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 +++++++++++++++++++++
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