EDIT: I think I have solved this issue by replacing the Pixhawk with another one, but that doesn’t explain what actually happened. If anyone has any insight, please add to this. Thanks.
I have a new scratch-built quadcopter. With the quad strapped down, I can run all motors and props at mid throttle for 20 minutes and the motors never even get warm. (less than 90F). I have a video of this test, see below.
If I take it outside on a calm day with no wind, and hover in Loiter for 10 minutes, all four motors get so hot I can’t touch them for more than a second (150-165F). I’m hoping someone can shed some light on this issue.
Here are some specs:
- T-Motor MN3508 380KV motors
- T-Motor AIR 40A ESCs
- T-Motor 15x5 CF props
- Pixhawk 1 running Copter 3.4.6
- Multistar 8000mAh 6S battery
- AirbotPower Power Module
- props have been balanced
- vibrations are very low and well within limits
- ESCs are calibrated (throttle)
- ESCs are set to the default “intermediate” timing (the only setting for these ESCs)
- 2500g AUW with battery, camera, gimbal, and all accessories
The ship is designed for endurance. In Loiter with the stick at mid position, it only needs ~20% throttle to hover (or ~14 Amps) so I don’t feel like anything is straining (or should be).
At one point I thought I had found the issue. I’m using custom, 3D-printed motor mounts and the center hole wasn’t quite deep enough so the motor shaft clips were getting caught and sticking. I figured this was surely the cause of my hot motors so I simply used my Dremel and made sure the holes had plenty of clearance. Unfortunately this didn’t seem to have any effect. The motors ran cold for my 20 minute, indoor bench test, then got hot when hovering outside.
I’m at a loss as to what to do next. Any ideas would be greatly appreciated.
Here’s the 20 minute (boring) indoor motor test. The motors never even get warm: