29 Nov
2014
29 Nov
'14
9:17 a.m.
Anyone remember Lionel trains? The power packs were AC (not DC as in
HO) and there was an impulse relay for reversing called an "E-Unit":
The old O gauge Hornby trains (old meaning 1930s) were also AC. The motors
were series wound, a single field coil on a pole piece assembly that fitted round
a 3 pole armature. The pole piece was in 2 parts, spring loaded to open. When
the motor was running the magnetic field kept it all together, but with no supply
voltage it would open up. There was a pawl mechanism operated by the moving
part of the pole piece which swapped the connections to the brushes, so reversing
the motor. So every start was in the opposite direction.
Do Marklin still make AC HO gauge locomotives? IIRC they used an overvoltage to
toggle the reversing relay.
-tony