S & S capo/Case hardening

[Mark Bolsius]

Hi Ron N and Bill Shull,
 It's not just a matter of hardening the capo, it's also important...vital
to reshape the capo bar! The reason for hardening it is that if you bring
the capo to a fine enough point to give a good clean termination, the string
will bite into the bar creating more problem than it solves. When the
combination of good profile and hardening come together the result is a
clearer, cleaner tone. The front duplex needs good termination all round to
work. Most pianos that have noise coming from that section will have big fat
capos and front duplex/V bars.

I speak from experience, the work that Ron Overs is talking about was done
to two piano plates in pianos that I have rebuilt. Both had unbelievably
noisy front duplexes and a string breakage problem. The work in one (a
Yamaha C7E) has been in heavy concert use for a bit over two years now and
the tonal clarity is still as good as when the job was just finished. No
string breaks since either....mind you I'd expect that, given that the piano
was restrung. The other was also a great success (though is not worked so
hard).

Its not just the capo bar that is profiled either, the front duplexes (or V
bars) are shaped and profiled as well. I'd recommend a look at the picture
on Ron's web site
www.overspianos.com.au
It may give you a better idea of what he does, it clearly shows the V bars
on one of his rebuilds.

The other alternative for anyone interested is to come to the Australasian
Piano Tuners Convention next year in Sydney (in early July, pre-Olympics).
Ron will be lecturing and showing at least one of his pianos there......stay
tuned for details!

Bill, I disagree that simply restringing and light preparation of the
surfaces will solve the problem. I've tried this and found that the problenm
recurred sooner than I had hoped, it is only a temporary solution. given the
costs involved in quality rebuilding, that can present problems with
customers later.


Regards to all
Mark Bolsius

 
 Ron Nossaman wrote:
Subject: Re: S & S capo/Case hardening
Date: Tue, 2 Mar 1999 2:05 AM

I haven't done any experiments on case hardening capos, so I really can't
speak directly to the pros or cons. I can throw in some peripheral
observations however, on what I have seen, heard, and done.

Half hard brass has a compression strength limit of about 50k PSI. The cast
iron average is around 100k PSI, with hardened iron going up to 200k, or
twice to four times that of brass. At the tenor/treble scale section break,
the string termination system changes from a softer brass agraffe to a much
harder cast iron capo. That's also where the whistles, zings, buzzes and
shrieks start - in the capo section. If harder is better, how does this
equate? If harder is better, there should be fewer noises in the capo
section than in the agraffes, not more. Shouldn't there? What's different?

Maybe the higher frequencies really do need harder terminations. It's just
an unfortunate coincidence that the noises start immediately above the
agraffe section. That's it, it's just one of those mysterious cosmic things
that we weren't meant to fathom, right? God's little joke on the designers
and techs. 

It's the front duplex, gang. When you touch the duplex and the noise stops,
why would the conclusion be that the capo needs to be hardened? This doesn't
compute. Increasing the draft angle and shortening the duplex lengths takes
care of the problem quite dramatically, and it's simple and easy to do in
the privacy of your own shop. I've done it. It works. It didn't take any
superhuman attention to the capo shape, or require any high tech induction,
flame, or transmogrificational case hardening. It's simple, it's (as nearly
as I can tell) reliable, it's measurable and understandable, and you don't
have to wear the pointy hat with the stars to get it to work. Occam was
right, in my opinion.

Ask yourself: why aren't we using high carbon steel agraffes, hardened to
the point of scratching diamonds? Evidence is that it doesn't seem to be
necessary. I wonder at the efforts gone to to attempt to make a suspect
design "feature" work when the simpler method is to eliminate the feature in
favor of something that does work. Why is it necessary, at any cost, to
retain the design feature that is the problem in the first place? If we have
the permission, the funding, and the ability to fix it, why not just fix it?


Just wondering.

 Ron