Overpull

[Farrell]

----- Original Message ----- 
From: "Bradley M. Snook" <bsnook@pacbell.net>
To: <pianotech@ptg.org>
Sent: Thursday, March 28, 2002 8:51 PM
Subject: Re: Overpull


>Results that are within 2-3 cents is good, I'm
> just wondering if we can do better? 

I would suggest that anything better on a big pitch raise (more than 30 or 40 cents) is just luck.

>I don't completely understand what goes
> on in the background of the software that you mentioned, but usually
> overpull is a certain general percentage (like 25%) . . . I am wondering if
> it is possible to calculate something that is note specific (like 23.42%,
> 24.01%, then 24.42%). Is drop predictable enough?

I don't think so. Not in my experience. Some pianos drop more than others. Sections vary. It also depends on how consistent the flat piano is (is every note EXACTLY 42 cents flat - or does it vary all over the place?). I'm sure you could come up with some formula to calculate some very specific overpull percentage, but there are many factors that you will not be able to characterize clearly that may affect the outcome.

Don Rose wrote:
> How does a pitch
> correction of 220 cents at A4 with a single pass tuning leaving A4 1.21
> cents sharp sound? Is that close enough?

Well, that's pretty good. Likely better than I could do in ten tries. Can you do that every time? Are you suggesting that every note ended up within 1.2 cents of target? And do you really pull notes 55 cents sharp during a pitch raise? I thought there was some potential of permanently deforming the wire when one goes beyond about 25 cents sharp?

Back to Bradley:
>Sure, that sounds really good. But my experience seems to be that after the
>correction as occurred, each note varies to a certain degree. I just wonder
>if corrections can be more controlled?

I don't know how. I think if a pitch raise puts the piano to a point where it is about where a reasonably stable piano would be a year after tuning, you are where you need to be - and likely as close as you are going to get - unless of course you are lucky.

>Here is a specific question: is there a difference in overpull when a string
>is 10 cents vs. 12 cents flat?

Yes. About 20%.

> And how do the surrounding strings effect the
>amount of overpull necessary for that specific string?

Closer strings affect it more, further affect less. In my experience notes within about five half-steps significantly affect a given note and notes further away have minimal effect (more or less - there abouts).

>This is just a simplified example:
>A2  A#2  B2  C3
>-10  -13   -9   -12 (from where they should be)

>Do the current locations effect the amount of overpull for each note?

Yes. Everyone uses slightly different overpull percentages that seem to work for them, but for me, tuning unisons as I go, I usually shoot for about 18% in bass, 21% in wound strings on the tenor bridge, 23% in the tenor, and 34% in the treble. I also ease off the overpull for the two notes before the bass/tenor break and within a couple notes of C88.

>Bradley M. Snook

Experiment. See what works for you and your syle.

Terry Farrell