At 9:26 pm +0000 6/5/07, jimialeggio5 at comcast.net wrote:
>So anyway, this is an official not quite baked idea...but I don't
>think its half-bake, so-to-say.
>
>I'd be interested in followups of anyone foolong around with the idea.
The Wixey gauge is indeed very interesting and handy, Thank you for
posting the information. I see that I can buy one on new on eBay
here in England for £25 postage free and will almost certainly do so.
HOWEVER this gauge suffers from one obvious shortcoming and that is
its resolution to only 0.1 degrees, which might not sound much when
you say it quickly, but in practice is equivalent to a card's
thickness (roughly 9 thou or 0.22mm) at the string rest given a
back-length of 5 inches (127 mm.), and a very significant percentage
of the actual range of angular deflection applied in practice. As
regards downbearing, an angular deflection of 0.1 degree represents
about 70 pounds-force at the bridges when applied throughout the
typical grand piano.
From what I can see of Dale's device and gauge, even if his gauge
stepped (go no-go), as it seems to be, in steps of 5 thou, he is
still able to measure the angle with half the tolerance of the Wixey
gauge, ie. to within 3' or 0.05 degrees. With a continuous wedge
gauge it is possible to achieve even better accuracy.
At 9:05 am -0400 4/5/07, Dale Erwin wrote:
>On a 5 inch string segment yielding a gap of .065 thous (as measured
>with the gauge in the picture) reveals that there is about 3/4 of a
>degree of residual net bearing. Now this is a new board set up at 1
>1/2 degrees. So I've squashed the board 3/4 of a degree.
In fact in this instance Dale's measurement could hardly be more accurate since
sine(3/4) x 5" = 0.0654"
but even supposing Dale is using a go-no-go gauge with 5 thou steps
and went to the 70 thou step rather than the 65 thou, the calculated
angle would be only about 0.05 degrees different. I've photoshopped
Dales picture to make it quite clear where the gauge rests, on the
speaking length in front of the pins.
That said, I'm sure Dale will agree that although this method is
quite accurate for measuring and demonstrating the angle after the
event, it is not the perfect method for setting up the angles before
the piano is strung.
JD
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