This
paper shell is made of stiff paper and glue the same as B and is
made about 3/64 in. thick. Two pieces of hardwood, EE, 1-3/4 in.
square and about 5/16 in. thick, are drilled in the center and
glued on the ends of the paper shell as shown.
The primary winding consists of 4 or 5 layers of No. 18 or 20
single cotton-covered magnet wire, the ends of which may be passed
through small holes in the wooden ends. If a drill small enough is
not available, the holes may be made with a hot knitting needle or
a piece of wire heated to redness. After the primary coil is wound
it should be thoroughly insulated before winding the secondary.
This may be done by wrapping with 4 or 5 thicknesses of paper.
The secondary coil should be wound with single covered wire,
preferably silk-covered, although cotton will do. The more turns
there are on the secondary the higher the voltage will be, so the
wire used must be fine. Number 32 to 36 will give good results,
the latter giving more voltage but less amperage. Each layer of
the secondary winding should be insulated from the others by a
piece of thin paraffined paper wrapped over each layer as it is
finished.
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