Curved Long Bridges

[Farrell]

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Comments below:

Terry Farrell
 =20
----- Original Message -----=20
From: "Bill Ballard" <yardbird@vermontel.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Saturday, April 19, 2003 9:57 PM
Subject: Re: Curved Long Bridges


> At 8:04 AM -0400 4/19/03, Farrell wrote:
> >We were talking about a bridge from a piano with a well-designed=20
> >stringing scale and long bridge (what other kind would you put into=20
> >a piano?). There was an inherent assumption that hockey sticks=20
> >belong on the ice, and not in a piano! Yes, axe that curve off the=20
> >low tenor end of that stick and see how it balances.
>=20
> Two points: Don't let your oeile get trompled.

What on earth is an oeile?

> That upright long=20
> bridge is actually straighter than a Steinway O's. In the picture,=20
> the tenor bridge is the closest.

Most (I think likely all?) well designed piano scales do not have any =
sort of a hockey stick curve at the tenor end of the long bridge. It =
gets fairly straight in that area. The curve to the bridge is in one =
direction only.
=20
> Nomer Doo: When you talk of balancing, I'm assuming that's along its=20
> length (as pictured). It's a long stick; find its balance point and=20
> both end will float in the air. I'm not sure that getting both ends=20
> to float in the air needs to be made any easier by editing the curves=20
> at the ends.

Thats just the point. The bridge from a well designed scale will only =
have the curve in one direction. In that way, the bridge forms an arc of =
sorts (portion of a circle - not that is is really circular though) - =
like the example I gave a while back with the donut sitting on top of =
the basketball. Put the pencil under the middle of the arc, and the mid =
section of the arc lifts up, but the two ends remain in contact with the =
surface of the table or whatever it was laying on. If you need a =
picture, I will send one.
=20
> I just got finished realizing that any crown in a ribbed board is=20
> incidental, and not required for support of the string load.

Where did this come from? The crown is usually designed in, not =
incidental.

> This=20
> meant that the underside of the bridge didn't need to be fitted to=20
> match board curvature (crown) parallel to the board and bridge. What=20
> remains is any extent to which the bridge may, in its path down the=20
> board, cross the "continental divide" (as 'twere), and thus need to=20
> have its bottom shaped to match this uphill/downhill contour. If this=20
> isn't done, I could imagine that the flat-bottom (for lack of a=20
> shorter word) bridge would would end up twisted in its cross section.=20
> Then the bridge would no longer be plumb to the string plane, but=20
> rather to the whatever point in the board's curvature you chose to=20
> measure it.

Not really sure where you are going with this stuff.
=20
> Maybe I pulled this thinking out of the oven too soon, maybe I should=20
> put it back in.
>=20
> >BTW: Is that a hunk of granite on that table? Where did you get it?=20
> >$$? Sorry, I couldn't resist - its the old geologist in me.
>=20
> That's right. One of two panels. That one 30"x60"x2.5", and the other=20
> 42"x78"x(2.5~3.5") Rescued from an abandoned granite quarry in S. ME=20
> 20 years ago. But that's a story for another time. Mark Dierauf,=20
> who's also on the list, might chime in on this one (seeing as how the=20
> statute of limitations has long gone).

Nice granite chunks, for sure. Darn good way to make a flat table!
=20
> Bill Ballard RPT
> NH Chapter, P.T.G.
>=20
> "I go, two plus like, three is pretty much totally five. Whatever"
>      ...........The new math
> +++++++++++++++++++++
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives
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