[pianotech] YC Capo Bars

[Roger Gable]

Jon,
I suggest an alternate repair. Reshape the original insert and have the 
machinist who is working with you check the hardness at the crown. It should 
be around Rockwell 40. If not, explore having it hardened. It could end up 
costing less to harden the insert rather than machine a slot. Also, the 
water hardened drill rod you obtained from your local supplier is probably 
too hard and may cause buzzing at the duplex. Additionally, I've always felt 
that the capo should have as few mechanical "interruptions" as possible. Let 
me explain. It is known that when energy passes through different mediums, 
an energy reflection is created. This is experienced by the submarines sonar 
when the sonar wave hits an area of different water temperature. It is, in 
effect, a different medium and a reflection is received back. The drill rod 
is a different medium from that of the cast iron, as well as the microscopic 
gaps that are sure to exist at the union of these two parts. An energy 
reflection from the vibrating string is certain to reflect back into the 
string. This reflection is going to be out of phase, creating an impedance 
imbalance that contributes to an ugly sound. This "pinched" sound can also 
be heard with laminated bridge caps or laminated soundboards.
Roger Gable

----- Original Message ----- 
From: "Jon Page" <jonpage at comcast.net>
To: <pianotech at ptg.org>
Sent: Sunday, September 19, 2010 9:53 AM
Subject: Re: [pianotech] YC Capo Bars


>A post last month showed the string impressions in the v-bar insert
> on a 1996 Weber grand.
> http://ptg.org/pipermail/pianotech.php/2010-August/027631.html
>
> I have a 1/8" rod to install into a machined slot. Photo attached.
> The machinist will level an area and mill the slot with a 1/8" round bit.
> Should the depth of the slot be .040" or more like .060"?
> -- 
>
> Regards,
>
> Jon Page