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SimonK Flashed Multistar ESC overheating?

#1
Okay, so I am not having much luck with multi's at the moment :(

Here is the story...
The other week whilst flying FPV my SK450 Deadcat dropped out of the sky. It was the first time I had flown it for any length of time (i.e. more than one battery). It was flying along happily and then suddenly an arm dropped, it flipped/tipped and I lost control.
Fortunately I found it thanks to the lost model alarm on the KK2.1 and the long grass saved it from any damage. By the time I found it it had sat for at least 30 minutes. After taking it back to the field I checked it over, plugged the battery back in and flew for another few minutes with no issue.

I put that one down to a poorly installed rx and dutifully fixed the antennas to make the most of the diversity signal and range.

Fast forward to today... I took the SK450 out again for a fly. The first time since the above incident. I flew the first battery LOS to check everything out. Second battery I put on the goggle but kept it local and over the long grass. Sure enough after a few minutes an arm dropped, I lost control and it fell like a stone.
This time I found it immediately and checked everything out straight away: Motor 4 was running but had very little power in it. Every time I throttled up the other 3 motors would lift but the craft would tip over motor 4.
I tried replugging the battery to restart the KK2.1 and even re-calibrated the sensors to no avail.

So, now for some quick specs:
Frame: Turnigy SK450 Deadcat quad
Controller: KK2.1 with Steveis V1.14S1 Pro firmware
Motors: Turnigy 2836/8 1100kv with 10x4.5 SF props
ESC: Multistar 20A with latest SimonK (kda.hex) firmware
Battery: 2200mah 3 cell Turnigy

Sherlock Holmes style deductions:
  • Both times the problem happened on the second or third battery used in quick succession
  • I am using a battery monitor and at no time did it beep so I can't say a cell died
  • The problem disappeared the first time after the model sat for a while but was still present when tested straight after the crash
  • I know from my IT days that "overclocking" any processor (which I am guessing is what the SimonK does) can cause overheating
  • I just ran the motors up in the garage (now an hour or two later) and the problem is gone again
  • It's was over 30 degrees outside on all flights

I'm almost certain that what I am looking at here is the ESC overheating. Of course the one thing I didn't do was actually feel the ESC after the crash to see if it was hot.

So, what do I do about it?
The ESCs are already out on the arms under the propwash. Should I remove the heatshrink to aid the cooling? Is it possible to "de-tune" the SimonK firmware or, even better, reload the original firmware to reduce the refresh rate?

Any thoughts or suggestions gratefully received (although I'd rather not have to buy another load of ESCs).

Mike
 

Cyberdactyl

Misfit Multirotor Monkey
#2
Sorry about the frustration.

Removing the heat sinks is the last thing you should do.

What you can check in regard to cooling, is if the heat sink tape is making good contact with the aluminum plate as well as ALL the FETS. I don't know if you flashed them, or if a re-distributor did it, but what I DO know from experience, messing around with an ESC without heat shrink can make the plate fall off. When sticking it back into position and applying more shrink, without paying attention, can make the tape wrinkle or fold providing an air gap off a FET or two.
 
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#3
before i start trying to help I am new here and only built one quad, I am a computer technician and we diagnose things really well ..... Have you tryed that ESC on another motor to make shure its the esc and not the motor ?
 
#4
Thanks for the replies...

Unfortunately the upgrade was done by yours truly and on top of that it was the first time I had done it so your suggestion is a likely one Cyberdactyl!

Malcurin - that is something I was going to do later on just to exclude the motor but the fact that it appears to be running normally now it is back in the workshop suggests the motor is okay (but never say never!).
 

jhitesma

Some guy in the desert
Mentor
#5
If it is overheating it's most likely the FET's overheating and not the processor overheating. That's a pretty beefy motor with an 18A max rating...but if it's like it's little brother the 28/26-6 that I have then it will draw more than it's rated for if given the right conditions. So with 20A ESC's you could be right at the limit if one of the ESC's isn't quite up to spec.

I've only looked at the little 10A multistars I have but their build quality didn't impress me at all. Not as bad as the red brick I fried, but still not something they'd like to put clear shrink wrap around and not something I'd expect to live past it's rating.
 
#6
I'll get the wattmeter out later and do some tests as well as checking the esc for physical damage.
I think I have some beefier escs from another setup that I can swap out to try if necessary.
Still, bit of a pain as I am loving the SK450 at the moment. Such a nice quad (when it isn't falling out of the sky!)
 
#7
Okay, on this singular occasion I am willing to accept any and all ribbing, teasing, name-calling etc. that you can throw...

I just pulled the plugs, hooked up my wattmeter and a different RX, plugged in a battery and ran up the motor. It was hardly spinning and drawing around 3.5 amps. There was also a high-pitched squealing noise coming from the motor.
But hang on a minute... the motor looks like it's turning at full revs...
.
.
.
.
.
wait for it...
.
.
.
.
.
yes, THE *@!#ing PROP ADAPTER HAD COME LOOSE!

So much for it working earlier on, I mustn't have been looking properly.

Sorry for bothering you all... :rolleyes:
 
#8
Quick update...

Well, there you go! The grub screw in the neck of the motor (pictured) was loose and when I was balancing props the other day I had managed to push the shaft down by around 2-3mm as I refitted them.
This meant the collar on the prop adapter didn't have enough shaft to grip and hence worked loose.

Fixed, the motor = fixed the prop.

I didn't even think of checking those screws during the build. Live and learn!

2014-03-18 20.12.08-600.jpg

Incidentally jhitesma, you were right to ask. I just checked the fixed motor and 25A draw at full throttle with these props :eek: Think I might prop it down a little...
 

Cyberdactyl

Misfit Multirotor Monkey
#10
I mentioned in another current thread, if you are going to use the collets, cut the shaft where the collet comes down flush on the bell, yet the shaft is fully inserted into the collet. Cut the shaft the same length, or maybe shaft 0.5mm short of the collet depth. Then, when your MR takes a tumble, all the load transfers from the prop to the bell without stressing. . . or at least minimizes the load on the shaft. This comes close to the structural strength of bell mounting the props.
 

crlock

Senior Member
#11
I mentioned in another current thread, if you are going to use the collets, cut the shaft where the collet comes down flush on the bell, yet the shaft is fully inserted into the collet. Cut the shaft the same length, or maybe shaft 0.5mm short of the collet depth. Then, when your MR takes a tumble, all the load transfers from the prop to the bell without stressing. . . or at least minimizes the load on the shaft. This comes close to the structural strength of bell mounting the props.
hmm now i understand why the short shaft motors exist :/
 
#12
Incidentally jhitesma, you were right to ask. I just checked the fixed motor and 25A draw at full throttle with these props :eek: Think I might prop it down a little...
When I saw 1100KV motor spinning a 10" prop on 3S I was immediately concerned with pulling over 20A of current. You just confirmed it and will go a long way to keeping your ESCs cooler if you run within their limits. Prop down to a 9" prop with a slightly aggressive pitch, like a Graupner style 9x5. You'll lower your current without feeling like you're giving up a lot of power.

hmm now i understand why the short shaft motors exist :/
This is an the risks imposed on motor shafts. Collets become loose, the shafts get bent, or the bell will spin around the shaft like the OP encountered.