ORIGINAL: crashland 73
they would make a good addition to an electric plane that would have enough RPM to get it to charge. then you could fly until your TX ran low. I would think anyway.
This can't work...
An electric motor is typically 80% efficient. 80% of the electric power absorbed in the motor gets converted to mechanical energy, 20% goes to friction and "I^2 *R" losses. (both make heat)
A generator is just a motor that is being turned instead of the motor turning the load.... you have the same 80% average efficiency.
About 90% of your motor's mechanical power would be going to pulling the aircraft through the air. So 10% of the mechanical power is going to be available to drive the generator. Now you have lost 20% of the electrical power to the inefficency of the motor... and just have 8% of the original electric power driving the generator... the generator loses 20% of that... so you now have 6.4% power going back to recharge the batteries.
You'd at BEST gain 30 seconds of cruising speed flight if the battery tended to give 10 min of flying. BUT... you added the weight of the gnerator... so you probably end up with a shorter total flight time.