Rolling to Pitch

[Avery]

Robin,

I have a rebuilder friend who ALWAYS, ALWAYS replaces the bridge 
pins. Even on the rare occasion when the bridge or bridge cap is NOT 
being replaced!

Avery

At 02:57 PM 8/19/2006, you wrote:
>Ron,
>
>Interesting point you raise about the bridge pin contact area 
>increasing over time.....are you suggesting that it is or could be a 
>good idea to very closely look for this when doing restringing and 
>possibly replace the bridge pins in toto??? I had not heard this 
>before but it surely sounds very reasonable.
>
>Thanks.
>
>Robin Blankenship
>
>----- Original Message ----- From: "Ron Nossaman" <rnossaman at cox.net>
>To: "Pianotech List" <pianotech at ptg.org>
>Sent: Saturday, August 19, 2006 2:25 PM
>Subject: Re: Rolling to Pitch
>
>
>>
>>
>>>Where is the movement in the string going when it
>>>can be lowered without tuning any pins?
>>
>>It's coming from the back scale as you pull the strings through the 
>>bridge pins with your roller. Contrary to popular belief, strings 
>>do render across bridges, it can happen quickly with big tension 
>>differences between front and back scales, or slowly over time. I 
>>expect you're adding at least 50 pounds to the string tensions in 
>>front of the bridge as you roll them, which is enough differential 
>>between tensions in the back scale, to pull the strings through. 
>>You've also put a heck of a load at an unnaturally high angle on 
>>the bridge notch edge during the rolling process, which didn't do 
>>the bridge cap any favors. After tuning, you left the piano in a 
>>far worse state of equilibrium than if you had just tuned it as you 
>>found it, because back scale tensions are still likely higher than 
>>they were when you got there, and will slowly more nearly equalize 
>>as the string creeps across the bridge with minor temperature and 
>>humidity changes breaking friction in small increments and letting 
>>it move. That will pull the front scale sharp again. It's getting 
>>less stable as it ages, I think, because the wearing bridge pins 
>>are presenting a larger contact area to the string, increasing 
>>friction, and making rendering through the bridge less likely with 
>>each passing year. So you're leaving a less stable tuning, on 
>>average, each time it's tuned. This isn't an uncommon thing in 
>>pianos living in rotten climate control conditions, where big pitch 
>>changes are necessary with each tuning. Go back and check it in a 
>>couple of weeks and see how it sounds. I expect you've got an 
>>unpleasant surprise waiting. Meanwhile, throw that roller away. <G>
>>
>>Ron N
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