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  • #16
    I bet unoriented AlNiCo 5 has a higher permeability also, but I can't find a spec sheet to confirm.

    I happened upon an interesting explanation about unoriented AlNiCo 5:

    https://books.google.com/books?id=_H...page&q&f=false


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    • #17
      Originally posted by Antigua View Post

      It's just like the core of as transfomer, the permeability of the steel reduces the reluctance between the two coils, as it does between the pickup coil and the strings.
      Permeability can only reduce reluctance in the permeable material, not in air where permeability is 1 and reluctance only depends on the length of the flux path.
      EMF does not depend on absolute reluctance either.
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      • #18
        Originally posted by Helmholtz View Post

        Permeability can only reduce reluctance in the permeable material, not in air where permeability is 1 and reluctance only depends on the length of the flux path.
        EMF does not depend on absolute reluctance either.
        I'm not sure what you're saying; the permeable material in question is in the core of the coil, a location where the impact of permeability is very significant.

        Each turn of the coil can be conceptualized as it's own single turn coil unto itself, part of a network connected in series. The permeable core reduces the amount "air" between the strings and the lowest turns of the coil, furthest from the strings, and that's why you get more overall output. The turns near the top of the coil, which are separated from the string almost entirely by air, are less impacted.

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        • #19
          Originally posted by Antigua View Post
          I bet unoriented AlNiCo 5 has a higher permeability also, but I can't find a spec sheet to confirm.
          ]
          I does, I verified.
          Interestingly, regular anisotropic A5 has different permeabilities along and othogonally to its preferential magnetization axis. The latter is much higher.

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          • #20
            Originally posted by Helmholtz View Post

            No, I was speaking of regular (anisotropic) A5. Unoriented A5 is just incompletely processed A5. It only charges up to around 70% of regular A5 and I wonder if it was ever used commercially in the old days.
            I've heard that the unoriented 5's can be different from each other [and that a regular A4 is a better bet].

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            • #21
              Originally posted by mozz View Post
              If it was cheaper, and i think it was, i'm sure it was used. I've read A2, A3, A4 are all unoriented.
              I spent several hundred Euros on permanent magnet literature. The most comprehensive (and expensive) book being "Permanent Magnet Design and Apllication Handbook" by L.R. Moskowitz containing a wealth of information on former magnet types and manufacturers - highly recommended to alnico magnet freaks like me.. The only mention of unoriented A5 I found in a German book describing a lab experiment showing how the field treatment resulting in anisotropic A5 improves the magnetic properties of the A5 alloy.

              And yes, A2, A3, A4 are all unoriented. A3 being the weakest* (when used in HB bar shape) should be the least expensive as it doesn't contain cobalt, so it actually is an AlNi, not an AlNiCo.
              * Actually A4 has the lowest remanence of all alnicos but has relatively high coercivity, both values influence the actual strength of a free magnet of given shape.
              A4 is also an example that shows that remanence and permeability are not related, as it has low remanence and low permeability. I could also show that the permeability of charged magnets is higher than that of uncharged ones.
              Last edited by Helmholtz; 06-16-2020, 04:56 PM.
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