[pianotech] capstain/wippen angle, was: key position at rest

[pmc033 at earthlink.net]

Hi, Vladan:	
	What I'm trying to say is that, in either case, there is a change in the
fulcrum point, and thus the ratio is changing.  Whether the hole is drilled
in the middle or on one side, there is acceleration of the hammer for a
constant velocity of the key through the stroke. If it were otherwise,
Steinway could not advertise it's "accelerated action".  (Could they?) 
Moving the pin location will not alter, increase, or decrease the
acceleration.  
	Your point that regular punchings and shims do also act imprecisely, and
may also have some ratio alteration in it, is well taken.  I'm not a fan of
altering the punchings by clipping one side, but if it works for the
better, I'm not going to object.  I had a problem with this treatment on a
Bosendorfer in our shop because the punchings were cut too close and had
torn through the hole and fallen out, thus making the keys unlevel. Now
somebody will tell me this was done at the factory!  I hope not.  
	Anyway, it is an interesting discussion in this thread about all these
aspects of action geometry.	 
 
	Have a nice evening.

	Paul McCloud
	
	
	


> [Original Message]
> From: V T <pianovt at yahoo.com>
> To: <pianotech at ptg.org>
> Date: 03/16/2009 10:13:05 PM
> Subject: [pianotech]  capstain/wippen angle, was: key position at rest
>
>
> Hello Paul,
>
> > Can someone explain how drilling the hole in the middle on
> > the half-round Steinway balance rail block would negate the acceleration
> > effect on the hammer?  As far as I can tell, having the hole in the
> > middle doesn't negate the effect.
>
> I am not sure if I understand your question re. acceleration, but if I do,
> here is what I think:
>
> On a regular action with flat bearings (punchings), the pivot point
shifts 
> as the key goes through its stroke. I see that Ron N. already responded
> about that. To visualize this, imagine an exaggerated key dip where the
key
> pivots against the player side of the punching edge when fully depressed 
> and against the opposite side when up. Indeed, the hole in the key wears 
> slightly because of that.
>
> There is even a "dirty" trick for changing the key ratio where you 
> intentionally place a raised step under the punching, a short distance
away
> from the pin with the intention of forcing the key to pivot about that 
> point and not where the pin is. This elongates the hole more.
>
> The regular flat felt punching (especially the thick ones) tends to
> compress and tilt with the paper punchings as the key moves, so it's not a
> really precise fulcrum point either.
>
> In the case of the S&S half round, the contact point is better defined
when
> the hole is centered on the half round. However, _if_ they really did
> intentionally drill the holes off-center, then I can see how the fulcrum
point would shift distinctly. Of course, the hole in the key would not be
> nice and round after a short while (and that is also the reason why I am
> not fond of placing shims on one side of the balance pin underneath flat
> punchings).
>
> Vladan
>
>
>
>
>       
>