Key Leads and Inertia

[gordon stelter]

If one is going to apply a stiffening top plate to a
key, why not make it a BOTTOM plate, that also acts as
a weight? In this fashion the center of gravity is
kept low, with, I would think, some very positive
advantages!  And the keystick is not weakened by
drilling holes for leads.
     In fact, why not a system of staggered, extruded
bottom plates which "nest" to provide just the right
balance and stiffness?
     Thump

[link redacted at request of site owner - Jul 25, 2015]
> Delwin D. Fandrich wrote:
> 
> > Most of the energy lost between the key end and
> the hammer goes into bending
> > the key. At action saturation the front of the key
> fully bottoms before the
> > hammer starts to move. I'm not sure how much key
> leading contributes to this
> > but I shouldn't think it was all that much.
> > 
> > Del
> 
> Del,
> 
> Your article on this topic in the Journal brings a
> new perspective to 
> how the action work. It seams like we are hell bent
> on calibrating 
> static balance and action leverage with out putting
> it into proper 
> perspective. Placing a tiny piece of lead it a key
> to achieve a balance 
> of 38g instead of 39g or making sure that all of the
> knuckles are in a 
> line to achieve a particular leverage seems overly
> picky and unnecessary 
> considering the magnitude of issues left unattended.
> These static 
> particulars are only relevant if the piano is played
> very softly. Once 
> the action gets up to speed (accelerated) inertia
> and compliance become 
> far more important.
> 
> In order to improve action efficiency I have been
> installing stiffening 
> top plates on actions with longer keys. I have done
> this on several 
> Steinway model Bs with good success. This seems to
> extend the dynamic 
> range while using a relatively soft light hammer
> (lighter hammers are 
> more efficient because they have lower inertia and
> bend the shank less).
> 
> You can test the compliance of a key by measuring
> how much it bends with 
> a known weight pulling down on the front end. Using
> this method I have 
> been able to ascertain which actions need this
> treatment. The 
> accelerated actions with all the leads near the
> balance rail are 
> particularly weak. Short keys are usually stiff
> enough.
> 
> I made the plates from 5mm maple and spruce (spruce
> in the high treble 
> only). New maple key buttons are installed as well.
> Longer .062" concert 
> grand key pins are installed (Pianotek). A new key
> stop rail needs to be 
> fashioned to provide clearance for the fallboard.
> Along the same lines, 
> when I make a new keyboard for the Model D I use
> maple and spruce for 
> the top plates - not soft basswood usually seen here
> (some don't even 
> have top plates).
> 
> View the photo on my wed site here:
> 
[link redacted at request of site owner - Jul 25, 2015]
> 
> 
> 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


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