testing during a "dry run" test fit, and once again after I install the rod over the bead of silicone caulk I use to eliminate rattling. It only took one incident requiring me to pull off a fingerboard to institute a rigid and paranoid regimen of tests. ;)
 
#15
Yes, I tested the rod alone (without the plug) and it adjusted fine. I put the plug in place and tested it and there was no change. I glued the plug in place (not clamped) and adjusted the rod with no problem (the glue was still wet.). It was only the next day that the rod started to become difficult to turn.
 
#17
Solved! Make sure the adjustment end of the rod has room to move up and down.

I figured it out. The part where the wrench goes (call it the nut) needs to be able move up and down (actually pivot) as the truss rod is adjusted. By having a plug in there this movement couldn't happen.

how the adjustment end of the rod moves

how the adjustment end of the rod moves


I chiseled out that part of the plug. I left part in because I talked to a guy at LMI and he said they recommend the plug.

Fix for too tight rod

Fix for too tight rod


Here I am trying to show the movement of the nut between loose and tightening the rod. The wood is for reference. You can see how the angle changes as you tighten the rod. The opposite happens in the other direction

Truss rod and at adjustment point

Truss rod and at adjustment point


Now I have to go back on fix this (somehow) on my 1st build.
 
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