Tuning levers

[kennys@kennyguitars.com]

> >Charles
> >I cannot remember the person who made this claim: ..." a piece of thick
> >walled tubing is stiffer than a solid rod of the same diameter and
> >material....therefore, boring a hole the length of the rod will increase
its
> >stiffness."  Is there any truth to this?  Is it true for all metals?  Can
> >anyone on the list verify this claim?
> >
> >Paul Chick
>
>
> Moment Of Inertia is used to determine relative stiffness of different
> cross sections in a given material.
>
> MOI of rod is (PI*diameter^4)/64, or 0.0491*doameter^4.
> MOI of round tubing is (PI*(OD^4-ID^4)).64, or 0.0491*(OD^4-ID^4)
>
> There is absolutely no way that drilling out a rod will increase
stiffness.
> For a given *mass* of material, tubing will be stiffer than rod, but for a
> given outside diameter, rod will be stiffer than tubing.
>
> Ron N


This is a very interesting  point.  I did some study and found that a tube
of a larger diameter say 7/8" with an 1/8" wall thickness was several times
stiffer and maybe half as masive as a 1/2" solid rod.  I did this several
months ago and don't remember all the details, but thought it might be worth
developing a titanium lever around.  I just don't have the resources to do
such a project.

Colin Kenny