The
armature tunnel was then carefully filed out and all taken apart
again so that the rough edges could be scraped off and the
laminations given a thin coat of shellac varnish on one side.
After assembling a second time, the bolts were coated with shellac
and put into place for good. Holes 5-32 in. in diameter were
drilled in the corners, A, and filled with rivets, also varnished
before they were put in. When put together they should make a
piece 2 in. thick.
This peculiar construction was adopted because proper stampings
were not available, and as every bit of sheet iron had to be cut
with a small pair of tinners' snips, it was important to have a
very simple outline for the pieces. They are not particularly
accurate as it is, and when some of them got out of their proper
order while being varnished, an awkward job occurred in the magnet
which was never entirely corrected. No doubt some energy is lost
through the large number of joints, all representing breaks in the
magnetic circuit, but as the laminations are tightly held together
and the circuit is about as compact as it could possibly be,
probably the loss is not as great as it would appear at first
sight.
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