Originally Posted by MADMAC
At the same power (approx.) does a brushed motor draw more or less amps than brushless?
Yeah, at the same power OUTPUT
on the motor shaft, a quality brushless motor will draw far less input Amps than a quality brush type motor. The problem with the brush type motors is the brush timing issue. The ideal timing on the brushes versus the magnets varies with the amps being pulled by the motor. So, if you time the brush type motor to ideal at full power, that timing will be way off at 50% throttle. The result is at 50% power, the motor efficiency is absolutely terrible. Or if you set the timing at 50% power, its way off at full power. I did a lot of investigation on this with an oscilloscope and my various Astroflight Geared 25, 40, and 90 sized Cobalt motors.
When you get into motors around 1KW or larger, the brushless motor efficiency approaches 90%.
Years ago, I built a 150% version of that Electrostreak that was popular in the late 1990's. The front end of that model was designed to allow easy swap out of the motor mounting plate. It was bolted to the front of the model.
That model started off with a $$$$ Astroflight geared 40 motor, with a 13X10 prop, and 22 Nicad cells with 2400 mah rating. Power was around 650 Watts. Flights were on the order of 3-4 minutes. On landing, everything was so hot I put together a blower to cool things off while recharging those Nicad batteries. You could not touch that Astro motor after a flight without burning your self.
Moving on to the present, that same model now has a Hacker A50-12S motor, and a 6S2P A123 battery pack. The prop was bumped up to a 15X10, watts is around 1200. FYI, that Astro motor turned the 13X10 prop at about 7000 RPM, the Hacker turns the 15X10 at 7600 RPM.
The motor is putting double the watts on the propeller shaft, and at the same time, flying time with the 4000 Mah A123 pack doubled to 6-8 minutes. And, at the same time, the overall weight of the model was reduced by a full POUND! The model will fly straight up, out of sight on that Hacker motor. And, the Hacker motor is only lukewarm after a hard flight.
So, in my case, with the same model, brushless motors far outperform the old geared brush type motors.
More reading info
Thread on 70 size glow engine conversion to electric
Hacker 6S2P A123 powered Models
Hangar 9 Kantana Model
Hanger 9 Twist 40 Model