[NSRCA-discussion] Cooling outrunners

[Rex LESHER]

Hi guys, I've been without power for the last couple days....   The mods I did to the spinner are on the D8 website.  I'm not sure how effective my process really is.  I can tell you that it works much better than not having any opening at all.  I did that experiment....  Chad touched on the real problem and I believe he is right on.  The spokes in the backplate and the closed sides between the openings in the spinner create too much resistance (spinning disc) for the appropriate amount of air to get directly into the motor.   I first tried just opening the sides of the spinner, and used that for my baseline.  Then, I used the modification as shown on the D8 website.  I figure that I dropped somewhere around 20 degrees on average.  After a few flights, I took the spinner off, and the motor cooled much better.  That tells me that in order to get the greatest cooling, you'd have to create a high pressure area in front of the motor...  
Now, I'm playing with ducting, forcing air around the can....  Time will tell, if I don't demag the motor!!!

Rex
  ----- Original Message ----- 
  From: AtwoodDon at aol.com<mailto:AtwoodDon at aol.com> 
  To: nsrca-discussion at lists.nsrca.org<mailto:nsrca-discussion at lists.nsrca.org> 
  Sent: Friday, December 15, 2006 6:16 PM
  Subject: Re: [NSRCA-discussion] Cooling outrunners


  Jim, 

  I think Rex Lesher modified a True Turn spinner to have 'inlet slits' to pull air into the spinner and back thru the motor.  I don't know if there were any tests to indicate if was effective.  Maybe Rex can comment here.

  I also believe there are some NASA airflow studies that indicate the area around the prop hub and some small amount of the prop as well as the spinner create an cone like airflow around that area that basically prevents air from entering the spinner slots, etc.

  Hacker has a fan like attachment on the back of the large outrunners than creates a negative pressure area inside the motor and draws air in thru the front of the motor for cooling.  there have been some tests retrofitting a similar fan on the back of other outrunners with similar success.  Basically a trade off in weight for cooling effectiveness.

  As you know, I run an AXI 5330/F3A with the chin cowl opening ducted to divert incoming air upward across the AXI.  It seems to work even on the hottest summer days.  No air from the cheek cowls is ducted toward the motor, it just passes thru toward the ESC and batteries.

  Don

  In a message dated 12/15/2006 4:14:26 P.M. Pacific Standard Time, joddino at socal.rr.com writes:
    It would seem the best way to cool outrunners that have holes in the case on the end that faces the nose ring, would be to bring air in through the spinner and through holes in the backplate.  Wondering if anyone has really thought about the optimum design.  I can picture internal vanes but perhaps cutting off the nose of the spinner and leaving a big hole would be adequate.  Anyone tried anything like this?

    Jim O


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