Assuming a total load of 300lbs, 2kw at the wheel will get you 28mph and 3kw will get you 35mph. 35mph is plenty fast for good flow without fans, though I'd encourage a number of blades in each cover as close to the stator as you can get. I think it's an important factor in how well our ventilated motors are cooling....similar speed in a 20", bigger load so higher power, smaller diameter motor, and no heat problems.
Here's what I mean by blades (bolted and epoxied so they can't come off or loose and ruin the motor)
An example with a 9C
- 9C vented covers with blades.JPG (47.82 KiB) Viewed 184 times
More recently with Hubmonster (same diameter as a magpie)
- SuperV with Hubmonster inside covers.JPG (46.58 KiB) Viewed 184 times
Unless I missed a change, Zappy has his 4 fans at the spokes of the stator with that aluminum sheet to seal the rest of the space off, so they help suck air into the swiss cheesed side cover. It's similar to what Arlo1 did, and I appreciate the benefit at lower speeds. Zappy is offroading, and Arlo does repetitive launches. I do think blowers, common for servers, would be far better. Mount the same way and point the output directly at the stator. You could also mount some with input and output on the same side of the motor to for a more turbulent flow on that side of the stator too.
This is what I mean by a blower, which would much more likely reach rated cfm in our use for motors.
- Blower fan pic.JPG (8.16 KiB) Viewed 184 times
Unless I lose a bunch of weight and start off-roading, then I don't foresee ever needing to go active to ventilate my motors. If I did run into motor heating, the change I would make is larger intake holes near the center and a V shaped ducting outside the motor to funnel more air toward the intake. That would create a high pressure region there, which would definitely help intake flow.
John
