Crash after numerous flights without problems

[chschmid]

Duke
Please put your logfile in a dropbox for download.

Cheers
Christof

[DUKE40]

I will do that as soon as possible, providing the complete setup and the logs of the flights today.
By the way the setup of the flight of the logs attached at the beginning of the thread does not exist anymore as the AQ was out of order (it was sent to Jussi for checking if anyhting can be done about it) and the setup has been changed, the props are other ones.
But the inbalance on pitch is most probably caused by the gimbal. I have now removed it in the hope of at least partly solving this issue.
I will check everything else.

[chschmid]

Oh I just crossed with Jussi.
Please provide the info needed. And Duke, dont fly. Post the log of your last DIMU experience as described. 45 sec good flight, and the nightmares. Check your battery. How do you know it was quickly discharged?

Cheers
Christof

[DUKE40]

Setup is as follows:
Spacewalk frame

spacewalk550.jpg (4.07 KiB) Viewed 12505 times

T-Motor MT2216-11
Graupner e-Props 10x5
Flyduino SimonK 20A ESCs
P-Ion 3900mAh / P-Ion 4600mAh both with 25C
MX-20 HoTT and GR-24
FW is r397 with DIMU and native HoTT Telemetry
all powerlines are at least 4 cm from the AQ, as the AQ is 4 cm above the frame.
Total weight without battery 1250g with battery between 1520g and 1640g
Gimbal had a weight of 255g

There was an AlexMos Gimbal like the one of Jörg on his Camcruiser (viewtopic.php?f=38&t=2920&start=70) which has been causing the inblance on pitch and is now removed.

Logfiles are now on dropbox, but I have no idea how to link them here so somebody else can see them.
https://www.dropbox.com/sh/v3e5aablupoz ... IZlcrJ31Va

@Christoph,
I assume it was quickly discharged as the telemetry indicated Low Battery level 2, meaning the voltage of the battery under load was below 10.5V (3S and level2 voltage is set to 3.5V per cell).

[chschmid]

Duke
Your batts are 3s and the voltage should not drop to nominal @ 24Amps (Hover).
Your batts voltage is to low for this setup. You need 80% throttle to hover. Thats why your mots saturate.
Your mots/props are terribly balanced. You have ACC values up to 5! (should be below 1, preferably @ 0.5 average.

What to do:
Use a 3s 4500 25C Lipo with 11x5 Props. That gives you 50% Throttle at hover.
Balance Mots/props. Make sure the props have a precise sleve to match the mot.
And you should be good with 12min flight time.

Cheers
Christof

[DUKE40]

Hi Christoph,

I am a little bit surprised, because my Quad hovers below mid stick which to my understanding would not mean that it needs 80% throttle to hover, but is rather below 50%.
Further at full throttle the current remains below 30A total, means per motor below 7.5A.
Concerning the balance, I have balanced the props, but not the motors, I have no idea how to balance the motors, never did that before.
But may be it is due to the battery you used for the calculation, P-Ion are more like Lipos than like A123, they have as well a maximum voltage of 4.15V and nominal they have 3.7V. Taking this into account might change a little bit the result.

Where do you see that ACC value of 5? I might have been looking at the wrong data all the time.

[chschmid]

Duke
Whats your throttle scale factor?
Regarding your batts, see attached logs. Given you always fly with a full batt, the voltage was best represented with the 123. So your voltage should be at 12.45V before mot start. But it is at 11.55 and drops to 10.3V . Just trying to help....

If you props are well balanced and you use a precise sleve, some other part of your frame causes a resonance. The vibs are way to high.

I attached some screenshoots for you.

Cheers
Christof

[DUKE40]

Hi Christoph,

I am happy that you are helping me understand where the root of my problems is, I just try to understand.
The sleves for my props fit very tight the props and the motor.
My throttle factor is 0,7
attached my params.txt
I will replace the prop adapters to be sure they are alright, they might have some inbalance due to the two crashes.
I will also perform some tests with and without props to see if I can find where the vibrations are coming from .
I will also first try to get it flying smoothly again before starting again with putting any gimbal or similar things on it.
If you see anthing else in my params that needs to be corrected, let me know.

I have 11x5 props here as well, it might be a try worth once I have made sure I have no vibrations coming from any other part than the props. Balancing the props should not be a problem.

[chschmid]

[bluuu]

Duke40, read my mini howto about balancing motors and props:
viewtopic.php?f=27&t=3269&start=20#p22845