I put away the Lionel for a while and got out the Marx set. I have added a few 7" cars to this set. Here is a video of it cruising leisurely along.
Here is a short clip of it really moving at about 12 volts..
I need to watch the voltage with my ZW. The Marx set is made for a 14 volt power supply and I don't want to toast the motor.
I like the Iron City car; it matches in size but has the modern trucks compared to the other 4 wheel cars.
Happy Holidays!
George