[pianotech] Tuning the duplex sections

[Ron Nossaman]

On 3/12/2011 2:34 PM, Joe DeFazio wrote:
>> *From:*"Don Mannino" <donmannino at ca.rr.com <mailto:donmannino at ca.rr.com>>
>> *Date:*March 12, 2011 12:50:57 PM EST
>> *...*
>> Another important factor which is, if I recall correctly, mentioned in the
>> old patents is the benefit to the tone and longevity of the string from
>> changing the wire movement at the capo from a bending action to a pivoting
>> action. When the duplex length is short or the angle very steep, the wire
>> is effectively locked down against the capo. When the angle is lower and
>> the length is longer, the wire can rock or pivot slightly on the capo,
>> reducing stress on the wire.

It will also be more prone to being noisy. A 15° counter bearing on a 
20mm front duplex allows plenty of flexibility for this rocking motion 
(which is what's responsible for pretty much all speaking length energy 
in the front duplex), with no "clamping" at the capo, and no duplex 
Banshees. Even at excessively high counter bearing angles, the string 
still rocks across the V bar, even with as short a duplex as you can 
realistically get. Take a string hook to a string just forward of the 
bridge pin, pulling it sideways to tighten the string on the pin. You 
can see the segment on the bridge top between pins bow as you pull and 
the string rocks around the pin.

Go back to the front duplex, even on something like an Aeolian M&H BB, 
with a 45° counter bearing. Lift the damper, and pluck the front duplex. 
The pitch of the tone you will hear is that of the speaking length. The 
displacement of the front duplex when you plucked it pivots the string 
across the V bar and levers the speaking length into action.


>In other words, the string cut might flare a little on
> both ends of the cut. Has anyone ever noticed such?

Not obviously. Any flare would be almost entirely on the speaking length 
side. The excursion of the duplex segment is very small.
Ron N