Ron Nossaman wrote: > > >So... you are gonna make me take a stance eh ??? I gotta bad feeling about > >this...grin.. but here goes.. > -------------------------------------------- > >Grin... so there you have it.. my humble musings on the matter for what > >they are worth. Now go ahead... :) tear me apart.. hehe.. > > I don't think you did badly at all. Grin.. nice to know I am not completely bonkers.. > > The biggest conceptual problem I see in all this is the notion that string > tension, with the tuning pins being levers, and the plate bushings being > fulcrums, will force a previously fitted pinblock away from the plate > flange. I don't believe it. I dont either, but I am not sure we are on the same wavelength as to why.. and I will explain my thinking. You draw up a situation where you figure the distribution of forces (leverage) and treat the top of the block and the bottom of the block (at least the bottom of the pin in the block) as two different entities to describe with straightforward leverage formula the distribution of the total leverage force exerted by the strings, via the tuning pins, on the block. And of course by treating the problem this way you get these huge differences in the top leverage visa vi the bottom leverage. I am kinda unconvinced that you can really do this..grin... and its simply because the block is a solid, continuous entity. Also.. since we are dealing with a fulcrum, we are also dealing with an force which would result in an object moveing in an arc, and not a straight line. From this point of view the block would only move "backwards" (in the case of bushed plates) in the context of the arc that the pin would follow if allowed to move on the fulcrum point. Looked at in this sense, the block is just an extension of the pin. The spaceing of the some 250 tuning pins will of course have to be averaged to find the exact arc, but the basic principal is the same. The only real difference I can see between the top of the block and the bottom of the block (with regard to the force being applied by the pin) is the ability of the wood at any given point to resist crushing. Be that as it may, the distribution of force on the block should be a continuous factor in keeping with the continuous nature of the block itself, and the direction of that force should move along the arc stipulated by the position of the fulcrum and length from the fulcrum to the bottom of the block. Now that may seem a bit confusing, as it is clear that the pin doesnt go all the way to the bottom of the block, yet the block is a whole solid thing, and it is this whole solid thing that has force applied to it. This is why I get the feeling that it is this "tilting" of the block (rocking I think you refer to it as) which is the major reason the block doesnt move much. The block wont go anywhere as the front and the back edge of the block are at opposite sides of this "circle" if you will, and as such (given the fact the the block is constrained from moveing upwards by the face of the plate, and downwards by the screws holding it) will tend to counter each other. Further any increase in "pressure" on any of these constaining forces will occur nearly directly against to them which can only increase the positional stability. The exact amount of divergence here would be decided by the difference between the length between the fulcrum and the point of force exerted by the strings, and the lenght between the fulcrum and the top of the pin block. If these two were equal, then there would be no horizontal movement at all. I fooled around at the workshop today with a few bits of wood and alluminum to check this out. I took a piece of alluminum to simulate a plate, screwed on a 1" by 2" to simulate a flange, and attached a "pinblock" and checked out what would happen given different situations when I applied tension to a string. As this post is getting too long I will write a separate post to tell you what exactly I did, and what happened. I think you may find it interesting... grin.. > > Ron N -- Richard Brekne I.C.P.T.G. N.P.T.F. Associate, PTG Bergen, Norway
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