It is time for the "Duh" question.  Airflow through an outrunner motor is from front to back.  So I searched for "what is the front" and all I got was "the end you mount the prop on with either an adapter or a collet. (it took them a paragraph to do that, don't you just love AI).  I am assuming the front is the rotating can so that a Front mounted motor would be pulling air in from the front of the motor that is in the back and pushing it out the back which is in the front.  Have I got this right? 

Ken

IIRC, Igor addressed this and the flow is from the aft going forward through the motor toward the prop shaft.  Do a search, I'm sure you'll find it.

I always assumed that since the motors are vented at both ends and we allow airflow through the nose section and mount that airflow was from the prop side back through the motor can, unless it has a built-in fan.

Best,    DennisT

Dennis the motor does pull air through from the rotating end to the fixed end.  I gave up trying to get someone to tell me what was the front since we mount them both ways.  Igor's notes and some actual tests by Mark Wood confirms that.  What that means is for a front mount (fixed end forward - that is where the wires come out) any direct airflow directed at the motor should be at the back and you need a large spinner gap to vent it.  For an adapter rear mount the opposite is true and vented spinners will help.  My expertise in this area is exactly two days old so please confirm!     My research was sparked by a discussion as to why I am using more battery than I should and I discovered, with some help, that the nose on Endgame III is the same venting as was Endgame II.  II had a rear mount and III a front. --- HEAT LOSS.
 
Ken

Dennis the motor does pull air through from the rotating end to the fixed end.  I gave up trying to get someone to tell me what was the front since we mount them both ways.  Igor's notes and some actual tests by Mark Wood confirms that.  What that means is for a front mount (fixed end forward - that is where the wires come out) any direct airflow directed at the motor should be at the back and you need a large spinner gap to vent it.  For an adapter rear mount the opposite is true and vented spinners will help.  My expertise in this area is exactly two days old so please confirm!     My research was sparked by a discussion as to why I am using more battery than I should and I discovered, with some help, that the nose on Endgame III is the same venting as was Endgame II.  II had a rear mount and III a front. --- HEAT LOSS.
 
Ken

Well, my test is not super definitive actually. I'd have to make a better quality video using a better smoke source but the majority of the air simply circulates around the motor.  The rotating end can suck some air in and it appears to be centrifugally induced and not very stable flow. When brought to the static side occasionally the flow would go in that direction as well which is why I say the flow is not very stable. This pretty much means that the motor will flow air through it based upon external influences such as how the ducting is configured. High pressure on one side and lower pressure downstream will definitely drive the flow. There is no fan on these motors so there isn't much that will induce flow nor to impede flow. I would not count on the motor taking care of itself for cooling inside a confined space.

I personally prefer front mounted motors primarily because they survive sudden contact with hard surfaces better. With either configuration, the installation has to be configured such that the air will flow through the space the motor is in. This means the area on the exit needs to be larger than the incoming area and the incoming area needs to be slightly larger than the motor passage area. What you don't want is the area behind the motor being pressurized in a way that it resists flow.   

My test is currently only a single motor test. I'll put a couple more on. and see if they behave any differently. I just picked the one that was on the bench and used it.