<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html>   John Hartman wrote: <blockquote TYPE=CITE>Richard Brekne wrote: > I would be very interested indeed in hearing how one would achieve uniform inertia > in the action while at the same time being able to vary hammer mass from bass to > treble. I suppose you had somthing in mind ? I don't' think you can get an even inertia in the action from bass to treble unless you make the hammers the same mass. Or compensate for the mass difference somewhere else. I don't think getting the action to have the same inertia in the bass and treble is the point. Getting it even from note to note and not making it excessive would be the objective.  </blockquote> That was my thinking as well. I would be interested in getting a bit more info on what he had in mind.> <blockquote TYPE=CITE>Richard Brekne wrote> > Isnt "balance"  rather <<by definition >> a static measurement ? Would you be so > kind as to expound a bit on what a "dynamic balance" is exactly ?... Dynamic balance relates to measuring and adjusting the inertia of an abject in rotation. You can statically balance a car wheel for example and it will run smooth at low speeds. You need to balance it dynamically if you want it to run smoothly at higher speeds. Inertia takes over when a body is accelerated faster than gravity (16 ft per second squared?). When we play the piano action most of time we are moving the parts in the dynamic range. John Hartman RPT</blockquote> I thought that was where you were going. And in that case I dont see how dynamic balance in this sense can be achieved in the piano action at all, at least not with the stationary mass of the key leads, hammers and for that matter all the wood in the action parts. Dynamic balance in this sense is really a mathematical construct to begin with, and is more or less the sum of an << infinite >> set of discontinous points of static equalibrium, is it not ? Even the tire example only uses the tires motion to identify a spot where static imbalance is significant enough to be << noticed >> as it were. Since the ratio of a piano action changes through the stroke I dont see how this can be achieved at all. I suppose some kind of non stationary mass scheme could be contrived.....but I dont think I want to go there at all :)  And I have to wonder if this kind of dynamic balance would be desireable even if it could be achieved. There is another perspective on dynamic balance I tend to think is more to prefer here. That would be each key showing consistancy in how its dynamic inbalance developes throughout the keystroke. This, I think, is rather nicely addressed by a system for balancing the action akin to Stanwoods when coupled with his method of leading keys. This being said, I would love to hear viable approaches for dealing with the issue, and more opinion on the above for that matter. Cheers RicB -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway <A HREF="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> <A HREF="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A>  </html>