[pianotech] Pitch Change (was: Grey market pianos, seasoned pianos, etc.)

[Tom Driscoll]

Ron
Late response to your reply on this evolving (revolving)  thread. Thanks to 
you and Joe G for the explainations.
 Best,
Tom D.


Subject: Re: [pianotech] Pitch Change (was: Grey market pianos, seasoned 
pianos, etc.)


> Tom Driscoll wrote:
>> Question : Tuning a piano where pitch is 2-3 cents flat and a string 
>> breaks @ let's say note C-64. Humidity hasn't changed unless profane 
>> comments muttered under ones breath is a factor but now three or four 
>> notes on either side of the break are  a few cents  sharp.
>> I thought with less force bearing down on the bridge at that specific 
>> point that the bridge rises and increases tension on the adjacent 
>> strings.  Is this a convenient but  incorrect explaination of what is 
>> going on here and does this fit somehow into our current  discussion?
>
> Good question. What's the downbearing load difference when the string 
> breaks? Let's say, arbitrarily, that the string would be at 160lbs at 
> pitch. Let's be generous and give it 1° of downbearing on the bridge. 
> Assume it's plain wire, around the hitch so the one string makes two 
> speaking lengths. The total downbearing for that string is about 5.6lbs. 
> That should be a fairly easy thumb press, so does pressing down on the 
> bridge where the string was bring those surrounding notes back down? While 
> the downbearing difference on the bridge is just 5.6lbs, the tension on 
> the plate has changed by 320lbs, and the up bearing on the capo has 
> changed by around 80lbs. A piano going out of tune with seasonal humidity 
> changes hasn't incurred the same localized stress changes in the plate as 
> occur when a string breaks, so direct comparison probably isn't very 
> enlightening. If my laptop will work, I'll try the press on the bridge 
> thing next week to see what it does. I don't know that it'll be of any use 
> since it adds a big damping factor that wasn't there with the string, but 
> it might prove to be a good source of further confusion. <G>
> Ron N
>