Moment of Inertia - numbers in the air !

[Isaac sur Noos]

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]
> >
> >
> > _______________________________________________
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>
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