MK3638 motors and all MK electronics on Cinestar 8 frame?

Discussion in 'Cinestar 8' started by John Gore, Oct 14, 2012.

  1. John Gore

    John Gore Member

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    Hi all. I am considering changing my airframe from Mikrokopter OctaXL to the Cinestar 8.

    Could I use the MK3638 motors, and full MK electronics I already have on the Cinestar 8 airframe?

    I do understand the Cinestar 8 using 14 inch props, but can I use the XOAR wood 12x6 props (on the MK3638 motors) which I currently have (don't see why not, but maybe I am missing something).

    What is the weight of the Cinestar 8 airframe vs the MK OctaXL? Do not want to loose too much flight time (I currently get 12 min with cx760 mounted, or 8 min with 7D mounted, using 8000mAh, or 22min without gimbal or camera).

    tks in advance
     
  2. Ozkan Erden

    Ozkan Erden Distributor

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    Hello John,

    Of course you can use MK3638 motors and 12" props. Depending on the payload, you can change the prop size to a bigger one, like 13". I used 12x3.8 carbon props to carry Nex5n and the hover gas was around %50 with this props. You will get more lifting capacity with 12x6, probably you will be able to lift 7D with a hover gas around %60 with 12x6 props.

    You will get less fly time with Cinestar when compared to MK frames since MK frames are much more lighter. I get just around 5 minutes flight time with one 6000 mAh Lipo (land with %15 capacity ) and Sony Nex5n onboard. AUW is around 5 kg I think. I use Tiger MT2814 KV770 motors and 14x4.5 wooden props. And I get around 7 minutes of flight time with 5D MKIII with 24mm lens, two 6000 mAh Lipo in parallel.

    I don't have the exact weights. I guess it's close to 1.5kg excluding the camera mount.
     
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  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    John: As far as I can tell you can move the MK boards over to a C8 -- you'll have to check all the parameters for the FC and NC are set correctly of course, but I'm not aware of any obstacles for doing that move.

    You might want to upgrade the firmware for the FC and NC to the current version while you're at it.

    Anyone else see any obstacles?

    Andy.
     
  4. John Gore

    John Gore Member

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    Tks for the input guys. I was mainly looking at the weight of the Cinestar 8 vs weight of the MK OctaXL frame. I am hoping to use the motors I already have (and all MK electronics). Why are 14 inch props recommended for the CS8 , and can I rather just stick with the 12x6 props I already have.

    From the replies so far it seems quite possible to make the airframe swap, keeping all motors and MK electronics in place, but what is the weight difference, flight difference?

    PS: Already flying all the latest firmware ;) (but good tip, tks).
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The C8 I have without a gimbal and battery (but including just three simple landing gear) is 6.1 lbs.
    The C8 I have with the 3-axis gimbal, no battery, no camera is 9.5 lbs.

    I don't have weight data for the MK Octa XL frame. Sorry.
    Andy.
     
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  6. John Gore

    John Gore Member

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    Thanks very much Andy! Not as heavy as I thought it would be. I actually think that is very close to the weight of the OctaXL frame.

    Anyone else know the MK OctaXL frame weight?
    I have one, but would have to strip off all electronics and motors to weigh it. lol.

    I will weigh my OctaXL with cinestar 2-axis gimbal and video downlink, 2 radian and 1000mAh 2s battery (without batteries or camera), that will give some idea of the weight differences (but I do not have 3 axis gimbal, so there is a difference there too to factor in, should be 400g I believe).
     
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    John: Just to be clear, the weights I gave you did include all the electronics and the motors....I don't have a bare frameset, I'm afraid.

    Andy.
     
  8. Adam Paugh

    Adam Paugh Distributor

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    Hello John,

    MK Okto XL framekit with 4pcs HiLander-26 landing gear with all the necessary hardware for assembly is 596grams.
    Greetings,
    Adam
     
  9. John Gore

    John Gore Member

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    Thanks Adam. Just weighed my OctaXL frame with all electronics and motor, props, etc on, with landing gear. About 2kg (but not a very accurate scale).

    Andy weighed his Cinestar 8 frame only with electronics at 6.1 lbs , which is about 2.7kg. So about 700g difference between the MK OctaXL and Cinestar 8 frames? Not really so bad, I expected a much better difference. Hmm.

    I currently hover at just under 60 A, at about 55% throttle with MK3638 motors, on all MK electronics (OctaXL frame). With 700g more weight, should I expect 70A on hover, and about 60% throttle needed to hover (with 7D mounted and 400g lens).

    For video I will use the cx760 mostly, so total flying weight is nearly 1kg lighter, and 15A less on hover.

    PS: Tks all for the input so far. Very informative!
     
  10. Adam Paugh

    Adam Paugh Distributor

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    Hello John,

    There may be other considerations besides GVW to consider when determining system amp draw. I always recommend for folks to visit an online eCalc for these types of calculations. Here is one:
    http://www.ecalc.ch/xcoptercalc_e.htm?ecalc

    Greetings,
    Adam
     
  11. Arthur Vieira

    Arthur Vieira Flight Squad

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    John,

    If I may.....
    I've done this "migration" for a friend some months ago. He had a MK Octo XL with a AV200 gimbal and bought a CS8 Frame. We moved all the electronics (after a good inspection and cleaning) and the gimbal, but the motors we didn't.
    If you can afford, consider changing the motors to the QC or similar. I'm saying this not to make Adam happy :D but for my experience the QCs are much better than the MKs, they have more power, their bearings are light years ahead in quality and they already have the bullet connectors that make the disassemble of the Cinestar possible.
    Just consider this: You will have a band new bird with the only moving parts already aged.

    Of course, I'm not the "owner of the truth" and this is only my opinion.

    Good luck,
     
  12. John Gore

    John Gore Member

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    Good tip. I have tried to use this before, but fail to find any Mikrokopter brand motors listed at all. Am I missing something?

    Is there perhaps a good substitute motor that I could use for the eCalc?
     
  13. John Gore

    John Gore Member

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    Tks for the advise. Im trying to find any differences between the mk3638 and the qc3328 motors, and battling to find any differences.

    My MK OctaXL is only a few months old, so not feeling a great need to replace all the motors just yet (not for wear anyway). But if the qc3328 motors are so much better, then I will consider that option.

    If I may ask...
    - How exactly are the "bearings better"?
    - How good are the Altigator motors with ceramic bearings by comparison? (these were also recommended to me)
    - If these qc3328 motors are more powerful than mk3638, will that mean they will hover at lower amps (if weight is same)?
    - The MK website warns against using any motors other than the mk3638 with the MK BL-ctrl 2.0 . I trust this does not apply to the qc3328 motors, and they are safe to use with the MK BLs?
    - Should I install heatsinks on all the BLs to better handle the extra weight / current load? (MK recommended this, I have bought the Altigator heatsinks but not installed yet).

    tks. Sorry for all the questions, any help / opinions would be greatly appreciated.
     
  14. Arthur Vieira

    Arthur Vieira Flight Squad

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    Hi John,

    All the infos I wrote on my previous message was from personal experience and not from specs. :)

    I had an MK Hexa XL that I used to fly with a Canon T3i or a Gopro. In 8 months I had to change the bearings of all the motors twice because the get a bit loose and start making some vibrations and this ended causing jello effect. After loosing a full day of work I decided to move to the Cinestar.
    Not it's been one year flying the CS8 with a Canon 5D and the 16-35mm lens (a much heavier setup). This year we flew in many unfriendly places, deserts, water falls, near trafic (polution), almost raining, over the beach, taking off from sand, etc, and all the motors are original, with the original bearings, since day one. I had to replace some propellers as they broke the tips during transport and from some light hits on trees, but the motors are still running strong.
    I don't know the Altigator motors, I read somewhere that ceramic bearings are good for high temp and high speed but in our case we need high lift (or compression) as the weight of the hole system is on 8 bearings only. Really don't know if ceramic is better, worst or just the same for us.
    As I said before, I "feel"them more powerful. I didn't find any specs to compare between the QC and the MK. But I do said. I had a MK Quad XL with MK that was flying ok, later I've changed to QC motors and that thing is a rocket now.
    The QCs are completely MK friendly. All my systems are MK, with the BL-Ctrls 2.0
    If you have bought the heat sinks, install them!!! :) I've installed on mine but, as I live in Brazil and here is very hot, sometimes I have overheating alarms from the BL, even with the heat sinks.

    Resuming: As I said before, if you can afford go for the QCs in my opinion but if, as you said, your motors are still new I THINK you can move them to the CS, just check them with the 14 Props for current consumption before any desoldering.

    And if you have any questions feel free to ask, this is the main reason for the existence of this Forum.

    Good Luck.
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    OK, Arthur: Can you teach me how to do only "light hits" please? <evil grin>

    Andy.
     
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  16. John Gore

    John Gore Member

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    Anyone have an answer for this please? tks
     
  17. Josh Lambeth

    Josh Lambeth Well-Known Member

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    It's called hedge/tree trimming... just a quick little *BZZZZ* and you loose a few leaves. ;)

    Josh
     
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Sorry, John. I don't know the answer -- and, if the lack of response was any measure, neither does anyone else.

    Andy.
     
  19. John Gore

    John Gore Member

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    Okay, thanks. But how can anyone recommend using this eCalc when it does not have the MK motors? Sure that make it useless in this context?
     
  20. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    That's a very good question, John. I'd be very interested to see what a "standard" CS8 eCalc screen should look like, if anyone out there has used eCalc for that configuration.

    Andy.
     

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