Counterbearing (& Kowmung report)

[Delwin D. Fandrich]

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Re: Counterbearing (& Kowmung report)
  ----- Original Message -----=20
  From: Ron Overs=20
  To: davidlovepianos@earthlink.net ; Pianotech=20
  Cc: tourism@oberon.nsw.gov.au ; Hans Guldberg ; Barbara Morgan ; =
suspence@ozemail.com.au ; John Spence ; Peter Dickson ; Robert Smith ; =
llobster@ozemail.com.au ; santon@ozemail.com.au=20
  Sent: Sunday, March 30, 2003 4:00 PM
  Subject: Re: Counterbearing (& Kowmung report)


  Hi David and all,


  I've just returned from a weekend away at the Kowmung Music Festival =
(held each year in the picturesque Blue Mountains town of Oberon, 2 =
hours drive west of Sydney). Visiting artists the Kutrowatz Duo (Eduard =
and Johannes) from Austria were again most impressive. Similarly =
impressive performances were given by a number of Australian pianists =
and instrumentalists over the two weekends of the festival. On Sunday 22 =
the Sandy Evans quartet performed in the first jazz concert to be =
featured at a Kowmung Festival. Her outstanding artistry on Saxaphones =
was complimented by drummer Toby Hall, bassist Lloyd Swanton and pianist =
Allister Spence, with guest artist Peter Jenkin on bass clarinet. For =
many Kowmung patrons, this performance would have been their first =
attendance at a jazz concert. The standing ovation they gave the quartet =
would tend to suggest that jazz will become mainstream, alongside =
classical, for future Kowmung Festivals.


  For those who may be interested, the English language version of the =
Kutrowatz Duo website can be found at;
  http://www.duokutrowatz.com/English/english.html


  The Kutrowatz Duo performed on our piano no. 3 and a B=F6sendorfer =
225. The original plan was that they would use two of our pianos, but =
since we are still building piano 4, we hired the B=F6sendorfer 225 form =
the ABC Ultimo Center. While Eduard and Johannes are most proficient and =
sensitive classical pianists, they seem equally capable of turning their =
hand to jazz repertoire when required. Their two piano transcription =
performance of Dave Brubeck's Blue Rondo A La Turk was most =
exhilarating. Although it was not included in the programme, neither was =
the heavy rain on the tin roof of the Middle Creek Cattle shed. In the =
true spirit of professionalism, they decided treat the audience of 300 =
with a work which would cope with the poor signal to noise ratio. The =
audience responded to the outstanding duo brothers with a standing =
ovation.


  At 6:58 PM -0800 29/3/03, David Love wrote:


    I meant to ask one other question.  My recollection is that the =
ideal angle leaving the capo section up to the counterbearing bar is 17 =
degrees.  I'm not sure why that number sticks in my head--I may have =
gotten it from a piece that Ron Overs wrote, or I may be mistaken =
entirely.


  I believe that, where possible, the counterbearing angle behind the =
agraffe section should not exceed fifteen degrees or be much less than =
10. While it is possible to set the counterbearing behind the agraffes =
to be higher than 15 degrees without risking wire breakage, it will tend =
to accelerate the deformation of the agraffe.

This has not been my experience. (See my Journal articles V-bars, =
Pressure Bars and Duplex Scales, June 1995 and Front Duplex Stringing =
Scales, August 1995.)  There doesn't seem to be any perfect answer to =
this question. The string deflection angle is a function of the string =
segment length between the V-bar and/or the agraffe and the first =
counterbearing bar. If this string segment is very short--as in the =
typical vertical piano design--the string deflection angle can be rather =
shallow (5=BA or 10=BA may be adequate. If this string segment is =
longer--say something of 35 or 40 mm--the string deflection angle is =
going to have to be some greater. In this case a deflection angle of =
20=BA or 25=BA will be required.


   This will lead to premature 'string noise'. Furthermore, while it is =
desirable to have quite a short string segment between the agraffe and =
the counterbearing bar/felt, the tendency of a great many manufacturers =
is to overdo it. If the segment is made too short, it will tend to 'shut =
down' the freedom of the speaking length. I ran some experiments back in =
1995 which proved this to my satisfaction. Now while I'm not prepared to =
publish details of this on the Pianotech list, for those of you who are =
interested, conduct your own experiment to draw your own conclusion. =
Just remember that human flesh has high hysteresis loss characteristics =
(quite a number of default 'experiments' are taking place elsewhere in =
the world as we speak). So if you are tempted to hold a test piece of =
metal in your hand, you will need to insure that you de-couple the =
hysteresis loss.
This is always a balancing act. Short string segments work just fine =
with rather shallow string deflection angles. This is the arrangement =
typically found in vertical pianos and is one which works quite well. =
Problems arise when the shallow deflection angle is coupled with longer =
front string segments as is found in the Steinway (and clones) vertical =
designs. And when steep deflection angles are used with short front =
duplex string segments.

=20
       What is the maximum angle in the capo section that you can get =
without risking breaking strings.


  I would not recommend over fifteen degrees in the capo sections.
It depends on the length of the front duplex string segment. Typically, =
in a grand piano, this is going to be somewhere in the vacinity of 25 to =
35 mm and a string deflection angle of somewhere between 15=BA and 20=BA =
will work quite nicely.

We have not found deflection angles up to about 25=BA to be any problem =
when used with the extremely long front duplex string segments sometimes =
found in oddly designed pianos.


    I would assume the materials would make a difference too.  In the =
capo section where the strings bear against cast iron, I would assume =
that they would tolerate less of an angle than where the strings where =
redirected by softer brass agraffes.


  I'm not so sure about this, but I have not conducted experiments to =
prove it either way. However, once the piano wire has cut a significant =
groove into a brass bar or agraffe (and it will), the friction can be =
considerable, regardless of the base material softness.
"Brass" agraffes are not always made of "brass." For some time Steinway =
used a material called (if memory serves) Silnic. This is a silicon =
bronze alloy also containing a small amount of nickel. The material is =
actually somewhat harder than the typical gray iron used in piano =
plates. It is an excellent material and the agraffes would have been =
quite good if the machining had been just a bit better.

Del

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