Repeated drops towards prop 3

[Pheliciano]

Hi guys,

I'm running a Gaui 500x with the Wookong M FCS and while It seems to run really well for the most part, I keep getting the same problem that leads to most flights ending in a crash.

After about 3-4 mins of flying in GPS or Atti mode, the quad drops towards prop 3 (rear-left) and crashes. It looks like the motor loses power. At the same time, the LED normally give 2 or 3 white flashes.

I tried re-calibrating but the problem remains. The only thing I have noticed is that the motors and booms where the ESCs sit are super-hot. I'm in HK and have been flying in direct sunlight with ambient temperature around 32-35 degrees Celcius.

Boom 3 is also the boom where I have a DSM Sattelite receiver mounted, although I don't know if this has anything at all to do with the issue.

Does anyone know what might be causing this? It's really frustrating, ecause in all other respects the copter is a pleasure to fly, but I'm not willing to take it to any kind of height or anywhere that would be difficult to retreive it when I know it could spak-out at any moment.

The motors and ESCs are the ones that come with the 500X kit.

Thanks,
Felix.

 

[suddenincline]

I don't think the sat receiver has anything to do with your problem I would swap two of your esc's and if still the same arm does it I would swap motors and recheck to rule out a motor or esc problem that should narrow it down a little bit for you. If still the same arm reset all of your WooKong settings re-calibrate and try again if it still does that then it is time to contact DJI about your Wookong.

 

[kloner]

this sounds like an esc failing. I'd replace the esc on the number 3 and try again....... i had a new hobbywing 18 amp do the same exact thing, replaced and never happened again. If you don't have or can't, try moving the #3 esc to another motor and see if it does it to that prop

I finally was able to figure mine out on soft sand cause it'd crash without breaking anything. First couple times couldn't tell what happened

 

[Pheliciano]

Thanks Suddenincline & Kloner. I swapped my ESCs around this morning and took it out to test and there were no problems today so I'm none the wiser. Today was cloudy and cooler than Friday, so I think it's probably a heat issue.

The ESCs sit inside the boom arms, and I did notice boom 4 was noticably warmer that the other booms after both flights today. before the swap-over it was always boom 3 that was hottest, so the heat has definitely moved with the ESC.

I'll swap out the ESC and find somewhere soft to fly it on another scorcher of a day and hopefully it'll all be good.

Cheers.

 

[snurre]

Rule #1a with the problem you describe: Remove bullet connectors between all esc and motors, just solder the cables together.
That is if you still had bullet connectors, of course...

Many types of connectors loose their tightness after some time of being constantly connected and that really pisses the ESC off.

 

[Droider]

Sounds like esc overheating and cutting out. If the MR has been crashed a number of times and the esc has been stressed it could have damaged the esc. Put a new one it and see if that clears it up.

Dave

 

[Dewster]

Rule #1a with the problem you describe: Remove bullet connectors between all esc and motors, just solder the cables together.
That is if you still had bullet connectors, of course...

Many types of connectors loose their tightness after some time of being constantly connected and that really pisses the ESC off.

I agree, especially after hard landings or crashes. My connections became loose after a crash. The 3.5mm bullet connectors were especially loose. I actually crimped the connectors so that they would keep a tighter fit while testing the reliability of my system after the crash. It works for now, but I will replace my ESCs for my new craft.

 

[Pheliciano]

Thanks for all the responses. I gave the old girl an overhaul yesterday: swapped all the ESCs out for some 30A ones I had from another project (which also required that the ESCs be moved to the outside of the booms); soldered all the connections between the motors and the ESCs; made a new power distribution loom for the motors, and soldered the ESCs directly onto it.

With a bit of luck that'll make sure I don't have that problem again, but I'll let you know how my testing goes over the weekend.

Cheers.

 

[Pheliciano]

I took her out for a test-fly today in similar heat to before, but added strong, gusty wind and had no problems at all. She fought valiantly in the wind too!

Cheers for the help.

 

[snurre]

Good to hear, Pheliciano

 

[Pheliciano]

It seems the problem is not quite as fixed as I thought. After upgrading the ESCs, I did a number of flights without any issues. I starting flying her much further and faster and with an Alware 3-axis gimbal and GoPro attached, and she didn't crash once. I did notice that the motors were pretty hot after flying though (I brushed my arm against a prop retainer after landing and got an instant burn) and I had to give them 10 minutes or so between flights for them to cool down to what I thought was an acceptable level (I'm not really sure how how hot the motors should/shouldn't be though, so that may not be important).

The addition of the Gimbal and GoPro knocked my flight times down from around 14 minutes to just under 7 minutes with my 3300mAh 4S LiPos, so this morning I tried her out with two of those batteries in parallel. I wasn't sure how she'd react, so I just hovered her about 2m above some nice long grass, and after about 4.5 mins, she dropped towards prop 3 again like a stone.

All the motors were hot after the crash, but motors 1 & 3 were incredibly hot! Directly after the flight I couldn't do more than brush my fingertip against the motors for a split second. After about 5 minutes I could hold my fingers on motors 2 & 4, but motors 1 & 3 were still so hot I could only touch them for less than a second. 10 minutes after the crash, motors 1 & 3 were still noticeably warm.

Take off weight was 2,150 grams all-in. I think it's pretty clear that it's an overheating issue (although please let me know if this may not be the case), but I'm not sure of the cause behind it. Do you think it's a failing motor, and if so, is it likely to be motor 3 or motor 1 that are at fault, or both? Or could it be that the motors are just not beefy enough to lift the load I have strapped to them?

The motors are 960kV Guec GM-412 and they're turning 10" props. Here's a video snippet of the crash

 

[kloner]

shouldn't be hot enough to burn anything. That's a definate problem. I'd be looking at smaller props and higher voltage if that's an option or get into the 28mm motors. weights you got, 750kv on 4s with 10" props would be a great combo

 

[Pheliciano]

So since I'm already running on 4S LiPos with 10" props, I should just need to swap out the motors with lower kV motors? I'm still fairly new to this, so I don't really know which motors you're referring to when you say "the 28mm motors". Could you give me a bit more info?

Cheers.

 

[kloner]

bigger diameter and lower kv, get's you more in the power band at the area you need it, lifting all that weight

how much you got to spend?

 

[suddenincline]

Could be wrong but those motors you are running are way to small for the load you are trying to carry. 920kv motors struggle at 1800grams and your over 2000grams you need bigger motors

Sent from my SPH-D710 using Tapatalk 2

 

[Pheliciano]

As little as possible, but as much as is necessary. Sorry to be so cryptic, but that's about the size of it. This is for commercial use, so we can spend as much as is needed to make this a reliable and stable platform, but since it's not making us any money yet, we can't afford to buy anything that's not strictly necessary.

 

[Pheliciano]

Here's a photo of the beast so you know what we're dealing with:
View attachment 5483

 

[kloner]

alot of guys use axi brand in this case...... the 2216 750 t-power would be popular as well as a 2814 750 t-power. 2814 will do it better but waste more energy doing it.

 

[Pheliciano]

Thanks Kloner and sudden incline. I don't really know anything about all the different motor specs and what they mean practically. which of the 2216s or 2814s would you recommend (i.e. 2814/6, 2814/10, 2814/12, 2814/16 or 2814/20?).

Thanks.

 

[kloner]

the slash refers to the motor companies code for the different kv, others just use the kv. you want 750-770 kv, and you want 250+ watts of power rating 350 is even better, that's like the fuse inside, too much watts = boom like you did