scaling question

[Ron Berry]

>I have an upright piano (a Dyer & Hughes, made in Maine) that I am
>restringing. The existing scale uses no half sizes.  I think I'd like to
>improve the scale by smoothing out things with the half sizes.
>My question is how do I determine where to make the changes.  Whether this
>involves a lot of string formulas and/or computer run programs, and whether
>this is likely to make a big enough difference to be worth the bother.  The
>existing scale is:
>
>13-----(8 unisons)
>14-----(6 unisons)
>15-----(6 unisons)
>  ---break---
>16-----(8 unisons)
>17-----(6 unisons)
>18-----(8 unisons)
>19-----(8 unisons, 2 on treb. side of break, 6 on tenor)
>20-----(6 unisons)
>21-----(4 unisons)
>
>60 unisons
>
>My first thought was to simply divide each size in half, but I run into a
>problem when it comes to the hitch pin arrangement in sizes 14, 15, 17, and
>20.  The old stringing was straight forward with no single strings.  If I
>divide a section of 6 unisons of a size into 3 and 3, I end up with an odd
>number of strings, so it seems that things won't work out so easily.
>Any help would be appreciated.  If anyone wants to help me out on this, I can
>furnish more information if need be.  Thanks
>

To really make any big changes you would definitely want one of the computer
programs beacuse there are at least 3 variables you want to watch as you
make changes.  I would say that adding half sizes up in the top part of the
piano won't really make enough difference to get too involved with it.  The
place where you can sometimes make a big change is at the bass-tenor break.
Most often that involves adding some more wound strings on the tenor bridge.
You can't make those kinds of changes without all the formulas or a computer
program.  The notes that have 8 unisons would be easy to add half sizes, but
I wouldn't go adding hitch pins just to add half sizes to the other notes.
Because the string scaling is only one part of the overall scaling of a
piano (hammers, soundboard, ribs, etc)  I would suggest that you only
consider rescaling when you hear problem.  Classic examples of scaling
problems are found at the break in an Acrosonic and in the early versions of
Yamaha GH1 (They have since added some wound strings on the tenor bridge).
The problem is that the first plain strings are too short and so they have
to be made thicker to get enough tension which then make their inharmonicity
soar. The highest bass strings usually have too little inharmonicity which
make for tuning problems across the break because of the different
inharmonicities.

Ron
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Ron Berry, RPT (Registered Piano Technician)
ronberry@iquest.net

Check out the Piano Page at http://www.prairienet.org/arts/ptg/homepage.html
for some great information and links about pianos!
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