NEW U7 motor tmotor

Discussion in 'Cinestar 8' started by kjetil tønnesen, Nov 22, 2013.

  1. Steve Maller

    Steve Maller UAV Grief Counselor

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    If you want something that’s safe for a bird, you should consider a truck. This strikes me as a dangerous and inhumane stunt.

    Your design for the coax is particularly dangerous with the lower set of motors clearly very close to the payload doors.
     
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  2. Lance Robb

    Lance Robb New Member

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    I can't see why anyone would want to drop an Eagle from height......??
     
  3. Dave King

    Dave King Well-Known Member

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    Lance what electronics are you using? Any more testing?
     
  4. Dave King

    Dave King Well-Known Member

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    I think you guys that are running 17 inch props over 27 pounds should really look at the 18 inch props. I sent KDE an email about wanting to use the 4014 for a X8 configuration at 30 pounds with 18 inch props. Here's what they wrote me back.

    Hello Dave,


    All of the information you sent me makes sense. We have been flying a X8 monster around at the 28 pound mark, getting 18 minute flight times with our 4014 motors.

    The 4014 is really the motor for this application. It’s the most efficient with props over the 16 inch range, with the 18 inch props it performs better then the 4012. Here is our spec sheet with the efficiency ratings in the far right column. You can see the 4014 on 18 inch props does really well.

    http://kdedirect.com/files/KDE_Direct_4014XF-380_M-R_Performance_V2.pdf

    Here at the very end of this video you can see one of our testing systems flying with 4014 motors and 15” props in this configuration. It handles the weight with no problem.

    https://www.youtube.com/watch?v=d2y0TUwHc1Y

    With 18” props your system would be just fine. The 4014 are really built for this.
     
  5. Tim Sessler

    Tim Sessler Active Member

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    Thats very interesting. Thanks for sharing.

    I am also just looking into upgrading my T-Motor 4012-09 (not the best choice for a heavy lift) and have been wondering about the prop size that I should get for my X8.

    Even 16" at 65% throttle should create a thrust of more than 30lbs (if those spec numbers are somewhat accurate). Why go to 18" propellers? I might be wrong with this assumption, but wouldn't bigger propellers increase the surface and reduce wind stability and responsiveness?

    Or differently asked: what are the advantages and disadvantages of 18" props?

    Thanks!
    Tim
     
  6. Dave King

    Dave King Well-Known Member

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    Tim

    Multirotor motors are usually designed to work with at least 2 to 3 different size props. Usually a manufacturer publishes specs for each size prop that it's compatible with. To give you an example lets use the Tiger U5 motors. They are designed to work best with 14-16 inch props. You can bolt up a 13 or 17 inch prop but it wont be nearly as efficient and in the case with the 17 inch props the motor probably wouldn't have enough torque to properly spin it. The U11 motor is made to run with 27 or 28 inch props. The KDE motors are a little different as they have a wider range of props. Usually the size of the prop will dictate how much overall thrust the motor will produce and at what efficiency it can do it in. The greater the efficiency the less current draw, and better flight times. Thrust needed is pretty much dictated by how much weight it has to lift or maintain in the air. You obviously need more thrust if your flying weight is desending or ascending. The faster the descent or ascend the more thrust.

    I like to think of in terms of cars. If you want a race car with a 427 inch motor to make 1500 hp you bolt on a 2 inch exhaust as the motor couldn't get the proper exhaust flow out to make that kind of power. If you need to lift 30 pounds you don't use a 14 or 15 inch prop unless you want to run a X12 or X16 or some configuration where each motor doesn't have to work as hard. One of the reasons why Coaxial configurations are so popular is so that you can run larger blades that are needed to generate higher thrust levels without having to have a huge impractical frame.

    To figure out how much lift you need convert your flying weight to grams. In my case 30K is 13608 grams. Divide that by the number of motors you will run (in most applications on this forum it would be 8). This would mean that each motor would need at least 1701 grams of thrust to maintain hover lifting 30 pounds. Now if you run a X8 configuration you need to add somewhere between 5-15% to that number for efficiency loss. SO to lift 30 pounds efficienty to maintain hover you would need 2000 grams if your X coaxial setup loses 15% efficiency.
    So in the case of myself that plans to lift 30 pounds with a X8 configuration, 18 inch props would lift my copter pretty efficiently and probably hover around 53%. If I chose a 16 inch prop my motors would need to run around 70% throttle at hover to maintain hover altitude.

    What are disadvantages of larger props? Cost is the biggest one (a pair of 18 inch props can cost $115), and the necessity to use a coaxial configuration (not that its really a disadvantage).
     
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  7. Tim Sessler

    Tim Sessler Active Member

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    Makes a lot of sense - thanks for the explanation! :)

    And you think that having a 2" larger prop does not affect the wind stability or responsiveness in any way negatively? It would seem logical that the bigger the prop is the more difficult it is to quickly speed or slow down each motor/prop (especially when not having the active breaking feature). But the size difference might not be that significant... ?
     
  8. Dave King

    Dave King Well-Known Member

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    Tim

    I honestly do not know. I am using active breaking with MK so I am not too concerned about how responsive it is but this is beta testing and we will see how it goes.
     
  9. Lance Robb

    Lance Robb New Member

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    Hey Dave, I'm running MK electronics with a Herc3 board on 6S, coaxial X8 with 18" carbon props and MC-20 Tx. So far it is performing very well. I'm still making small adjustments to everything and haven't really done any serious flying with it but what I have seen so far the KDE motors are performing very nicely and with considerably lower amperage for the same load as with the U7 motors.

    Flying at 15kgs AUW it comes back with the motors and powerboard only luke warm. I'm planning to get some more flights in the next couple of days and will let you know how I get on.
     
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  10. Michael McVay

    Michael McVay Active Member

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    Good explanation Dave...+1 from me.
     
  11. Michael McVay

    Michael McVay Active Member

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    Lance,

    I am quite interested in anything more you can tell me about the Herc3 board. I have been thinking about giving one a try for a while. I recently read that it, like MK, has the active breaking and regenerative current back into the battery. How was it to set up and get running with the MK FC? Apparently they have been tested with many of the U series motors as well as the KDEs without issue.

    Michael
     
  12. Lance Robb

    Lance Robb New Member

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    Hi Michael, Yes the Herc3 has those features and is probably the most advanced powerboard available at this time and it's 6S capable (there is an 8S version available also)

    I had originally bought a Herc2 board and sent it back after hearing stories of them failing whilst in flight. I'm told, it was more to do with the motors overloading the boards than the boards simply failing...Anyhow I returned it and decided to wait for the Herc3 which has some neat features not found on other boards, including current and temperature overload protection. One of the biggest pluses for me, was that the Herc3 talks to the MK FC and if you have a Tx with Telemetry, it relays all the important info back to the Tx. The Tx even speaks any warnings, switch changes and by flicking a switch it will speak all the telemetry fields. That is a real plus when you don't want to take your eyes off flying the MR

    Programming is is via a USB adapter which plugs in and is used to set the I2C addresses for each of the ECS and the other programmable functions such as Active Freewheeling etc. It's quite straight forward and I got it sorted first time round.

    I had a set of U7 420Kv motors and the Herc3 ran them without any problems. The motors made a terrible screeching noise when at between 40% and 50% throttle. I was told the noise was from the cooling slots in the motors and it very well may have but it didn't sit right with me so I replaced them with the KDE Direct motors and there's no nasty noises and the MR flys better than it did with the U7s

    http://www.andreasbaier.de/index.php/en/herkules-iii-generation-3

    Regards,

    Lance
     
  13. Gary Haynes

    Gary Haynes Administrator
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    Lance, Andreas's Herkules boards, for some reason, have never taken hold in the U.S. While at NAB I talked with the guys from Kopterworx. They love the board, have sold a lot of them, and were enthusiastic to say the least about how they perform on large platforms. Herkules seems like it has turned out to be solid performer in the ESC arena. And I haven't seen any real chatter about failures for more than a year (Herk2 boards).
     
  14. Lance Robb

    Lance Robb New Member

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    Gary, there were a few Herc2 boards burnt up in flight.......This is going back a few years now and looking back the motors then were a lot more power hungry than what we have nowadays and simply overloaded the board and fried them. Andreas built in safety measures to protect the Herc3 boards along with temp and load telemetry via the FCso the pilot can monitor what's going on in flight

    They're a good board and coupled to MK electronics are a great marriage.......
     
  15. Steve Maller

    Steve Maller UAV Grief Counselor

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    Maybe they need a US distributor? I’m not aware of anybody stateside who stocks/sells them.
     
  16. Gustav Raberg

    Gustav Raberg Member

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    We fly the Herkules III and its great!! Never any problem with it. Telemetri board and you have all info in your transmitter. The one who get the distribution going in US will earn some money!!
     
  17. Bryan Harvey

    Bryan Harvey Member

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    What is you hover throttle percentage with 15kg on the KDE motors?
     
  18. Tom Gear

    Tom Gear New Member

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    Hi everyone

    I planing to build a heavy lifter with u7 and cinestar frame.
    Around 12-15kg (with gh4 sometimes less)
    flat octo
    16x5.4 tiger
    2x8000mah 6s or 2x1000mah 6s
    movi with red epic

    There are a few questions left, maybe you can help me.

    420 or 490kv?
    Is the frame with 2.5mm cfk strong enough?
    Do you recomment using aluminium clamps?
     
  19. Chakradhar Raju

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    U7 490 KV Tiger Motors and No response from Distributers and Company for Returns..
     
  20. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Chakradhar:
    Could you be more specific -- what you wrote seems like a headline -- what's the rest of the story, please?

    Andy.
     

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