Let off

[Dave Nereson]

----- Original Message -----
From: Bradley M. Snook <bsnook@pacbell.net>
To: <pianotech@ptg.org>
Sent: Sunday, April 07, 2002 9:53 PM
Subject: Re: Let off


>  . . .  what is
> wrong with setting the let-off as high as possible?. . . . Isn't closer
better? Just as long as the hammers
> don't block the strings. I really don't get the 'three times the thickness
> of the core' thing. That seems like a lot of lost power and control. Or is
> that just a good 'standard' for pianos that are never regulated?
>
> Bradley M. Snook

    I too, always thought let-off should be as close as possible.  And in a
finely-regulated concert situation, it should be.  But a few times I have
regulated old actions, setting the let-off a little too close.  Then after
the jacks have compressed the let-off punchings in their new positions,
hammers can start blocking.
    Also, when Yamaha came out with the "silent piano" feature of their
upright Disklaviers, they discovered they could have let-off at about a half
an inch and it didn't affect power and control all that much.  Not for 95%
of piano players, anyhow.
    The core of the lowest bass string on a 9' Steinway is #27 wire, which
is .067" in diameter.  Three times that is .201", a little more than 3/16",
but not quite 1/4".  That seems a bit wide to me.  The reason for setting it
wide is supposedly so the string can't vibrate against the hammer when the
hammer is held up close to the string by the repetition lever.  The only
time this is the case is after a very soft blow -- so soft that the hammer
didn't go into check.  In that case, the string wouldn't be taking much of
an excursion unless this very soft blow immediately followed a very heavy
blow, which might happen once in a blue moon.
    I dunno, I usually set let-off in the low bass at about the thickness of
the whole string,  and taper it up to about 1/16" in the treble.  1/32" is
getting too close to where a hammer could block on certain types of blows,
in my opinion, especially if the let-off button has recently been turned,
has new felt, has springy felt, or, as someone else said, if the hammer
shank is a bit rubbery, or if the keyframe isn't perfectly bedded, . . .
    --David Nereson, RPT, Denver