[pianotech] Capo Bars

[David Love]

Thanks Ron for the detailed reply--and everyone else's contributions as
well.  

One other thing I wonder about is the mass of the struts themselves.  The
Bosendorfer, for example, with its drop in super heavy capo (and short
counterbearing lengths) seems universally devoid of leaks and falseness in
that section.  What exactly is the hardness of the material on the bottom of
that removable capo as compared to hardened cast iron?  Also, has anyone out
there ever experimented with increasing the mass of that strut by some
artificial means on other pianos?  Curious as to the effect?

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Overs
Sent: Wednesday, March 04, 2009 1:08 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Capo Bars


Yes, this is a way to build a capo' with a controlled profile and a 
hardened surface. When the first Yamaha grands came out in the late 
70's with the V-pro plates, they used a bar under the capo just as 
you've described. I seem to remember from their literature at the 
time that they mentioned a hardness of C60 for the bar. Piano wire is 
typically about C45, and a mild steel nail would be around C20.

I have also experimented with the inserted bar, finding that it is 
critically important that the bar is seated well all along its 
length. If there are any sections where the bar is not being 
supported by the cast iron groove the tone will be weak and short at 
that point.

The other question of course is how many manufacturers are actually 
hardening bars. Of the two that I know of, Yamaha and Steinway, 
neither of them are hardening the front duplex bars. One of the 
reasons why I suspect that Yamaha stopped using the inserted bar was 
that with the combination of string approach angle, bar radius and 
hardness they were using, there were quite a few string breakages. I 
have found that string breakages are definitely more common when the 
bar is hardened, if the piano is being regularly serviced by a 
technician who drags the strings all over the shop during tuning. If 
the tuning is carried out with minimal string movement once the piano 
has fully settled down, I have found that the string longevity on 
pianos with hardened bars is very good.

I've just published a page on my website, which is actually a 
"more-information" page for the Australian market, and supplementary 
to a small advertisement we are running in Limelight magazine (a link 
to the page is included in the ad'). The page is mostly a promo' for 
rebuilding during the economic down turn, but you can see the front 
duplex images down the page in the 'Photogallery' section. There is 
some explanatory text under each image.

http://overspianos.com.au/more_info.htm

On the page I have images of a D which we rebuilt recently, with an 
image of a new Hamburg Steinway immediately below it. Both images 
show a close-up of the front duplex bars. Steinway don't harden their 
front duplex bars, and I suspect that this is why they use such a 
flat top surface. We shape the front duplex bars down to the same 
radius as we use for the capo, and harden them also. For some pianos, 
when the customer is prepared to pay the cost, we grind off the front 
bars completely and make new front duplex bars. This allows us to 
relocate the bars closer to the capo, to reduce noise, and to set the 
front duplex distance to a de-tuned length, with respect to the 
speaking length of each note. This helps to further reduce string 
noise. But I believe that the biggest factor in counter-bearing noise 
is length. Make them shorter and noise reduces.

At this time David, we have settled on hardening the original capo 
bar after profiling, ie. we don't use the inserted rod idea. This is 
not without its problems. The most usual is that many manufacturers 
repair flaws (blow holes and such) in their capo bars by drilling and 
fitting a plug (which is probably made from mild steel) into the bar. 
This is very common in Steinway pianos, which unfortunately is the 
piano which we rebuild more than any other brand. The plugs will not 
harden because their carbon content is too low. We have been grinding 
them down with a die grinder and welding the hole with cast iron. 
This is a difficult process and we often have to repeat a repair, 
since it is common to have the repaired fillet crack post hardening. 
The other problem with hardening is that a lot of paint and filler 
gets burned off the bar during the hardening. Over the years we have 
gotten better at this, so we burn a lot less of the paint than during 
our first year of hardening (1995).

Hardening still is a big job if it is taken on as part of the 
rebuilding process. I still believe it is worth it, because the tone 
in service sounds like a new piano for longer. I also believe that it 
is worth hardening the front bars. For domestic clients who typically 
have their piano tuned only annually we reshape the front bar but 
leave it unhardened. But for commercial clients I regard hardening 
the front bar as essential.

>Secondly, if I were to do that to a piano where I have some concerns 
>about the hardness and or consistency of the capo, what specific 
>material and diameter would be best to use for the rod insert?

My experience is that the inserted rod option is more trouble to fit 
compared to the work involved in shaping and hardening. So we 
continue to reshape and harden. If you harden an S&S bar today you'll 
now be rebuilding to S&S standard, which clearly is not strictly 
their own standard, it is something which they took from somebody 
else.

I can't comment on recent US Steinway D bars since I've only rebuilt 
one 1925 piano, and that was back around 1990, when we were reshaping 
but not hardening (we see very few US made S&S in Australia). All our 
other S&S rebuilds have been Hamburg instruments. Our first D, in 
which we hardened the bars, was for Queensland Conservatorium. 
Steinway wrote a damning report, criticising us for hardening the 
bar, saying that we 'knew nothing about tone-building the Steinway 
piano' (I have a copy of the report, which was kindly and anonymously 
faxed to me by an unknown supporter). They claimed that we had ruined 
the piano and that it would have to be sent back to Hamburg to have a 
new plate fitted. This banter went on for six months, during which 
time I got very little paid work done. After months of shouting down 
the phone, the problem subsided. Eventually, the institution was 
talked into a new D. The 'modified' instrument ended up in the hands 
of a dealer, who was a known slick operator but he also was quite a 
piano player. I heard reports that he claimed it was one of the 
nicest Ds he had played - not that it means much, but it felt like a 
little compensation for the effort and trouble we had been through.

I don't know when Steinway actually started hardening their bars (if 
anyone has this information I'd like to know), but it certainly was 
happening by 2000, since we've rebuilt a 2000 D which had hardened 
capo bars. On this particular instrument the hardening had shelled 
off at the lowest end of the capo, so we had to re-profile the bar 
and harden it again, but I'd say that most of the time with these 
pianos it should be possible to simply fit new wire, although the 
front duplex bars are soft and of a large radius, and I do believe 
that the front bars are a source of noise also. We've found that the 
pianos are a bit cleaner, even if we just reshape and harden them, 
without fitting a new re-positioned front bar.

Since S&S are now having all their plates for both Hamburg and NY 
made at their Kelly foundry, it would be interesting to know if they 
are hardening the capo's for the US pianos. If any of you have a late 
US D in your care, check out the capo bar surface with an inspection 
mirror. If you can see string grooves where the strings have been 
moved, they are not hardened. If the strings can be moved easily 
without marking the bar they are hard. I'd be interested to know. It 
is quite possible that the US bars are not being hardened, because 
the Hamburg plates are being hardened in Hamburg after the plates 
arrive from the US (I've got a photo of the machine they use for the 
process - which a visitor to the plant, at a certain time, sent to me 
via email from somewhere which shall remain un-named).

Sorry for the length of this post. I'd better go to work. I'm 
currently getting covered in compound buffing another model O 
rebuild, which is a bit of a yawn since the client wasn't prepared to 
fork out the funds for the cost of a tenor bridge (the economic 
downturn killed off the tenor). But I've done the maths for this 
model now. It looks like a very suitable model for an upgrade.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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