I recently built my new hexacopter with the APM controller harware/software and so far I love it so much more than my Aeroquad, multi-wii, or KK2.1 controllers! I seem to have a motor/esc problem though that causes one of the motor/esc combos (motor #1) to fail (I’m guessing over heating). This causes the hexacopter to roll to it’s right and head towards the ground. Fortunately this only happens near the end of the battery (8-9 min) or midway through the 2nd battery if I don’t give it time to cool down. I’ve attached the log file, but you can see just before the 4 minute mark that the throttle to Motor1 starts to increase and become unstable. Motor2 likewise decreases and tries to compensate, but if I left it in the air any longer the throttle would have eventually maxed on motor1 and the copter would have rolled itsenf into the ground. Does this look more like a motor or ESC failure?
Another questions I have is why the motors and esc’s seem so hot after running. My hexacopter is a ~3ft home built wooden frame that weighs about 2.1kg with battery and all. My motors are rated to max thrust of 860g at 20A and I have 30 amp ESC’s. If you do the math you see that the each of the 6 motors should only have to put out 350g for lift (40% thrust). After 8 min I seem to use ~4500mah of the 5400mah in the battery, which I believe means I’m drawing about 33.75 amps (4500 * 60/8). This is only 5.625 amps per motor/esc so they shouldn’t be hot at all.
Any insight about the heating or motor/esc failure would be appreciated. Thanks
Your assessment of a problem with ESC or motor looks dead on. I’d recommend a “finger test” also. After flying, if only for a short time, put a finger on the ESC and #1 motor and compare the temperatures to your other ESCs/motors.
Electrically speaking, motors are extremely simple, especially compared to an ESC. Motors tend to fail mechanically, like from bad bearings or damaged magnets. And often that can be sensed by twirling the motor with your finger. See if there’s any binding or roughness in motor 1.
My bet would be a flaky ESC as they are more complex than motors. It could be some sort of heat issue causing it to cut back after you’ve been flying a while.
If your amperage estimates are correct you really shouldn’t be seeing a lot of heating of motors. It could be that your ESC timings as set in such a manner as to cause the heating. For example high ESC timing will give more power but may cause motor heating. It’s less efficient on high. Also the ESCs PWM timing for controlling the motor can cause ESC heating if it’s running a very high PWM rate.
Thanks for the reply. Yeah I figured it was probably the ESC also. I’ve moved them out farther onto the arms so they are under the props to help with cooling, hopefully this helps solve the problem. Thanks
So it looks like it was the ESC’s overheating. I moved the ESC’s from in the main body of the copter to out on the arms beneath the props and that seems to have solved the problem. I was able to fly 3 consecutive batteries with no issues. Hopefully that wasn’t just a fluke
