[TCML] Tesla's spinning egg of Columbus
evp at pacbell.net
Tue Nov 18 17:37:10 MST 2008
On Sun, 16 Nov 2008, Ed Phillips wrote:
>> No particular reason to use a toroidal core except that they
>> look kinda neat - rectangular or square core would work equally well.
Unless you're trying for historical accuracy:
A laminated core of iron wire is probably easier to wind with roughly
circular cross-section (use hose clamps?)"
Hose clamps would probably act as shorted turns. Just wrapping with cloth tape would do just fine and would be in accordance with tradition.
When I attended the University of Missouri [1942-1944] a regular yearly even was Engineer's week with open houses in the various engineering deparments, coinciding with St. Patrick's day ["St. Patrick was an Engineer!"] and one of the standard EE exhibits [in addition to a pretty good TC of course] was "The Egg". The core was a toroid at least a foot in OD and looked to be of extremely ancient vintage. Don't know what the material was because the core itself was wrapped in varnished or shellacked cloth which was brown with age, almost like the pictures of mummy wrappings. The windings were cotton-covered wire, again indicating age and the thing was run two phase with a big capacitor feeding one winding. There was some kind of an egg but other objects were used too including, if I remember right, a little aluminum tea pot laid on its side. The coil was covered with a sheet of plywood so the spectators didn't really know what was happening until the exhibit keeper took the wood away.
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