No Power Yamaha Experiment.

[Bill Ballard]

At 11:26 AM -0600 5/25/03, Roger Jolly wrote:
>Then started screwing down the glides,  until I could just start to 
>pull the paper slips out from under the front rail, then back off so 
>the paper was just gripped by the rail.
>
>On average the front of the keys were raised 1/16".  Without losing 
>any contact points from the front rail.  No lifting of the back rail 
>was observed.

  I tried this on one glide of a Stwy O out in the shop (a dial 
indicator on the BR and a second one on the key level). The BRail to 
Key Height lift ratio was 1:1.7, as we might expect from our key 
leveling experience. The tissue shim didn't budge until 0.035" of BR 
lift, the equivalent of adding 0.059" of new dip. An extreme amount, 
except when you're roughing things in in the shop. The FR didn't 
start to knock until ~70 mils, that's lifting the BR 41 mils. That 
knock was under a mil.

So we've got 35 mils of BR lift before the FR ever stirs. Who knows 
what our operating limits are, in this case how much the frame warps 
in the coldest driest winter and the hottest muggiest summer. As you 
and Ric point out, it's going to be a local value based on local 
conditions. Not just of the climate swings, but of the particular 
construction and grain selection  in the keyframe.

But we shouldn't worry about this uncertainty, considering that the 
part about lifting BRs which really has consequences, and immediate 
ones, is the effect of this extra keydip/aftertouch on the action 
regulation. Maybe in fact, aftertouch is going to be the fine tuner 
of the keyframe spring. Which surprises me because I had been told at 
some point that inordinate amounts of spring in the keyframe were a 
sign of ham-fisted/brained regulators who should have regulated dip 
the proper way.

Maybe, if the action is put together well enough and the keyframe 
properly fit at the front and back rails, the BR can be set at a 
certain extra height above its free-floating amount (seasonable warp 
included), then the keyframe will always come back to a standard 
amount of spring. If we use this BR height as the basis for dip and 
aftertouch, then a few odd months later, the glides can be used to 
bring the dip/aftertouch back to their proper place. That of course 
assumes that blow is returned to its place. (Aren't non-jagged hammer 
lines a blessing to work with in circumstances like these.) Maybe, as 
long as we know how far this adjustment of BR height is from the 
height we'd like to hold it to, this could be used to touch up 
aftertouch on a seasonal basis.


>The key level had moved a little, checked before and after with a 
>48" straight edge.

We know key level to be quite sensitive.

>There was a significant improvement in tone, particularly in the 
>treble. Cleaner sounding and more power.

This I'm curious about. Is this improvement in tone something similar 
to that of finding the correct strike point? Is it a range which you 
enter and then pass through? Did it seem to you that the improvement 
was best found at a particular level of BR height?

>Conclusion:  I think the key bedding was optimized.

When you say "optimized", are you speaking generally of the bedding, 
or are you referring to a particular setting of the glides?

>Will there be potential problems with humidity swings? Not sure, 
>time will tell. But gut feel says yes.

I think we can safely assume that season changes will show up in 
something as sensitive as this. It will be interesting, now that we 
can track small amounts of motion in this setting, how much it will 
turn out to be, and where within that we can pick a BR height.

At 9:37 PM +0200 5/25/03, Richard Brekne wrote:
>Its really quite amazing the difference in
>play/sound/power you can achieve by adjusting up or down these glide 
>bolts. And
>there seems to be a certain range of settings withing what is acceptable solid
>bedding. Obvioiusly I have a new play tool :)

I'd love an elaboration, Ric. Thanks to you and Roger for this 
thread, and and thanks to Ron'O for posting the application of the 
dial indicator.

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

"We mustn't underestimate our power of teamwork."
     ...........Bob Davis RPT, pianotech '97
+++++++++++++++++++++