I was just thinking about some drones and remembered that some cheap brushed drones actually have a gear on the prop and motor and are not directly driven. Then I thought about cars. Like you dont wanna drive down the highway in 2nd gear at 7000rpm, itd use up a lot more fuel than 5th gear at 2500rpm etc.

So with that in mind, a motor becomes more efficient and can produce more thrust with a gear than without one?

Hmm to simplify it, lets say you want to run the propeller at 16000 rpm, direct driven the motor would run at 16000 rpm, and lets such each motor is consuming 5 Amps around 7.4 volts.

With a 2:1 gear ratio, there would be some efficiency loss between through it, but the motor would need to run around 8000 rpm now instead of 16000 rpm to produce the desired 16000 rpm at the prop.

The load should clearly be bigger on the motor than without the gear ratio at the same motor rpm of 8000 rpm, so should draw more current, but would it draw less current than 16000 rpm direct drive? Assuming it doesnt need to change speed much.

I mean for a car its using less fuel with a bigger gear ratio to run at the same speed.