[Files] Re: B 458198, string deflections

Kent Swafford kswafford@earthlink.net
Wed, 28 Sep 2005 10:01:10 -0500


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Following up:

My observations do not confirm the presence of significant grooving =20
on the bridge, no evidence of aggressive string seating, just some =20
scuffing as the route of the string over the bridge changed. Try this =20=

view and note that the damage to the bridge is more obvious:

http://tinyurl.com/dkjo2

https://www.moypiano.com/ptg/files/attachments/9f/c1/94/30/dscn1194.jpg

I'm still convinced that the high angle of string off the backscale =20
side of the bridge is a source of the damage.  The pins along the =20
speaking length side of the bridge do not show significant movement.

http://tinyurl.com/7jr3m

https://www.moypiano.com/ptg/files/attachments/5b/74/6f/a4/dscn1199.jpg

The difference in string deflection angles is presently somewhere =20
around 6 degrees. Speaking length angle about 12 degrees, and back =20
scale angle about 18 degrees. I have a hard time believing that =20
amount is insignificant, and in any case, whatever the difference is =20
now, the difference was originally much greater than what it is now.

http://tinyurl.com/7chcu

http://tinyurl.com/dzpz4


https://www.moypiano.com/ptg/files/attachments/8c/a1/4c/b3/dscn1205.jpg

https://www.moypiano.com/ptg/files/attachments/56/32/bf/df/dscn1206.jpg


Kent



On Sep 22, 2005, at 8:22 AM, David Love wrote:

> Judging from this picture the severe indentation and the slightly =20
> angled indentation that leads to the new string position, it =20
> appears as if the migrating pins were caused by very aggressive =20
> string seating.  In other words, someone actually banged the string =20=

> down so hard at the pin that they moved the pin.  If that=92s the =20
> case, then it=92s not likely that the pins will keep moving =20
> (especially since some of the lateral force is being taken up by =20
> the bridge cap itself and the groove in which the string is =20
> riding.  I haven=92t really followed this thread from the start, but =20=

> termination have to be compromised, it would seem.  I=92m not sure I =20=

> follow how this would effect the crown of the soundboard.
>
>
> David Love
> davidlovepianos@comcast.net
>
>
> <image001.jpg>
>
>
>
> ------------
>
> On Sep 21, 2005, at 7:32 PM, Ron Nossaman wrote:
>
> > The bridge will probably be OK, especially as that angle self
> > corrects, but the net side bearing is what I'd be concerned about.
> > The strings are trying to pull the bridge left. I'd be looking for
> > concave crown and a killer killer octave pretty quickly, maybe as
> > soon as a couple of months if the climate control lets the RH get
> > below 35%.
>
> Fascinating. The piano has a dual-tank Dampp-Chaser with undercover.
> It really hadn't occurred to me that this alignment might cause
> soundboard problems. I was just worried about the bridge, still am,
> and have seen this configuration on many S&S instruments. I guess
> I'll be re-checking the crown as I service the DC over time.
>
> Thanks.
>
> > Did the restring include lowering the plate?
>
> No.
>
>


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