key levelling -- crown?

[Dave Nereson]

----- Original Message -----
From: Charles Neuman <piano@charlesneuman.net>
To: <pianotech@ptg.org>
Sent: Thursday, November 15, 2001 10:00 AM
Subject: key levelling -- crown?


> I just learned that when levelling white keys, some people put a small
> amount of crown in the key heights, maybe 1/32". What's the point of it?
> And does 1/32" really make any difference?
>
> The only reason I can think of now is that it might have some subtle
> visual effect. If it's some ergonomic thing, I would think it would be
> much more than 1/32".
>
> Charles Neuman

    I saw on some PBS program that the ancient Greeks noticed that a
perfectly straight line viewed from certain angles can appear to have a
slight slump to it, so they "crowned" the floor level and the steps leading
up to floor level of their temples, or at least they did on the Parthenon.
But reasons I've heard for
crowning the key level on a piano are 1) to counteract the faster
compression of the balance rail punchings in the middle of the keyboard, due
to more frequent use, and 2) on some pianos, the keybed is crowned, so the
key level has to be crowned to maintain uniform key dip.    --David Nereson,
RPT, Denver