C88 Hammer Position/SPR

[Tony Caught]

----- Original Message -----
From: "Delwin D Fandrich" <pianobuilders@olynet.com>
To: <pianotech@ptg.org>
Sent: Wednesday, November 14, 2001 3:26 AM
Subject: Re: C88 Hammer Position/SPR


>
> ----- 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?

Since the modern piano has not basically changed since 1890 "in days of
past" In the days when pianos were built with wooden frames, then with part
iron frames, then as the tension on the piano increased more attention was
given to where the hammer struck.
is in most cases prior to 1890.  However a few pianos have slipped by even
in modern times with inncorrect SPR's as I am sure you will agree.


I also have measured many pianos to calculate the SPR and agree that they
are all over the place. Possibly because there iron casting methods were not
that great and also possibly because most of the pianos I measured were
uprights of the middle price range.  We have to remember that there were
some 5,000 piano manufacturers in the late1800's and most of them did not
produce Bechsteins, Steinways or Bluthners. There was also a gentleman of
repute in Canton, China, who, in 1984 patented (in China) the raising of the
strike point in the upper treble of the piano from 1/8 SPR to 1/19 SPR.
>
> 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
>
My main point in writing my muddled reply to the original question was that
the advise given (correctly) was 1/8" from the top but not why 1/8" from the
top.
What I am trying to say is "First things first. SPR"
Then why! should have been the next question. Then what is the difference in
hitting in a 1/8th SPR and a 1/7 SPR and how does it affect the tone and
carrying power of the piano.