Originally Posted by solentlife
Very true .... I've run both Out and In runners .... both up to 5000kv formats .... difference ? Haven't been able to detect significant benefit other than slimmer motor body allowing exhaust flow of fan to be cleaner / less obstructed with the inrunner.
Whatever you do ... it all still obeys Physics Laws ... you don't get anything for nothing. You may gain a little by increasing efficiency of motor by a few % points - but that's it.
In my view - the biggest gains are got by :
a) Better battery to provide the power needed
b) Clean efficient ducting.
correct, and most of the efficiency differences can be attributed to minor heating differences. one thing an inrunner does better is get the windings heat to the case of the motor for better heat sinking , IF the motor is in the airflow or in a alum housing. an outrunner is easier to cool using a standoff, no alum housing needed, so again, not a big difference overall.
the biggest efficiently gain is in dropping the kv to the magic point where minimum heating occurs , not from having an in or outrunner. , imo