You are seeing a bit more than that with actual performance but close enough. Looks overloaded to me.
2500m ?
thanks, Maybe it can be made better with an inch more prop pitch, but yeah… not in the hills.
yes, we flew even on 2800m AMSL with this setup before the things started to get weird, but there we got sometimes the message “potential thrust loss”.
That could be worth ~10% in thrust loss from SL. Even more reason to start with a higher thrust/weight
You don’t want to see that ever. That means output(s) are at max command and stability will be lost.
In one of the videos I think i could hear the frame shuddering. Regarding props I would try going smaller along with reducing pitch.
I don’t know what you are basing that on but just to be clear:
It’s a 34kg TOW Hexa with MN801 120kV motors, on 12S with 28x8" props right?
And it exhibits hover outputs ~1650µs and a MOT_THST_HOVER value of 0.37 (Expo @ 0.79).
So, A thrust/weight < 2:1 (1.6:1)
No mystery here.
A smaller prop such as the 22" suggested would not leave the ground.
update of current status:
we found a broken motor cable within the manufacturers tension reinforcement…
we’ll keep you updated.
nomaly a two inch difference would work on any craft especially if you changed the motor like i said.
when the last time you used 24" props on a build and can you show me a photo? I have made quads with 24 props.
The DJI uses 21" props and that seems to be a good overall size to weight for a mapping tool.
So you are suggesting the MN705 125kV motors and 22" props for this craft? Or 24", or 28"?
He seems open to revision but what are you suggesting to improve the thrust/weight?
My thinking is 28 size craft is not the best tool for the job, They have a good frame but the extra weight is overkill. The T-motors and escs have made issues historically. At some point they could hire a real helicopter do the job. I don’t mean any disrespect but a lighter craft could be the ticket.
Also a Y6 custom frame would give you an advantage if one motor fails. Still mapping is a big job.
Could be a good test case for a simulation using Realflight.
we did a flight with the fixed motor cable today and everything worked. at least.
no tunig done so far and the payload was mounted without damping. for me we found the issue, tha cable of motor 6 was dmaged due to bad soldering and obviously now that it got worse, when you look on the current of the escs the M6 went up quite high sometimes that lead to more and more damage till it ended up with breaking completely. now it feels completely hard as it got “welded” 
we did a flight today in very windy conditions and freezing cold but it felt satisfying without any issue so far!
monday we check the tuning and then we pray for good weather!
regarding the overweight topic: we stick to that frame now but we will implement bigger motors (MN805 105kV) just to get a bit more of spare power, or TOW will stay at 33-34kg (including 900g more for the new motors - but as they are not in the center it shouldn’t stress the frame more at all.)
we often fly with our scanner on a real heli but this isnt the most effiective solution for small jobs.
i think the mathematics with the new motors will be on our side and we can easy go to high altitudes then carrying 25kg (payload + batteries).
thanks so far for you all help!!
here is the log if anyone want to check the basics now: WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free
Looks good, yaw is nice, pitch and roll just need and Autotune.
Z axis vibrations are just getting a little on the uncomfortable side, so keep an eye on that or see if you can make an improvement.
In the MissionPlanner servo page, disable all the RCin settings that are assigned to the servo 1->8 channels. Obviously dont disable the motors assigned to the Aux outputs (servo 9+)
1 Like