20 tons of tension

[Delwin D Fandrich]

Clyde Hollinger wrote:

> Friends:
>
> As I was tuning a late model Schimmel studio piano today I noticed it
> had no back posts, really no back at all that I could see, other than
> the soundboard and ribs.
>
> Which got me to wondering -- how much of the 20 tons of tension is
> usually on the back and how much is on the plate?  Only once before did
> I see a vertical piano without back posts, an old upright.  I also
> remember about 20 years ago a salesman pointing out the rather thick
> back posts on Everett studio pianos as an indication of their high
> quality (I knew much less about pianos then than I do now).  How
> important are those posts really?
>
> Clyde Hollinger (who is getting tired of adding RPT Lititz PA)

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Clyde,

It depends on the specific design.  Many designers have done this over the
years:  Bush & Lane, George Steck, Mathushek (sp?), Rippen, Knight, Schimmel,
Yamaha, Kawai, to name just a few.  One of the best sounding (old) vertical
pianos I've ever seen was a Geo. Steck with no backposts rebuilt by a friend of
mine.  (I confess, I designed the soundboard, ribs and stringing scale for the
piano.  The new design used one of my impedance bars.)  Even without the new
soundboard design, this was an outstanding piano.

Schimmel vertical pianos are generally regarded as excellent pianos, both in
terms of performance and stability.

It all depends on the way the plate is designed.  Some plates, such as those
used in the Baldwin vertical pianos, would break long before reaching scale
tension.  (This is not a criticism of these plates -- they are designed to share
the load with the back assembly.)  These plates probably weigh half as much as
the Schimmel plate.

Several things have to be considered when leaving out the back post assembly.
    1)    The plate is going to have to be heavier and the casting is going to
be more complicated.  Usually it means designing a full parameter plate.  You'd
better be working with a good plate foundry.
    2)    Mounting the soundboard solidly can be a problem.  For good sustain it
is important that the soundboard be well supported.  This is easy to do with a
back assembly, somewhat more difficult without one.  It is usually solved by
making a frame for the board and bolting that to the back of the plate.  As long
as it is well designed and engineered, this can work very well.  All things
being equal, you should not be able to hear the difference between the two
designs.
    3)    Mounting the sides can be tricky.  Normally the sides are glued to the
back assembly.  Obviously, if there is no back assembly some other method must
be devised.  Usually they are bolted to the plate.  Of course the sides of the
plate are not naturally square so some type of shimming must be devised.
    4)    The plate is sometimes, though not always, mounted further back in the
case, so the rearward bias of the center of gravity can be a problem.  The piano
might be "tippy."  There are several ways of overcoming this problem.
    5)    Marketing might be a problem.  American buyers are used to seeing
those big heavy backposts out there.  In some cases I think that there have been
imported pianos that could probably survive quite nicely without backposts that
have been given three or four very thin posts for just this reason.  If the post
is less than 25 or 30 mm thick, it's pretty much worthless from a structural
standpoint.

There are, I'm sure, more points of consideration.  This just scratches the
surface.  The bottom line is that very good, structurally sound and acoustically
viable pianos can be built either way.

Regards,

Del