seeking clarity, was relevance of bridge pin spacing

[Gene Nelson]

Not quite sure how to ask this question:

As Frank and Ron will position front bridge pins to conform to their scale 
design, then vary the rear pin positions as required to avoid pin 
interference in the bridge core and use spread sheet to accomplish this, 
this leaves me a bit confused while trying to make sense of what I am doing. 
Not confused about the math.
If I change the front to rear bridge pin spacing using my jig/patterns (I 
can design them to maintain consistent string offset) and strive to position 
the front pins for the same scaling reasons, is this not the same thing? In 
my case both front and rear pin positions would be shifted from their 
position on the original bridge.  Maybe in Frank and Ron's case the hitch 
pins have not been positioned yet? Am I missing something?

Regarding scaling I use PScale. When I plug in my ideal scale with 53mm at 
note 88 the tension is flagged as high (above 66% brake point) for the top 3 
or 4 notes using .032 wire. This piano had no evidence of broken strings 
(originals were old and rusted - probably original). It should be safe to 
stick with this scheme? Going to a larger wire size does not appear to help 
nor do I think it would be a good idea. When Ron refers to "smaller radiused 
hardened bars" he is refering to capo and a pressure or bearing bar above 
it?

Gene
----- Original Message ----- 
From: "Ron Overs" <sec at overspianos.com.au>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Monday, December 31, 2007 9:27 PM
Subject: Re: C88 length, was relevance of bridge pin spacing


> Hi all,
>
> The nominal C88 standard for the Hamburg D used to be 53 mm. They appear 
> to have reduced their C88 length to 49 mm in their latest iterations 
> (since at least 2000). I'm rebuilding a circa 2000 piano at the moment - 
> in which we're completely re-scaling the treble sections.
>
> Their latest Ds are heavier in the hitch plate area (which I prefer), and 
> the scale is fully revised to be shorter than previously, but still does 
> not conform to an accurate log-style scale. While overall it looks to 
> conform more or less to log style, there are significant note to note 
> variations. The breaking percentage with the new scale is even lower than 
> previously at note F21. So I don't suppose we can expect to see a scaling 
> improvement in the clones any time soon.
>
> For all of the Overs 225 pianos we have produced to date, we have used 53 
> mm for C88. This length does put the wire under considerable stress when 
> using smaller radius hardened bars. I've had a few more string breakages 
> with this speaking length than I would like, and I suspect that this may 
> be why S&S have taken their speaking length on the D back to 49 mm.
>
> Frank's post regarding spacing concurs generally with my own practice. I 
> have a spreadsheet which is incorporated in the overall scale design 
> spreadsheet, which calculates the rear pin row offset with respect to the 
> XY location of the front row pins. This allows us to alter the front/rear 
> pin spacing to ensure that there is no intersection of the bridge pins 
> within the bridge.
>
> I also note that some piano 'designers' have been known to shift the front 
> pin row instead of the back pin row, to avoid intersection conflicts. They 
> should be referring to some basic piano-design 101 rules here. The 
> disastrous effect this practice has on tunability and stability should be 
> more than obvious.
>
> Happy new year,
> Ron O.
>
>>  >  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 me, note 88 is always 54mm, regardless of the size of the piano, but 
>>then I am not trying to make everything fit on an existing bridge.  I am 
>>always starting out with a blank sheet of paper (i.e. cyber space).
>>
>>Frank Emerson
>
>
> -- 
> OVERS PIANOS - SYDNEY
>    Grand Piano Manufacturers
> _______________________
>
> Web http://overspianos.com.au
> mailto:ron at overspianos.com.au
> _______________________
>
>