The Casey Jones drive has a small HO size motor with a worm gear directly driven to the rear geared axle. There is no flywheel on the motor. The drivers are not sprung.
It runs ok, but it is a plastic engine with a slug weight. It's not going to pull a lot of cars.
The drivers do look pretty nice. If my kitbash comes out nice I'm going to convert it to a NWSL gearbox.