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My new MK heavy lift copter project

Discussion in 'Cinestar 8' started by Dave King, Jan 4, 2014.

  1. Steve Maller

    Steve Maller UAV Grief Counselor

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    Snow?
    It’s so unfair...the forecast for tomorrow is 79°F and sunny here, and my copters are grounded waiting for parts. :mad:
     
  2. Dave King

    Dave King Well-Known Member

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    Got the new motor plates this morning and spent the last few hours assembling everything. Motor plates fit nice except I had a few plates where the center hole was just a schoch too small. It was rubbing up against the center shaft of the motor and it was binding the motor a little. I took some 200 grit sandpaper and just reemed the opening a little bit. I just checked all the motors and they are all working right so its about time to take a test run outside. Weather is almost identical to that of when I tested the U5's. I'm going to weigh this new combo first and then take it for a spin.
     
  3. Howard Dapp

    Howard Dapp Active Member

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  4. Dave King

    Dave King Well-Known Member

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    I went out for my initial U7 test flights with the 3 axis gimbal like I did before. So I get it up in the air and for some reason the gimbal keep spinning and it was throwing the balance off quite a bit because its loaded down with all these extra batteries to simulate the payload I will be using. So I had the copter up and down 3 times trying to figure out why the gimbal was spinning before it started raining so I had to head inside. When I went inside I found the pulley for the pan belt somehow came off and it was just freeflying. I had an extra one so its fixed and now I'm just waiting for the batteries to charge. The weather is clear so I think I'll get a clean run.

    I did some manual altitude holds and I was seeing my sticks values hover around 140-145ish which puts me about 56% throttle to maintain hover. The copter weighed in today about 25.2 pounds or 11.4KG. I was also seeing larger current differences between the odd and even motors which I didn't see before with the U5's. I recalibrated the ACC and the copter is balanced and its ready to go back out for another test.
     
  5. Steve Maller

    Steve Maller UAV Grief Counselor

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  6. Dave King

    Dave King Well-Known Member

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    I went back up and somethings wrong. The copter is doing some abnormal vibrating/oscillating. It just doesn't sound right. The motors sound like they are really working hard and they just don't sound right. I've seen current peaks as high as 155 amps and motor temps are as high as 55 degrees with nothing more than hovering and circling around my house. Preliminary observations are that this is too much motor and the MK electronics don't like them. If I add up the first three flights I got about 12 minutes total but the voltage was still 22 volts.

    Right now I am going ahead and removing the motors and seeing if I can find anything abnormal.
     
  7. Dave King

    Dave King Well-Known Member

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    Here's data comparison so far. The current and motor numbers are not balanced and much higher with the U7s.

    U7 data
    Elevation(GPS) : 2.745 13.45 32.003 m (min/avg/max)
    Altitude(Barom.): 0.85 14.48 34.85 m
    Vertical speed : -2.06 -0.02 4.2 m/s
    Max speed : 16.4 km/h
    Max target dist.: 16.6 m

    Sats : 8 9 10

    Voltage : min. 21.7, max. 23.8 V
    Current : 0.5 89 154.2 A
    Wattage : 11 2006 3392.4 W
    Capacity: 17283 mAh

    Motor1: 0.0 17.6 34.0 A Temp: 21 47 56 °C
    Motor2: 0.0 6.2 9.9 A Temp: 18 32 40 °C
    Motor3: 0.0 15.5 29.0 A Temp: 19 39 49 °C
    Motor4: 0.0 5.6 8.8 A Temp: 18 26 33 °C
    Motor5: 0.1 14.3 29.0 A Temp: 20 31 45 °C
    Motor6: 0.0 6.3 11.6 A Temp: 18 34 39 °C
    Motor7: 0.0 14.3 28.0 A Temp: 20 38 48 °C
    Motor8: 0.0 7.5 13.4 A Temp: 18 38 45 °C

    Magnet Field: 99 104 112 % (ok)
    Magnet Inclination: 58 64 73 deg

    No errors found ;)

    U5 data
    Elevation(GPS) : 0 22.28 53.88 m (min/avg/max)
    Altitude(Barom.): 0.2 26.87 58.55 m

    Vertical speed : -2.78 -0.02 2.49 m/s
    Max speed : 45.8 km/h
    Max target dist.: 16.6 m

    Sats : 7 9 12

    Voltage : min. 21.2, max. 24.8 V
    Current : 0.5 63 87.1 A
    Wattage : 11 1445 2072.98 W

    Capacity: 20983 mAh

    Motor1: 0.0 8.6 14.5 A Temp: 5 12 21 °C
    Motor2: 0.0 8.5 14.0 A Temp: 7 13 23 °C
    Motor3: 0.0 7.1 11.9 A Temp: 6 11 20 °C
    Motor4: 0.0 6.8 12.1 A Temp: 4 9 21 °C
    Motor5: 0.0 6.4 12.0 A Temp: 5 9 19 °C
    Motor6: 0.0 7.6 12.2 A Temp: 1 9 21 °C
    Motor7: 0.0 6.3 10.4 A Temp: 4 9 16 °C
    Motor8: 0.0 9.8 15.6 A Temp: 4 13 22 °C

    Magnet Field: 102 104 110 % (ok)
    Magnet Inclination: 51 64 79 deg

    No errors found ;)
     
  8. Michael McVay

    Michael McVay Active Member

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    Those odd number amp draws are really high and the even numbers are really low. I would have expected to see all the amp draws more in line with your even numbered motors based on the weight you were carrying. You should have had 28 pounds of thrust at half throttle drawing 9 amps per motor. Less weight should have been lower throttle level and lower amp draw than 9.

    Have you found anything out of the ordinary yet?
     
  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    This may sound a little crazy, but I see somewhat different numbers for the Magnet Inclination, despite the fact that youre presumably flying in exactly the same place.

    I wonder: are those U7 motors so beefy that their magnets are disrupting the MK’s compass?
    Is it possible that it could be that different than with the U5s?
    Is your compass effect at 0?
    Are you flying purely manual?
    Maybe try again with the Navi board disconnected.

    Those are some scary numbers.
     
  10. Dave King

    Dave King Well-Known Member

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    I have the motors completely out and I don't see anything out of the ordinary.
     
  11. Michael McVay

    Michael McVay Active Member

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    Dave, I just got my motor mounts for the U7s today as well. The center holes are definitely too small. The holes measure out to 10mm with my calipers and the shaft on the U7 on the bottom is also 10mm. The first U7 snapped into the mount so tight that when you spin the motor the mount turns with the motor bell. I just had a custom U7 mount drawn up and 3D printed as a model. I have a local shop with a water jet that will cut them from carbon fiber (I just received a 3mm sheet big enough to cut out about 40 of them). I am doing a top and bottom version for coax - one side with 4.4mm holes for press nuts and the other side with 3.1mm holes for the M3 bolts.

    I was initially thinking that maybe the new MK braking feature was having a hard time slowing them down and getting them back to speed in the expected time, but would now venture to guess that one or more motors may be slightly rubbing up against the mount (probably like having a bad bearing x 10). If that slowed one of your motors the others spinning the same way would probably draw higher amps trying to make up for the one that was experiencing some friction.

    ...just a guess based on the mounts I got and how tightly the shaft snaps into the center hole.
     
  12. Dave King

    Dave King Well-Known Member

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    Steve they are huge magnets! Yes I think they are completely different compared to the U5's to be honest. These motors just don't seem smooth in flight in sound or through visual observation. IMO these motors need a matching set of ESC's. I have the compass setting at factory stock and if I remember correctly it was 64. I flew 2-3 minutes in PH mode, 2-3 modes in complete manual mode, 2-3 minutes in AH hold, and 2-3 minutes in AH and PH mode. No difference what so ever between any of the modes.

    I fixed the gimbal problem but it didn't help at all. The copter was definitely vibrating as you could see the gimbal vibrating.

    I"m uploading some footage of the flights. My wife only shot a couple minutes of the flights. It should be ready soon.


    I am ready to switch back to the U5's to make sure everything goes back to normal. If it does I"m keeping the U5's and going to 16" props.
     
  13. Dave King

    Dave King Well-Known Member

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    Michael this morning I took some sandpaper and opened up the holes just enough. That got all the motors turning nice and smooth. I really took my time with this and made sure that the motors were not binding. When I took the motors off with the mounts still on them they were all spinning freely and don't show any signs of bearing problems.
     
  14. Michael McVay

    Michael McVay Active Member

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    Sounds like you got that one covered. If I try these mounts, I am going to have them drilled to make the opening at least 2mm larger. I worry that if the motor (while putting out a lot of power) flexes at all on the mount it could rub. I'll definitely let you know how the custom U7 mounts turns out when we switch from 3D print to carbon production version. I wish I could have just bought them, but at least I am going to get what I was after in the end.

    Have you posted anything to the MK forum about the new 3.0 board being able to handle U7s?

    The second pilot that flies with me has always flown WKM so we are going to try that with a 60amp ESC - hopefully by the weekend.
     
  15. Steve Maller

    Steve Maller UAV Grief Counselor

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    Hey Dave, another thing I was thinking about is vibration isolation for the Flight Control board. Those motors and props are putting out a huge amount of energy, and I wonder what kind of stresses they’re putting on the Cinestar chassis, and whether some of that is translating to oscillations or other physical interference on the FC board. In all my fiddling, I seem to have misplaced the rubber isolators for my FC board, so I’m going to have to dummy up something for my copters while I wait for some more.
     
  16. Howard Dapp

    Howard Dapp Active Member

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    My money is on the speed controllers. Can the controller's timing be adjusted in koptertools? Prop/motor leveling and copter balance have been eliminated so it has to be something with the controllers. Share that video with Holger, I bet he'll know the problem immediately.

    Have you flown with the nav control and all other add-ons disconnected?
     
  17. Howard Dapp

    Howard Dapp Active Member

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    What has me stumped is the copter is not yawing like crazy. You would think with all of the odd numbered motors drawing that amount of amps you would see a great deal of yawing, even if the odd numbers are fighting against the even numbers to keep heading, there should be some back and forth yawing.
     
  18. Howard Dapp

    Howard Dapp Active Member

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    One other thing you might check is motor balance. Remove props and use the koptertool to run each motor individually, feel for excessive vibration along the booms. Just some ideas
     
  19. Michael Braun

    Michael Braun Member

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    Do you have all the motors levelled?
     
  20. Dave King

    Dave King Well-Known Member

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    Michael

    The more I think about it is is possible that when the motors get warmer that that shaft expands a tad and is causing issues. I don't think i would have been idling in hover as high as I was. I was calculating more like 48% about 8% more anticipated.
     

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