JIMRPT@AOL.COM wrote: > In a message dated 8/24/1999 4:01:03 AM, richardb@c2i.net writes: > > << If you replace the pivot with a wider, rounder surfoace,then > the flexing of the string is dispersed in several directions, thus increasing > friction and thereby wear. >> > > Richard; > I am not Ed nor am I a University web site but............. :-) > Whatever result widening/rounding a surface of any given material would > give, increasing wear (i.e. quicker, deeper grooves) is not one of them. To > decrease wear on any given point all one needs to do is spread the load which > in effect is what "rounding" a termination does. Given a harder material and > a softer material, both subject to grooving, and giving both materials a face > with a V shape of the same crossectional size the softer material will will > develop grooves faster than the harder, all other things being equal. > If you change the shape to U shape for the softer material and keep a V > shape for the harder material the 'groove rate' would approach equality, and > depending on cross sectional sizes the softer material may groove much more > slowly than the harder, all other things being equal. Conversely If you use > the V shape for the softer material, and the U shape for the harder, the > softer material will develop grooves much faster than the harder, again all > other things being equal. > While there may be more 'friction' on a 'moving' entity across a wider face > than a narrow face this added friction does not relate directly to more wear > on the surface that remains stationary, i.e Capo bar except as a coefficient > (?) of hardness would dictate. > > Now as I understand Ed's contention he says that increasing the hardness > and increasing the cross sectional size will cause grooving much faster....If > my understanding of what he says is correct then I must respectfully disagree > with him. Load spreading is a well known principle and not a theory. Load > spreading is what allows a 50 ton tank, with 'tracked' propulsion, to > traverse sandy terrain without sinking in too deeply...whereas the same 50 > ton tank with four or six 'wheels' would sink in much further and perhaps not > be able to traverse the same terrain as its tracked cousin. The difference > here is 'load spreading', or 'footprint' and it is mostly linear the same as > a wires termination at the capo...the same principle applies..........i.e. > more footprint less grooving/less footprint more grooving...ya can't have it > both ways Cuz :-) Compelling post to be sure.. But still you, Ron and others showing skeptism do not address directly the contention that we are not dealing with load spreading in the sense you describe. With a string vibrating under tension, and terminated at a given point, the contour of that point determines to no small degree the vibrational axis of the string. Now if it is true that a pivot termination provides for a high degree of only "up down" vibration at that terminiation point, and that a rounded broad point allows for sideways movement at that point, it stands to reason that there is going to be more wear and tear. Again, I have to say I cannot accept the "load spreading" explanation unless this contention is adequately refuted. I will make my own analogy. Take a board and set it up on a straight sharp edge, weight both ends so that the board is in balance, and rock the board. (I will leave out the vibration for the moment, but you could just as well put it in there). The board is going to have a very strong tendency to rock in a plane perpendicular to the sharp edge. There will be wear on both the board and the edge. Now round off that edge and make it a bit wider, keep all other things the same. The board now will show an increased tendency to move in direction not 90 degrees from the rounded edge. Such a condition add to the wear equation an element of ... shall we say grinding ???. Now as strings vibrate in different planes (we have all seen this and it is easily observable) there will be a tendency for the string to try and vibrate at the termination point in the same plane the rest of the string is in at any given time. If the termination point doesn't inhibit this then it allows for it. No way around that. To use your own analogy about the footprint. It is also a well know fact that you will sink faster into a mud hole if you rotate your feet and work your way down then if you keep your feet still. All this relates to the degree of wear on the capo bar, and the string itself. Ed himself does not speak much of the degree of wear on the capo bar, those statements are my own conclusions drawn from his explanations of the differences between clamped and pivoted string behavoir. He does hint (by my reading) in this direction tho. Eds point is more that the grooves created (and in any case there will be grooves) are not in themselves the important point, it is that the grooves should not be allowed to be the source of string buzz. His contention is, and my experience supports this, that the V profile at around 0,5 mm is best suited to prevent this. When in addition this condition decreases string stiffness, allows the string to vibrate more freely at its full length, (this is from Benades book on the Fundementals of Music Acoustics), increases the propogation of higher partials (also from Benades book, due to decreased stiffness), then the reasons for accepting the V bar at 0,5 become very compelling indeed. If one first accepts the V profile then one has to accept that with such a profile there will be string breakage if the material of the profile is to hard. Thereby the need for softer iron. As to the rest of this buisness about the V-pro plate, its real hardness (and not what it "seems" to be), this I suppose will have to wait until someone with the means to measure the hardness can produce the data. Until then I suppose its useless to delve further into the buisness of if and how and eventually why the "harder" plate will be the source of a metalic colouring of the total sound picture. > > > Now Ed says that a harder plate with a rounder capo will cause deeper > grooves? Misunderstood. see above > > > Jim Bryant (FL) > P.S. Besides I thought the general consensus of thought here was that the > V-pro plate seemed "softer" than the sand cast plate. <:( Like I said, there has been one statement about the Skin of the plate, Mark Bolsius stated that it was his impression that the V-Pro Plate was softer, and also states that the sand cast have a harder shell, Other then that there were no specific declarations as to the matter. Ed says they are harder, and they certainly (my experience) take greater effort to file. Again, I suppose if we are to get any further along this matter of which is the harder plate needs to be firmly established beyond anyones doubt. Richard Brekne I.C.P.T.G. N.P.T.F. Bergen, Norway
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