[NSRCA-discussion] Cooling outrunners
Chad Northeast
chad at f3acanada.org
Sun Dec 17 08:05:24 AKST 2006
The RPM is way too slow to move a lot of air. Tru-Turn did some
experimenting on this concept as well and found that you need to spin up
very fast to get any real flow out of it.
Pletty was going to install a fan on the 30-10's, but for the same
reason did not. Their experience with fans on smaller engines for helis
etc told them that anything below about 15k rpm was not very effective.
I just want to point out that the 30-10 Evo vs. the original 30-10 has a
vast improvement to cooling. I run mine at 3kW in flight peak and
around 3.3kW static (motor will deal with 3.5kW fairly easily), and even
in the heat of Muncie it rarely goes over 140F on the can. This is with
a normal TT spinner and only a single duct from the chin pointing at the
motor. You would smoke the original motor in seconds in the same
environment!
The stator on the Evo is hollow to allow air to flow through the center
of the motor, as well a lot more open area on the front of the motor.
Chad
Dave Reaville wrote:
> Hi Wayne
>
> Actually Chad and Rex (I think???) had already done that but I was a
> little concerned with leaving sufficient material after the spoke
> removal :-) so I decided not to. I am not sure just how much
> additional flow would be created but it's certainly worth considering.
>
> Dave
>
> ----- Original Message -----
> *From:* Wayne Galligan <mailto:wgalligan at texasairnet.com>
> *To:* NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>
> *Sent:* Saturday, December 16, 2006 8:23 PM
> *Subject:* Re: [NSRCA-discussion] Cooling outrunners
>
> Dave,
>
> You could go one step further and grind an airfoil in the
> remaining spokes to aid in pulling the air in.
>
> Wayne G.
>
> ----- Original Message -----
> *From:* Dave Reaville <mailto:dkrev at shaw.ca>
> *To:* NSRCA Mailing List
> <mailto:nsrca-discussion at lists.nsrca.org>
> *Sent:* Saturday, December 16, 2006 2:09 PM
> *Subject:* Re: [NSRCA-discussion] Cooling outrunners
>
>
> Re: Outrunner Cooling
>
> FWIW I have made some other changes to the spinner that have
> helped a little. I removed three of the spokes of my backplate
> to assist in weight loss :-) as well as increase flow through
> the motor. Picture here
> http://members.shaw.ca/patternwestnews/pictures/planes/tttrim.htm
>
> I am also going to make some minor changes to the spinner
> itself by increasing the prop cut-out forward. These openings
> coupled with the ducting that Chad used towards the rear of
> the motor should provide adequate cooling for the Plett. I
> understand the Evo has bigger openings to assist in cooling
> but I think it's very important to make sure that
> the backplate spokes, when mounted, align properly to allow
> unrestricted flow through the openings. It's possible to block
> the flow if improperly installed or if it rotates on it's own.
>
> I have seen Rex's spinner in action and it appears to me to
> assist in cooling.
>
> Dave R
>
> ----- Original Message -----
>
> *From:* Rex LESHER <mailto:trexlesh at msn.com>
> *To:* NSRCA Mailing List
> <mailto:nsrca-discussion at lists.nsrca.org>
> *Sent:* Saturday, December 16, 2006 9:52 AM
> *Subject:* Re: [NSRCA-discussion] Cooling outrunners
>
> 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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