[CAUT] Fw: capo bar reshaping

[Jeff Tanner]

And then, I've heard the S&S C&A techs just say shoeshine it with emory 
cloth.

You're right.  Huge can o worms.
No.  This isn't intended to rebut your recommendations or provoke 
controversy.  Just pointing out how far apart the differences are.

Jeff

----- Original Message ----- 
From: "Alan McCoy" <amccoy at mail.ewu.edu>
To: <caut at ptg.org>
Sent: Wednesday, September 10, 2008 5:53 PM
Subject: Re: [CAUT] Fw: capo bar reshaping


> Hi Paul,
>
> The email came through the first time. But the issue is a can o worms. The
> proper shape of the capo depends on who you ask. If it is too pointy and 
> not
> hard enough, you quickly get grooves, which gives the capo a too flat
> bearing surface. If it is too flat (as it is when grooves have been cut 
> into
> an otherwise sharp profile) then you will probably have noise (string
> sizzle) at the capo. Also part of the puzzle is the angle between the 
> string
> plane and the duplex segment up to the counterbearing. If it is shallow it
> won't cut grooves as quickly, but it may not terminate the string 
> properly.
> If it is steep, there is a tendency for cutting grooves. So what you need 
> is
> a decent counterbearing angle (anywhere from 12 deg to 20 deg though 
> you'll
> get arguments aplenty about what's the best angle) and you can get away 
> with
> a shallower angle if the counterbearing segment is shorter (long and 
> shallow
> will often give duplex noise especially if the length of that segment
> happens to be harmonically related to the speaking length). Also you need
> the capo to be properly hardened. And it needs to be profiled to some
> radius. Talk to Ed McMorrow and he will advocate a very sharp (0.5mm 
> radius,
> I think). While others will advocate more like 1.5mm (about 1/16"). Me? I
> use a Stewart MacDonald diamond fret file and file it to probably around 1
> to 1.5mm radius. As a rebuilder (of sorts) and somewhat pragmatic I worry
> less about the capo itself and more about the counterbearing angle and
> length of duplex segment. That is really the only easily changeable part 
> of
> the equation. I know that some will harden the capo, but I don't have that
> skill yet. But I do alter the front duplex when I think it will be some
> benefit. Just finished grinding off the counterbearing bars of the piano 
> in
> my shop and will replace the bars with half-round brass. The angle won't
> change much at all, but the segments will be significantly shorter (less
> than 30mm my eyeballs tell me, though I haven't measured yet).
>
> Like I said, can o worms.
>
> Alan
>
>
> -- Alan McCoy, RPT
> Eastern Washington University
> amccoy at mail.ewu.edu
> 509-359-4627
> 509-999-9512
>
>
>> From: Paul T Williams <pwilliams4 at unlnotes.unl.edu>
>> Reply-To: "College and University Technicians <caut at ptg.org>" 
>> <caut at ptg.org>
>> Date: Wed, 10 Sep 2008 12:29:47 -0500
>> To: <caut at ptg.org>
>> Subject: [CAUT] Fw: capo bar reshaping
>>
>> I'm not sure if this went through yesterday.  I'm trying again.
>> ----- Forwarded by Paul T Williams/Music/UNL/UNEBR on 09/10/2008 12:28 PM
>> -----
>>
>> Paul T Williams/Music/UNL/UNEBR
>> 09/09/2008 01:23 PM
>>
>> To
>> caut at ptg.org
>> cc
>>
>> Subject
>> capo bar reshaping
>>
>>
>>
>>
>>
>> Hi List,
>>
>> I'm working on a plate from a 1926 Steinway M that had been breaking lots
>> of string along the capo.  Both sections broke about the same number of
>> strings per semester.  Upon pulling the plate and looking carefully at
>> both sections, the top section was really flat (plus grooved and crusty)
>> and the lower section was more pointed like we like, but way deeper
>> grooved (and just as crusty). So, my conclusion is that both too deep of
>> string groove and too flat a capo surface experience the same amount of
>> string breakage.
>>
>> Now, I can't remember the width of the "peak" of the capo, but seem to
>> think along the lines of 0.5mm-1.0mm (top to bottom of whole capo)
>>
>>  Is this a bit too sharp? Could someone please remind me the proper
>> "shape" before I begin filing?  Do all the string grooves need to be 100%
>> gone?
>>
>> Thanks for the input!
>>
>> Paul
>
>
>