Ultralight 6" "Der Verbrannte"

By SQunX on Aug 14, 2022

10  308  4

I wanted a bigger (but still pretty light) endurance / longrange build than my previous 4".
In search of something similar other people might already have done I stumbled upon Scott Tomlinson's Black Opal 6.
I was fascinated by it being able to stay in the air for such a long time, and by only feeding it with more voltage it becomes a fast racelike flyer.
This is great!
that covers two different builds I wanted to make, this one could do both!

But my frame choice fell on the slightly lighter Druckbär Ultralight.
for the motors I chose the same 2203 from TMotor as Scott did.

the first flight wasn't that successful.
the ESC obliterated itself in flames and took two motors with him.

I'm still not sure if it was a faulty ESC or user error.
a few weeks later I discovered that the current and telemetry cables from the ESC to FC were switched, maybe that led to the fire?

damage report:
ESC complete failure
FC fine
frame a little burned on the surface otherwise fine
VTX was on top so it is fine
cam the plastic back probably saved it from the worst. it's a bit molten otherwise unharmed
battery only cosmetic damage, it's a bit smoked on the outside. unplugged it as soon as possible (burned my finger a little bcs everything was super hot. it was just on fire duh)
was letting it sit on the asphalt for about 2 hours, it might puff up or explode.
checked voltage and everything after that and it was (surprisingly) just fine.

I am still too scared to fly it on 6S again.
but it flies



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dafunk   Aug 17, 2022  

Nice build. So close to to sub250 too. I did a similar 7inch build 3 years ago but everything was so much heavier at that time...and cheaper ! !

SQunX   Aug 17, 2022 

thank you!
yea, stuff got expensive...

Junnicutt   Aug 16, 2022  

yeah with arms that thin and bi blade 6" props its not surprising it got hot. that's like the perfect storm of making filters have to fight the hardest. since its so light and the blades so large the rpm filters were probably being faded out since they are set to go only so like 85 to 100 hz i think before the fading range kills their effectiveness to go lower. if you try again go with a stiffer frame at least at first then really check blackbox logs and dial in the filters. you could also test with low pitch tri blades or 5" blades, anything to raise motor rpm to something rpm filters are more familiar with and low pass can do more. but to be honest I'd guess the frame resonances will be low too, but that is a nice design just maybe pushed too far. I'm amazed it flew at all without just "shooting to the moon". that's a cool idea though. great idea and awesome work on all your builds. i loved that black opal build too.

SQunX   Aug 16, 2022 

I was completely expecting it to be on the edge of performance.
already tried flat 5" tri props, sadly doesn't work. it kinda works on 4S but it has no real power and runs pretty warm.
I might get the race conversion kit for it, that has thicker arms.
but that kinda defeats the whole ultralight thing.

but thanks for all the praise!

I'm trying to keep up my work, trying new stuff out scratching on the limits.

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