Tony, My take is that with the upright piano opened up, and the fan pushing air over it, the temperature of the strings drop, thus causing the rapid rise in pitch. And when the fan is off the string temperature rises and the pitch drops. Just how slow or rapid the humidity is affecting this situation is open to debate, or careful measurement and study by someone (looking to publish a paper in the Journal?). Tuning with fans on is another complication as the fan beating the air alters the way we hear beats! Yes extremes make our life difficult. Best, Patrick On Tue, Jan 11, 2011 at 5:58 AM, Tony Caught <acaught at internode.on.net>wrote: > Hi Will, Ron, David, Patrick, Gene & et all > > > > I will bow to your wisdom. It seems that the majority opinion is that the > temp change is the cause of the pitch changing whilst tuning a piano. > > > > Possibly my time in Darwin Australia has coloured my opinion of this affect > due to the extremes in humidity and lack of change in temp. > > > > However, I will give you a scene of every day tuning during the “wet” > season. > > > > It is 2PM and I am to tune a piano in a house in Nightcliff. The temp is > 33C and the RH is 80% (Min temp the previous night was 26C. The windows > are open and the room temp is the same as outside. Ceiling fans are on. > > > > Now we have two scenes > > > > 1. I open the upright piano and start tuning, (my average tuning > time is 50 minutes) Mute middle section, set a scale, tune up two octaves > and check F5 to F3 and find a double octave beat of 1.5 to 2 wahs per > second. The piano has in a space of 15 minutes gone sharp in F3. Forgot to > turn the fan off. > > 2. I turn the fans off, open the piano, Mute middle section, set a > scale, tune up two octaves and check F5 to F3 and find a .5 wah per second. > F3 has still risen but is acceptable, me, I am now sweating like a pig. > > > > I have always believed that when the fan is on it pushes the moist air into > the piano which causes the soundboard to swell, action movement to slow or > stop and a lousy tuning. > > > > I learnt to switch the fans off, work fast, tune a piano is 30 minutes and > cover it up The get paid and go home to change clothes for the 3rd time. > > > > Now you may say that the fan being on has caused the temp inside the piano > to rise by 2C in tem faster than it would normally and that rise in temp has > caused my tuning problem or you may say oh, but this is extreme conditions. > > > > Sure I will always leave a piano for 3 weeks to stablise the MC after I fit > a Dampp-Chaser system before I tune it and yes, I know that temperature also > affects the tuning pitch of a piano but ? > > > > > > Tony Caught > > acaught at internode.on.net > > > > *From:* pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] *On > Behalf Of *J Patrick Draine > *Sent:* Monday, 10 January 2011 10:45 PM > > *To:* pianotech at ptg.org > *Subject:* Re: [pianotech] pitch and temperature > > > > The change in the soundboard etc.'s moisture content is much, much slower > than the affect of temperature changes on the strings (and, the plate more > slowly than the strings). > > I suggest you read Ron N's post again. > > > > Keep dry (cousins are sandbagging in Gympie; it's just cold here in > Massachusetts), > > Patrick Draine > > > > On Mon, Jan 10, 2011 at 4:14 AM, Tony Caught <acaught at internode.on.net> > wrote: > > Hi Ron, > > The land I take it is in the middle of the swamp with a few gators for > company. > > My Take. > > "a loaner sat on the moving van in freezing weather overnight" > > Drives the moisture out of the soundboard. > > "brought on stage indoors in a warm theatre" > Soon as the piano hits the air it starts to absorb moisture at a > (scientific > word) fantastic rate. > Soon as you open the piano to tune it the moisture absorbsion rate > increases. > > I found out a long time ago that removing a piano from indoors at 21 > degrees > C and 40%RH to outdoors at 32 degrees C and 80% HR and then tuning it to be > to say the least, challenging. The temp does not change that much but the > piano keeps changing whilst you are tuning. > > Now you say that the strings change 1/2 way through the tuning. The > question > is is this caused by the soundboard expanding or shrinking or the strings > expanding or shrinking. > > Or, my head just shrinking so the sound is expanding. > > Tony > > > > Tony Caught > acaught at internode.on.net > > > -----Original Message----- > From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On > Behalf > Of Ron Nossaman > Sent: Monday, 10 January 2011 3:33 PM > To: pianotech at ptg.org > Subject: Re: [pianotech] pitch and temperature > > On 1/9/2011 8:57 PM, Gene Nelson wrote: > > Thanks everyone, > > I was trying to come up with a chapter technical on the subject. > > Possibly an approach from co-efficient of expansion for steel piano > > wire, isolating for the one thing that moves the fastest and possibly > > the most? The math is beyond me. > > The math is pretty simple, and I'm math deaf. The expansion coefficient > of music wire and gray iron are pretty close. The difference is in the > cross section of the parts. It takes little time for a temperature > change to migrate through 0.040" diameter wire compared to 0.5" iron. > That's it. > > > > My challenge was a couple years ago in the winter, a loaner sat on the > > moving van in freezing weather overnight, brought on stage indoors in a > > warm theater and I had about an hour to work with it. > > Gene > > There's the problem. The strings changed fairly quickly, maybe up to > half way through the tuning, where the plate caught up about four hours > later. This is an impossible situation, and any tech who hopes to > anticipate the changes and accommodate them to all come together in a > good tuning at a specific time is eligible for a really good land deal I > have available in Florida. > Ron N > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110111/8e209ec4/attachment.htm>
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