seeking clarity, was relevance of bridge pin spacing

[Ron Overs]

Gene and all,

>. . . In my case both front and rear pin positions would be shifted 
>from their position on the original bridge.

Correct - the front rows are adjusted for scale correction, while the 
rear rows are adjusted to achieve an optimal layout while ensuring 
front/rear-row pin clearance within the bridge body. As Ron N 
mentioned in a previous post, its better to make the spacing 
wider/longer in the low bass, particularly in long pianos where the 
angle between the strings and bridge line converge more. It reduces 
the length of the bridge notching, and there's no down side.

>   Maybe in Frank and Ron's case the hitch pins have not been 
>positioned yet? Am I missing something?

The re-scaled layout is derived using a rubbing from the original 
bridge as a starter guide. String spacing errors are corrected at the 
same time as the new speaking lengths are marked out on the rubbing. 
A thin veneer strip is placed between the rubbing and the original 
bridge. After the new scale and spacings have been finalised, the new 
bridge-pin hole positions are punched through to the veneer strip 
below, which is used as a template for drilling the new bridge cap, 
and is retained for all future rebuilds of this iteration of the 
model. Here's a link below to an image taken from our recent 
re-scaling of a newish Hamburg D (2000 manufacture).

http://members.optuszoo.com.au/kristieovers/chrstch7.jpg

The new lines for the front and rear pin rows can be seen against the 
original rubbing. Notice that the speaking length of the note 
directly under Wal's right hand is being shortened by approx 1 cm. I 
left the original C88 at 49.5 mm, and lengthened F21 out from its 
original 1823.5 mm to 1860 mm (on the older Ds, F 21 was nominally 
1830 mm). We found that there were quite dramatic speaking length 
adjustments required from around the middle of the temperament area 
down, which explains why the chromatic thirds between G35/B39 and 
G#36/C40 are always problematic when laying a temperament in the D. 
The re-scaled bridges make the job of laying a smooth temperament 
very much easier. Surprisingly, the new version of the D scale is no 
better than the first version we re-scaled on a circa 1962 piano, 
back in 1992.

Re-scaling these pianos with a transition bridge is a much better 
rework (as Ron N has done), but in this case the piano is only seven 
years old, so I decided to keep the original bridge root and 
soundboard as an economy measure.

Below are some image links, taken from a recent rebuild of a 1992 Steinway D.

http://members.optuszoo.com.au/kristieovers/st.mary's1.jpg
An overview of the piano

http://members.optuszoo.com.au/kristieovers/st.mary's2.jpg
Close view of the front duplex bars. In this case the client wanted 
to retain the original bars, so the originals were reshaped and 
hardened.

http://members.optuszoo.com.au/kristieovers/st.mary's3.jpg
View of the base section, showing the EN plated agraffes. The base is 
revised, but with the same speaking lengths.

http://members.optuszoo.com.au/kristieovers/st.mary's4.jpg
Close view of the new multi-laminated bridge cap. This cap has seven 
layers of 0.5 mm rock maple. The rear aliquot blocks are packed 
slightly higher to fine tune the downbearing in this instance.

Ron O.

-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron at overspianos.com.au
_______________________
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