madman
I discovered that the voltage range put out through the rheostat, wasn't fine enough for the task.
That's because, as you have discovered, the rheostat is a current limiting device rather than a voltage reducing device.
As the load in the circuit rises, the effect of limiting the current will be a drop in voltage, but this will not manifest in your light duty application.
If you power a single #53 lamp with the rheostat, you will find that it does not dim the lamp at all.
