Quick action lubrication:

[Farrell]

I don't understand Richard: "but the jack center pin... Hard to imagine how overall action friction could be influenced by action parts that have no motion."

The jack moves after its foot touches the let-off button. If the jack center is tight, it is harder to push the key down for that portion of the keystroke.

Now I realize that won't be affect measured touchweight by the traditional measurement method (before let-off). But it sure will be part of the picture for anyone playing that piano!

Terry Farrell
  
----- Original Message ----- 
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: <pianotech@ptg.org>
Sent: Monday, April 08, 2002 10:05 AM
Subject: Re: Quick action lubrication:


> Mike and Jane Spalding wrote:
> 
> > Hi Richard,
> >
> > How does friction between the roller and rep lever/jack tip affect down weight?
> 
> Good points and descriptions in my book Mike, But Bob was refering to the jack centerpin, the whippen spring, and the repetition lever centerpin.  Non of these is in motion really before letoff..... or what ? ... Maybe the whippen spring might depress just a hair depending on the regulation, and in that case the levers center would move just a tad as well.. but the jack center pin... Hard to imagine how overall action friction could be influenced by action parts that have no motion.
> 
> 
> > Think about the "magic line".  The roller/jack contact area can only lie on the magic line at one point in the keystroke, even under ideal conidtions.  Whenever the contact area is above or below the line, i.e. at every other point in the keystroke, something is sliding.  Some actions, due to poor design or poor selection of rebuilding components, do not operate under ideal "magic line" conditions.  On my Frankestein action model, for instance, the roller/jack tip contact starts a couple millimeters above the line, and rises further above it during keystroke.  At let-off, the two surfaces have slid about 1.5 mm.   If they weren't already slicked down with Tef & Mac, I would lube them now and report the change in downweight.
> >
> > Hope that makes sense
> >
> > Mike Spalding, RPT
> 
> Cheers !
> RicB
> 
> --
> Richard Brekne
> RPT, N.P.T.F.
> Bergen, Norway
> mailto:rbrekne@broadpark.no
> http://home.broadpark.no/~rbrekne/ricmain.html
> 
>