> >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
This PTG archive page provided courtesy of Moy Piano Service, LLC