Sorry, it wasn't NC that did the tests, it was AEORC themselves.
http://www.rcgroups.com/forums/showt...hlight=cooling
NC has recommended these rotors to me on many occaisions though, hence I thought he did the testing. This 'feature' is on the whole family of rotors, but I'd expect the result to be similar throughout

I have now read that thread and watched the video. I very much doubt the cooling effect claimed with the fan running (all the claims were based on a fan without any blades). With the fan running, the pressure differential would cause the air to flow, if anything, in the opposite direction. A couple of people have concluded this by observing carbon brush dust on the back of the fan, for brushless motors. And 6 degrees of cooling, if it's real, is not worth a loss of thrust and efficiency, esp. in the small sizes where thrust is low to begin with. Not clear to me what problem they are trying to solve ... the motor sits in a minature hurricane, one would think that's enough cooling.

Not really actually, I've burnt a few out. Given these motors are so inefficient, any help dumping that wasted heat is a good thing...

So you think it's the motor itself that is inefficient, and not the fan/duct? I think the "cooling" strategy, as well as the very high rpm and the poor fan/duct fit are the problem with efficiency. I am not a motor design expert so there may also be something about the design of the high kv motors that causes them to be inefficient, but I think it's fan pitch and fit. At high rpm with the rather pronounced pitch, unless your model is moving very very fast, it seems to me the motor is sucking on low pressure cavities in the air stream. If and when I get a couple of units with straight and concentrically mounted motors from the factory, I am going to smooth the inside of the duct, and then try to put a tape "seal ring" around the fan annulus inside the duct, and further I will block the cooling vent, and then we will see if this thing puts out any better thrust figures. I may even put one in a lathe and cut a groove for an O ring seal, if the material is thick enough. There is also leakage around the skirt of the hub, where it meeting the bearing tube.


As for the cooling effect, I think the reason the motor is cooler after running with the air channel open, is that the motor is producing less thrust (due to air leakage in the reverse direction through the hub), ie doing less work, drawing fewer amps. I can achieve the same result (cooler motor, less thrust) by running an "uncooled" EDF at lower RPM. If the cooling effect were real, the temp drop would be higher.

Until I see the temp results with volt/amp/thrust results for the two scenarios, I won't be convinced that it's not just a marketing gimmick at the expense of thrust.

I've tested the 30mm version, and came up with ~55% motor efficiency at 100w (derived from Io, kv and Rm), and 30-35% total system efficiency (from thrust, shaft power and exhaust area). That gives around 55-60% fan efficiency. I didn't check blading vs duct losses.

For a given motor temp, I think you'll get more thrust out of the 'venturi' models, for a given shaft power, with it closed and faired would be best. If you want, grab a GWS 40mm rotor and trim it down to 30. The blades are pretty much identical.

As for sucking on low pressure cavities, I'm not sure where you're going with that... Air can't cavitate, it's a single phase fluid. Also, as established before, the air at the motor is higher pressure than anywhere else, otherwise the fan doesn't work!

My thoughts on these units: They're small. That hurts both electrically (seen any 90+% efficient, 10g motors recently?) and aerodynamically (Lift/drag ratios suffer at low Re). They're not the best designed, but I'm working on that. I don't think I'll make any massive gains over the current design in terms of thrust/power though.

Try with the vent plugged up, and let us know if you gain thrust / drop temp. I'll plug mine up then too!

The 40,45,50 new ducted fans are ready now.( 8 blades rotor+ new fan)

Do those ones also have crooked motors, rubbing fans, and impellers that fly off/shear off?

Anyone care to recommend a replacement motor for the 35mm unit ... I finally got my plane flying (built a new fuselage and changed out the batty so AUW is now less than 200g) but the ESC is now indicating "motor anomaly" and the motor is stuttering/chirping, it won't spool up. I think the motor is toast. This is the latest in a long string of disappointments with this 35mm EDF "Plus" unit. I wonder what the "Plus" means .... "Minus" would be more appropriate.

Ideally, I would like to get at least the same thrust from the 35mm unit with more efficiency (ie not sucking up 23 amps on a 2S). I had to go to a Castle Phoenix 25A ESC after my AEORC 15A ESC went up in smoke.

Vh2q,

Check this out here. If the 35mm shroud can handle a 20mm motor, this may be a good way to go. I know when I step up from sub 30mm, it's going to be a no brainer. The Tacon motor is DIRT cheap. 35mm may not exist for me.
Ksqm