THAR WE GO POSITIVE, SCIENTIFIC, REPEATABLE FACT/TRUTH, case closed, let's move on. :-( Terry Farrell PS: WTF? On Apr 3, 2010, at 7:33 PM, Gerald Groot wrote: > I did read that William, thank you. After reading more of it as > well, it appears to me that there is much more speculation than > positive proof either way from either Ric or John. > > I visited with Dr. Yat Lam Hong all afternoon today. He is a man > FULL of information and is most willing to share it. How he manages > to retain it all is beyond me. I wish I had that kind of memory. > For those of you that do not know Yat Lam, he is an extremely > knowledgeable RPT. > > I asked Yat Lam Hong his philosophy on what he thought was the main > cause of why pianos go out of tune so drastically from seasonal > changes and his immediate reply was "humidity." He went on to say > that "humidity causes swelling and contraction of the sounding board > sending pitch up and down.." A pure and simple answer. I asked > him about the rim being a factor. "Possibly some, but no, not > much." Adding: "It would be a very small factor as would the > sounding board near the rim because it is glued down there. The > bass section changes tuning and pitch also but not nearly as much as > the tenor section. One reason is because it is closer to the edge > of the piano. Whereas the tenor section of the pianos bridge runs > down the middle of the sounding board where it swells and contracts > the most." > > We both agreed that there some other factors that do come into > play. Some of them have been mentioned here such as heat or > lighting. We both think however, that the major contributing factor > is the sounding board swelling and contracting. So, I stand firmly > by what I was taught. We had other things to do so we dropped it at > that. > > Jer > > > From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] > On Behalf Of William Monroe > Sent: Saturday, April 03, 2010 1:59 PM > To: pianotech at ptg.org > Subject: Re: [pianotech] Pitch Change (was: Grey market pianos, > seasoned pianos, etc.) > > Hi Gerald, List, > > Having sifted through the archives......... ;-] > > OK, so my memory did serve. Here's an excerpt from Ric Brekne's > posting of the math that shows resultant pitch changes due to rise & > fall of a soundboard. This shows minimal effect on pitch due to > soundboard deflection. Here's a link to the archives as well with > the thread, " Soundboard Deflection and Pitch Change / was > Downbearing." > > https://www.moypiano.com/ptg/pianotech.php/2006-August/thread.html#194422 > > William R. Monroe > > > > > > > > > > Ric wrote: > > > > .............Let me illustrate..given the following, and by all > means check my > > figurings... (for the moment disregard the width of the bridge and > deal > > in simple triangle trig) > > > > > > > > - an undeflected string tension of 160 lbs. > > - string diameter of 0,8 mm. > > - front length of 50 mm. > > - back length of 25 mm. > > > > This yields a front length frequency of roughly 4248.88 Hz. f = > SQRT((T > > > > * 398 *10^6)/(L^2d^2)) > > > > > > If you then deflect this string 1 mm upwards you get a string > deflection > > angle of a whopping 3.46 ¤, a downwards force of 9.59 lbs, and a > > frequency of 4248.98 hz. Thats only a change of 0.106 hz.... at note > 88 > > > > > > or there abouts. Even a 2 mm deflection would'nt increase the > frequency > > of the string more then 0.42 hz and that would at the same time > cause a > > string deflection angle of 6.87 ¤ !! and a downbearing force of just > > > > > > over 19 lbs... for just one string ! You'd be quickly over 3000 lbs of > > total downbearing force on the soundboard... > > > > If these figures are correct... then clearly soundboard deflection can > > nearly be ignored when it comes to pitch changes. > > > On Sat, Apr 3, 2010 at 9:55 AM, Ron Nossaman <rnossaman at cox.net> > wrote: > Gerald Groot wrote: > I have read what has already been written in this thread, > currently. Ron, > I'm not going to sift through the archives. The dissusion has been > and > still is being presented now. I'm merely adding to it as you are > giving my > current thoughts on the matter again, as you are. > Have YOU had the time to do all of these measurements yourself? If > so, I > don't know how you managed to find it let alone have the patience > for it. I > haven't nor do I have the desire to do so. Taking measurements is > not the > only proof available. When does logic and common sense ever come > into play > here? > > It comes into play immediately when you find how much a soundboard > has to move to produce the required tension changes. Yes, I've taken > a whole lot of time trying to learn how things actually work, rather > than assuming that what I was taught was correct. It used to be > common sense that horse hairs in the rain barrel turned into worms. > I take the time because I'm interested in learning something real. > > Ron N > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100403/3496e682/attachment.htm>
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