Seating/false beats

[Ron Nossaman]

Hi all,


Susan, your logic is good, but only if the bearing is negative in the low humidity cycle. I have no doubt this happens in some pianos (it sounds hideous!), but I would put this scenario in the "low incidence/exception" category. Most of us (you included,
admit it <G>) wouldn't expect to be able to improve the sound of one of these failed pianos by seating strings. The condition you describe would be a winter thing. You envision the strings staying up into the summer cycle to need tapped down at that time.
 Most of this type of "repair" is done in the winter when the false beats are worst. There are lot's of flat soundboards out there, I grant you, but I am trying to minimize the variables and concentrate on viable, serviceable instruments.

I also still think CA, or epoxy is a good idea for all the stated reasons, etc, etc. I wouldn't, however, assume that the bridge would then be safely sealed enough to apply any experimental lubricant. I've found that a lot of disasters can be avoided by s
imply making a mental list of all the possible reasons not to do something non-standard. If you can't scare yourself off this way, it might be worth trying. I learned this by doing it backward too many times. There is nothing quite so educational as stepp
ing off the path. Experiment in logic FIRST, then hardware. Education is always expensive.

PS: I have more news/observations/conjecture on grooved bridge pins I'll post later, after everyone's had a shot at this level. I'm trying to clean up as we go to minimize backtracking and wandering. I hope everyone understands and doesn't take umbrage. (
Isn't that in North Carolina?) Anyway, I appreciate everyone's indulgence. More later.


Ron Nossaman





At 09:58 PM 4/21/97 -0700, you wrote:
>Hello, Ron, Steve, Rick, Horace, and list --
>
>Just the kind of response I was hoping for. I am much happier with larger
>forces accounting for the motion up the pin. As soon as I saw Steve Brady's
>contribution, the question of downbearing came much more strongly into play.
>
>Instead of some motion of the bridge _past_ the bridge pins raising the
>string (in wet conditions), why not a collapse of downbearing during dry
>season, so the string had negative bearing? Of course it would want to rise
>to neutral, which also explains why it wouldn't go up and up and up. It
>would only go the minimal distance necessary to balance the negative
>downbearing ("upbearing"?) against the increasing side-bearing of the
>leaning bridge pin.
>
>Please pardon me if someone already said all this, way back when. It's been
>a really long, rich thread.
>
>The string would also be urged up by hammerblows in heavy playing, though
>that wouldn't be the main reason for rising, just an excuse for slipping
>"up" there. It wouldn't go sharp, since in negative bearing the path
>touching the bridgetop would be longer, not the one slightly in the air.
>
>Once it was "up" there (really, at the same level as before, the board has
>sunk away from it) vibration from playing would notch the pin, so it
>wouldn't automatically go back down when humidity swelled the board again.
>Actually, it only goes "up" by hanging a ride on the notch in the bridge pin
>which it has made in the winter time.
>
>Most of the time most of the strings would get back down off the pin when
>the board rose again and restored downbearing. These things are erratic, and
>don't happen to every note all the time. Only if the notch were sufficiently
>"sticky" or deep would it stay up, and the greater the sidebearing the more
>likelihood that it would stay up. (I believe that is consistent with earlier
>postings to this thread.)
>
>Staying "up" on the notch in summer (wet) would only increase the natural
>tendency towards sharpness caused by the swelling board; as Ron has noted,
>the path is longer when a string is off the bridge, assuming threre is
>downbearing.
>
>The trick now would be to take methodical downbearing readings, of the front
>and rear lengths, in the problem section, of many pianos, over several
>years, in areas with a strong seasonal humidity shift. (whew) Then one could
>correlate near-neutral or negative bearing on _particular notes_ with the
>"tick"  of reseating, and see if it all adds up. The pianos would have to be
>of good enough quality for really consistent sidebearing. That way one could
>back up anecdotal evidence with something a little firmer. (And of course
>_I_ can't do it: seasons are too genteel here.:->)
>
>Don't know if this is a real answer, but I sure have had a lot of fun!
>
>CA glue around the pins still seems a good idea, for good terminations,
>whether or not the string rides up. The worse the humidity swings, the more
>important firming the pins and protecting the wood from moisture would be.
>Would CA glue around the pins protect the wood enough to explore other
>lubrication than just graphite?
>
>Signing off, unless some wonderful new notions appear!
>
>
>Susan Kline
>skline@proaxis.com
>P.O. Box 1651,
>Philomath, OR 97370
>
>Variables won't; constants aren't.
>
> Ron Nossaman