Capo bar revisited

[Don McKechnie]

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Hi Ron,

Thanks for the reply. I should have remembered that you have been doing
work in this area as well. I have the same question as Fred.

Don


> Subject:
>            Re: Capo bar revisited
>       Date:
>            Thu, 29 Jan 2004 08:29:45 +1100
>      From:
>            Overs Pianos
>         To:
>            College and University Technicians
>  References:
>            1
>
>
>
>   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
> _______________________
>
> Web http://overspianos.com.au
> mailto:info@overspianos.com.au
> _______________________
>

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