soundboard springs

[Fred S. Sturm]

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    Here at UNM we have lots of Hamiltons with factory installed
soundboard springs. Very interesting. It seems there were problems with
the 30 or so instruments that were ordered when the building was built
(and never a one replaced since, of course), and they were sent back to
the factory. When they returned, they had bolts through the pinblocks
(five each, through the regular screw holes in the top of the web,
drilled through the back with nuts and washers), and soundboard springs
throughout. At least so I surmise from what I have heard and observed.
This apparently happened in the mid 60's.
    Anyway, the soundboard springs are compression springs that seem to
be automotive valve springs, and the way they are set up is as follows:
1) Metal supports made of 1/8" x 1" steel, each straddling a back post.
Hard to describe with words, but I'll do my best. There are four bends
in each support, so that there are "ears" sticking out on each side of
the back post, each with a spring bearing on it and the soundboard. They
are angled to follow the contour of the bridge.
2) The springs each have a tensioning device: It's basically a bolt and
a nut, but the bolt has a combination flat/broad head and a hex - kind
of like a bolt with a washer welded to the top of its head. The spring
is pushed towards the board with the nut. There is a washer between nut
and spring, and a broad washer with felt on the side toward the
soundboard that the spring bears against. There is also a rubber bushing
between threads and spring.
    Over the years, I have tended to remove these gizmos as I have come
to do more or less major reconditioning to the pianos. When I first
removed one, it was to see if I could tell any difference. I couldn't. I
think the tech who was here around that time saw those and decided to
adapt them to a few of the grands. I have removed all those over the
years, again without being able to tell a bit of difference.
    I'm not writing this with the intention of saying soundboard springs
won't work. My own take in my own situation is that they weren't needed
in the first place. And I'm not at all sure that springs that heavy are
appropriate. That same tech who I believe installed the springs in the
grands had his own notions about the need for crown, so he took pianos
with relatively flat boards, cut cracks parallel to the bridge,
extending halfway through the ribs, jacked up the board and put hardwood
wedges in the rib cuts, and shimmed the board. I've seen several of
these masterpieces, and they sure have lots of crown, but none has a bit
of carry or tone. Fortunately he didn't do it to any at the university.
    Anyway, maybe what I have described will be food for thought for
someone wanting to experiment.

Regards,
Fred Sturm
University of New Mexico

Richard Brekne wrote:

> Was wondering...
>
> The installation of these springs as I understand it is such that two
> beams are used as a support for a piece of something or another that
> will hold the spring tight against the panel / ribs at some point.
> What would be the advantage or disadvantage of mounting a stronge
> enough piece of steel  lengthwise parallel to the beams and attach at
> the rim and back side of the keybed / case area instead ?
>
> Or is this another one of these parcealip trees to bark under ?
>
> RicB
>
>
> Delwin D Fandrich wrote:
>
>>
>>       Del: The springs you mentioned in your April 2001 note.
>>      McMaster Carr, 4 inch compression springs.  I don't have
>>      the part number at hand, but I will later in the day -- if
>>      that matters.  No, I was just curious. Good luck. I'm
>>      looking forward to reading about your results. Del
>>
>
>
>
>
> --
> Richard Brekne
> RPT, N.P.T.F.
> UiB, Bergen, Norway
> mailto:rbrekne@broadpark.no
> http://home.broadpark.no/~rbrekne/ricmain.html
>

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