I finally got my electric Impact in the air yesterday with the telemetry working. I thought the motor temp data was kind of interesting.
The sensor is on the back of the motor so it probably doesn't see and direct airflow but I'd guess there is a lot of turbulence inside the fuse. Anyway here is the info:

66F at turn on
68F at take off about 2 minutes later (Had to wait for a plane on the runway)
92F at 2minutes into the flight (a fairly linear fast rise)
99F at 6 minutes into the flight (lower rate of temp rise)
101F at landing and motor turn off which was 6.5 minutes after take off
124F at 7.5 minutes after take off - the peak temp
121F at TM turn off 8 minutes after take off

I should point out I was being a good boy and keeping the current down on the new batteries so most of the flight was at half throttle. The total consumption was only about 2 AH. I turned the motor off after landing because there was mud all around the plane so I decided not to taxi back. So it took me about a minute and a half to walk down and turn it off.

I believe the cooling in the air looks ok but I'm concerned about the rise after turn off. I guess one could say the internal temp of the motor must have been over 124F in order for the external temp to keep climbing after the motor was turned off. I'm not sure what to do about this if anything. How does one decide if he needs to improve the cooling in the air? What is the standard for acceptable motor temperature? Any thoughts.

Jim O

Your temps are fine. I would worry about anything over 145

Jim O,

What type of motor ? outrunner or can with gearbox.. Also you what to look at the wire temp on the windings..
I have a AXI 5330/18 and the winding temps are 109-112 on a cool day out..

Scott Anderson
NSRCA D3 AVP
Team Tanicpacks.com

I checked Andrew Jesky's last year at a contest just as he landed found the same thing as you within a few seconds the temp started to rise, but very cool when landing, in fact if I remember right just a little over ambiant. This was a Hacker C50-14XL standard, so with no cooling vents in motor would be expected. Internal heat coming out to case.
Steve Maxwell

jim,

if my memory serves me correct, you're using a hacker C50/gear setup. for high-revving motors such as tango, hacker and neu, these temperatures are considered normal, if not even low. a C50 will survive 170F (75C) without damage. also the build-up after landing is ok, the magnets don't mind getting hotter when there is no current flowing. what would worry me more: if i would see the temp rising like this continuously, when flying full bore. it should reach its peak after a couple of verticals, and then stay glued at, say 140F in 70F-wheather. if it doesn't, it might be an indication that your cooling vents (especially the outlets, which should always be twice the size of the inlets, as a rule of thumb) aren't effective enough. that's the time you get that dremel out again, then! all of our fine motors now have eff. rates of over 90, some nearing 95%. if you're producing 2kW, that leaves you with something between 100 and 200 watts of heat. get rid of that, and you'll be running that motor forever. get rid of only 80%, and during a "full size" contest flight in 90F-wheather, you might cook it, because the generated heat will cumulate. it's like with race car brakes: even the biggest F1-brakes melt at courses like vancouver, because the straights between the brake zones are too short for the brakes to regenerate, and, as with brakes and boxers, same goes for our motors: they never come back!

cheers

roger

Hi Jim,
The temp rise after flight is normal, especially for an inrunner, as the thermal conduction path from magnets to outside world is primarily through the shaft and bearings. My AXI 5330/18 when run at 63A WOT lands at less than 15 F (7C) above ambient, with a post-landing dwell of about a minute, and then cooling. That's measured with an IR thremometer aimed at small black plastic tape tags on the motor case and winding, to get a well defined emissivity. Metal, even anodized aluminnum, reads low.

regards,
Dean P.

Thanks Roger. Yes I am using the Hacker C50-14XL. From what you are saying, it looks like I haven't really tested my cooling system yet as I only reached a little over 100F in the air, about 35F above ambient. It did seem to be flattening out there for the power I was using. Where did you get the info on magnet temperatures/current, etc.? I'd like to learn a little more about these motors.


Dean, it sounds like you have it made. I take it the 15F rise was measured after landing. I'm using an EagleTree sensor on the back surface of the motor which probably gets the least airflow. The temp measured on the ESC never went over 71F.

Jim O

Hi Jim,
Yes, the ESC temps never seem to be a problem. Even the Castle HV45 handled flying in the mid sixty-amp neighborhood, just fine. It rose maybe 10C, though I have switched to the HV85, and can barely measure temp rises. It's well cooled, too. Have you seen the ductwork I have placed in the cowl of my Funtana testbed? Take a peek.
Dean