Ah yes, the two Pedullas.....Actually, they are just about finished, finally! As you've probably read, I went through a sequence of rough times that kept me from working in my shop for about 18 months. And that all happened right as I was about to get started on the surgery on the Pedullas.
Anyway, this spring I turned the Pedullas over to Randy Robinsen, another Luthier here in the same building as me. He got going on them, with some technical guidance from me. We routed off the fingerboards in my big green pin router.
Here's what we discovered about the truss rods:
Inara's 4-string, the earlier one, had a conventional Double-Acting Double-Rod truss rod, similar to the ones that everyone sells today. However, it was installed upside down. Normally, you install these truss rods with the rotating rod (which has the nut on it) on the bottom. In this Pedulla, it was on top, which made the operation reversed. You had to turn the nut counter clockwise to bend the neck backward. The nut is brazed to the rod and can't be removed. In Inara's bass, it got snapped off.
Mike's 5-string, a newer one, had a completely custom truss rod design. It's a single rod that's left-hand thread on one end and right-hand thread on the other. It threads into anchor blocks at both ends. Turning the rod CCW spreads the blocks apart, bending the neck back. The outward end of the rod is machined into a small square. You have to use a special wrench to turn it. This is the end that frequently gets rounded off, as it was on Mike's bass.
The good news for both of these basses is that there's plenty of room in the necks for a conventional modern aftermarket DADR truss rod. Hardly any trimming or filling needed. So, that's what Randy is doing. Both Pedullas are being fitted with standard DADR truss rods, which will rotate in the conventional direction. It turned out to be a simpler repair job than we expected.
So, to answer Stefanos question, your bass probably has the custom truss rod. You are seeing a threaded rod sticking out, which was square, but is now rounded off? Or are you seeing a steel cylinder which had a hex socket in it, but is now rounded out? Either way, it can't be fixed from the outside. The fingerboard has to come off, and the whole truss rod replaced. The good news is that you can use a commonly available aftermarket truss rod. I think Randy is using ones from LMII.
Warning: There may be two large 1/4" steel dowel pins in there, used to align the fingerboard to the body. They are directly under the first and last white dots. If you hit them with a router, things will go flying. We almost hit them when cutting the fingerboard off Mike's 5-string.
