[TomMckenny]

The wheels drive the propeller.

Place the vehicle on a moving treadmill with the wheels rotating at the speed of the treadmill belt so it is unmoving in the middle of this treadmill. The wheel gearing would drive the propeller. Notionally, the propeller adds thrust to the vehicle more than it adds resistance to the wheels and causes the vehicle to move forward on the treadmill.

But consider, if you put an ideal toy car on a treadmill with a friction less axle etc, it would obviously never exceed the treadmills speed. At best it would stay mid treadmill for ever.

The idea is that some combination of additional gears and propeller would allow that toy car to continuously to speed up, theoretically infinitely. Understandably there is skepticism about this.