To evaluate the slot, I “routed” a simple oval, with a 9″ radius on one end and a 10″ radius on the other. I then painted the slot and area where the car would run with flat latex paint, as is common practice.
Finally, the track was taped with 1/4″ wide copper tape and directly connected the rails to my adjustable power supply. I printed this handy tool from thingiverse, which worked great.
https://www.thingiverse.com/thing:2008389
I grabbed a car and set the power voltage to where the car would just stay in the slot and let it run for several hours at a time, accumulating almost 15 hours of running.
The slot showed no wear, however the motor in the car clearly didn’t like all of the continuous operation.