M9 Gimbal failure & repair or replacement

[timrowledge]

I have a pair of M9 Hall gimbals in my Taranis X9E. They've been doing their job quite nicely since 2018 but now it seems the sensor on the elevator axis is failing.

The symptom is the elevator reacting very slowly, almost as if it has a decidedly humpy & non-linear curve with slow-down. Very odd. It *isn't* the servos because the problem shows up in the channels monitor page on-TX. I spent quite a while examining the programming to make sure it wasn't an actual curve with slowness but the simulator worked as expected. After dismantling the TX and pulling the tiny sensor board to inspect it, to my surprise things started working properly once I reinstalled the sensor. I spotted a tiny bit of debris and concluded something had been interfering just enough.

Unfortunately today the problem is back and I rather suspect that means I need a replacement part. I doubt I can get a replacement sensor easily, so that means the entire gimbal - unless anyone has ideas to the contrary? Has anyone else seen this kind of problem?

 

[gnichola]

My sons X7 had that same issue. He had a small EDF I was flying and at first I thought there was something wrong with the trim, as I would try to roll out of a turn and it would keep on rolling. I landed checked controls and gave it a look and everything was working just fine. Took it back up, same thing, so I landed again. This time I saw the ailerons moving slowly.
I pulled the back and checked the wiring and I found nothing wrong. It was very strange. I have a bit of electronic hardware in my background, but not enough to understand how the gimbal could do what it was doing. To me, it really seemed like a software buffering issue. However, I replaced the gimbal and all was well with the world.

 

[gnichola]

I just found a video, and it looks like it wasn't my son's radio, but my own (sorry, at 62, my memory, she ain't what she used to be)

 

[timrowledge]

Yep, that's pretty much it; though it's even slower responding than mine. Imagine the fun of landing a thousand-dollar hotliner with that effect.

 

[Wayne]

I recall seeing that before. May I suggest unplugging the gimbal and inspecting that connector. Clean anything you may see and replug and retest. Also look for any worn wires.

 

[timrowledge]

Interesting; at least it means I'm not simply imagining it. I'll check connections at each end again. Perhaps it's a soldering problem - my X9E is in a custom case and I had to extend some cabling.

 

[timrowledge]

Well, after opening up the case and pulling the little sensor board it is working again, just like before. No findable loose connection or poorly seated connector, nor worrying wire. I dunno, it's so very annoying when you can't find a fault that explains the problem.

 

[Wayne]

As I recall the X9E did suffer from wire fatigue on the stock gimbals, but sounds like you already upgraded them..?

 

[timrowledge]

Yep, upgraded back in 2018 and had no trouble until this recent thing. After fiddling again it's working as expected but it's hard to trust an intermittent glitch.

 

[timrowledge]

Just to update and close the loop - I replaced the gimbal. I did discover a loose wire for the elevator *trim* in the process but I'm a little puzzled if that can cause the main gimbal to behave oddly.

Anyway, fixed (hopefully!) and flown a few times without further issue. And now the flying field is shut down because of fire risk. And I burnt out three motors in the last month somehow, all in planes that have been flying for many years. Bugger.

 

[Wayne]

The hot weather will take a toll on motors that may have been close to the heat limits in the cooler weather.

Glad you got her back to flight status.

 

[timrowledge]

Yeah, it's a *bit* warmer than I'd like but all three of the motors have been in use for over a decade. The AXI 2826/12 actually had excellent cooling (in a large Cub cowl) and yet burned two of the windings and melted/softened enough of the magnet glue to have 4 of the magnets end up loose. The GliderDrive motor was in a very closed hotliner nose, and somehow it's survived ten years of pulling 95A through a nominal 70A ESC! I made some cooling and reduced the prop size...