I think we've all done this experiment without thinking about it. Many a pin I've turned that has barely held. If I can get the pin to stop, it has good chance of holding the tension. But if the pin is moving when pressure is released on the tuning hammer, it will not hold, and usually moves 1/4+ turn. If it is a junker piano and it is a pin in the extreme bass (which is usually the case), I know as soon as the humidity drops that string is going to go way out. I just tell the customer that the pins are very flakey and probably will not hold through the winter, and I try to sell a CA job. Sometimes you encounter a piano with pins so loose you know they aren't going to hold. But when you check 6 to 12 months later it is still in reasonable tune. If they hold, they'll hold. If the static friction goes down enough that the tension overcomes it, it will start turning. And since the dynamic friction is lower, the pin will continue to turn until the tension goes down enough that it will no longer overcome the dynamic friction. When a pin slips that string goes very flat all at once, not gradually flat. Dean Dean May cell 812.239.3359 PianoRebuilders.com 812.235.5272 Terre Haute IN 47802 -----Original Message----- From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Sarah Fox Sent: Monday, March 28, 2005 10:20 AM To: Pianotech Subject: Re: Aha! was flat facts Hi William, I see and understand your point, but the micro-slippage I'm talking about is NOT with respect to the entire pin at one time. I'm talking about microslippages of small fractions of the mating area between the pin and block that accumulate over time. Dean, I also understand your point about static vs. dynamic friction, but if we're only talking about small portions of the entire pin-to-block contact area, then indeed we can be talking about "microjumps." Y'all have my curiosity piqued. I'll try this experiment with a little Hamilton that has a decent pinblock but isn't very well humidity controlled and isn't tuned on a very frequent basis. Perhaps y'all can help me to establish the experimental parameters? What minimum and maximum tuning pin torques??? I'll select a few pins to meet with those parameters and monitor them. I'll measure the angle closest to horizontal that I can hang my tuning hammer from these pins, as measured with an engineer's compass/level. Or perhaps I'll use some sort of spring-loaded clamp, as the measurements might be more repeatable. I won't be able to get to it for a few weeks, but I think I'll definitely do it. Sounds interesting. Weird that this hasn't been done before!! Peace, Sarah ----- Original Message ----- From: "William R. Monroe" <pianotech@a440piano.net> To: "Pianotech" <pianotech@ptg.org> Sent: Monday, March 28, 2005 9:16 AM Subject: Re: Aha! was flat facts > Not sure if I made myself clear on that last bit, "What's more, this assumes > that friction is constant, whatever the pins position in the hole." What I > mean is, if static friction has been overcome and the pin started to move, > is it not possible that after the tiniest movement, the pin encounters a > structural "something" in the block which results in an increase in friction > in that position, stopping the pin's movement? > > Respectfully, > William R. Monroe > > ----- Original Message ----- > From: "William R. Monroe" <pianotech@a440piano.net> > To: "Pianotech" <pianotech@ptg.org> > Sent: Monday, March 28, 2005 8:13 AM > Subject: Re: Aha! was flat facts > > > > Dean, > > > > True, static friction is greater than dynamic friction. However, as long > > we're splitting hairs here, define jump. What I mean is, it is easy to > > imply that if the pin overcame the static friction it would then make some > > large movement, resulting in a large pitch change. I think arguing that > it > > jumps vs. makes micro movements becomes an issue of semantics. Your jump > > can be my micro movement. What's more, this assumes that friction is > > constant, whatever the pins position in the hole. I'm unsure if this > would > > be the case or not. > > > > Respectfully, > > William R. Monroe > > > > ----- Original Message ----- > > From: "Dean May" <deanmay@pianorebuilders.com> > > To: "'Pianotech'" <pianotech@ptg.org> > > Sent: Monday, March 28, 2005 8:00 AM > > Subject: RE: Aha! was flat facts > > > > > > > Static friction is greater than dynamic friction. If a tuning pin moves > > > it jumps, it does not turn in micro movements over time. > > > > > > Dean > > > Dean May cell 812.239.3359 > > > PianoRebuilders.com 812.235.5272 > > > Terre Haute IN 47802 > > > > > > > > > > -----Original Message----- > > > > From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On > > > > Behalf > > > > Of Ron Nossaman > > > > Sent: Sunday, March 27, 2005 11:38 AM > > > > To: Pianotech > > > > Subject: Re: was flat facts > > > > > > > > > > > > > > > >> I don't really buy into the "tuning pin turns" theory. > > > > > > > > Me either, nor the wire stretching. Music wire doesn't continue to > > > > stretch over time unless it's tensioned at it's yield point - then > > > > it stretches, necks down, and breaks. > > > > Ron N > > > > > > > > _______________________________________________ > > > > pianotech list info: https://www.moypiano.com/resources/#archives > > > > > > > > -- > > > > No virus found in this incoming message. > > > > Checked by AVG Anti-Virus. > > > > Version: 7.0.308 / Virus Database: 266.8.3 - Release Date: 03/25/2005 > > > > > > > > > > > > -- > > > > No virus found in this outgoing message. > > > > Checked by AVG Anti-Virus. > > > > Version: 7.0.308 / Virus Database: 266.8.3 - Release Date: 03/25/2005 > > > > > > > > > > > > _______________________________________________ > > > > pianotech list info: https://www.moypiano.com/resources/#archives > > > > > > > > > > > > > > _______________________________________________ > > > pianotech list info: https://www.moypiano.com/resources/#archives > > > > > > > > > _______________________________________________ > > > pianotech list info: https://www.moypiano.com/resources/#archives > > > > > > > > > > > > _______________________________________________ > > pianotech list info: https://www.moypiano.com/resources/#archives > > > > > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives > > _______________________________________________ pianotech list info: https://www.moypiano.com/resources/#archives
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