I copied Josh Lambeth's cooling fan idea and adapted it to my own cinestar 8 fitted with all MK boards including the MK power distribution board. I purchased the same Scythe 120X120X12mm fan. I had to make some small modifications to get it to fit and work right. Because I have the upgraded MK ACC sensor, the clearance from the battery plate to the top if the flight control board is a less. I switched to 60mm standoffs for the extra clearance. I have just enough clearance between the fan and the new ACC sensor on the flight control board. I mounted the fan to the bottom of the battery plate using 1/8 aluminum. It's a bit overkill but I didn't want any flexing on the fan that would put the fan up against the ACC sensor. I also have about 3/16 of an inch between the top of the fan and the bottom of the battery plate so that it has enough space to draw air in to push down on the power board. I have it powered up and its definitely blowing a good amount of air on the Power board. The fan hardly draws any current, I kept a voltage monitor on a 2200 mah battery and it only dropped the voltage 0.2 of a volt after 5 minutes. The fan is also not very loud, not that it would matter once the angry bees start singing when the copter is in the air. So I did some testing today and here's the results. Weather data 75 degrees Pressure 30.09 Dew point 62 Humidity 63% Altitude 1223 above sea level Corrected density altitude 2590 My copter specs - My CS8 is heavily equipped and has a 7D on it that has a flight weight of 15 pounds. I run 2 QC 6200 batteries and 14X14.5 XOAR props. I made 2 flights Flight one - The fan is turned off Flight time 3:43 I hovered for 163 seconds. Motor data Motor1: 7.1 10.0 12.7 A Temp: 34 66 83 °C Motor2: 6.0 8.2 11.6 A Temp: 36 62 79 °C Motor3: 3.8 10.9 13.6 A Temp: 37 78 97 °C Motor4: 0.6 8.4 11.4 A Temp: 36 67 82 °C Motor5: 0.5 10.4 13.1 A Temp: 35 66 77 °C Motor6: 0.2 8.6 10.8 A Temp: 37 68 81 °C Motor7: 0.0 4.4 5.6 A Temp: 37 68 83 °C Motor8: 0.0 8.5 11.4 A Temp: 37 66 80 °C After it started hovering the highest motor temperature went from 81 degrees to 97 degrees in about 2 minutes of hovering with the copter not moving an inch. Flight two - The fan is turned on Flight time is 5:25 I hovered for close to 4 minutes with the copter not moving an inch. I did the exact same flight path and hover as the first flight to make everything the same. Motor Data Motor1: 0.2 11.2 14.5 A Temp: 34 53 57 °C Motor2: 0.0 9.3 12.0 A Temp: 37 54 62 °C Motor3: 0.0 11.6 13.2 A Temp: 42 67 73 °C Motor4: 0.0 8.7 10.7 A Temp: 41 56 61 °C Motor5: 0.6 11.1 15.9 A Temp: 33 51 58 °C Motor6: 0.4 9.0 11.3 A Temp: 37 57 66 °C Motor7: 0.1 4.8 6.3 A Temp: 38 65 73 °C Motor8: 0.6 9.4 11.2 A Temp: 36 58 65 °C I almost doubled the hover time but my motor temps have reduced significantly where they actually held their own and stabilized without any increase. Here's the difference in temperature between the two passes, the peak numbers are incredible. AVG PEAK Motor 1 13 26 Motor 2 8 17 Motor 3 11 24 Motor 4 11 6 Motor 5 15 19 Motor 6 11 15 Motor 7 3 10 Motor 8 8 15
That's pretty impressive, Dave. Very important for those considering flying in very hot areas. Interestingly enough, I made several long flights (8-10 minutes) up in the Wine Country last week in 90°F+ weather, and never saw my ESC temps get above 88°C, and they averaged around 80°C. My copter was flying with the GH3 on board with an AUW of 14.2 pounds. I'm running the MK stack with dual 8000 4S LiPos. BTW, I'd look at your motors and make sure they're all perfectly vertical. Those current number variations smell like an out-of-plumb motor somewhere.
Good test there Dave! I wonder what your board will look like after going thru a swarm of fruit flys.
If it was me, I'd put some screen material on both sides, as you wouldn't want a stray wire or something to get in that thing. While I'm sure its current draw is quite low, if it doesn't have a clutch and it gets jammed, that current draw could become quite considerable really fast!
Or just put a fuse in the DC supply to the fan? Then the screen wouldn't reduce the airflow.... Andy.
It's pushing air from under the battery plate down to the power board. The fan doesn't work if its reversed wired, the only way to reverse the flow is to flip the fan. I don't think pulling heat off the Mosfets would be as efficient as pushing air down on to it. However my air conditions are pretty good compared to some of you, and maybe these tests wouldn't be as efficient pushing extremely hot air on to the board if its in 90 degree humid air with a 100 degree heat index. I'll have to do some more testing in hotter, wetter air. The only thing I do know is that when I have flown in very soupy hot air this summer is the motor temps cool down when you slide the copter from side to side by getting air flow on to the board.
Thanks. I think there's a combination of heat, weight, humidity and copter efficiency (motor efficient, efficient of CG etc) that all play a roll in motor temperature. I actually went through my copter for two hours this morning and making sure everything is perfect including the alignment of the motors. If anything I haven't checked my CG in a while which might be a little off. One of the motors also could probably stand new bearings.
Yeah I thought of that as soon as I seen how I have to mount the fan to push the air. I was dissapointed that it wouldn't work of reverse polarity like some fans do.
One thing I forgot to mention is that my power cables from the PDB felt really hot today. Hotter than I ever felt. Upon inspection I realized that I am only running 12 gauge wire. Where you guys getting your 10 gauge wire?
Hi Dave, I've also placed fan in my CS6 but I have three and it went well. I've seen your consumption you've posted and I have something similar, you have the motor 7 (5.6A) below average amperage consumed by the others (12A), this is normal?, there is something to worry about ? Gustavo.
It is better to have all the motors around the same current. When they're not, the copter's not working as efficiently as it can. I have found the cause is usually one or more motors that are not perfectly vertical on their booms. But it can also happen because of a balance problem with one of the props or motors, the copter being generally imbalanced, or even a bad bearing in one or more motors.
Gustavo My opinion is that its something with the BL with the way its reporting current. I had the PDB I'm running now originally and had the same reporting issues of lower current with that BL. I then had a BL go bad and didn't have time to change the individual BL so I used my backup Power distribution board. Instantly the numbers were much more even and #7 was right with the others. However I crashed my copter and damaged that board which prompted me to go back to original board. I'm not worried about it because it flies fine and truly believe its the way the BL reports it.
I've had about 25 flights on the copter since the fan has been installed. It's worked flawlessly and has even kept the motor temps below 80 degrees in high 80 degree weather with flying weight of 15 pounds. Haven't seen any 90 degree days since I installed it but I'm confident now that its a permanant part of my copter now.