CW Motors Overheating While CCW Stay Cool

According to the Mission Planner logs, the outputs of motors 3 and 4 are double that of motors 1 and 2. Consequently, motors 3 and 4 quickly overheat.

3691103377?profile=original

I'm trying to get my new multi dialed-in but after only 5 minutes of hover attempts [at about 45% throttle] both of my CW-rotating motors (3 & 4) get so hot you can't touch them, while the CCW motors remain cool. All calibrations have been re re re re re-run. ESCs, radio, accelerometers, compass, and everything appears to be balanced — fore-aft CG, props, etc. — yaw seems stable, I even disassembled the motors, balanced the bells, lubricated the shafts and bearings with EPIC oil for electrics (note that these motors are new and have less than 15 minutes run time on them).


To make matters worse, This is only the third real attempt to get a stable hover but I can't quite get there from here. I still require manual trim input on the Tx of about 5% right roll and 5% up pitch for it to behave as well as it does in the video. I'd love for it to be rock steady but I'm not sure know how to get there and with two overheating motors there's no way I'm going to attempt to fly outdoors.

I have an email in to HK tech support but no reply yet.

If anyone is interested the video is here and sample log files are here:

2014-03-09_2015-26-22.log

2014-03-08_2015-17-29_2062807.zip


For safety, the skids are covered in foam pipe insulation and a prop protector stick was added to each arm (the sticks are from 2 carbon fiber arrows -- $3.50 each at Walmart).

And yes, the props are right-side up =)

Specs

===================================

Frame: Tarot Iron Man 650

Arducopter: 3.1.2

Props: APC 12x4.5

Motors: NTM Prop Drive 28-30S 800KV

ESCs: Turnigy Plush 40A

Battery: Turnigy 40C 5A 4S

Flight controller: APM 2.6 w/uBlox GPS

Receiver: FrSky D8R-II PLUS (modified antennas)

Transmitter: ER9X with FrSky ACCST 8CH module

Weight as shown: 2.4kg

Thanks!

My current PID settings:

3691103391?profile=original

2014-03-09 15-26-22.log

2014-03-08 15-17-29 62807.zip

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Replies

  • Ahhh... what's the motor-to-motor spacing (longest) on your quad?

    All my scratch builds are clones of the 3DR model B. M-to-M spacing of about 62 cm (longest), 43.5 cm (shortest).

    -=Doug

    • 775mm.

      • So with a longer moment arm and the firmware thinking stock 3DR (version C had shorter arms than B, less M-to-M spacing), your PIDs would need some tuning.

        Cool beans.

        Tune on Dude!

        -=Doug

        • =)

          • Is it just me or is helping people diagnose their APM problems more fun than Soduko and crossword puzzles combined?  lol

  • Holy (put your deity) in a Sack.

    Did you start with default PIDs?

    Frankly I have never, ever operated in anything other than Stabilized mode with stock settings (hears all the code team members groaning). At least you wrecked my theory that the PIDs are nothing more than a placebo to entertain/distract folk into thinking the machine will do all the work for them.

    Carry on! In the true nature of Science, you will have to get it running well, but then induce the offending PID settings to see if they really do cook the same motors again.

    (I won't hold my breath.. <grin>)

    -=Doug

    • HHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!  Yeah. I never moved out of stabilize mode, but the default PIDs are for one of 3DR's smaller quads I think -- "ill suited" to my bird.

      ; )

      As an side, I think it would be awesome if the Mission Planner developers added some PID templates as starting points.  Something takes into account basic weights and thrusts.

      • That's actually a really good idea.  Along similar lines, a section of the forums where people list the technical specs of their builds along with their settings and performance figures would be nice too.  Something like that would have really saved me a lot of time shopping for parts.  Battery sizes, total copter weights, flight times, and other details would have helped me pick a build that aligns with my intended use case.   I'm still struggling with my alt hold tuning...

  • It was the #@7*ing PIDs!

    =\

    I tethered the bird to a rig and and then went back through the calibration info. in the Wiki and decided to be more aggressive with my 'P' settings.  Tuning still has a long way to go but now all 4 motors are operating at the same temperature.  Weird.

    Thanks for the help guys!

  • Well, nuts.

    In retrospect, if your control inputs are as expected in regards to pitch & roll (right stick Mode 2), your APM -> ESC wiring must be correct...unless you have reversed everything on your TX to compensate for it....which leads me to recommend checking your INPUT wiring again -- just to be sure. Crossing up the inputs could be adjusted for in the TX..I think.

    Yep. A conundrum.

    Here's another stretch -- how is your TX set up to operate? Heli or Airplane mode? (should be Airplane).

    Heli modes will often vary 2 channels with throttle/collective (left stick Mode 2) movement. One for collective, the other for tail rotor pitch (or tail motor rpm if with one). You only want one change to be seen during the RC calibration as seen in Mission Planner with a change in throttle.

    Another thought -- do you have a programming card for your ESCs? Check to make sure a dynamic brake is not enabled.

    (Counterpoint -- how could you have had the amazing luck to get exactly the two CCW motor ESCs in that state?)

    -=Doug

This reply was deleted.

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