C88 Hammer Position/SPR

[Delwin D Fandrich]

----- Original Message -----
From: "Tony Caught" <caute@optusnet.com.au>
To: <pianotech@ptg.org>
Sent: November 10, 2001 12:47 AM
Subject: Re: C88 Hammer Position


>
> The bass from A0 could be at 1/7 to 1/9 of the speaking length, depending
on
> the tone that that particular designer wanted. (American pianos were
mostly
> 1/8)

So far, so good.


>
> Even so, tis the treble we are talking about.
>
> In those days of past it was acceptable to set the strike point at 1/8th
on
> C88 and 1/8th on A0 then draw a straight line, then place your bridge at
> 7/8th the length below and the upper bridge or aliquot thingee at 1/8th
> above.  This is in design and casting frame and fitting bridges etc.)  Now
> the action is fitted in relation to the hammer hitting the strike point
and
> every part has exactly the same travel as the keyboard is parallel to the
> strike line.  Then you find that you want a brighter sound in the upper
> treble, so you bend the hammer shanks up to find that nice sweet point.

But here, I wonder...in what days?

I don't think this was done much, if at all. Certainly by 1900 it was well
understood that while a strike point ratio (SPR) of 1/8th was good for the
bass and tenor, it had to be altered for the treble. Early writers spoke of
a SPR at C-88 of between 1/12th up to 1/20th of the speaking length. If
memory serves, Wolfenden mentioned a SPR of 1/16th in the first edition of
his book.

>From there the SPR will slide down toward 1/8th (+/-) and get there
somewhere about the middle of the scale. I say 'about' because I've measured
enough old (and new) scales now to realize many pianos don't come all that
close to this so-called ideal. Especially across the bass/tenor break it is
not uncommon to find substantial discontinuities in the SPR. Either it
wasn't/isn't considered all that important by some designers/builders or
they simply were/are really careless.

As well, every designer seems to have his/her own technique for getting to
this point--and this point is not clearly defined. Nor is it particularly
important. It's pretty hard to tell the difference between a SPR of 1/7.5 vs
one of 1/8.5 on longer strings unless you run into this variation across a
bass/tenor break. Then it can contribute to the general voicing problems
that exist through this area. But, in general, selecting the 'correct' SPR
is most critical at C-88, becoming considerably less so by mid-tenor and
below. So, consistency is important, but the absolute numbers--within
reasonable limits--are not.

Personally, on a new drawing I start with a SPR of 1/14th at C-88. With a
speaking length of 54 mm the centerline (c/l) of the hammer will
(theoretically) strike 3.8 mm below the V-bar c/l. If you can actually find
either the V-bar c/l or the hammer c/l, that is. In real life, both can be
some elusive.

Anyway, if you start at this point you'll have a bit less bending to do.

Del