Tuning levers

[Ron Nossaman]

>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