robertdo Posted June 28, 2011 Report Posted June 28, 2011 Do you think the head of the bolds would be large enough to reach the Sacconi plateau?
James M. Jones Posted June 29, 2011 Author Report Posted June 29, 2011 There is a natural tendency (which I am gradually overcoming) to think of violin plates as loudspeaker cones... which they are not. One look at the Strad3D animations will show that immediately. At Oberlin this year, Evan Davis showed some theoretical modelling of surface radiators that indicated higher acoustic radiation efficiency for stiff edges vs. soft edges. I've beed suffering from the Plates as Loudspeaker syndrome since I began building... my teacher said it was false and....Well put it this way....I was taught to question authority, soooo..... It is a natural thought to see a comparison..If you don't have access to something like the 3D project to show the mechanical action that is really happining...Nowdays I'm recovering slowly... After seeing the 3D project, and revewing a paper a while back that showed OUT of plane movement as the radation mode of vibration, I'm thinking that a stronger edge would result in greater percentadge of Out of plane VS in plane vibration.....Don does this sound like what you are seeing in the models? Rodger....Thanks for gettin the thread back up...sometimes (for me)after looking at something it;s good to take a break and then come back with a fresh perspective...my question for you is do you see the plateau of the high arched models? I see the viola by strad has one ...nice writting BTW thanks...
Don Noon Posted June 29, 2011 Report Posted June 29, 2011 After seeing the 3D project, and revewing a paper a while back that showed OUT of plane movement as the radation mode of vibration, I'm thinking that a stronger edge would result in greater percentadge of Out of plane VS in plane vibration.....Don does this sound like what you are seeing in the models? That seems like a possible result of stiffer edges, but the Evan Davis work was more theoretical: for center-driven discs of equal area and equal natural frequency, the one with clamped edges would produce slightly more sound for a given driving force as compared to the disc with simply supported edges (i.e. thin periphery). Effective mass would be less, too... quicker response? While this is far removed from an actual violin plate, some of the trends might apply. It's also another clue that the loudspeaker cone concept might be best avoided.
Roger Hargrave Posted June 29, 2011 Report Posted June 29, 2011 I've beed suffering from the Plates as Loudspeaker syndrome since I began building... my teacher said it was false and....Well put it this way....I was taught to question authority, soooo..... It is a natural thought to see a comparison..If you don't have access to something like the 3D project to show the mechanical action that is really happining...Nowdays I'm recovering slowly... After seeing the 3D project, and revewing a paper a while back that showed OUT of plane movement as the radation mode of vibration, I'm thinking that a stronger edge would result in greater percentadge of Out of plane VS in plane vibration.....Don does this sound like what you are seeing in the models? Rodger....Thanks for gettin the thread back up...sometimes (for me)after looking at something it;s good to take a break and then come back with a fresh perspective...my question for you is do you see the plateau of the high arched models? I see the viola by strad has one ...nice writting BTW thanks... Lots of Strads have been altered even in the c'bouts (concave instead of convex curves from the linings are a give away). So its difficult to say but I think that they all had this platform to a greater or lesser extent.
Johnmasters Posted June 29, 2011 Report Posted June 29, 2011 I've beed suffering from the Plates as Loudspeaker syndrome since I began building... my teacher said it was false and....Well put it this way....I was taught to question authority, soooo..... It is a natural thought to see a comparison..If you don't have access to something like the 3D project to show the mechanical action that is really happining...Nowdays I'm recovering slowly... After seeing the 3D project, and revewing a paper a while back that showed OUT of plane movement as the radation mode of vibration, I'm thinking that a stronger edge would result in greater percentadge of Out of plane VS in plane vibration.....Don does this sound like what you are seeing in the models? Rodger....Thanks for gettin the thread back up...sometimes (for me)after looking at something it;s good to take a break and then come back with a fresh perspective...my question for you is do you see the plateau of the high arched models? I see the viola by strad has one ...nice writting BTW thanks... I have made this offer before, but you are a new person to me. If you buy the student version of ABAQUS finite element analysis, it will cost 100$. Or if you are a student at a university, it is free. You dont't need to learn to draw in it. I will send anyone decent models of a shell-element top, back, corpus etc. They work well to show the normal modes. You can change the wood properties. You will need to understand constraints etc, I can help anyone with this. I think it is a good excercise and the models are better than Schleskie's movies.
Will L Posted July 1, 2011 Report Posted July 1, 2011 Hi all, First of all, it's been driving me crazy that this is being called the "Sacconi plateau," since he's only reporting what he believed Strad to have done. I'm curious if anyone who may have opened a Sacconi instrument found that he followed Strad's short (north to south), wide upper blocks? In discussions with several makers over the years their belief was that with the advent of the morticed neck the longer, narrower block became a better choice.
James M. Jones Posted July 1, 2011 Author Report Posted July 1, 2011 Hi all, First of all, it's been driving me crazy that this is being called the "Sacconi plateau," since he's only reporting what he believed Strad to have done. I feel the same when they say Chris Columbus "discovered America"..."It's a little like discovering Bagels, I'm wondering if other maker of the day used "it" the S. plateau.
Will L Posted July 1, 2011 Report Posted July 1, 2011 I wonder that, too James, I've never heard it mentioned with any other maker.
Doc Eastman Posted September 9, 2011 Report Posted September 9, 2011 I have a question about this discussion of uncarved areas around the blocks and in general. Sacconi (page 66 Thickness for the belly and back of a violin) shows a distinct 3.3 mm thickness area around the entire perimeter of both plates. Considerably broader (est about 20mm) on the back and less on the belly. Measurements differ from those taken of the 1694 "Maria Ex-Muir Mackenzie" Stradivarius "long pattern" that "except for a small repair to the pegbox..suffered no structural damage..the inside work is so fresh that it has almost the shocking appearance of a modern copy" (quotes and measurements from Roger Hargrave from The Strad Poster, The Strad 1985). Here, the thickness right out to the edge is 2.5-2.6 mm all the way around. From these comments this is not due to later reworking of the plates. Obviously not a significant structural problem as this Strad has survived 300+ years with repair to the plates. Apparently a minimum of 52 were made, with 8 fine examples cited by the Hill Brothers. The "Milanollo" Strad poster of the 1728 instrument show thicknesses of 2.15-2.6 at the UB and LB and a little more at the points 2.7-3.2 and Cs 2.4-3.1. I was taught to put the shelf in, but have been following the posters and carrying the thinness as close as possible to the linings without disturbing the glue joint. I even further thin the back close to the lining joint at the edges after glue up and mould removal. Have to leave a little margin of error on the top. Why the difference? What do expert makers do? Is there a right answer?
Michael_Molnar Posted September 9, 2011 Report Posted September 9, 2011 Doc, Did you read this entire thread?
Doc Eastman Posted September 9, 2011 Report Posted September 9, 2011 Doc, Did you read this entire thread? I guess I didn't put my question is the right place or phrase it correctly. I believe I have read this dialogue about three times. I have expanded the browser to view the whole thread, I believe. The thread is about the area to the sides of the endblocks, and whether they should be carved or left uncarved as suggested by Sacconi. That is not the issue I raise. My question is different, and relates to the potential plateau that Sacconi shows of 3.3 mm on the rest of the plate. I put my question about the rest of the plate here because i couldn't find any other posts on this issue (admittedly very new at this). My issue is with the discrepacy between the posters and Sacconi at the perimeter of both plates. In someone has explained this elsewhere please enlighten me.
Doc Eastman Posted September 9, 2011 Report Posted September 9, 2011 I guess I didn't put my question is the right place or phrase it correctly. I believe I have read this dialogue about three times. I have expanded the browser to view the whole thread, I believe. The thread is about the area to the sides of the endblocks, and whether they should be carved or left uncarved as suggested by Sacconi. That is not the issue I raise. My question is different, and relates to the potential plateau that Sacconi shows of 3.3 mm on the rest of the plate. I put my question about the rest of the plate here because i couldn't find any other posts on this issue (admittedly very new at this). My issue is with the discrepacy between the posters and Sacconi at the perimeter of both plates. In someone has explained this elsewhere please enlighten me. Just ran it again,11 pages, 211 posts. Fascinating stuff. My post clearly in the wrong place. Probably why nobody responded. I tried again in a post on back graduation. Sorry to bother you. A serious question deserves serious consideration...
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