I made a little translation : 1/400 sec : speed of the hammer is 40 miles/hour - the speed of the hammer is said to go as up as 50 miles/hour at the most. What is the acceleration, say for a 45 mm travel ? ------------------------------------ Isaac OLEG accordeur - reparation - concert oleg-i@noos.fr 19 rue Jules Ferry 94400 VITRY sur SEINE tel: 033 01 47 18 06 98 fax: 33 01 47 18 06 90 mobile: 033 06 60 42 58 77 ------------------------------------ > > Hello, Slight correction about that famous video of a piano > action at > work. > > At forceful play, the key bottom (on that movie) before the hammer > have even moved - I let you imagine the bending. > > 1/400 sec is a range of time where the hammer travels its 45 mm , or > the key move 10 mm. > That means in that short fraction of time we have an > acceleration from > 0 to 65 km/h > > No doubt force at work are certainly enough to generate a lot of > bending. > More details as soon as I'll have them > > > Best Regards > > > ------------------------------------ > Isaac OLEG > accordeur - reparateur - concert > oleg-i@noos.fr > 19 rue Jules Ferry > 94400 VITRY sur SEINE > tel: 033 01 47 18 06 98 > fax: 33 01 47 18 06 90 > mobile: 033 06 60 42 58 77 > ------------------------------------ > > > > -----Message d'origine----- > > De : pianotech-bounces@ptg.org > > [mailto:pianotech-bounces@ptg.org]De la > > part de John Hartman > > Envoye : dimanche 28 decembre 2003 15:21 > > A : Mark Davidson; Pianotech > > Objet : Re: Moment of Inertia of grand action parts. > > > > > > Mark Davidson wrote: > > > > > > > I made an attempt to relate hammer, wippen and key > > inertia to total > > > reflected inertia here: > > > > > > https://www.moypiano.com/ptg/pianotech.php/2003-August/140901.html > > > > > > > > > Mark, > > > > Thanks for sharing this with me. Just yesterday I came to > > exactly the > > same conclusion. I am doing a drawing to show the > > acceleration ratios of > > the wip and shank in relation to the key. The fact that we > > both came up > > with the same formula is encouraging but to be sure we need > > to have Don > > go over it. > > > > Have you plugged in the MOIs? It looks like the shank and hammer > > contribute about 12 times or more of the total I as felt at > > the key. If > > the formula is right it shows how unimportant changes to > > the key MOI is > > in relation to overall efficiency. Also, if there is any > benefit to > > pattern leading it is not to make the action feel even > from note to > > note. Adding lead to the key is not the big evil commonly > > thought unless > > it has some effect on repetition. > > > > I think we are going to find that the biggest problem with > > increasing > > the mass of the action parts is the losses due to bending > > and compliance. > > > > I still need to complete the kinetic model of the action > > but I can see > > ahead to the next step. Maybe you are already there. Is > > there a way to > > convert the kinetic forces developed at different levels of > > play into > > static loads. Then we can see how these loads bend the > > shank and key. It > > would be great if this could lead to a formula for finding > > the terminal > > velocity of the hammer. > > > > John Hartman RPT > > > > John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] > > Rebuilding Steinway and Mason & Hamlin > > Grand Pianos Since 1979 > > > > Piano Technicians Journal > > Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015] > > > > > > _______________________________________________ > > pianotech list info: https://www.moypiano.com/resources/#archives > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives
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