Bridge design

[Overs Pianos]

---------------------- multipart/alternative attachment
>Del wrote:
>>  This theory also explains why
>>  so many builders were reluctant to put a dog-leg into the bridge at
>>  plate/scale breaks to maintain good scaling. They were not just being cheap
>>  or negligent.
>
>Ahhhhhhhh. I have a 5' 10" 1900 Bechstein awaiting rebuilding and 
>the long bridge has absolutely NO HINT of a dogleg at any of the 
>breaks. The curve is perfectly consistent. I had noticed that a long 
>time ago and felt surprised that a manufacturer like Bechstein would 
>be so cheap as to not go the distance of putting on a proper dogleg. 
>Now I know that being cheap is not likely the answer. Thanks.
>
>Terry Farrell

That just depends what their design priorities were since, when 
there's no dog leg, the tension percentage adjacent to the plate 
struts will be a complete disaster (I have the 6' scale in my 
collection so I know this to be the case). The top break can be laid 
out with good scaling and virtually no dog-leg by using the width of 
the bridge top, running the bridge pin field to the back on treble 
side of the strut and vice versa on the bass side. But the second 
break down will definitely be a scaling problem unless a dog-leg is 
incorporated. Although this will involve quite a deal of extra work 
when shaping up a bridge, it definitely does yield tuning stability 
benefits if the scale is not compromised across the struts.

The Bechstein 6' and 5'10" scales are further examples of instruments 
which were designed with the last note on the long bridge at note B27 
- a very poor choice (113 cm speaking length on the 6' piano) for a 
piano of this length. I just can't understand why such instruments 
are still being built with such ordinary scale designs. Its just a 
waste of metal, wood and felt.

I just took delivery of a brand new Samick SPG-158 for repair (thanks 
to a careless forklift driver). This piano, with its new wide-bodied 
back, was being heralded as a new and more advanced design from 
Samick. What a frustrating instrument! It would appear that the 
designer just didn't have the first clue when it comes to scaling the 
first instance, and bridge placement on the board in the second. 
Furthermore, the bass bridge is suspended for its entire length, and 
the low end of the treble bridge has been placed so far out on the 
body of the board that it sounds like a duck just before it crosses 
over to the bass bridge. The back scale on the low bass is too short 
(45 mm) with a wider than necessary hitch riser (35 mm). This, in 
combination with an English eye which takes up 23 mm of the 45 mm 
back scale is guaranteed to ensure that the low bass virtually 
doesn't exist. The front duplexes are, as usual, too long and the 
counter bearing angle in the mid section is excessive. The scale has 
a hockey stick low end on the treble bridge with bichords for the 
last four notes on the same bridge. While the sound board panel is of 
solid spruce, already there is considerable compression adjacent to 
the sound board panel joints, and the maple bridges are not quarter 
cut. Wow, what a giant leap 'forward' to 1920.

I very much suspect the designer's brief might have been, above all 
else, to design a new piano with a wide body (there seems to be an 
obsession with wide bodied designs ever since the Bostons turned up - 
but they all seem to suffer from poor bridge placement from what I've 
seen). What on earth is the utility of a wide body design, if the 
many other critical design issues that should be addressed in a 
modern design were not understood? While the general level of finish 
was a distinct improvement (apart from the fact that damper wire 
guides were drilled out of position and the wires are buzzing on the 
strings), it not much use if the piano doesn't produce a satisfactory 
tone?

Ron O.
-- 

        OVERS PIANOS
Grand piano manufacturers
________________________

Web:   http://www.overspianos.com.au
Email: mailto:ron@overspianos.com.au
________________________
---------------------- multipart/alternative attachment
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/pianotech.php/attachments/5f/46/04/82/attachment.htm

---------------------- multipart/alternative attachment--