S & S capo/Case hardening

[Ron Nossaman]

At 12:49 PM 3/1/99 EST, you wrote:
>Ron  and list:
>
>Although I do not speak with the same eloquence as Ron, nor the same knowledge
>of metal hardnesses, 

* Hi Bill, you got me. I confess that I looked up the info on hardness just
for this. It seemed like a valid point. 




>I think that the purpose of the front duplex has been
>missed here.  We don't get zings from the agraffe section for a simple reason:
>The agraffe section is designed to exclude them.  We get zings from the duplex
>section for a simple reason: The duplex section was designed to "include"
>them.

* Not missed at all, I said early on that the intent of the front duplex was
to make noise. It seems that folks want to pick *which* noise they make.



>Ron, your solutions to the problem (increased angle and shortened segment of
>the duplex) show that those solutions are effective in getting rid of zinging,
>but not necessarily an argument against "V" bar hardening.  Redesigning may or
>may not move towards the intent of the designer, but simply restringing that
>section with a light capo surface preparation of the capo is often as adequate
>a solution.

* No, it's not necessarily an argument against v bar hardening, but it's a
much more simple and sure fix than the rather speculative and "iffy"
hardening process. Which is more predictable, understandable, measurable,
and reproducable, given a well shaped V bar in both cases? With a hardened V
bar, you may very well still get unwanted zings and whistles, whereas with
the higher draft angle and shorter duplex, you most probably won't. The
higher success probability of the latter would make it my first choice if I
was allowed to do it. I'd rather just do it once.  



>The problem is that the capo is designed for an incomplete termination of the
>string.  Until significant loss of power occurs in this section the capo is
>probably in good shape.  When loss of power and tonal aberrations are
>percieved from a distance, it may be time to restring and lightly resurface
>the capo.  In certain circumstances rehardening the "V" bar may be needed:
>heavy use with many restringings/hammer replacements, or where the plate
>surface was poor to begin with, either from poor manufacturing or from
>exhuberant filing/grinding.

* Perhaps, but I would suspect soundboard problems as being the prime
suspect in the cause of loss of power in this area of the scale, though V
bar wear may very well be contributory. The need for hardening being
determined by what - visible damage to the bearing surface?



>TIG welding is not particularly expensive, nor is it particularly
>transmogrific.  It is inconvenient and increases our risk when we cart the
>plate to the welder.  But rehardening, when needed, provides an effective  way
>for the rebuilder to maintain the duplex scaling intent of the manufacturer.
>Other approaches with this same intent have been made, including the insertion
>of a rod into a groove made into the capo.  Rehardening seems to be the best
>way to keep the duplex as original as possible. 

* Ok, there's the qualifier. If keeping the design as original as possible
is the imperative, then shape and harden away with my blessing and best
wishes. I consider it a design flaw in the first place, considering the
problems the bloody things subject us to, and think it ought to just be
corrected and get it over with.


>Ron, I am a comparatively recent caut and pianotech list participant, and I
>continue to appreciate your way with words....Even if I might not alway agree
>-
>
>Bill Shull
>U of Redlands, La Sierra U

* I've probably learned more disagreeing with accepted attitudes and
knowledge than I ever did by acceptance without question. I've changed my
mind more than once too when someone had a better argument. I do tend to
charge right in rather than going through social and procedural niceties,
but I don't mean to attack. A disagreement ain't a war, but a social
maladroit like myself pushes the wrong buttons sometimes.

Thanks for the reply.
 Ron