[NSRCA-discussion] Cooling outrunners

[Chad Northeast]

The problem with a lot of composite fuse models (Twister included) is 
that the inlets in the chin and cheeks are often right at the rear or 
even behind an outrunner.....so ducting toward them is very difficult.  
I have to agree that a proper ducting system is crucial for cooling.  I 
use a very simple short radius 90 bend in a peice of depron that pulls 
air in from the chin, I see about a 20C rise in temp without it, other 
than that I dont really do anything special.  The motor will operate at 
up to 170F without complaining so as long as its 20-30F below that all 
is good :)

Chad

Rcmaster199 at aol.com wrote:
> I've had a chance to fly Dean's set-up recently and battery/motor 
> temps were relatively low....on the order of 105-110F, which is just 
> warm to touch. Weather was moderate at around 60F, but I've witnessed 
> the model flown in 90F heat with a just a slight increase in 
> powerplant temp. Folks inclined to run electrics would do well to 
> study Dean's photo in an earlier email. This is definitely a good way 
> to do it, is lightweight and balsa sheet is cheap.
>  
> MattK
>  
> In a message dated 12/18/2006 8:09:53 PM Eastern Standard Time, 
> bob at toprudder.com writes:
>
>     Dean,
>      
>     I was thinking that proper ducting would be a lot easier than
>     trying to engineer a way to force the air through the spinner.
>      
>     KISS.
>      
>     Bob R.
>      
>
>     */Dean Pappas <d.pappas at kodeos.com>/* wrote:
>
>         Hi Jim,
>         I have fiddled with this a fair bit, and the setup I am using
>         now produces very modest temperature rises on the AXI.
>         I see less than 15C rise after a P-07 with 84 A W.O.T. current
>         draw at the beginning of the flight. After the flight, static
>         W.O.T is more like 75 or 76 A.
>          
>         The inlets total up to just about 1 square inch, which is
>         ducted straight to an airbox that surrounds the front of the
>         motor. The inlet airbox is about 5/8" deep from front to back,
>         and has plenty of volume, just because it needs to evvelop the
>         front of the motor and the cowl inlets. The airbox has a hole
>         through wich the motor can passes, and the hole is extended
>         with a sleeve that runs back to near the aft end of the
>         rotating part of the motor.
>         The wrapped balsa sleeve has maybe 1/8" clearance around the
>         motor. The high pressure air in the inlet airbox is forced to
>         either flow closely over the outside of the motor or through
>         the holes in the motor.
>         For motors such as the Pletty, where the prop drive does not
>         stand proud of the front of the motor can, a drive extender
>         washer maybe 1/2" long will improve cooling by providing some
>         volume inside the inlet airbox, and allowing the air to "turn"
>         to flow along the motor axis. This is actually important.
>          
>         The warm air then dumps into the aft end of the motor
>         compartment, which is segregated from the rest of the cooling
>         pathg to the batteries.
>         An separate outlet gets rid of this air. In my case, it is
>         simply a hole in the bottom of the "scale" cowl of the
>         Funtana. Ideally, the aft end of the cheeks that everybody
>         seems to be putting into their designs would be an ideal low
>         pressure-high velocity outlet, but everybody belnds them into
>         the fuse instead of leaving a back end exit like the Pylon guys.
>         You could just have the motor sleeve dump into the fuse above
>         the batteries, but rear-facing exhaust stacks or a fake
>         turbo-prop exhaust would look cool and be functional. I'll try
>         to post some low-res pictures on the list.
>          
>         later,
>         Dean
>          
>          
>         Dean Pappas
>         Sr. Design Engineer
>         Kodeos Communications
>         111 Corporate Blvd.
>         South Plainfield, N.J. 07080
>         (908) 222-7817 phone
>         (908) 222-2392 fax
>         d.pappas at kodeos.com
>
>             -----Original Message-----
>             *From:* nsrca-discussion-bounces at lists.nsrca.org
>             [mailto:nsrca-discussion-bounces at lists.nsrca.org]*On
>             Behalf Of *J.Oddino
>             *Sent:* Friday, December 15, 2006 7:13 PM
>             *To:* NSRCA Mailing List
>             *Subject:* [NSRCA-discussion] Cooling outrunners
>
>             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
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion