This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Ric, A conceptual tool that helps us visualize this problem is the "free body = diagram". Draw a hammer and shank, then draw an arrow for each force = acting on the hammer: gravity, jack, rep. lever, center pin, string. = period. Between let-off and impact, the jack, rep lever, and string are = not in contact with the knuckle. The list of forces acting on the = hammer/shank assembly consists of gravity and center pin. period. Both = are acting to decelerate the hammer. keystroke before let-off, and rebound after impact, are more complicated = because there are more forces involved, and they are not all acting in = the same direction, but the method would be the same. hope this helps, Mike Spalding RPT ----- Original Message -----=20 From: Richard Brekne=20 To: Kevin E. Ramsey ; Pianotech=20 Sent: Sunday, April 27, 2003 5:25 AM Subject: Re: hammer velocity =20 "Kevin E. Ramsey" wrote:=20 Richard BrekneI believe there is a letoff position (just under 1mm) = that is so close that the hammer does not have a chance to start = de-acceleration. I havent gotten into all this side of things very much = yet, so I am not sure of myself here, but isnt there some sort of "left = over" force that keeps an object in acceleration for some small period = of time even tho the origional applied force is removed ? Like a bullet = coming out of a rifle ?? Doesnt that meet its maximum acceleration some = few milliseconds after the explosion of the shell ? RicB No, = Richard, no "left over" force is there to continue accelerating an = object after it's direct influence is removed. If you really want to = know what happens inside a rifle, feel free to write me privately. No, = the bullet doesn't continue accelerating after leaving the barrel. The = only thing that I think could possibly continue accelerating a hammer = after the jack has tripped would perhaps be the flex of the shank = becoming straight again, but at 1 mm, I'm not sure that it could be = measured without high-speed cameras to capture the action. In = reality, the pianist has the skill to adapt to the instrument, and still = make music. All we can do is to provide them with the best regulated = and voiced instrument we can, and they can take it from there, if they = are truely "musicians".Kevin. Well like I say guys... I havent brushed up my inertia physics in a = long time :) Another fellow (who knows I like Star Trek series) wrote = privatly to me as asked me if I'd ever seen the episode where the = Enterprise does a saucer seperation... and he aske me "now is the saucer = accelerating away from the ship, or is the ship just slowing down = faster"... I kinda got the point :)=20 Still, there does seem to be some pent up force in the entire system = that is throwing the hammer upwards. Key and shank flex are two that get = mentioned a bit in this connection. Seems to me that all this is the = direct result of the amount of force put on the keyfront. Just where and = how this pent up energy gets released I am unsure of. Within the space = of 1mm of key travel perhaps ?=20 btw... the rifle thing... I dont think I mentioned anything about = after leaving the barrel... did I ? I think I said quite clearly after = the initial explosion.=20 Cheers=20 --=20 Richard Brekne=20 RPT, N.P.T.F.=20 UiB, Bergen, Norway=20 mailto:rbrekne@broadpark.no=20 http://home.broadpark.no/~rbrekne/ricmain.html=20 =20 ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/b0/b5/0f/ea/attachment.htm ---------------------- multipart/alternative attachment--
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