Dual truss rod install specs?

billikenn · Post by **billikenn** » Wed Dec 07, 2005 4:51 pm

When installing dual rods:

should they both be parallel to the neck centerline?

are they both supposed to be the same distance from the centerline?

how to determine how far from the centerline they should be?

Guitar is set to be 25.5" scale Neck-thru
1 11/16" nut
2 1/8" at body

Josh

rickfan60 · Post by **rickfan60** » Thu Dec 08, 2005 7:37 am

They are parallel to the edges of the neck and they should be equidistant from the center line.

david_schwab · Post by **david_schwab** » Thu Dec 08, 2005 8:55 am

The edges of the neck are not parallel.... it tapers towards the nut.

The rods should probably be parallel with each other. They might not have to be, but that's the way I always do it.

I spaced mine about 1/2" to 3/4" from each other. If you want one rod to control one half of the neck, then you want them farther apart than closer... but usually you adjust them both equally anyway.

rickfan60 · Post by **rickfan60** » Thu Dec 08, 2005 10:51 am

Yes, the fingerboard tapers but the rods are not parallel with each other. They are farther apart at the body end that at the headstock end. They are more or less parallel with the sides of the neck not each other.

rickfan60 · Post by **rickfan60** » Thu Dec 08, 2005 12:59 pm

Here is a picture of the body end of the rod channels on a 4001 without the fingerboard. It is easy to see how far apart they are normally but this further illustrates it. The rods on a 4001 are a 1/2 inch apart at the nut and a full inch at the body. I suspect guitars follow the same geometry but scaled down. If the rods were parallel, they would not be able to apply a twisting force to the neck. The ability to counter a twist is the reason to use a double adjustable rod system in the first place.

rickfan60 · Post by **rickfan60** » Thu Dec 08, 2005 7:44 pm

Here is another example. This is a 4004C with the fingerboard removed. Notice the angle of the truss channels. The packing remained attached to the underside of the fingerboard. It should be part of the neck itself.

david_schwab · Post by **david_schwab** » Fri Dec 09, 2005 9:00 am

I would guess they used a table saw to cut the slots on the 4001, and used the edge of the neck against the guide.

johnhall · Post by **johnhall** » Fri Dec 09, 2005 9:53 am

Mmm, no. Prior to CNC, these were done with a shaper, using the typical blade on an arbor that also has a ball bearing.

Also, I really don't think it would make that big of a difference if the truss rods slots were parallel. It would still adjust twist- but keeping the slots the farthest apart possible gives the best mechanical advantage.

billikenn · Post by **billikenn** » Fri Dec 09, 2005 12:59 pm

The packing strips you mentioned, were they the same width as the TR routes, or wider?

Any idea approx. how thick they were?

Thanks for the info guys!
JP

Risky to go without them?

rickfan60 · Post by **rickfan60** » Fri Dec 09, 2005 1:19 pm

The packing, as used by RIC, is meant to be a structural part of the neck and is only found on instruments that have the new style truss rods. It is the part that takes the load off of the back of the fingerboard so that errant neck adjustments won't pop the fingerboard off. The old style rods pressed against the back side of the fingerboard and could launch it if improperly adjusted. The packing is VERY precisely cut and fitted into the neck slab. The side of the packing that faces the truss rods is curved. That is, the packing is thinner towards the ends than it is in the middle. This provides the rods with a surface to push against so they can counter the pull of the strings. I have an old Rick fingerboard on my desk right now and I measure the ends of the packing at 3/32" and 5/32" in the middle. The truss channels are cut to follow a similar curve. The center of the truss channel is closer to the back of the neck than are the ends. I can provide more pics if you would like to see more detail.

billikenn · Post by **billikenn** » Fri Dec 09, 2005 3:57 pm

Thanks for the details
I dont think further photos are necessary because it doesnt sound like something I can replicate
(atleast not yet, Im building an overhead CNC router over winter and spring quarters)

Any suggestions to a feasable option. I would like to use something similar to the premanufactured Hotrods from stewmac...

Perhaps I could locate a properally sized rectangle carbonfiber tube, glue that into the trussrod channel then slide the rod in dry?

JP

billikenn · Post by **billikenn** » Fri Dec 09, 2005 5:54 pm

After some googling, I was unable to find any rectangular CF tubing. Let alone one that has inside dim ~7/32 X 7/16.

I could use something in a C-channel shape, any ideas on material?

I dont want to resort to anything other then wood glue to attach the fretboard incase I have to remove it.

rickfan60 · Post by **rickfan60** » Fri Dec 09, 2005 6:23 pm

IMHO Hotrods are the best design for truss rods especially if the neck is to be reinforced or made of very strong woods with multiple laminations. The cool thing about them is that they can move the neck forward or backwards and don't apply compressive or expansive forces on the wood like traditional rods can. Depending on your project, you probably won't need to reinforce the neck if you are using Hotrods. You don't want the neck to be TOO strong.

dale_fortune · Post by **dale_fortune** » Fri Dec 09, 2005 9:36 pm

I can speak from 1st hand experience: the truss rod slots were cut on a table shaper with a multi tip fly cutter as we called it. It was a solid carbide cutter mounted on a 5h.p. spindle shaper. The neck stock was cut to exact dimensions, then the truss rod nut cavity was routed by Mike Rodriquez, next step, it was run across the table shaper for the truss rod slots to be cut. Here are the dimensions: depth:5/32nds of an inch, width:7/32nds of an inch for each T.R. slot. The total width of the slots at the neck pick up was: 1 5/16ths inches from outside to outside edge. The total width at the truss rod nut cavity was: 21/32nds inches from outside to outside edge. These were the dimensions we used on the early to mid 70's Basses. The wood shop was a fun place to work!

billikenn · Post by **billikenn** » Sat Dec 10, 2005 12:16 am

Ill bet it was, talk about a good life experience.

So, using the Hotrods - do I need to worry about them applying pressure to the back of the fretboard?

There's no such thing as too strong unless you work in the aeronautical industry.

but I only meant the CF to transfer the truss rod load into the neck stock, I dont think any more strength is necessary. So if I can just install directly under the fretboard without worry, then thats what Ill be doing...

Josh