I don't do a great deal of custom pickup work, but for things like old lap
steel pickup magnets or the occasional evil experiment, I'm getting tired
of the crude recharging of pickups with permanent magnets. I know it can
be done well, and I've a handful of magnet holders I've made to get an
even field across the length of a pickup, but I'd still like a bit more
convenience and control. So I've been meaning for some time to make a
coil system for discharging and recharging, and was hoping someone
may have some suggestions on a few details.
My main question is, does anyone have a ballpark wattage I should be
shooting at for adequate power? Here's my general design idea if it helps.
Two coil system, one stationary on bottom, and a moveable one on top.
Perhaps laid out similar to an arbor press, or simply guide rods past the
ends of the coil and a simple clamping system. The idea is simply to
clamp the magnet(s)/pickup to be charged between the two coils, in as
simple a means as possible. My designs for projects like this often tend
to form around the shape of materials near the top of my scrap bins, so
finer mechanical aspects are still up in the air. Dimensionally, thinking
1"x4" by 1" height soft iron cores, in efforts to keep the charging field
(relatively) straight and even across the entire pickup.
Where I start with making the coils depends on a sense of what an
appropriate wattage would be to start with . If I was looking at the
100-200 watt range, then a lawn tractor battery would be fine and
economical. If I needed to be closer to the 800-1000 watt range, I may
not want to heat the coils with the 75 amps, and would perhaps start
looking for a higher voltage DC power supply. Unfortunately those get
expensive once you want more than a few amps. I could make some sort
of a rectifier I suppose, but the simplicity of a car battery appeals to me
more. I won't be trying to charge any neodymium or samarium cobalt
here, but more along the lines of things like alnico 2 or 5.
Of course decisions on wire gauge, turns, etc., all depend on those
variables, so I'm just fishing for suggestions on wattage range here. Of
course this would all be different with AC, but I'm just concerned with DC
at the momet. Should I ever want to use it as a demagnetizer I have a pile
of Variacs to bring voltage to whatever I find necessary. Those and a few
good heavy rheostats for dropping the DC voltage from a battery for
adjustment as well.
I know the actual workings should be more appropriately discussed in
joules, oersteds, gauss, ampere-turns, etc. If you think the idea is too
simple, too small, or can't be solved in volts, amps, watts, and trial and
error, let me know.
Any thoughts are welcome.
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