Alan's Maxim and partial answer to: Puzzler for a rainy Sunday afternoon ...

[David Skolnik]

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Alan -

I'm sure I'm not saying anything you don't really know already.  It's the 
spiral of action regulation refinement.  You say

>The jack height adjustment, or more correctly the repetition lever height 
>adjustment, must be made before letoff, drop, etc

but adjusting the rep spring will change the rep lever height ( and hammer 
line),  and changing the checking height will require an adjustment in the 
strength of the spring (maybe), and you can't really assess checking height 
without having some kind of let off...etc.   Small measurements are always 
critical, sometimes. :)  At some point, the effects of further refinement 
become, spiritual, philosophical, or egotistical, (or pathological) but not 
discernibly physical, so the process can cease.

>But too little (jack too high, lever too low) takes the rep lever out of 
>the ball game entirely as far as repetition is concerned.

As always, I may be wrong, but it seems that your description above is 
actually reversed.  If the lever is too low, the jack will not easily, or 
at all, return under the knuckle.  In subsequent key stroke,  hammer will 
be propelled ONLY by rep lever, which, of course, cannot produce let off.

While I am unfamiliar with the particular piano in question, I am reminded 
of a similar problem I had with some early Renner USA - Steinway 
replacement parts.  I found establishing stable hammer line almost 
impossible.  The process of adjusting the rep lever height seemed to go 
directly from being too high (slight lost motion & unstable hammer line) to 
too low - jacks would resist complete return.  I ultimately tracked the 
problem (I believe) to a discrepancy between the arc inscribed by the top 
of the jack and the profile of the top of the rep lever arm (cradle?)  If 
regulated precisely at the same height, at rest, the arc of the jack top 
would dip below the lever profile as soon as it's travel began, thus 
eliminating the tactile sensation of the jack dragging along the 
knuckle.  By the time one was able to accomplish the standard 
benchmarks...slight drag and hammer wink, the jack top was significantly 
above the lever, and resisted return.

David Skolnik


At 09:42 PM 10/30/2005 -0600, you wrote:
>Phil has it (I think).
>
>The jack height adjustment, or more correctly the repetition lever height 
>adjustment, must be made before letoff, drop, etc. Because we are dealing 
>with something in the order of 2/10ths of a millimeter that has to be 
>adjusted by feel, it is easy to have it wrong even if it "looks" right.
>
>I learned, in this challenging little experience, that a very, very slight 
>change in height makes all the difference in the world. Too much of a gap 
>creates obvious lost motion detectable by slowly pressing the key down. 
>But too little (jack too high, lever too low) takes the rep lever out of 
>the ball game entirely as far as repetition is concerned.
>
>Now here's a true confession: I honestly don't know why this made such a 
>difference, but after much frustration, I rechecked this adjustment, 
>raised the lever (lowered the jack, relatively) and was THEN able to set a 
>letoff and drop just as sweet as you please. Prior to that, no combination 
>worked! Key point: The adjustment on this note looked just like it's 
>neighbors--and they regulated just fine.
>
> >>> I'd actually appreciate explanation or comment from you who have 
> regulated so many more actions than I.
>
>As Yamaha so aptly states: "One large difference between a grand action 
>and a vertical action is that the grand has the repetition lever. However, 
>the lever loses its value in direct proportion to how poorly is is 
>regulated. Remove all lost motion, but make sure the jack can return under 
>any circumstance. Then the repetition lever can live up to its name."
>
>So here, brand new and hot off the press, is "Alan's Maxim":  If you are 
>having trouble regulating an action, back up a few steps and make sure you 
>have good regulation in those earlier steps.
>
>Might save ya some tears some day!  ;-}
>Alan Barnard
>Still Larn'n, Thank'e, in Salem, MO
>
> > [Original Message]
> > From: Phil Bondi <phil@philbondi.com>
> > To: Pianotech <pianotech@ptg.org>
> > Date: 10/30/2005 6:44:10 PM
> > Subject: Re: Puzzler for a rainy Sunday afternoon ...
> >
> > Spring tension non-existent?
> > Jack too high in the window?
> >
> > ..this is a good puzzler,
> >
> > -Phil Bondi(Fl)
> >
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives

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