Andre: > A softer punching feels softer but allows for a less defined >aftertouch and partially absorbs the energy. >This becomes more clear if we think again about the sea saw with the >two children. If we remove the car tyre and replace it with a more >compact piece of rubber, the impact will be harder because it is not >as much cushioned by the more flexible car tyre. > >A firmer punching feels less soft but allows for a more defined >aftertouch and absorbs less energy. >If we again think about the sea saw, then it is undeniable that the >harder impact will also be felt on the other side of the sea saw, >which literally means a harder impact on the string, because the >firmer punching effects the outcome, as Stephen Birkett noted. I can only conclude at this point that there is a mechanism for the properties of the punching to influence the outcome. I haven't demonstrated any further yet, e.g. that there is actually any measurable difference imparted to the properties of the hammer on impact, let alone that there is any objectively observable difference in tone production. Much more research would be needed to do justice to that problem. The anecdotal evidence as reported by Andre and many others here suggests that that study would be rewarding and interesting. Paul: >I may have missed something, but isn't the hammer disconnected from >the rest of the action-the wippen and key-when the jack moves away >from the knuckle, which is to say the hammer free flies to the >string with its developed momentum. This free flight means the keys >is no longer driving the hammer. So, how can the resilience of the >keys "cushion" (front rail punching) have any thing to do with the >impact of the hammer to the string and affect tone? Certainly the hammer is disconnected from the jack at impact time with the string or else it would block. Under some circumstances there is a period (about 2.5ms) during which the front of the key is compressing the front punching while the jack is still escaping from under the knuckle. The proposed mechanism for influencing hammer impact might be via the effect of the key front deceleration on the motion of the hammer, energy stored in the hammershank, and so on, immediately prior to its release (the seesaw (teetertotter to some) analogy is a good one). For instance, a hammer that has acquired more or less "whip" may impact the string in a different manner. This subject is intimately connected to the more general old chestnut of whether different touches can create different tone on the same instrument. If the answer to that is yes it must surely be explained by nonlinear dynamic effects. Stephen -- Dr Stephen Birkett, Associate Professor Department of Systems Design Engineering University of Waterloo, Waterloo ON Canada N2L 3G1 Director, Waterloo Piano Systems Group Associate Member, Piano Technician's Guild E3 Room 3158 tel: 519-888-4567 Ext. 3792 fax: 519-746-4791 PianoTech Lab Room E3-3160 Ext. 7115 mailto: sbirkett[at]real.uwaterloo.ca http://real.uwaterloo.ca/~sbirkett
This PTG archive page provided courtesy of Moy Piano Service, LLC