Key Leads and Inertia

[gordon stelter]

Frankly, I think that some extrudeed, lightweight
aluminum key, basically a shell buttressed with
reinforcement along stress lines to stiffen it, would
be FAR better than the 16th Century technology we are
dealing with!  And it should be hinged on a lateral
pin ( at the bottom, on a pivotable plate ) to
eliminate all "wobble". And weights ( not poisonous
leads, either! )  could be affixed to the inside with
bolts and lock washers along an adjustable track for
exact balance.
     Thump


--- Phillip Ford <fordpiano@earthlink.net> wrote:
> 
> > At 12:11 PM 5/1/03 , you wrote:
> >>The direct quote from the second link is
> >>"The well-known Steinway "accelerated action"
> works because it adds 
> >>acceleration to the hammer motion by use of a
> rounded support under the 
> >>center key bushing. This causes the pivot point to
> move forward with 
> >>keydrop thus shortening the front side of the key
> and lengthening the 
> >>back side and thereby causing the capstan to
> accelerate for a constant 
> >>keydrop. This illustrates the importance piano
> designers place on 
> >>accelerating the keydrop, and the arm weight
> method ensures that we take 
> 
> >>full advantage of gravitational acceleration to
> control the tone. The 
> >>effectiveness of the "accelerated action" is
> controversial because there 
> 
> >>are excellent pianos without this feature.
> Obviously, it is more 
> >>important for the pianist to control this
> acceleration."
> >>
> >>Now this is a new one to me. And Phil Ford who
> just last week wrote such 
> 
> >>a nice nearly error free essay on the reasoning
> for the accellerated
> action :)
> 
> 
> Does this mean that I don't get my Ph.D.?  I guess
> they meant it when they 
> 
> said my degree was BS.
> 
> Essay?  That little thing.  Just wait for my 30 page
> article in the
> Journal 
> on this subject.
> 
> I've heard this idea (about change of ratio as the
> key is depressed on the 
> 
> half round supports) before.  Why don't we take some
> real numbers.  Assume 
> 
> the radius of the half round dowel (with felt) is
> 10mm.  Assume the 
> distance from the balance pin to the point of
> contact between the back of 
> the key and the rest felt is 200 mm.  Do the
> trigonometry and you get that 
> 
> the change in tangent point of the bottom of the key
> and the dowel
> for 
> the depression of the key is about 0.5 mm.  How does
> that affect the key 
> ratio?  Let's say before key depression it's 200mm
> from the balance point 
> to the measuring point, and 100 mm back to the
> capstan.  Ratio = 0.500. 
> So 
> after key is depressed the numbers are 200.5mm and
> 99.5mm.  Ratio = 
> 0.496.  A change of 0.8 %.  Is that significant? 
> You tell me.  I would 
> guess that most factories are not controlling the
> distance from balance
> pin 
> to capstan within a half a millimeter, so this
> effect is in the noise.
> 
> >>The idea of a significantly changing key ratio
> tho.... is intriguing !
> >>
> >>Thanks Cy
> >>
> >>Cheers
> >>
> >>RicB
> 
> Also, since we're having some conjecture on the
> purpose of the accelerated 
> 
> action, here's what Steinway thought it was supposed
> to do:
> 
> According to Steinway patent 1,826,848, the half
> rounds 'reduce to a 
> minimum the frictional resistance offered to the
> rocking action of the 
> keys, and consequently they make provisions for easy
> depression of the
> keys 
> with a corresponding rapid and forceful
> re-positioning thereof'.
> 
> And from patent 2,031,748 the weighing off scheme is
> 'to reduce the weight 
> 
> toward the outer end of the keys and reduce the
> motion of the weight in
> the 
> movement of the key'.  And 'the main objects of the
> invention are to
> reduce 
> the distance the weights or leads have to travel in
> the depression and
> rise 
> of the keys and the inertia which has to be overcome
> in the movements of 
> the keys, and to weigh off the keys proportionately
> to the quickness in 
> action of their respective hammers so that the
> playing of the piano may be 
> 
> accomplished with less fatigue and muscular effort
> and greater ease and 
> facility be had in the playing'.  An interesting (to
> me) aside is that
> this 
> patent states that they are shooting for a 50g DW
> and 20g UW at the bass 
> end, and a 45g DW and 27g UW at the treble end,
> tapering in between.
> 
> Inertially,
> 
> Phil F
> 
> 
> 
> Phillip Ford
> Piano Service & Restoration
> 1777 Yosemite Ave - 130
> San Francisco, CA  94124
> _______________________________________________
> pianotech list info:
https://www.moypiano.com/resources/#archives


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