Yes, I’ve had difficulty locating T-motor CF props, and for the cost of these (the “Supreme Light” models), I can afford a few spare sets for testing. I’ve got a full set of 16”, 17” and 18”. Using these saved me around $1,000. Once I figure out the optimal size, I’ll give the T-motors props another go (assuming they ever come back into stock here in the US).
The the maiden flight is complete. First of all, I’m flying it at an AUW of 25.6 lbs, which is at least 3-4 pounds heavier than my target AUW because all I have here to strap to it is a 10lb barbell weight. A few issues I discovered... I got numerous compass errors, but I think they were caused by the LiPo wires not being twisted. I landed and did another flight and got no errors. My current draws are pretty high, and I wonder if that’s because I have the 17” props on there. I’m going to try the 16” props, and I think that might help. BL temps were very good, as I was just sitting in dead air for most of this flight. The copter feels very maneuverable and steady, and feels quite nimble, even at this chubby weight AH and PH were good, but didn’t spend much time with those, as this was the maiden flight, and I was concerned about the compass errors. I’m going to order the external compass now that they’re in stock at QC. MK Version: FC HW:2.5 SW:2.06a + NC HW:2.0 SW:2.06a BL:V3 Flight date: 4/20/2014 1:30:14 PM Flight time: 1:30:14 PM.2 - 1:36:16 PM.6 (362 secs, 00:06:02) Batt. time : 364 secs, 00:06:04 Start Lat./Lon. : 37.4553395 / -122.440544 Elevation(GPS) : 0 8.35 19.18 m (min/avg/max) Altitude(Barom.): 1.25 11.86 23.7 m Vertical speed : -1.67 -0.04 3.02 m/s Max speed : 23.9 km/h Max target dist.: 5.1 m Max distance/LOS: 48.3 m / 52.3 m Sats : 10 10 11 Voltage : min. 20.9, max. 23.5 V Current : 0.5 83 125.3 A Wattage : 11 1837 2618.77 W Capacity: 8355 mAh Motor1: 0.0 11.0 16.5 A Temp: 26 41 45 °C Motor2: 0.3 9.4 14.7 A Temp: 26 34 46 °C Motor3: 1.0 10.1 14.9 A Temp: 33 39 49 °C Motor4: 0.2 11.0 16.5 A Temp: 25 39 48 °C Motor5: 0.3 10.6 16.3 A Temp: 31 36 47 °C Motor6: 0.4 9.4 14.6 A Temp: 22 41 48 °C Motor7: 0.1 7.7 12.0 A Temp: 26 38 45 °C Motor8: 0.0 11.8 18.4 A Temp: 25 40 46 °C Magnet Field: 99 112 131 % (!) Magnet Inclination: 55 66 76 deg Errors / warnings: Error "ERR: Magnet Error" (22) occured 82 times!
So here is some IMHO very interesting data. As you probably know if you’ve been following this thread, my choice to use a X8 configuration is done with full knowledge of the sacrifice in performance. But the advantage is theoretically balanced off by the ability to run significantly larger props, assuming the motors can handle it. That’s one of the reasons I moved up to the KDE motors from the smaller Avrotos. I purchased 16”, 17” and 18” props with the thought that I’d try them all. I did my first couple flights today with the 17” props, and saw hover throttle numbers a little higher than I wanted, although I was flying the copter much heavier than I probably will in practice (see above). So then I swapped all 8 props for the larger 18” ones, and did a similar flight. While the copter felt mostly the same on the sticks, the GPX file told a different tale. I am quite pleased with the hover throttle numbers (most of these two flights were spent just sitting above my backyard). I think this graph tells the tale of the advantage of running larger props, at least in this case. If I ever wondered about the advantages that the Mikrokopter stack has with the amount of data that you can use (and I never have), this is a great example of what that data can teach you.
Steve the sensor should take care of the issue. Did you get a chance to measure throttle in hover with AH off? [EDIT] Sorry I just read your next post.
Question is that data with the copter strapped to the ground? Reason I ask this is because I see you have data that shows 255 stick position which is all the way up. Am I looking at the data correctly to say that with the stick centered in the 127 posiition your about 56% throttle with the 18" blades? Your current number are pretty good based on the KDE specs of 16 amps per motor around 75 throttle.
Dave, this data is all based on actual flying, not tethered to the ground. I used the formula of getting the correct value of the “RCSticks” field of the GPX file, adding 127, then dividing by 255. The graph is pinned to a reasonable range (45%-70%). What you’re looking at in the couple of spikes is a rapid ascent where I did “punch” it just to gauge the responsiveness at this heavy AUW.
That is very encouraging data Steve. That will give you plenty of headroom for what you will actually fly and give you the flexibility down the road to fly that much weight. How did you like the way PH responded with 2.06a?
Until I sort out the compass errors I’m getting I’m not going to do any PH testing. I probably should do a compass calibration, though. That might help. I haven’t re-calibrated since I upgraded everything on the copter. As a rule, I don’t do compass calibrations very often...they’re a complete PITA. I always cut one of my arms or a wrist or something. I need to build some kind of rig to help me do them. I saw somebody did something with some little wheels that looked brilliant. I think it was Andy...
Steve, here's what I'm using. For the X8, Front boom (1) and Right boom (3) are just stubbs (1 for navi, 3 for battery tray). I have a 3' piece of 3/4 pvc I simply use as a temporary extension. Yeah, I still loose a little blood, but I curse less.
That looks great, but I worry the wheels will break the LEDs on my arms. Clearly you’re not worried about that...I guess I could put some velcro or something soft on the wheels to cushion them. Thanks!
Steve I thought I would share this with you as its interesting to see the different ways evereyone is mounting the external compass. http://forum.mikrokopter.de/topic-46024.html
I like the 3D Printed case for the compass -- the other installations all look a tad, err...."fragile," to my eye. Andy.
Just thought I'd add my experience on prop quality.. the Foxtech "Supreme CF" are nearly identical to the T-motors and only a few $ cheaper. Usually always available on their site... the "Supreme Lite" are much cheaper and good quality but not meant to carry heavy loads. You'll get flex.
Well, I was flying them yesterday at over 25 pounds AUW, and they seemed fine. I was flying at eye level using the AJL method of aligning my props, and i didn't notice any flex, but that's just at hover. Each prop is theoretically suspending 3+ pounds, which I tried just now, and didn't see any more flex than I did with a similar size T-motor prop. But that's a very unscientific approach.
So today I strapped on the MōVI for its first ride with the new powerplant. The AUW is about 3-4 pounds less than my test rig (10 pound barbell weight) and the copter flew almost effortlessly. I had my GH3 on it. The gimbal needs some tuning, as it was kind of all over the place in Majestic mode, but that’s ok. I did park the copter in AH/PH (solid as a rock in 5-10mph breeze over the seacliffs) and play with the DX8 a little and that was fun. But the cool thing is my hover throttle is all the way down to about 45-48% or so at this weight, and it’s only pulling 65-67A at hover. Despite that, I did get a low voltage warning at about 13 minutes, but I consider anything over 10 minutes to be gravy, as I don’t imagine flying longer than that 95% of the time. I do have some 10A and 16A batteries coming from Tattu, so those oughta be interesting. I’m still using my 8A 6S Zippys (two at a time). Here’s a photo of the copter after it landed, and the graph of my hover throttle. Very good progress!