Building a heavy duty magnet charger

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Additional shaped pole pieces are useful for charging flywheels, rotors, etc. The shapes and uses of additional pole pieces have been particularly well described in GEM May-June '77, pg. 16, and March '87, pp. 26 and 27.

Winding the coils
Insulating washers for the coil ends are cut from 5/16 inch thick fiberglass or other insulator and are epoxied to the core ends before winding. One washer for each coil should be prepared with brass terminal screws as shown. Allow ? inch of core to protrude from each washer. To prevent shorts, the core must be insulated. Cut manila folder into a strip, wind and cement it to the core between insulating washers. A half inch overlap prevents any possibility of shorts between the core and wire.

The use of magnet wire is important because wire with thick insulation can't be densely packed. Magnet wire is available from motor rewinding shops, transformer shops and suppliers specializing in magnet wire. The yellow pages of larger cities usually list these. 40 pounds of 10 gauge heavy formvar insulated magnet wire is required-20 pounds for each coil. Try to purchase two 20 pound rolls rather than one 40 pound roll. The exact number of turns is not important so don't bother counting turns, just wind until 20 pounds of wire is on each coil.

Wind the coils on a lathe using back gears and clutching. Mount the core with terminal end facing the lathe tailstock and run the lathe in reverse to make winding easy to view. This will insure winding direction and poles match those in the photos. Two people are required, one to operate the lathe clutch, while the second layers wire onto the core with gloved hands. If a lathe is not available, coils can be wound by attaching a crank with bolts threaded into each end of the core. The bolts may be run through wood supports which act as bearings and support the coil during the winding. 10 gauge wire is very heavy and a lot of force is required in order to make the windings neat and tight.

The actual winding is started by scraping off a half inch of insulation and poking the wire through the start hole in the insulating end washer and soldering it to a lug on the terminal marked '1'. The wire is then wound in layers progressively on top of each other. Try to keep the layers uniform with adjacent turns touching tightly. As winding progresses, it will be more and more difficult to prevent the winding from becoming scrambled. Eventually some scrambling will occur, but try to keep it to a minimum. After most of the 20 pounds is wound, the winding should be planned so the wire will end near the terminal end of the coil. Guide the wire through the notch on the insulating washer, scrape the insulation off and solder it to a lug at the terminal marked '2'. Tighten a nut and lock washer over each lug. Repeat the procedure for the second coil except mark the terminals '3' and '4' instead of '1' and '2'.

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