Coaxial Cinestar...

Discussion in 'Cinestar Misc' started by Benjamin Rowland, Jan 26, 2013.

  1. Chris Newman

    Chris Newman Member

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    Thanks for the input Brad!
    How hot do your lipos generally get and what specific brand do you use? Appreciate the help!
     
  2. Brad McGiveron

    Brad McGiveron Active Member

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    On a hot summer day they get to be fairly warm... not hot.

    Make sure you are running EC5's or better on your connectors.

    I use a few types but mostly Thunder Power.
     
  3. Shaun Stanton

    Shaun Stanton Active Member

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    I have a question, are people finding better results using the same size props on top and bottom? I have read a bunch of conflicting information on the inter-webs on this. Some claim both should be the same size as long as the bottom prop is spinning faster.

    It would seem to make some logical sense that if the top and bottom are the same size and pitch that the top prop would be pushing some of the air away from the bottom one. Also any one notice any extra vibration on the bottom props? Having flown a Coaxial Airplane before ie a Cessna 337 Skymaster, a common issue was that the air from the front propeller would knock at the rear prop. A way to mitigate it in an airplane was to have the front prop at a slightly shallower pitch then the rear one.

    Any thoughts?
     
  4. Ryan McCrae

    Ryan McCrae Member

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    I just ordered some 16x5 for my coaxial skyjib. Im thinking of getting a set of 16x7s for the bottom. Can you tell me the flight time difference bettwen all 16x5 vs 16x5 and 16x7 props.
     
  5. Brad McGiveron

    Brad McGiveron Active Member

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    I didn't really notice much flight time increase. Maybe more from the fact the whole system was working slightly less and the top motor temps were more in line with the bottom. Maybe 30 secs but its hard to tell.


    Shaun, I gave up on listening to the majority of whats out there. Most of the info is based on theory and non similar payloads which don't translate to the much heavier setups. Also there are so many factors involved in each persons conclusion that there are no guarantees two peoples tests will yield the same results.
    Yes your theory makes perfect sense and its was the reason I tried it. :)
     
  6. Alex Smart

    Alex Smart Member

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    I´ve been doing some testing with diferent size props and equal props etc.
    I think that the most important,and this is backed up by increase of flight time, is that both motors are working the same, therefore,consuming the same amps and getting to similar temps.I regulate this in the mixer table and obtain info from Graupner Hott TX, or GPX files.
    Here a MK 12 rotor, MixER all 64 /2x6000x4s / Top APC 1245-Botom CF 1365./= 10min flight,bottom motors warm!
    Same Choper with botom motors at 50 in Mixer=14 min,motors more or less equal temps.
     
  7. Steve Maller

    Steve Maller UAV Grief Counselor

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    Makes me nervous that the motors seem to be making a high-pitched barking sound. :D

    Looks super stable. Curious as to how the MK FC handles the 12 config. Are you using a stock CS6 frame and booms?
     
  8. Shaun Stanton

    Shaun Stanton Active Member

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    Yeah that makes sense I guess I will try different combos and see what I can conclude. My new CS8 coax that I am putting together is going to use WKM with the FF motor control instead of MK. I will turn my current flat8 into a coax also with the MK as a backup and whenever a large camera is not needed.
     
  9. Bryan Harvey

    Bryan Harvey Member

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    I was thinking the same thing.

    Is there some HL motor/prop combinations that I could upgrade to on the standard CS frame that would allow carrying a RED with decent flight times?

    It seems the flat heavy lifters always go with a larger frame, but Im wondering about what kind of performance increases you could get with just using more powerful motors/ESC combo and higher pitched 14" props (this length being the only limiting factor) on the standard CS frame.
     
  10. Todd Livdahl

    Todd Livdahl New Member

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    I'm running into the same YAW issues as well. Here is my X8 with the new DJI A2 FC, the thread is here: http://www.rcgroups.com/forums/showpost.php?p=27234402&postcount=78
     
  11. Jason Toth

    Jason Toth Active Member

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    We find the standard DJI motor configuration works best on our X8's.

    With an AGW of 35-40lbs our gains are:
    Pitch 125
    Roll 125
    Yaw 150
    Vertical 200
    Attitude 100/100
     
  12. Todd Livdahl

    Todd Livdahl New Member

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    Have you tried this Mix above? You don't have any left Yaw issues? I'm using the 15X5 props (same size top and bottom), maybe your props are working different than mine. Also, what is your setup for 35/40lbs AUW?
     
  13. Brad McGiveron

    Brad McGiveron Active Member

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    Todd, which one are you using? The above one or the stock DJI one ?
     
  14. Todd Livdahl

    Todd Livdahl New Member

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    Above one, I tried DJI stock and Yawing left was horrible. After taking off 15lbs of weight Yawing left was better. But it seems the above mix works best for me. I'm just trying to figure out why.
     
  15. Brad McGiveron

    Brad McGiveron Active Member

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    Its because on the stock one the tops all turn one way and the bottoms turn another. The top is more efficient an thus you get more effect from them. You can counter it with different props on bottom to lessen the advantage the top has. Or use that mixer above as you have done.
    Now with that mixer and different props on bottom you will get slightly more efficient lift and even temps on all motors.
    I am Just finishing an A2 build so maybe there's a difference between WKM...
    That has been my experience with big weights and those mixers.
     
  16. Jason Herring

    Jason Herring Member

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    What s
    what size booms are you using?on the x8
     
  17. Steve Maller

    Steve Maller UAV Grief Counselor

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    Right now I'm still using the stock CS 450mm booms. But I have 500s on order, and I'm going to test them both and see if there's any difference in maneuverability or flight times. I'm planning to use 15" props for now, so I don't need any more than the 450s.
     
  18. Todd Livdahl

    Todd Livdahl New Member

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    I know the tops are turning one-way and the bottom turns the other. I'm just wondering if Jason is using all the same props on top and bottom and why his config works with no issues compared to mine
     
  19. Brad McGiveron

    Brad McGiveron Active Member

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    Its magic I guess
     
  20. Todd Livdahl

    Todd Livdahl New Member

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    Magic huh :) He must have something else configured differently.
     

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