#16
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There are 3 main variables to resonance: mass, stiffness, and size. High mass=low frequency High stiffness=high frequency Large size=low frequency So if you lighten up on the bridge, frequency will go up. But if you reduce the torque on the soundboard (lower string tension, or setting the neck angle for a lower target string height), then you can loosen up the bracing without the soundboard going S-shaped over time, and get the frequency back down that way. It's a good trick for small guitars, which naturally tend toward high frequency. In general, light-and-loose guitars are louder than stiff-and-heavy. But louder means that any unevenness in the frequency response will be more obvious, so it's harder to make them sound "good". Quote:
No, but I think the location is important. For example, dead weight added by a thick layer of finish over the whole soundboard will probably have a different effect than dead weight added by brass bridge pins. But the saddle, pins, and bridge plate can be considered part of the bridge, since they're all in about the same place and more or less rigidly connected to eachother. |
#17
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One of the reasons pinless bridges are used is to facilitate lattice bracing, which can be directly under where the bridge would be, possibly causing interference with bridge pins. While the bracing can be arranged that theee is clearance, it remives freedom of placement |
#18
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Think of it like this, you have a plastic bucket full of water. Will you try to pick it up by grasping the lid, or by the bottom of the bucket? ( I know, poor analogy)
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#19
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I see where you're going, and I do believe that you may be able to make a lighter than normal bridge by using a lexan plate to anchor the strings. There are other ways. I slant the saddle back about 8°, which greatly reduces the load the saddle puts on the front of the slot, so the slot can be closer to the front of the bridge. I angle the pins back at about the same angle. The bridge is full height for the front half, the back half angles from full height to about 1/16" thick. The last bridge I made was madrose and weighed less than 20 grams.
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Rodger Knox, PE 1917 Martin 0-28 1956 Gibson J-50 et al |
#20
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I remember reading about a bridge design in Symogi's book, I forgot the luthier now, but he designed he bridge to be more or less an I-Beam laying on it's side such that the I-beam flanges were the front and rear of the bridge and the web was in the middle. This was done mostly on the wings of course but the idea was to loose weight while retaining strength. |
#21
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I've retopped a couple plywood top guitars (and have one now) where the bridge had rotated at least 20-25 degrees, warping the top - and the bridge didn't release. Peel is not the problem if you glued the bridge right, and you have sufficient support under the bridge. It could be just 1-2mm past the back of the bridge if you want. Of course if you designed a flexible bridge plate that's another story. |
#22
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#23
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By lowering the point on the top of the bridge where the string emerge , there will be less leverage creating shear on the bridge . Combine that with a bridge shape that can enhance strength and the ability to place mass/weight directly under the bridge and easily change the shape and the mass/weight of the anchoring piece , in my case lexan , it should be possible to reduce shear and tune by mass/weight via the bridge area . Since there is no requirement of a surface for pins to anchor to like in a conventional bridge , bridge design can be optimized for stiffness with no real sacrifice . As long as the bridge can handle the load created by the saddle/s it's shape and mass/weight can be modified as needed or desired . I made this pinless bridge to a design that it actually does not need because that design is based on a pinned bridge . I could have greatly lessened the effect of shear by making the lever much shorter . Because mass/weight can now be added or taken away as desired , I can add to the bass side and/or limit/lessen the treble or any combination that I choose via the plate under the bridge plate that anchors the strings . By having the strings anchored to this plate , it makes the plate an integral part of the bridge . Please excuse me if I am using inaccurate terminology . |
#24
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Notwithstanding the inaccurate terminology, your logic is not sound.
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#25
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A string travels straight upward from a fixed point and is under tension . At a point , that string changes direction . At the point that the string changes direction there are no forces in play . |
#26
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OK .
Bridge plate thickness .125 Top thickness .125 Bridge thickness .375 Total .625 Bridge plate thickness .125 Top thickness .125 Bridge thickness .150 Total .400 While these are random numbers that mirror real world numbers , I am using them to try to show my point . Will these 2 setups have identical forces acting on them given that saddles height , string anchor point and string tension are identical ? I say no . |
#27
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I believe, regardless of how the bridge is shaped, you can diagram any bridge by its base length, height at top of saddle (relative to top of the soundboard), and distance (average) from front of bridge to saddle. I postulate, that if the interface between bridge and saddle is strong enough, for bridges of equal "triangular" diagram, it doesn't really matter much where the string is anchored as far as how the bridge affects the top, because the length behind the bridge is so short that the string at that length acts as a rigid bar, and any difference in stretch would be negligible.
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#28
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#29
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Otterhound: You appear to be confusing shear with torsion (twisting). Shear forces will remain the same as they are dependent on string tension, which does not change. Torsion is a function of leverage and can be loosely defined, in terms of the bridge, by the length of the base in relation to the height of the saddle off the top. I.e.: 1 3/8" x 1/2", which is typical in my work. Perhaps counter-intuitively, it doesn't make a lot of difference whether the bridge is pins or non-pins. The conventional bridge nearly everybody uses is rigid enough that it is best thought of as a solid unit including the saddle and the bridge pins AND the strings from the saddle to the ball end. By extension, the top and bridge plate directly under the footprint of the bridge are part of the mass equation, but perhaps less so of the torsional equation, and not at all of the shear equation.
The important point here is to think of the bridge (from the side) as a solid triangular geometric form with a specific variable footprint, depending on design. The problem with lowering the height is that since the shear does not change, the footprint cannot be diminished, and the top structure must be able to hold the tension, while at the same time the torsion has been reduced below the level required to drive the top. The up shot is that the guitar may act overbuilt, sound thin, and lack volume. . . or so I'd expect. I have written of this concept before and taken some criticism, but it is how I think of it and it has served me well. Also, your suggested bridge plate is a bit thick IMO. I believe few go over .1", and I find .075" very adequate. This thread has proven more interesting that I first expected. |
#30
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Diagrams of what Bruce stated.
I'll repeat this one from my response in your other thread. (From http://www.mimf.com/phpbb/viewtopic....=1126&start=20) Last edited by charles Tauber; 12-22-2017 at 09:16 PM. |