--- Richard Brekne <Richard.Brekne@grieg.uib.no> wrote: > > Jim, Keith, and Roy. > > Thanks for prodding my brain a bit. I actually saw > what it was I misunderstood a > little while after writing my last. And by doing > much the same as you both > suggest. I had thought that Jim was outlining some > requirement for the momentum > of the hammer crown to be perpendicular to the > string at impact at the same time > as a hammer with a 90 degree rake was to be > perpendicular to the string. Of > course I couldnt make this add up :) > > But I do still have a little itch on my left > temple. Jim mentioned that it > would be desirable to put the center pin on the > string plane for both grand and > uprights. That would indicate to me he's got > something else in mind then just > the gravity assist on rebound for an upright. > > I think the diagram below shows what I am confused > about here. While the tip of > the hammer would certainly have its momentum > orientented horizontally, the angle > of the hammer itself is far from perpendicular to > the string at impact. And the > longer the hammer bore the larger that angle would > be. Isnt that going to cause > several other problems ? It would have an increased > tendancy to stress the joint > of hammer and shank. The hammers center of gravity > wouldnt be perpendicular > either... or what ? > > Perhaps it is a misconception, but it has always > been my understanding that the > maximum amount of energy that the hammer can impart > to the string occurs when > the shank is paralle to the string, and the hammer > perpendicular to both. Jims > post seems to be saying something else. Or what ? > > > Cheers, and thanks > > RicB > > [Image] > > Keith Roberts wrote: > > > Try this. Take a hammer/shank/butt and with a pin, > affix it through the > > centerpin to a piece of paper. Scribe the arc made > by the end of the shank, > > Then drill a hole through the center of mass of > the hammer and scribe that > > arc. You can see that the center of mass is moving > down at an angle to the > > strings when the bore distance is set up at the > center pin distance. If you > > cut loose this missile (which is sort of what > happens when let off occurs) > > it would immediately begin to tumble...... > > Keith Roberts > > > > > Ric: > > The crown of the hammer would move in a different > arc than that of the shank. > > When the hammer shank is vertical, and the arc it > travels in is at it's apex, > > the tip of the hammer is on a downward descent. > Draw a straight line between > > between the tip of the hammer and the hammer > center pin. When that line is > > vertical, the tip of the hammer is moving straight > into the string. The > > shank would be tilted back. Thus, putting the > center pin closer to the > > string means that the tip is hitting the string on > a > > more horizontal plane. It makes sense. Maybe > it's a question of which arc > > you want to worry about. > > > > Roy Peters > > -- > Richard Brekne > RPT, N.P.T.F. > UiB, Bergen, Norway > mailto:rbrekne@broadpark.no > http://home.broadpark.no/~rbrekne/ricmain.html > > __________________________________________________ Do you Yahoo!? Yahoo! Web Hosting - establish your business online http://webhosting.yahoo.com
This PTG archive page provided courtesy of Moy Piano Service, LLC