[cameldrv]

It's hardly $30k to buy a gas drone. You can buy a Cox .049 engine for $50 or so.

You're looking at a fixed wing aircraft though with one of those. What's made the quadcopter drone possible is the high torque and instantaneous throttle response of small electric motors, combined with fast control electronics. The conventional way to fly a small helicopter is just like a full sized helicopter, with a main rotor and a mechanical swash plate.

With the right control electronics, these can easily be made into drones, but people tend to not like them as much anymore because they're mechanically complex and finicky. The electric motors are simple, and when one goes bad you just drop in a new one.

[twic]

Could you couple one of those engines to a generator, and use that to power the electric motors? You'd need a battery or supercapacitor to handle change in throttle demand that outpaces generator response too.

[jsjohnst]

Weight is the limiting factor. Try to find a generator that can output up to 400amps at 25V (what my big drone draws) and yet weighs less than five pounds including fuel.

I think that’s a more impossible goal than increasing power density in batteries is.

[danmaz74]

400 ampere??

[scotty79]

https://youtu.be/7zMPodObo-Y

This guy tries to make gasoline powered generator for large drone.

[yardie]

Thermal to mechanical to electrical to mechanical. That’s a lot of energy conversions and with each conversion you lose a lot of efficiencies.