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ctviolin
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 Posted: Fri Feb 01, 2013 2:25 pm Post subject: Using cycloid curves in violin making... |
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From another post;
| actonern wrote: | "...but now I use a method that's much more complex that accounts for the distortion of the long arches and any twisting of the body..."
That's "flies to molasses" kind of talk!!!
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actonern,
Flies to molasses?
Exactly.
This material is available in general, out there in cyberspace already.
I'd recommend searching the topic using the "terms" as a search words in another violin forum, where it was discussed fairly comprehensively in the recent past (the last three to four years - perhaps a bit longer)
http://mathworld.wolfram.com/CurtateCycloid.html
Of course, it is a fairly simple idea, as shown above - where an arch may be drawn by rotating a circle with a specific point that leaves its mark as the circle rotates. It leaves a "cycloid curve", an arch with a recurve leading to another arch with the same properties.
The properties of the arch left, all depends on where in the circle the point (or the 'hole' for the pencil lead) is.
That it can be used to describe the arches that exist on violins by certain makers from the past, is what makes it of interest to violin makers today.
Of course, violins from long ago will show much in the way of stress, wear, plate movement & etc., because of localized pressures, plate movement because of string pressure or bridge pressure, and all the rest.
But an argument can be presented that such makers originally used such curves and they can be used today.
The exact shape of the outside of the plate(s) is what this curve type describes.
Their (the plates) thickness is another matter altogether. Which means that the cycloid may not be used to describe the inner plate surface shape. (necessarily)
An entire book could be written, I would guess, about how to manage these curves along with all the minute particulars having to do with violins, edge work, and all the rest of the plate particulars.
Then again, that's vioiln making...
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Last edited by ctviolin on Fri Feb 01, 2013 4:43 pm; edited 2 times in total |
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ctviolin
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| Posted: Fri Feb 01, 2013 2:31 pm Post subject: Re: Using cycloid curves in violin making... |
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| ctviolin wrote: |
An entire book could be written, I would guess, about how to manage these curves along with all the minute particulars having to do with violins, edge work, and all the rest of the plate particulars.
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I'd be interested in discussing this subject further with anyone inclined to discuss such matters.
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actonern
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| Posted: Fri Feb 01, 2013 5:35 pm Post subject: |
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Hi Craig:
I was reacting to Michaels earlier post as follows...
"A chain doesn't make the recurve. The inflection point of the curve from convex to concave is a crucial part of it. I started with the curves on the Strad mag posters, and fed their heights and widths into cycloid generating software to give me the idealized, curves, undistorted by time, for those violins, but now I use a method that's much more complex that accounts for the distortion of the long arches and any twisting of the body. That first step was a great improvement in my results, thought."
In other words his "moving beyond" simple cycloids...
I have tried to do my best to shape the arch according to the cyloid profile, but "moving beyond"??? Someday! |
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Michael Darnton
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| Posted: Fri Feb 01, 2013 7:11 pm Post subject: |
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Not beyond cycloids--beyond distortion. All the evidence we have is distorted. Copying the distortion works to a certain extent, but for a new violin it's important to figure out how a new violin should be. This centers, first of all, on coming up with plausible long arches for top and back, then building on that.
It may be obvious to us now that something cycloid-like is how a violin arch should be. For the last 200 years or so some type of replica of a Cremonese violin has been the norm. We accept some of the genuine oddities that are peculiar only to generated cycloids as self-evident--things like how the arch is more serpentine when it's low and wide, and fuller towards the edges when it's narrow and high. Those things are not obvious, though we're now used to them. For instance in 1650 or so the English makers didn't see a violin arch that way, nor did the Dutch, the French, the Germans, the Poles, the Venetians, the Brescians, the Romans, or any other local school of violin making. Only the Cremonese. Without understanding the uniqueness of this type of arch, and how different it is from what makers come up with on their own when they're not looking directly at Cremonese models, you can't appreciate how Cremonese it is.
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actonern
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| Posted: Fri Feb 01, 2013 7:55 pm Post subject: |
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Thanks for the clarification.
Since they didn't have computers and software back then they would have had to use little disks.
I take it the way to size the wheel for any given point of the arch is to measure the distance from one trough to the other, and that distance is the circumference of your disk. Then poke a hole through the disk at a point that is (from the centre of the disk) equal to the maximum height of the arch (at that cross arch point.) Then roll and trace...
The location of the lowest point of the trough from the edge... any ideas on how that was determined? One can do a pretty good job by eye, but is there any evidence of ratios or other means of arriving at it? |
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Michael Darnton
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actonern
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fjodor
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| Posted: Sat Feb 02, 2013 4:41 am Post subject: |
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After reading Michaels posts on the subject over the last years and having used cycloids on all the violins i made so far (2 1/2 ) , I must say, that to my unexperienced eye, you can certainly make nice looking archs with the help of them.
On the second violin i had one template for every cm of the plates (probably got the Idea from reading about Sam Compton 
I have to admit I haven't paid much attention to old violins and the placement of the low point of the scoop etc. but tried to place the lowest spot closer to the edge in the c-bouts. |
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actonern
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Michael Darnton
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actonern
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| Posted: Mon Feb 04, 2013 9:53 pm Post subject: |
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Way better... especially the upsweep profile towards the edge crest and how it changes depending on where on the plate you are.
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fjodor
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| Posted: Tue Feb 05, 2013 4:13 am Post subject: |
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Interesting pictures!
Do I interpret the Folinari right? It looks like it has almost no scoop and the arch rises almost directly from the edge.
(Interesting to me as my grandfather made his violins like this)
I tried to find a picture that shows the arch of the violin I made with the many templates I did'nt find a good one but here's a picture that shows both the front and back plate.
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