In a class given by Richard Davenport he demonstrated that over centering the hammer by 2 mm resulted in a reduced DW of 4 grams and an increased UW of 1 gram. The balance weight is reduced by 2.5g as is the friction. Let's assume this is true. Of additional interest to me is this: The change in downweight is measured from the rest position. But the downweight can be measured from any point in the stroke. If you measure the downweight from a point, say, when the hammer is halfway to the string, you will get a reading that is something less than the downweight measured from rest position. But the downweight measured from the halfway point should not vary as much between the over centered and normally centered hammers. If we hypothesize, for the moment, that measured starting from the halfway point, the downweights are equal. Then in the normally centered hammer there would be a 4 grams greater difference between the downweight measured at rest and the downweight measured halfway through the stroke. Another way of saying it is that the rate of change of resistance through the key stroke would be greater in the normally centered hammer than in the overcentered hammer. If that is true, it suggests to me that the overcentered hammer would have a "smoother" feel. The key would not feel as though it is falling away from you once you got it moving or that the resistance goes through a more sudden change. On another matter, the loss of power from an overcentered hammer I believe comes from the hammer delivering a glancing blow to the string (if it is not perpendicular on contact). Raking the hammer out should solve that problem. David Love >From: Newton Hunt <nhunt@optonline.net> >Reply-To: pianotech@ptg.org >To: pianotech@ptg.org >Subject: Re: Fw: bore distance: was Re: hammer replacement >Date: Sat, 30 Jun 2001 07:26:25 -0400 > >This discussion on hammer bores is great. Now we need some numbers so we >can >specify what we want and how any changes will effect action performance. > >This is exciting stuff. > >More, more! > > Newton _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com
This PTG archive page provided courtesy of Moy Piano Service, LLC