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That's an excellent question, and a rather uncommon one. Are you in the field of electromagnetics or particle physics? I have considered using a flux concentrator but I haven't actually tried it. As you know, a flux concentrator could be made from a cylindrical piece of copper or aluminum with a radial slot cut from one end to the other to create a thick C-shaped cylinder. There are several reasons why I've not tried this approach. Because of the presence of the slot in the concentrator, there's a substantial non-uniformity in the shape of the magnetic field inside the concentrator that creates non-uniform shrinkage forces between the coin and the concentrator in the area directly beneath the slot. This causes a noticeable "kink" in the shrunken object at the location beneath the slot in the concentrator. While this often does not matter for many industrial applications, it is very undesirable from an esthetic standpoint for coin shrinking. There are a couple more subtle reasons as well. Joule losses within the flux concentrator mean that significantly more energy (60-80%) needs to be applied to the work coil in order to obtain the same degree of shrinkage forces. This means that the capacitor bank must be charged to a higher initial voltage before each shot. However, because a robustly built larger diameter work coil would no longer disintegrate, the capacitor bank and spark gap would now see a complete ringing oscillatory discharge. A high-Q ringing discharge is very stressful on both the capacitor bank and the trigatron switch (spark gap). To insure survival, the maximum voltage rating of the capacitors in the bank must be at least twice the maximum charging voltage to prevent overvolting the capacitors during voltage reversals. Also, significantly more energy is now dissipated within the spark gap since it is the main lossy component in the discharge path. Energy that was previously dissipated in the exploding work coil and plasma ball is now expended in evaporating the main spark gap electrodes and more frequent tear down and maintenance of the trigatron. Expendable and inexpensive magnet wire work coils only take about 30 seconds to wind, so I've chosen to use this approach instead of making major design changes to the system and fabricating custom flux concentrators. However, if coin shrinking ever became a high volume enterprise, I'd definitely reconsider the possibility of using flux concentrators and heavy-duty work coils. Best regards, -- Bert --
: Why don't you use a flux concentrator to shrink quarters? It would seem to me
: that it would save you from a disintegrating work coil each time, and you
: wouldn't get the effects such disintegration causes.
: Is there some reason why not?
:
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