This drives for maximal use of scrap, cheap but labor intensive. If you use a core, perhaps the combined cores from 10 to 30 discarded microwave ovens could help.
How is the strength of the magnet scored? It is really driven by ampere turns. How long does the field have to last?
Based on what i have seen so far, my approach would be on the order of
10 turns of 1/4 inch copper tubing supplied by 1 or 2 lead-acid (auto) batteries.
I realize I'm coming into this thread a bit late, but did you give any thought to bypassing the power supply completely and building an AC electromagnet?
I dimly recall plans for building one of these from year... er, decades back in a hobbyist magazine (Popular Electronics?); one of its interesting features was that it would pick up non-ferrous metals.
Anyone know how AC and DC electromagnets compare as far as efficiency when both are powered from an AC source?
Frank McKenney
--
A striking fact of the last two years of financial trouble is how
accountability has differed in the public and private spheres. On
Wall Street and across the country, decades-old firms have failed,
fortunes have vanished, and some former captains of finance face
jail or fines. In Washington, meanwhile, most regulators and
Members of Congress remain on the job, often with enhanced power.
-- "Bernanke\'s Second Chance" / Wall Street Journal 08/26/09
What
Once the iron saturates all reasonable measurements are iffy at best. The force measured will be limited by saturation flux in the iron.
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