Piano Rims (rambling post)

[Farrell]

Oh, boy. What a bunch of great questions. I have a few ideas, but being that
I am certainly no expert, I will sit by the sidelines anxiously awaiting
input to this series of questions. What fun!

Terry Farrell

----- Original Message -----
From: "Phillip L Ford" <fordpiano@lycos.com>
To: <pianotech@ptg.org>
Sent: Friday, December 28, 2001 2:48 AM
Subject: Piano Rims (rambling post)


> Buyer Beware:  Rambling Post
> Caution:  Many questions are posed - none are answered.
>
> I've been pondering some things I've seen posted here over the past few
weeks
> along with a few (non-original I'm sure) thoughts of my own.
> Among them, in no particular order:
>
> Ron N - several links related to bamboo
>
> Del F - thoughts about floating soundboards in the bass region
>
> Del F - comments on Chickering's undercut or relief of some of their rims
in the bass region
>
> Stephen B - comments on older makers who deliberately made rims lighter in
an attempt
> to 'tune' the flexibility of the rim-soundboard system
>
> Del F - rims play no part in maintaining soundboard crown as soundboards
are so
> compliant (is that the right word?) relative to rims
>
> Mason-Hamlin website - rim is absolutely essential in maintaining crown
>
> Various posters - discussions of waves, vibrations, etc. ad nauseum
>
> Conventional wisdom that rims should be massive to provide some sort of
solid inert
> support for the soundboard
>
> My own observations that many pianos that I like the sound of have massive
> rims (both heavy and stiff)
>
> My own observations that many pianos with light or flexible rims have less
than
> stellar sound
>
>
> To come somewhat to the point,
> I've been pondering whether rims should be massive or stiff or both and
why?
> Should the mass and stiffness be uniform or should it vary and why?
>
> Some time ago I suggested that bamboo might be an interesting material for
piano
> rims.  Bamboo has very high strength and stiffness relative to its weight.
If you take
> a maple rim as the standard then the bamboo rim could be stiffer and
stronger while
> being lighter.  Would this be a good thing?
>
> My experience is that the pianos I like have massive rims.  However, if
you look at
> wood property charts for American hardwoods you'll notice that density and
stiffness
> go hand in hand.  If you pick a denser wood you get a stiffer wood.  So
maybe the
> pertinent thing about the pianos I like is that they have stiffer rims,
not more massive
> rims (the density is perhaps inconsequential).  Also, the pianos with less
massive or
> stiff rims that I don't tend to like tend to be low quality pianos.
Perhaps the reason
> that the sound is less than stellar has to do with the design and quality
of fit and finish
> rather than the fact that the rim is not massive or stiff.  Perhaps the
lightness or flexibility
> of the rim is coincidental.
>
> If the rim needs to be massive, then why?  I've heard it said that it is
> 'to reflect waves' back into the soundboard.  But I've also seen a few
posts lately
> that suggest that waves don't travel in the soundboard.
>
> If the rim needs to be stiff, then why?  Is it to resist the tendency of
the perimeter of
> the board to move outward or inward as the board vibrates?  If the board
is so much
> more compliant than the rim then how does having a stiff rim help you?  Is
it to
> prevent the tendency of the perimeter of the board to move up and down as
the board
> vibrates?  If so it would make more sense to make the rim deeper rather
than thicker,
> which seems to be contrary to accepted practice.
>
> If the rim needs to be stiff then why float the board or make undercuts in
the rim
> at certain spots?  Apparently the rim doesn't necessarily have to be stiff
in these
> areas.  Maybe the rim should be stiff or heavy in some areas but not in
others.
>
> How do the rim braces fit into this? I've heard it said that they are only
there to
> keep the belly rail from rolling.   If the rim needs mass then the braces
aren't
> helping much.  You'd be better off putting the material into a thicker rim
and
> eliminating the braces.  If the rim needs
> stiffness then many brace configurations don't help much in certain
directions.  Many
> are good at increasing stiffness front to back but do almost nothing side
to side.
> Do you only want the rim to be stiff in one direction and not the other?
>
> If you want soundboard flexibility is it a good idea to thin the rim as
some of the
> old makers did?  It seems you would transfer energy to the rim which isn't
seemingly
> very efficient at transfering it to the air, but perhaps it is - there's a
fair amount of
> surface area there.
>
> Perhaps you could carry this to an extreme and have the soundboard resting
on
> a thin knife edge around the perimeter, as in a guitar or violin.  Why
would this
> be a bad idea?
>
> I'm interested in any thoughts or comments that you would care to share.
>
> Happy New Year.
>
> Phil F
>
>
> ---
> Phillip Ford
> Piano Service & Restoration
> 1777 Yosemite Ave - 215
> San Francisco, CA  94124
>
>
> --
> Click here for your very own create-a-date adventure from MatchMaker
> Go to http://ecard.matchmaker.com/dating.html