[GreenKeys] Why Dual Coil Electromagnets? ANSWER

[Brooke Clarke]

Hi:

One the same day that I posted this question what may be the answer arrived in 
a big box.  Inside was another Self Winding Clock Co "Western Union" clock 
which I ordered because it has a big seconds hand.  Movement # 402,449 a much 
higher number than 39,580 made in the early 1910 time frame.

But the treasure part is the synchronizing coil.  There's only one!
Whereas the all the normal clocks I've seen have a pair of coils about 1" dia x 
2" long this newer clock has the single coil that's about 1 3/4" dia x 2.5" 
long.  Also instead of being driven directly from the telegraph line like the 
older S.W.C.C. clocks this one has a relay driven by the line that uses the 
local battery to drive the single coil.  Both the older and newer clocks use 
the local battery to light the red "lightening bolt" lamp.

There's one very noticeable new feature to the new coil, it uses a laminated 
core.  Yesterday I was reading "Solenoids, Electromagnets and Electromagnetic 
Windings" first edition 1910 second edition 1914.  It just barley mentions 
laminated cores in relation to AC plunger solenoids and nowhere else.  There is 
a lot information on iron clad electromagnets.

This single coil has an armature that's of strange to me construction.

Now to figure out when laminated cores showed up in "DC" electromagnets?

More at:
http://www.prc68.com/I/SWCC2.shtml#SC

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com