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Michael and all,
>This close-up shows a metal shim which fell out=20
>of a place between the "dam" and the underside=20
>"nose" of the plate on my S&S 'A' . I stood it=20
>on the soundboard near its normal location. I=20
>can only hazzard its use as being intended=20
>to convey the pressure of the fully strung piano=20
>from the web to the dam and sound board. Any=20
>other ideas? It is about 1/4" thick.
Take a look at the plate strut shown in your=20
image, and note its vertical position relative to=20
the string-plane of the strings. The string plane=20
will run between 35 - 50 mm below the centreline=20
of the plate strut. Clearly, the total string=20
tension ( which will be between 16 - 18 ton for=20
an A) will be trying to bend the struts down at=20
the strut ends and up in the middle. Steinway=20
have chosen to use quite small struts in this=20
design, and this bowing of the struts will be=20
tend to be worse with their instruments than say=20
a B=F6sendorfer, which has much deeper and heavier=20
struts (B=F6sendorfer don't use a horn system). The=20
horn - wedge - tension collector system allows=20
the back beams and case structure to take some of=20
the load on the opposite side of the string=20
plane, relative to that of the struts. This will=20
help to prevent the bowing of the struts, stiffen=20
up the whole assembly, and hopefully, result in=20
better tuning stability and sustaining tonal=20
qualities. A Steinway plate might still survive=20
the string tension if the horn wedge was left=20
out, but I'd be a bit nervous about its long term=20
prospects, if it managed to get to pitch without=20
collapsing.
> You can see the gap into which it fits. It was=20
>nor glued in place - should it be?
No
> I doubt it as the glue would give a deadness and tend to be elastic in=
situ.
>Now all the strings are off, the soundboard=20
>gives a healthy bass "thwummm" of G# 0 @ A=3D431=20
>when tapped with a fingers on the bass bridge.=20
>Having vacuumed off all the debris of ninety=20
>years I am about to gently wash the plate and=20
>soundboard with a damp cloth from a bowl of=20
>water with washing up liquid in.
Now that you've got it unstrung, I presume that=20
you will be lifting the plate to see what's=20
happening with the board.
A couple of compression ridges are visible in=20
your image, to the right of the horn wedge.
Have a look at the following graphic I've drawn for you.
=46or a piano as old the one you're dealing with,=20
there will be no way that the crown remains in a=20
healthy condition. I know that some believe this=20
is possible, but if you make up a plywood=20
straight edge, with a cutout for bridge=20
clearance, you will see immediately what I am=20
referring to.
Almost all 90 year old boards will have collapsed=20
to conform to the image graphic above. There will=20
usually be some residual crown either side of the=20
bridge, with a 'valley of collapse' running right=20
along the line of the long bridge. You can=20
usually place a straight edge under the bridge,=20
on the under side of the board, and it will rock,=20
showing that the crown has turned inside-out=20
under the bridge. You can also try this on new=20
pianos on the showroom floor, only to find that=20
there is often an early onset of the syndrome.
Older boards in the second top string section=20
will usually collapse as per the lower image in=20
the graphic shown above. Again, using a plywood=20
straight-edge, this is easy to see. Now they'll=20
be some who'll swear and declare that their 100=20
year old 'wonder piano' still sounds as good as=20
the day it was made even though the sound board=20
might have sunken a bit. Well, I doubt that this=20
is possible. While older instruments may still=20
sound somewhat like a piano, they will in almost=20
all cases sound significantly inferior to what=20
they once were.
Well there you go Michael. There's a little=20
project for you. Knock up a plywood straight edge=20
during the week, and pull the plate next Sunday.
We've currently got a little project of our own=20
going on at the workshop, doing a 'mouth-to-mouth=20
job' on a collapsed sound board for a retired=20
client. The patient in question is a Howard=20
grand, which by the look of it was made by=20
Challen of London. It was a bit short and 'honky'=20
before we de-strung it, so I was already=20
suspicious of the board. It turned out to be dead=20
flat with a few small checks, which got=20
significantly worse once we jacked it to what we=20
judged to be an appropriate crown (I was a bit=20
concerned that we might push the board of the rim=20
altogether, but it held despite the creaking and=20
groaning). While the crown is jacked we're giving=20
it a heavy coating of epoxy on each side to=20
produce of sort of epoxy/floppy-spruce sandwich=20
(you never know, it might sound like a Hamburg D=20
after all that epoxy - though I'll try to keep my=20
expectations somewhat tempered). We'll set it up=20
with just a small amount of positive bearing to=20
see what sort of 'twilight performance' we can=20
get out of it (there was no bearing anywhere at=20
the time of pull-down). I gave David Love a call=20
about the epoxy treatment, since I hadn't done it=20
for over twenty years, and I remembered him=20
talking about the procedure on-list some time=20
back. As usual, David is a wealth of knowledge=20
and was very helpful. We're also gluing a new set=20
of bridge pins into the 'sad' bridges with West=20
System epoxy.
Here's a few images of the process under way,=20
with two showing the jacking operation.
Note that this piano has a sensible cut-off=20
arrangement, whereby the inner rim and cut-off is=20
bent as one piece. Very nice. The sound board is=20
grossly under-engineered, but its going to have=20
to stay that way. Both the piano and its owner=20
are in retirement. This work might allow to piano=20
to be reasonable company until she, ie. the=20
owner, leaves this mortal coil.
The 'jack' ends are made from free machining 5/8"=20
hexagonal stock which is tapped with a 3/8"=20
internal thread. Threaded rod (which is cheap to=20
buy) can be cut to the desired length for jacking=20
any piano. Two 5/8" or 16 mm spanners can be used=20
for adjusting the jacks
Now I must get to work. I got up at 5 am to leave=20
home around 6.30, and its 7.45 already. Aaaaah -=20
the distractions of life. Now Michael - about=20
that board?
Ron O.
--
OVERS PIANOS - SYDNEY
Grand Piano Manufacturers
_______________________
Web http://overspianos.com.au
mailto:ron@overspianos.com.au
_______________________
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