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PostPosted: Wed Jun 10, 2020 8:50 am 
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Last edited by Geoffrey Ellis on Thu Jun 11, 2020 12:28 pm, edited 1 time in total.

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PostPosted: Wed Jun 10, 2020 8:57 am 
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Geoffrey Ellis wrote:
chas wrote:
Geoffrey Ellis wrote:
This made me wonder if he accidentally hit the zero key an extra time when typing that number :-)


For bore measurements, it says 0.01 mm now, so your speculation about an extra zero might be correct.


Ah! That does seem more reasonable :-) I just went back and saw the correction (and I know I didn't imagine it because when I quoted the blurb from his website earlier, I cut and pasted that text into my post, so it's original). And as I observed before, getting a bore measurement accurate to .01mm is still staggeringly accurate and impressive. But .01mm is more in the realm of the believable (or at least applicable). As you say, measuring wood to anything more precise seems unnecessary given it's organic nature. And I don't think changes in bore dimension of that fineness are acoustically relevant if ones aim is to reproduce a flute. I think that in a laboratory, someone with the right gear might find a way to show that such tiny changes in a bore can create measurable effects on the behavior of air molecules, but I don't think any human beings will be able to notice it (not at the level of changes that are measured in ten thousandths of an inch).

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PostPosted: Wed Jun 10, 2020 9:08 am 
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an seanduine wrote:
Ok, what you are asking, Geoffrey, is at once both trivial and complex.


Hmmm. Well, I hope it's not trivial in the pejorative sense! Perhaps trivial in the "here is an interesting piece of trivia!" sense :-) Certainly complex, and the entire subject is highly interesting to me so I appreciate the background--that's exactly what I was wondering about. How did the old time (or ancient, even) practitioners of metrication arrive at their unchanging standard? It sounds like there is plenty of history on the subject.

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PostPosted: Fri Jun 12, 2020 2:49 am 
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Did Chris inherit Andrew's collection of flutes, or are they still with his daughter? Just wondered as it says on the web site that Chris will be putting some historical flutes up for sale.


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PostPosted: Fri Jun 12, 2020 6:44 am 
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an seanduine wrote:
Now this is where trigonometry comes into play. When I was a pipefitter ...


As a student at uni I read a mathematical subject. I spent my summers working as, essentially, a fitter's mate. They had to wait for me to catch up when it came to discussing distances and angles. They were manipulating triangles like darts players subtract.

an seanduine wrote:
Same thing with measurements. This was the same process the Egyptians used to calculate the pyramids, and the Phoenicians used on David´s canal. Maudslay used projections and ratios to successively correct his original lead screw. Infinite approximations/refinements give theoretically infinite precision.


First chapter of Scriba and Schreiber's 5000 Years of Geometry was a real eye opener. They weren't doing mathematics as I understand it (i.e., the thing invented by the Greeks) but they were bleedin' clever!


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PostPosted: Fri Jun 12, 2020 2:12 pm 
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Always a fun read: https://www.amazon.com/Ancient-Engineer ... 0345482875

Bob

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PostPosted: Sat Jun 13, 2020 6:34 am 
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All this talk of unworldly precision reminds me of a story that sets it all back in context. An overseas visitor checks out a tinsmith's workshop in Cornwall. "What tolerance do you work to?" "Oh, we don't work to tolerances", says the owner of the workshop. "We gets it right, and then it's near enough".

The moral of the story is clear. It's easy to go well beyond the precision required by functionality. The important thing is to get it right. We are still arguing about matters such as bore constriction which can have an impact (in my experience) of up to 2mm (extreme cases!). So precisions of 0.01mm - 200 times better - have to be viewed in that light.

http://www.hdowns.co.uk/library/the-engineer.php reminds us of meaningful pre-metrication units of precision such as the gnat’s knacker....

The Meaning of Life, we are reliably informed, is 42. Presumably 42 +/- the last significant digit, according to normal engineering practice. So somewhere between 41 and 43. But, as revealed in that wholly remarkable book, the Hitchhikers' Guide to the Galaxy, the big question is: "what is the question". We need to answer the big questions before getting bogged down in minutiae.

A job we should set Tunborough, when he has some time on his hands, is to determine what level of precision is required to keep a flute within some reasonable level of accuracy, eg +/- 10 cents.


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PostPosted: Sat Jun 13, 2020 8:20 am 
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Terry McGee wrote:
The moral of the story is clear. It's easy to go well beyond the precision required by functionality. The important thing is to get it right. We are still arguing about matters such as bore constriction which can have an impact (in my experience) of up to 2mm (extreme cases!). So precisions of 0.01mm - 200 times better - have to be viewed in that light.


Yes, when it comes to flute bores and the issues of tone and tuning, harmonics, etc., anything much beyond .1mm is theoretical and not really practical (you are not going to notice it). I do think it's cool that such precision is possible and there are a lot of endeavors that need/benefit from such precision, but wooden flute bores aren't one of them :-) When I measure a flute bore, I try to be accurate to .001" (.05mm), knowing that such fussiness is probably overkill.

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PostPosted: Sun Jun 14, 2020 5:21 am 
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The wooden flute offers us so many challenges. Let's imagine a typical wooden flute made back in London in the 1840s. Probably made by a cottage industry worker in an unheated shed behind the house. It can be cold in London....

Then the poor instrument finds its way to say the goldfields in Ballarat, in 1850's Victoria, Australia (I'm looking at you, Rudall & Rose #5501). It gets hot in Ballarat, and dry - I know this as I grew up there - so the flute tries to shrink. The bore of the head and barrel cannot shrink, as they are metal lined. (They did crack. Quite dramatically.) The unlined body sections could shrink, and did. But they shrank proportional to their diameter, so the upper body sections shrank more than the lower body sections. So the conical bore is now not just smaller, but also less steep.

Then of course we had tenon collapse due to thread wrapping. #5501 shows evidence of that. So we've introduced three choke points in addition to the other distortions.

So let's just summarise so far...

Head and barrel bores remain at original dimension
Top LH tenon compressed by thread constriction, while subsequent body most shrunk. Botton LH tenon compressed by thread constriction.
RH section body moderately shrunk, and bottom tenon compressed by thread.
Foot least shrunk.

And we obsess over the quality of data we draw from these poor things?


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