Reddit mentions of The Original Lighting Antenna Flipping Spinning Tumble Buggy, Color May Vary (Red or Blue)

Please feel free to ask me any questions. I'll be glad to advise as best I can. The constant voltage power supply will really help isolate the voltage variable, and as I assume you know, power is wattage, and wattage is the product of voltage and current. As was discussed earlier, varying battery voltage WILL affect your results; get rid of that variable altogether. If you need some ideas on what to use for a power supply, let me know. Do you have the brand and model number of the car, or can you tell me where you found it? I wanted to see if I could find the electrical specs.

EDIT: Found it.

EDIT 2: The thing operates on two C batteries in series, so 3v. I see that there are LEDs for the antenna and headlights. You could de-solder that, or just cut the wires, to simplify things a bit, allowing you to remove or replace the body. Something that concerns me is the "Flipping Spinning Tumble" thing. I don't see any electronics that makes this thing do any of that, nor does anything in the gearing look to be doing that, but it is hard to tell from the one picture. I would consider disabling any of that spinning/flipping stuff. I would also consider removing a gear in the series of them leading to the axle farthest from the motor. Reason for that is to help with your experimentation: Center of gravity close to the drive wheels versus away. With it being 4WD, well, that reduces your options.

Aside from a bench-top power supply, I'm struggling to come up with what a suitable constant 3V power supply would be... that isn't nearly as common as 5v, 9v, or 12v supplies which could be taken out of... oh, wait... Do this: borrow a power supply from an old computer of most any kind. The 3.3v of an ATX power supply would be able to handle 20A or more, WAY more than you'd be drawing. Yep, do that. The orange wires should be 3.3v. The blacks will be common.

Okay, what's next? :)