Truss Rod expansion/contraction influence ?

[MarkinLA]

Hi.
We had a nice chat in my post :" So sick of tuning up" 7/24, 3:02...
Please see my final entry on that..
Here, I am bringing up a discussion of truss rod metals. Do we know if this too plays a role in going in/out of tune ?
We can agree wood (other than maybe petrified or ebony) expands and contracts further and likely faster than metal. My concern is that because metal likely stays colder than wood at any given room temp I wonder if this is something to ignore as being an immeasurable influence, or if it is something to give serious consideration (If it hasn't already). IE. Fingerboards of either ebony or rosewood and their sitting right above the truss rod in the neck..M

[charles Tauber]

Originally Posted by MarkinLA

My concern is that because metal likely stays colder than wood at any given room temp...

It doesn't. Doing so would violate the laws of thermodynamics.

It might take longer or shorter for the metal to reach the same temperature as the wood, but, given sufficient time, they will both be the same temperature.

We can agree wood (other than maybe petrified or ebony) expands and contracts further and likely faster than metal.

That isn't agreed upon.

First, wood is an anisotropic material, meaning it has different properties in different directions. One of the properties that differs is the amount that it expands and contracts. Wood expands and contracts a negligible amount along its length: more across its width and thickness.

This table give the coefficient of thermal expansion for a variety of materials, including some metals and "wood". Wood has a smaller coefficient of thermal expansion than most metals, indicating that it will expand and contract less when subject to the same change in temperature. Metals will also likely react to temperature variations faster than wood.

https://www.msesupplies.com/pages/li...more%20rows%20

[MarkinLA]

Thanks. Interesting report ...M

[charles Tauber]

A few decades ago, Kramer made various aluminum guitar necks. The thermal coefficient of expansion of the aluminum was sufficiently high that, so rumour had it, as the necks cooled during a break between sets, the necks would back-bow and have to warmed-up again prior to resuming the set. Others reported constant tuning issues until the instrument reached a stable temperature.

https://www.talkbass.com/threads/why...tch-on.794224/

I've not heard any reports of that happening with necks made of wood.

[John Arnold]

The differential expansion of wood is due to its absorption and release of moisture. I am not sure it behaves the same thermally, but its thermal expansion is so slight that it normally can be ignored.

[Frank Ford]

Originally Posted by John Arnold

The differential expansion of wood is due to its absorption and release of moisture. I am not sure it behaves the same thermally, but its thermal expansion is so slight that it normally can be ignored.

Additionally, wood expands and shrinks across the grain, not with it. It does NOT get longer and shorter. . .

[Taylor Ham]

My guess is that within normal (comfortable) temperature ranges, the thermal expansion of the truss rod wouldnt contribute hugely to neck relief or tuning.

[mirwa]

Originally Posted by Taylor Ham

My guess is that within normal (comfortable) temperature ranges, the thermal expansion of the truss rod wouldnt contribute hugely to neck relief or tuning.

I think you will find that those of us that work with wood believe it would not be a measurable difference, therefore it makes no difference to tuning at all

Steve