Dan Padova posted:Interesting. In all the years I've been in this hobby, I have never taken the time to understand those early transformers. So each contact on the transformer is a step in voltage and the restate is used to make the transition smooth ?
Those transfomers, first sold in 1914, were not developed for use with locomotives with automatic reversing. Lionel first showed automatic reverse units in its catalog in 1927. Also in that year, Lionel introduced the No. 81 "controlling rheostat", It was replaced by the #95 in 1934. The #95 had a reverse control button instead of the on-off switch.
Before there was automatic reversing, the brief current interruption from moving the contact lever didn't matter. After that, an external rheostat was needed for continuous current with speed control.
By experimentation, I've learned how to best use one of those transformers with the rheostat. With that Type B, I would begin with the B-X range. See what voltage is needed to run your locomotive at the highest speed that you want to see and leave it set for that voltage. Then use the rheostat to reduce the speed. It would be a most unusual locomotive that wouldn't stop before you moved the controller so the full resistance of the coil is in series with the motor. If you can't get a high enough speed with B-X, then go to A-X. The maximim of 12 volts for C-X won't move any prewar locomotive that I have.
Interesting side note from the 1936 catalog - the 1029 included with Lionel Jr. sets is referred to as a "Speed Control Transfomer". The older style is called "Multi-volt transformer."
