Ref: The chart you sent showing current draw: The figures in the right-hand column - are they showing the current for one motor only, or did you test all four? It might be informative if we could see the current draw for all of the motors. (I’m thinking maybe something is wrong in the circuitry between the PDB and the ESC’s - like maybe in the frame deck that the ESC’s are soldered to. But then, I’m kinda new at this drone stuff, so maybe I shouldn’t sound of here…)
Hi Jerald,
Thank you for your suggestion, I’m actually using a 4-in-1 ESC, so I haven’t had to include PDB wiring in my design. The central column shows the amp draw for all four motors, and the column on the right shows the amp draw from each (all divided by 4). I didn’t include the power draw of the FC and receiver because 0.19A is negligible. The column on the left is based on the factory results published online:
Okay, didn’t know about the 4-in-1 ESC set-up.
Hi
This is a bit of a long shot, but we seem to be in that territory now 
Have you got some smaller props? maybe 1245 or even 1045.
In the video they do not seem to be moving that fast at 100% throttle (I know it’s difficult to tell with the camera strobe effect) I’m just wondering if they are trying to move too much air, not reaching high enough speed.
Cheers
Steve 
Also…
can you give exact part reference for the 4in1 ESC, FVT Sky’s come in various sizes
Thanks
Steve
I may be off topic now but my quad won´t lift too. My FC got fried and accidentally bought the SPF3 Evo that doesn´t support PMW, so I also bought a Spektrum SPM4648 serial receiver. I remember my FVT LittleBee 20Amps working on oneshot 125 while on PMW. Now no protocol seems to work. Is itt because I´m using a new protocol for the receiver? Any ideas for new escs? Preferably from HobbyKing since this is turning way too expensive already. Thanks in advance /Anton
Hi,
It would be tough to believe the props are the issue, they are 16x5 inch and seem well designed, so at the very least the amp draw should be higher than in the tests, especially if they are struggling to move more air than they should.
My last option is to program the ESC via USB through the FVT link card, it is currently being shipped. Just for reference, I tried running the ESC off a 3S battery and the props were barely spinning, so there is clearly an ESC programming issue.
The ESC is a Favourite SKY series Brushless 30A 4 in 1 Quattro ESC, not sure of the exact part reference.
I will let you know how the testing goes once the part arrives
Hi all! Apologies for the silence, been really trying to wrap my head around this whole lack of thrust issue.
I recently bought a Digital Laser RPM meter to test whether I may have been sold the wrong kV motor (desperate times = desperate measures!). The motor kV the manufacturer specified seems to be ok. The motor maxes out at 5818 RPM @15.1V (380kV). Below is the video of the test.
So the next logical step was to test the motor under load. I attached the 27g 16x5 carbon fiber propeller and run the RPM test again. This time I got only 3337 RPM! The manufacturer chart says this size prop should rotate at at least 4500 RPM, and explains why I’ve been getting only 610 grams thrust per motor at 100% throttle.
I have e-mailed the manufacturer and customer support and they suggest the propeller may be too big, hence the low rotation speed. But wouldn’t too large a prop mean an increase in current draw? At 100% throttle and with a 15x5 prop, current draw is quoted at about 8 amps, yet with a 16x5 prop it can’t even crack 4 amps in my actual tests.
So to dispel the myth that too big a propeller somehow causes lower current draw, I attached 20g of weights onto the propeller (total prop weight 47g).
The motor went from drawing 3.9 amps to 4.8 amps at 100% throttle. So if my 16x5 prop were truly too big and overloading the motor, it should draw over 8 amps based on the manufacturer’s chart.
So, to sum it up, I’m out of options. I don’t believe replacing the propellers will be of any use, and I’m not sure replacing the motors will be of much help either (plus motors are pretty expensive). Kindly advise what I might be able to do. I’m about to walk away from this DIY project altogether 
Hi, I’m just looking at a table you have uploaded and I can something that in my opinion nobody pointed out.
You want your machine to hover at about 50% throttle so at 50% throttle the thrust has to be at least 2.65kg witch is equal to the weight of your machine.
Your table shows that at 50% throttle you will get 340g per motor/prop so a total of 1.36kg (this will not hover)
I have built a Tarot 650 with 380kv motors and 14x5 props and I use 5S battery.
The total weight is 2.5kg.
I have used ecalc.ch to estimate what esc/battery/motor/prop to use.
I hope this helps.
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I’ve just put your config in the ecalc.ch and it looks like it should fly, though the trust to waight ratio wants to be closer to 2.
If you live in the UK you could pop round to me, we can have a look at it, a fresh pair of eyes might just do it
Did you do any tests with different ESCs?
Hi Greg,
True, with their current thrust delivery the max weight per axis would actually be about 340g. But based on the manufacturer specifications of the Sunnysky X4108S 380kV, max throttle with this prop should give me at least 1200g on 4S, not 610g. I mean, the motor itself weighs 130g, so 340g load per axis would be a ripoff by the manufacturer 
I first tried with an AUW of 2.65kg, but once that didn’t work, I removed many of the non-critical components, and run it on one cell instead of 2, and yet still didn’t take off with the new AUW of 1.98kg.
Also, I’ve tried with at least 3 different ESCs, the current draw is the same for each. From my research, I’ve seen ESCs don’t “push” current, they simply deliver what is requested by the motor, so my guess is the motors are at fault. THey draw 4 amps at max throttle, only half of the ~8 amps the manufacturer specified.
Oh and unfortunately I don’t live in the UK, I live in Kenya, indeed it would’ve been nice to have a fresh pair of eyes take a look
I think you are right about the motors, the ESC only delivers what the motor demands.
Unfortunately a lot of companies don’t have very good QC practices today and the after sale service is non existing.
It is likely to be a faulty winding in your motors, did you try with different motors?
Hi all,
So this is just to let you all know I FINALLY solved the problem! 
The motors I was using were the issue.
Having never built a quad before, I followed the advice of an online blogpost, and bought the SunnySky X4108S-17 380KV motors. However, their amp draw at full throttle was suspiciously low, and I was never able to get enough thrust to even get off the ground. The drone would just dance around lazily.
https://www.youtube.com/watch?v=YETUQj0Mp3k
A word of caution: do not take your chances with this motor! Trust me, there’s probably a reason SunnySky discontinued it’s production.
Swapping out these motors for the GARTT 4112 400KV motors instead, the difference, even at low throttle was immediately apparent. Check out the thrust test I did below:
https://www.youtube.com/watch?v=wLU8lg2XsRA
Having bought only one initially, I took the plunge and shipped in the other 3 motors (choosing the wrong motors is a very costly endeavor btw, wasted over $150 on bad motors) and I finally took flight at 1am on September 29th, 11 months after starting the project! With an AUW of 2300g (no payload), the drone starts to take off at just 40% throttle, a clear indication of the thrust potential.
To sum it up, if you ever have problems with lack of thrust, always check the amp draw of at least one of the motors, ESCs will rarely be the issue, as they only give the motor what it requests. Also, ESC issues normally manifest in other ways, like a stuttering motor.
I’ll post a full flight video soon, but for now I’d just like to thank you all for the support and advice with this issue, and I do hope this information will be of use to someone 
Nice one, I’m glad you have sorted it out Happy flying
Well done Sherlock
Look forward to seeing the video
All the best
Steve
Thanks Greg and Steve 
Indeed I had to put on my Sherlock hat for this one 
Here’s a short video. Didn’t want to fly too high because there’s an airport nearby, plus I’ve sort of never flown a quad before, so I didn’t want to take chances. Thanks!