Capo bar revisited

[Overs Pianos]

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>Hi Lance,
>
>Thanks for the update and sorry to hear it did not work out to your 
>satisfaction. It is clear from previous discussions that there is no 
>guarantee all the cures mentioned will work. Regarding the capo, 
>sometimes we get lucky, sometimes not. I have been leaning towards 
>the school of thought that suggests good tone can be achieved 
>without the front duplex section ringing at a higher harmonic of the 
>speaking length. Yes, that would mean major rescaling for Steinway, 
>etc. (Not likely to happen :-) It seems to me that a lot of problems 
>could be solved by this design. Pardon me if I'm incorrect, I 
>believe Del has proposed this on the lists and in the Journal.
>
>Don

Don, Lance and all,

If you measure the front duplex lengths relative to the speaking 
lengths, of Steinway and Yamaha grand pianos in particular, you will 
find that both have attempted to set the front duplex lengths to a 
harmonic length of the speaking length, ie.  a 1/2, 1/3, 1/4, 1/5 . . 
. 1/10, 1/11  etc.  This practice is a sure-fire way to allow for the 
production of lots of string noise. Furthermore, most manufacturers 
do not harden their capo and duplex bars to prevent the strings from 
deforming the bar profiles - if indeed they bother to shape them 
properly in the first instance. Yamaha harden their capo bars but 
leave the front duplex bars soft (we know this because we have 
reshaped several late Yamaha piano capo bars and front duplex bar 
sets, and their capos are quite hard when removing metal with the die 
grinder tungsten burrs). Both capo and front duplex bars are capable 
of producing noise. Steinway Hamburg claim to be hardening their capo 
bars with a laser treatment, but an inspection of any modern Hamburg 
piano will reveal that their bars are being deformed very nicely by 
the piano wire, regardless of their claimed hardening process. When 
we harden the bars of our pianos there is no deformation of the bar 
from the string. Indeed, the strings can be aligned with ease 
throughout the service life of the piano, since they don't cut 
grooves into the bars as they will when the bars are too soft.

I know that Mr McMorrow is not in favour of hardening capo bars, and 
I should like to discuss this matter with him at some time should the 
opportunity arise. But we have found that when hardening is combined 
with careful shaping of the bearing surfaces and a deliberate 
detuning and shortening of the string segments, the result is highly 
satisfactory.

One disadvantage of hardened bars is that the tuning pins fields must 
be aligned properly to the speaking lengths segments, to allow the 
strings to run straight from the tuning pin through the various 
string segments. If the string segments are not in line there will be 
a tendency for the strings to migrate along the duplex and capo bars 
as the piano is tuned. Thankfully if the bars are hardened the 
alignment process is simple, but its annoying if the strings continue 
to wander throughout the service life of the instrument.

I have proven to my satisfaction that tuning the front duplexs to 
their respective speaking lengths is a recipe for disaster.

I have conducted experiments whereby a moveable front duplex is set 
precisely to a harmonic of the speaking length and it definitely 
causes those levels of string noise which many of us have come to 
detest. After moving the front duplex to detune it from the speaking 
length the noise disappeared. However, if the chosen duplex length is 
around 40 mm it will be noisy no mater where it is positioned. So the 
typical grand piano front duplex lengths chosen by many manufactures 
is a contributing factor to the production of string noise. Notice 
that you rarely hear string noise from upright pianos, yet there is 
often a short string segment between the V bar and the pressure bar 
which is undamped. The short, typically around 20 mm, string segment 
of the upright piano tends not to produce string noise because it is 
too short to be active. In the grand piano, with front duplex lengths 
which are often up to 40 mm or more in length, noise is almost 
guaranteed.

Our approach to this problem in recent years has been to remove the 
original front duplex bars with an angle grinder, and manufacture a 
new set of bars with a small radius rounded apex which is hardened to 
prevent deformation. After measuring the speaking lengths of the 
string sections concerned we enter the information onto a spreadsheet 
which is designed for the purpose, choosing the shortest possible 
de-tuned front duplex lengths for each note. We then move to the 
plate which has been previously levelled (if necessary, with 
motor-vehicle body filler) to accept the new set of duplex bars, to 
determine the height of the duplex bars in their new positions to 
establish the correct height for the bars (which will be tapered in 
height along the length of each bar) to allow all strings to run to 
the capo at the desired string angle. We set the string approach 
angle to no greater than 15 degrees or less than 12. A higher 
approach angle will tend to produce less string noise, but any angle 
over 15 is likely to allow the small radius hardened capo and duplex 
bars to act like string cutters, and will shorten the string service 
life. We have found 15 degrees to be the practical maximum angle 
which will allow for a satisfactory service life with the bar radii 
that we use. Of course you could use a larger bar radius with a 
higher string approach angle and that would be fine, but with the 
small radius bars we use 15 degrees is the maximum approach angle.

For those of you who haven't heard a piano with a deliberately 
de-tuned hardened small radius capo and front duplex system, please 
link to the mp3 sound samples of our piano no. 3 online at;

http://overspianos.com.au/samp.html

The treble tonal clarity of this piano is not a fluke. All our pianos 
(including the rebuilt instruments) have the same characteristics. It 
is satisfying to have found that it is possible to put the problem of 
string noise behind us, provided that we are prepared to step beyond 
slavishly following that standard which was set over a 100 years ago.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:info@overspianos.com.au
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