No Power Yamaha revisited

[Bill Ballard]

At 9:48 AM -0400 5/26/03, A440A@aol.com wrote:
>Once the glides are in contact, the action cannot move, UNLESS
>the keybed is not absolutely rigid.  But we know the keybed isn't.  This is
>easily seen by depressing the pedals under a very lightly bedded set 
>of glides and
>observing them to lose contact with the keybed.

On a Stwy O and M, I didn't see more than 5 mils of sag while coming 
down on the sustain pedal. Apply both pedals and I couldn't get more 
than 8 mils. These Stwy keybeds may not be absolutely rigid, but they 
are stiff enough. *mils  is easily covered by the 20-25 mils we're 
talking about as a reasonable working amount the BalanceRail can be 
lifted.

>So,  the extra power and tone being ascribed to heavier loading on the
>glide buttons may possibly be a function of preload on the keybed?

I don't think the keybed needs stiffening. What I think needs to 
happen is that the keyframe (already properly bedded) needs to be 
free of the possibility of the rails bouncing around under unusual 
conditions. This is accomplished by springing the frame upwards at 
the BR. How common a problem bouncing keyframes are, and how real is 
the need to tie the rails down using this force-of-spring? I don't 
know.

At 10:53 AM -0600 5/26/03, Roger Jolly wrote:
>I wonder what the pressure would be at the balance rail pin 
>location, on a forte blow.

Whatever the forceful tromp on the pedals was it only produced 8 mils 
of deflection. A dial indicator positioned over a note halfway 
between glides and set, Ron Overs style, to reference the underside 
of the block, barely showed 3-4 mils under a sharp blow. Even a 
forceful six-note, two-hand chord didn't increase it that much. BTW 
one needs quick eyesight to observe the maximum deflection in such a 
test: it doesn't last long.)

At 9:36 PM +0200 5/26/03, Richard Brekne wrote:
>I guess that the added stress of the bolts being turned down a bit 
>just makes the whole frame a bit stiffer, perhaps causeing the back 
>rail to strain up against the dags contributes to this ??. But I 
>dont really see how the increased stress beyond solid contact by the 
>glide bolts is doing what it seems to be doing.

I don't see either. Nor I actually didn't hear anything on either 
this O or M, both pianos at a local private school. Neither did the 
chairman/pianist. The O didn't need any help, tonally. The M of 
course is long overdue for hammers. And I was told to expect a 
dramatic change.

Also there appeared to be less room for lifting than I though. I 
couldn't get much above 25 mils of BR lift from neutral, before I 
started bumping into the FR lifting.

At 10:37 PM +0200 5/26/03, Isaac OLEG wrote:
>With a light bedding, I guess that under forte blow there is a 
>distortion that travel from the front of the keyframe towards the 
>back, as the back want to raise because the frame is not stiff 
>enough.

IOW, the back rail on an unsprung keyframe has an easier time lifting 
off the bed than a sprung one? I think we all belive that something 
is happening, and I believe that we all have something similar in 
mind: rendering the keyframe more stable in "rough weather and high 
seas". My best guess is that the upwards spring stiffening the frame, 
makes its less likely a surface where energy can get damped, absorbed.

Which brings me to wonder what the bellymen on this list would think 
about a keyframe sprung this way over several decades. Would the 
adjustment no longer be possible after a half a century because the 
cross-slats had taken  a "set"?

Bill Ballard RPT
NH Chapter, P.T.G.

"No one builds the *perfect* piano, you can only remove the obstacles 
to that perfection during the building."
     ...........LaRoy Edwards, Yamaha International Corp
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