Violin Forum/Message Board

[ctviolin]

[R Mac]

John,

Thanks for pointing out the underlying math that the computer program conceals. I am afraid it is lost on me, though.

It's remarkable, how different one human brain can be from another. To me, the math is opaque and artificial, and the physical derivation with a rolling disc is beautiful. To you, the disc is a barbarous approximation, and the math is sublime truth.

I sometimes wish I could have the sort of experience that a mathematician has when he sees an elegant proof, or a beautiful derivation; but alas, it seems ever denied to me. Perhaps just a glimpse of it would have kept me from flunking calculus.

Mac

[John Masters]

[actonern]

John:

A question about the CNC machine.

I'm guessing the router bit has a profile of some kind where it does the cutting.

When the machine is routing out the arch in the mid bouts, where there is a pretty rapid change in profile, does the outer edge of the bit cut away more than it should? Does the question make sense?

So, for example, if the router bit was 1 inch in diameter at the business end, (extreme example) the outer edge of the bit would be removing stock 1/2 inch away from the centre, which I imagine is what the computer is controlling for in terms of height at any point. in a rapidly rising situation, like the rise from the edge to the centre of the arch, that outer edge of the bit would cut away more than it should? Even if its shaped in a round profile?

Best regards,

Ernie

[John Masters]

[actonern]

Just curious... with that setup how long does it take to take a full size fiddle back and have it outside arch machine finished, start to stop?

E

[John Masters]

[John Cadd]

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[Michael Darnton]

The hanging chain fails in the very most important spot of the arch: the recurve. I don't much care what's going on in the middle, where the chain works. Most of the muscle regarding sculpting the behavior and sound of a violin is in controlling the scoop around the edges, and only curtate cycloids absolutely prescribe the shape in that area. Half templates offer the most flexibility in that you can move the scoop around with them while still maintaining the same curves.
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[John Cadd]

0000

[Michael Darnton]

The importance of the recurve area is my own understanding after having seen a lot of fine violins that didn't make sense otherwise. Then I realized that my templates fit the edges but often not in the center, and that half templates follow better than full.

I think there is a logical explanation as to how this can work, but it needs a lot of words and drawings. Bear in mind however that the center is thick and inflexible, so central curves logically should matter less there than around the thinner and more flexible edges. Consider also that enforcing a consistent strategy around the perimeter will give a cohesiveness that doing something random or by eye will not. I don't believe that CC curves are the only way to achieve this, but they certainly do fit the original violins well, since it's a natural outgrowth/byproduct that doesn't need to be thought about. With other methods you'd have to be aware of that need, then figure out a way to make it happen, where with cycloids it just happens on its own.
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[John Cadd]

0000

[Michael Darnton]

The robust edges are an obvious thing for people with neophyte eyes to latch onto, but the arching of these instruments is also quite a bit different in ways that really matter, specifically, shallower scoop very much towards the edge. That also forces the center area to be flatter which may be of some smaller importance on the top between the f-holes. This can also be seen in early Brescian violins, some long pattern Strads, and late Guadagnini violins, the tonal characteristics being somewhat similar among all of those groups, to the extent that they are similar (they are all somewhat different in various details, so it's not a 1:1 correspondence). This is a common strategy among some more modern makers, too, and it's a very effective approach in cellos as well. Carried to extremes it leads to a more compressed tonal range and more aggressive behavior that appeals to some modern players.
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new blog at my site! http://darntonviolins.com/blog
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[John Cadd]

0000

[John Cadd]

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