From "Farrell" <mfarrel2@tampabay.rr.com>
Comments below:
Terry Farrell
----- Original Message -----
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
> >stringing scale and long bridge (what other kind would you put into
> >a piano?). There was an inherent assumption that hockey sticks
> >belong on the ice, and not in a piano! Yes, axe that curve off the
> >low tenor end of that stick and see how it balances.
>
> Two points: Don't let your oeile get trompled.
What on earth is an oeile?
> That upright long
> bridge is actually straighter than a Steinway O's. In the picture,
> 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.
> Nomer Doo: When you talk of balancing, I'm assuming that's along its
> length (as pictured). It's a long stick; find its balance point and
> both end will float in the air. I'm not sure that getting both ends
> to float in the air needs to be made any easier by editing the curves
> 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.
> I just got finished realizing that any crown in a ribbed board is
> incidental, and not required for support of the string load.
Where did this come from? The crown is usually designed in, not incidental.
> This
> meant that the underside of the bridge didn't need to be fitted to
> match board curvature (crown) parallel to the board and bridge. What
> remains is any extent to which the bridge may, in its path down the
> board, cross the "continental divide" (as 'twere), and thus need to
> have its bottom shaped to match this uphill/downhill contour. If this
> isn't done, I could imagine that the flat-bottom (for lack of a
> shorter word) bridge would would end up twisted in its cross section.
> Then the bridge would no longer be plumb to the string plane, but
> rather to the whatever point in the board's curvature you chose to
> measure it.
Not really sure where you are going with this stuff.
> Maybe I pulled this thinking out of the oven too soon, maybe I should
> put it back in.
>
> >BTW: Is that a hunk of granite on that table? Where did you get it?
> >$$? Sorry, I couldn't resist - its the old geologist in me.
>
> That's right. One of two panels. That one 30"x60"x2.5", and the other
> 42"x78"x(2.5~3.5") Rescued from an abandoned granite quarry in S. ME
> 20 years ago. But that's a story for another time. Mark Dierauf,
> who's also on the list, might chime in on this one (seeing as how the
> statute of limitations has long gone).
Nice granite chunks, for sure. Darn good way to make a flat table!
> Bill Ballard RPT
> NH Chapter, P.T.G.
>
> "I go, two plus like, three is pretty much totally five. Whatever"
> ...........The new math
> +++++++++++++++++++++
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