It could be a voltage drop issue. What size wire are you using for powering up the ESC's?
When I swapped over the ESC's on the X-mode Alien on Monday, I thought I'd try and save a bit of time by soldering bullet connectors onto the end of 14AWG wire that was about 1 metre long. The 14AWG wire was soldered directly to the ESC's. Plan was to calibrate the ESC's then cut off the length I needed to hook the ESC up to the power distribution board on the quad. I thought this should save me some time having to solder bullet connectors onto the ends of the power supply wires on the ESC each time.
I connected the bullet connectors to an adapter to plug into an XT60 battery connection, the ESC servo connection to a receiver, nothing from the ESC's, no tune, nada.
I checked the voltage at the ESC and it read over 11.7 volts, but I reckon there was simply not enough oomph to fire up the ESC and motors due to voltage drop. I trimmed the wires to the approximate length I needed to hook the ESC's up to the pdb and bingo, they started to sing.
To cut a long story short, I think you will find that the thrust test will most likely give you the answers you are after with the problem you are having with the motors not firing on all cylinders. It could be voltage drop, it could be the ESC's are going over the max burst amperage. They really are a handy piece of kit.
I tested my emax 2206 1500kv's with 5 inch props and got similar results to your 10 inch props, simply no power coming out of the motors.
Hi Marschy,
Apologies, it's a long post.
I'm using 16 AWG, which is the same as the wires on the old tricopter - about 10-15cm less distance on each connection. The only difference is I left the smaller pigtails on (approx 10 cm), I'd say they would be 18 AWG sized, I'm thinking I'll remove them and replace them with 16AWG to be sure. I have a bunch of 14 AWG so I can always try using it instead but it will be harder to fit them inside the arms. Having said that I checked the resistance compared to the old harness and I was getting 0.3 ohms on both old and new, so there doesn't appear to be a dry joint in the way either. One difference is that I used to do a short DC line (3s) to the ESC and the long run to the motor, now I do a long run (2 wires - 30cm) to the ESC and do the AC as the short run (3 wires approx 10cm). I think the AC lines are 18 AWG, I might replace them as I did on the other harness. Also a quick voltage test, only 0.2v of drop from battery to ESC (no load).
I did some static tethered tests and outdoor flight tests today. I reconfigured the ESC's, turns out I had a few odd settings which weren't helping. I recalibrated the current and voltage settings on the PM. I max out at about 28 amps, so only 9A per motor - for 10x4.5. For 11x4.5 I max out at around 32A. These were via the PM and also a separate power meter.
I started doing a thrust test (10x4.5) but just as I get to 50% throttle the scales packed it in. No not as i was setting up, dead in the middle of my testing - maybe my motors are so good they broke the scales :-). So I will go and buy a new pair of scales tomorrow. What I did get was at 9.5A I was generating around 800g of thrust at around 50% throttle which is pretty good. As I started to spool up to a higher level the scales stopped working. I was drawing around 14A at full throttle but no idea of how much thrust it was generating, but I would say I hit the 1kg no probs. It would explain why at 9A (that is close to 100% throttle on the pixhawk), I'm having trouble getting off the ground once the battery is loosing a few volts, as 3*800 is only 2.4 Kg of lift, so it would be less than that - at 1.5kg AUW I can see why it struggles.
Interesting is that via the Pixhawk I am getting 28A as max for the 10x4.5 while flying (so only 9A per motor), this would imply that I have spare capacity as I can get the ESC and motors to 14A on the bench...... The motors do get a bit warm at that level but well below the 200W level.
Static test at of 11x4.5 at 28A gave me a duration of around 9-10 mins, the 10x4.5 at 22A gave me around 13 mins. On my old frame I was getting around 18A for a hover and was getting 15mins of real flying time if not a bit longer.
On the flight test I took the camera off and it made a huge difference on 10x4.5 - I could take off at 60% or less throttle with a fresh battery and after 8 mins still hover at 80%. I think my issue is largely a weight issue based upon this. The camera would only be 40-60g at most, this makes me think my extra 100g is really affecting me. I was finding I could fly until the battery got to 4200mah but after that it struggled to stay in the air.
Plan is to swap that FR4 out as it is heavy compared to the CF. Still struggling to understand why it is so heavy, it shouldn't be. I'll also order some more 1mm CF and I'll loose another 15g if I redo the plates. On paper the wooden tri should be 50-100g heavier but for some reason its the other way around....
I also tinkered with some of the settings, such as hover throttle, etc.....
I may have to take a few days break as I'm on standby to head up to the NSW north coast.
Chris
