Rolling to Pitch

[Robin Blankenship]

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
>