Half punchings on balance rail

[V T]

Hello Cy,

As far I know, there are two changes that S&S made
when they introduced the "accelerated action".

One was a new bearing surface at the fulcrum, as
opposed to the flat felt punching that other pianos
use.  From an engineer's standpoint, that looks like a
cleaner solution because the new bearing has a more
defined contact point, and that point is exactly at
the center line of the balance rail pin.  I don't
think that this contributed to the "accelerated", it
just was part of the overall design change.

The really important change was that they moved the
lead closer to the balance rail.  This reduced the
inertia of the key sticks.  Over the years, the lead
seems to have migrated more and more to the front.

There may have been some other changes too, but I
don't know what they were.

The idea with the cut-off punchings is actually quite
different;  this is an attempt to move the fulcrum
point away from the center line of the balance rail
pin, usually in a direction that will lower the key
ratio.  It's not elegant in the sense that it forces
the key to pivot around an axis that is not centered
in in the pin, but the alternative would be to move
the capstans or the balance rail pins.  Both are much
more work.  So in a sense, it's a "poor man's" way of
changing the action ratio.

Vladan

=======================================

Does this have any similarity to the S&S "accelerated
action"?  I can't
remember the details, but I think there's some angled
part right at the key
fulcrum.

--Cy Shuster--
Bluefield, WV

----- Original Message ----- 
From: "V T" <pianovt@yahoo.com>
To: <pianotech@ptg.org>
Sent: Tuesday, September 07, 2004 9:42 PM
Subject: Half punchings on balance rail


> Hello Bob,
>
> That makes perfect sense - by changing the fulcrum
> point, you are changing the overall action ratio. 
The
> number of interest is the Balance Weight (DW+UW)/2,
> and that has to drop when the action ratio drops. 
In
> other words, it will take less force to push the key
> down when the ratio is smaller.  Note that the
> friction, which is (DW-UW)/2, stays approximately
> constant (very slight change).
>
> Best regards,
>
> Vladan


	
		
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