Sarah Fox wrote: > Hi Ric, > > You wrote: > > > The leads output more force then it > > takes to accelerate them in all cases because they are (as seen by the > finger) > > on a second class lever > > Ah, but with very forceful playing, the keystick accelerates very quickly, > and the downward force exerted by gravitational acceleration on the key > leads pales by comparison to the upwards force of the keystick/leading > against the finger (in direct opposition to the downward force that is > accelerating it). The greater the inertia, the greater this force. Case in > point: place a 1 kg mass on each side of the balance rail. Adjust BW to > something very reasonable. Now pound the key and try to produce your > loudest fff. If you're a really strong pianist with really heavy arms and > beefy fingers, you might be able to produce an mp. Why the difficulty? > It's because the "oppositional force" of the key inertia is far greater than > the small amount of assistance the key leading might give you (with regard > to touch weighting). AhHaahah... :)... Sarah... granted that gravitational acceleration on the key is nothing compared to the resistance against the finger too accelerating the key faster then gravity itself would do... but once done, that inertia doesnt simply dissapear into blue heaven. Nor does it simply get burried in the key bed. It applies its force against whatever is resisting... and that includes the stuff sittting on the capstan. While your 1 kg is perhaps illustrative, I suspect that the mass levels we are dealing with combined with accelleration levels possible alter the picture you are trying to draw here. Compounded by the fact that in your example the inertia levels in the key are many times that of the "top action" which is the reverse of what we are dealing with. In anycase... you've gone and given me one of my headaches... hehe.. But I'm willing to be convinced I'm wrong here. Tell you what... this is measureable actually. Take an action model set up so it can be run both ways. Contrive some way of measureing the output force... how high the hammer will throw a 50 gram weight for example... or get really fancy measurement equipment... then exert a 5 kg force downwards and measure the difference. If you are correct, then the set up with the whippen assist spring will throw that 50 gram weight higher. But this is the opposite of my present understanding. At this point tho... seems like its time for the pudding to be proved me thinks. I'll grant you have quite the edge on me when it comes to schooled in physics (at this poin anyways....grin..) so until we get some numbers out there.. both measurementwize and theoreticalwize... I'll have to defer further comment.. beyond thanking you for yet another one of these head scratchers that I am now simply forced to start digging for an answer too... just to make sure ... grin. Cheers RicB > > > How do key leads and wip springs change in downward force at different > levels of play? They don't. Gravitational force on the keyleads is > constant. Spring force is also constant (for a given position in the > stroke). The only difference is that springs can move very rapidly, owing > to their very low inertia, and lead weights can't. So with rapid key > acceleration, the leads fight back, while the springs don't. Yes.. but beyond the force exerted by the springs they do nothing, where as the inertia accumulated by the keyleads is used as leverage until the key hits bottom. > > IMO, the only function of keystick inertia is to make the piano feel > "familiar" to pianists who are trained on pianos with lots of keystick > inertia. However, I doubt it results in a better instrument, and I would > expect that the instrument will ultimately evolve to a lower keystick > inertia and a heavier hammer. > Well, you line up with David here... and nothing would please me more then to see this particular subject defined and cleared up once and for all. Seems to me tho that the argument has raged so long that if the answer was as simple as you seem to be saying.... the controversy would have been dispelled years ago... > > As you suggest, it would be interesting to tease out the relative > contributions of these different components! Interesting... !!??? grin... at this point it would seem imperative.. hehe > > > Peace, > Sarah > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html http://www.hf.uib.no/grieg/personer/cv_RB.html
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