Wound Trichords

[Overs Pianos]

Hi Sarah,

>I'm one of those "WHY" folks and have been for some time.  All I've heard in
>response is "BECAUSE."  Sometimes I hear as much as, "because it's hard
>enough to get two of them wrapped buggers to get along, but three is almost
>impossible."  Then I consider my own piano, a 1933 "D" clone, in which I
>have 7 monochords, 4 bichords, and 9 wound trichords.  IMO, the trichord
>notes sound pretty good.  But then again, they seem to be well made and in
>pretty good shape.  I have no trouble tuning them, and they get along just
>fine with each other.  (I've also heard that it's hard to wind a good string
>that small, so I'm apprehensive about replacing any of these wound trichord
>strings that seem to get along so well.)
>
>But at long last,  after all this confusion,  I see the following
>argument... yours...

Have a look at Ron N's post. He sets out some of the scaling detail 
which I didn't include. My experience with re-scaling concurs with 
his.

Trent Lesher's post was an excellent round up of contributions thus far.

>  > Trichords and Bichords at the lower end of the long bridge are a work
>>  around for breaking too low.
>
>... and then the lightbulb goes on!
>
>The wound trichords in my piano are on the upper end of the bass bridge, not
>at the lower end of the long bridge.  I have nothing but steel above the
>tenor break.  I think the same is true of the "D?"

Indeed. The cross over of the D works OK if the strings are expertly 
wrapped. For the D we've just re-manufactured the re-scaling included 
replacing the 7 bass trichords for bi's. There is a slight 
disadvantage substituting the trichords with bi's when constrained to 
similar speaking lengths, since the % break needs to be slightly 
increased to maintain Z. But the ease-of-tuning advantages are worth 
the small increase in tension required. I believe there's absolutely 
no justification for using trichords covers in the high bass of any 
piano (unless one considers cloning certain existing product to be a 
marketing advantage). Bichord covers will be cheaper to build, with 
no disadvantages, and they will in all probability exhibit superior 
tone (via improved matching, as other commentators have mentioned).

>You suggest that "if Chickering were given the option of having his time
>over again, in 2004 he would probably have opted to use bichords, using a
>core wire about two half gauges smaller than the last plain wire, with a
>speaking length of between 12% to 14% shorter than the last plain wire
>speaking length and wound with a 0.2 mm copper wrap."  On my piano, the
>speaking lengths of the upper end of the bass bridge get "squeezed" just a
>bit for the last several notes

What do you mean by "squeezed"?

>, and then there's a jump in speaking length
>on the first plain wire on the long bridge.

This is quite normal.

>  The last wound trichord on the
>bass bridge is about 17% shorter (1450 mm) than the first plain wire on the
>long bridge (1745 mm).

This is similar to the S&S D, though the D's cross is slightly more 
severely shortened, with the E20 trichord group @ 137.1 cm reduced 
from F21 at 183 cm.

Typically the crossover shortening is greater for concert pianos 
(though in many cases they would be better off with less). I suspect 
that this is one reason why some manufacturers have chosen to use 
trichord covers in the high bass, since it allows them to chose 
components for a good Z cross at a slightly lower % break. But is 
isn't necessary, especially when one considers that a shortening of 
the transition speaking lengths (25% in the case of Steinway's D) 
often result in the high end of the bass bridge being placed too far 
out from the adjacent rim. There is often too much sound board 
activity in the high bass (and too little at the bottom end). If the 
shortening was revised to say 14%, the bridge could be better placed 
with respect to the rim, and the % break could be reduced while 
maintaining a good Z cross. Such a scaling layout would require 
careful control of the note spacing for the bridges and hitch pin 
fields. But with today's computer generated layouts it should be a 
piece of cake.

>Anyway, yes, I can see how putting wound trichords on the lower end of the
>long bridge could be a problem!

Many manufacturers do this. Both bi's and tri's are a problem. As Ron 
N mentioned, the best solution is to change to bichord covers on a 
new shortened-speaking-length tenor bridge. This will surely help to 
make that silk purse from the proverbial sows ear.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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