relevance of bridge pin spacing

[Gene Nelson]

<What's your "ideal" C-8 speaking length?

 Original for this piano was 53mm. I have looked at 54 and 52 - neither will 
work out much more than the top octave. So 53 appears to be ideal for this 
piano.

<For the #8 pins, I have three row spacings - 16mm, 18mm, and
 20mm. Where the back row of the higher unison interferes with
 the front row of the lower one, I'll use either the 16mm, or
 20mm to get around it. Otherwise, the rest is 18mm.

Possibly the original bridge pin spacing from notes 35 to 66 were not random 
afterall. Must look at this more closely. This brings up another thought: I 
also should be looking for more unison spacing fudge room because I 
eliminated the original hitch pins and replaced with verticle. I came as 
close to original alignment as possible but I am certain that any errors are 
waiting to haunt me when I finally do the bridge pin layout. The original 
bridge pin diameters of the top section were .091 (cannnot find replacements 
for this size) and I will use .086 - possibly will gain some small space 
advantage here as well.
Thanks
Gene
----- Original Message ----- 
From: "Ron Nossaman" <rnossaman at cox.net>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Monday, December 31, 2007 11:33 AM
Subject: Re: relevance of bridge pin spacing


>
>
>> The original cap front to rear bridge pin spacing averages 18mm from note 
>> 88 to 67 and from 66 to 35 it varies from 19 to 24mm.
>> My questions are: Is there anything that could be intentional about this 
>> apparently random spacing? Can I change it to 16mm from note 88 to 66 and 
>> 20mm from 66 to 30 without adverse effects? If there are adverse effects, 
>> what would they be?
>
> I'm not sure anyone can say for sure one way or another, but I think the 
> low tenor spacing is so wide to compensate for the low angle of the string 
> line to the bridge down there, and minimize the amount of wood removed by 
> notching. I don't see any acoustic or structural benefit, but from a 
> practical perspective, it would be easier and quicker to notch by hand. I 
> use 18mm spacing, with a little narrower unison, in the top section, for 
> #7 pins. Switching to #8 below the top section, the unison goes to the 
> width used for the rest of the bridge. For the #8 pins, I have three row 
> spacings - 16mm, 18mm, and 20mm. Where the back row of the higher unison 
> interferes with the front row of the lower one, I'll use either the 16mm, 
> or 20mm to get around it. Otherwise, the rest is 18mm. The bass has #9 
> pins, with 18mm spacing. There's nothing magic about any of this that I'm 
> aware of, but this works well for me.
>
>
>> I have looked very closely at the scale of the plain steel wires and 
>> found that if I use the Wolfenden ratios for speaking lengths of octaves 
>> and semitones I can create an ideal scale from note 88 to 58 if I shorten 
>> the bridge pin spacing by the above amounts - it will give me the fudge 
>> room needed. Beyond note 58 to note 35 the tension is slightly low and I 
>> can raise it by about 1 to 2 pounds for every 1mm increase in speaking 
>> length and the shroter front to back bridge pin spacing will allow this 
>> change.
>> I have been told that I am splitting hairs.
>
> Well, yea, you probably are, but then how wide was the hair in the first 
> place? What's your "ideal" C-8 speaking length?
>
> Ron N
>
>