oly 9

Hi, Im new to electrics but thought I'd ask a question. I have read the info about sizing the motor esc etc. The question is why could you just use a motor set up slightly larger than this formula stated. Would this be less work for a bigger motor and use less battery? I think that if you had the required rpm and the correct prop the speed would be the same? The motor would be working less and drawing less amps for the same rpm? The down side would be additional cost. Any other info some informed experienced flyers had would be helpful.

Dr Kiwi

Yes, you can use a somewhat "bigger" motor to serve the same purpose... running a motor below its rated maximum (often over-stated by manufacturers and distributors) is a good thing for efficiency and longevity... same with ESCs (don't run 'em at >80%). The only downside would be if weight is absolutely critical... the extra grams from over-sizing motor and ESC might be enough to compromise flight performance.

chuckk2

You can use a larger motor.
Remember that the load on the motor is a combination of the aircraft weight, propeller, battery voltage, and speed.
Ideally, test stand load should be the maximum load, assuming the propeller does not stall.
Let's say that a motor is rated at 45A continuous current, and 55A max for about 5-15 sec.
The test stand load should not exceed the max, and should be at or slightly above the continuous rating.
There is an efficiency factor as well. The RPM has a significant effect on it.