KDE 5215 435kv Coax MK Octo

Discussion in 'Cinestar 8' started by Ryan McMaster, Feb 15, 2015.

  1. Justin John

    Justin John Member

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    Waiting on some larger props to arrive in - We tested 18 inch Foxtech blades only because Tmotors were out of stock - Foxtech's didn't really work out.
     
  2. Sam Fleishman

    Sam Fleishman Member

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    Are you flying x8 or flat 8? What's your amp draw at hover? My next move is going to the 16" tmotor and about 17,000 mah of 8s. Lipo weight is a few hundred grams heavier than my usually 20,000 mah on 6s.
    I got 4 minutes with 8200mah 8s on 18" props. These motors on 18s props is way overkill for a red setup, correct me if I'm wrong.
    As far the esc and motor temps kde assured me my temps are well within operating limits. On 8s it's ice cold after plenty of climbouts in 75 degree ambient
     
  3. Justin John

    Justin John Member

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    Flying X8 Amp draw is yet to be determined due to broken sensor but e calc is saying about 95 -100amp in hover - I think 18 inch will do the trick for me, I was toying with the idea of going to a 18 x 8 beachwood but Ecalc isn't showing much efficiency gains - just more amps

    I'm also thinking of going to a 19 inch but have to move to xoars for that. - We aim to fly the ronin with 10lbs of camera -

    I also should mention that I'm using a very conservative 5000 - MAH per 10,000 batt I stick on there. I like to keep my batteries treated nicely. On my main rig I can do a Movi M10 10 lbs of camera weight and 10 minutes of flight time in the 50% - 60% battery usage - Plenty of emergency reserves.
     
  4. Justin John

    Justin John Member

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    Using this method. My batteries last more than 200 cycles and still show limited signs of wear and tear. If your using gens ace --- note they are usually 15 c - not the 25c they claim. I've since gone to Aga Powers 30c
     
  5. Sam Fleishman

    Sam Fleishman Member

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    If you think you're amps are too high and already at 34% hover why go up in prop sizes. I thought I was over propped at 18" I feel like there are multiple trains of thought here.
     
  6. Howard Dapp

    Howard Dapp Active Member

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    I was referring to using a lower kv motor like the kde 5215/330kv with a 20" or larger prop.
     
  7. Howard Dapp

    Howard Dapp Active Member

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    Justin, with your current X8 setup running kde 5215/435, 75A kde controllers and 16x5 props at approx 35lbs AUW you're able to get 10 mins of flight time from 20,000mah of lipo with 50-60% usage? Just wanting to confirm the exact specifics.
     
  8. Thijm le Grand

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    Correct Sam. Hoover point needs to be @ 50/65%. otherwise change prop/voltage?kv
     
  9. Alex Smart

    Alex Smart Member

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    Hi,
    I´m a little concerned about that motor-prop combo to, I just got a SjX4 with A2 and T-M4014 330kv, it´s running 15.5 top and botom and the throttle was at 60% with no payload, total lack of power:confused: I´m aiming at 24lbs AUW, should I change props or go for different motors??
     
  10. Thijm le Grand

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    At what weight and voltage where you testing?
     
  11. Alex Smart

    Alex Smart Member

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    No payload.only batteries so I guess around 6 or 6,5 kg
    Volatage 6s, 2x 8000, 30C.
    Throttle over 50% to take of and very slow ascencion at full throttle.
     
  12. Thijm le Grand

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    330Kv is kinda low and not easy to predict whats the best solution.
    According to the spec’s, you could test 16” and also 17” depending on your frame.
    16” might be just enough with 10kg @ 60/65% hoover. 17” is I think to large for this motor (3500/3700rpm) and can result in higher amps usage/esc temp and slow response from the flight controller in windy conditions.
    New motors are quite expensive but better for efficiency and headroom if one motors/controller fails.
    The 400kv version would be enough with 15”, but test 16” First (cheapest solution. Also nice to have with future motors for bigger payloads)
     

    Attached Files:

  13. Alex Smart

    Alex Smart Member

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    Many thanks Thijm, I really need to get this right asap as I have a few shoots mid april, I think that if I can sell the 330kv fast I will just go for new motors(praying)!
     
  14. Thijm le Grand

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    Ok. Post the results
    Btw the 400kv version with 16" is @ 10.5/11.3Kg about 1 Amp per motor more efficient then the 15"
     
  15. Alex Smart

    Alex Smart Member

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  16. Thijm le Grand

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    Looks good

    Edit; But ads 400gr in total. This motor is more for 11-12kg. other maybe better at your current wight!
     
  17. Alex Smart

    Alex Smart Member

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    So what motors would you go for? My aim is to lift a Gremsy h6-Movi5 with a BMPK4k, Im sanding teak decks on yachts in order to get it right, long hours little money so its very important I invest in the right gear!
     
  18. Thijm le Grand

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    Difficult to say. I have no knowledge on these components.
    Maybe other can help here on expected wight.
     
  19. Michael McVay

    Michael McVay Active Member

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    Alex,

    When trying to pick the right motor and prop combo I find it most helpful to start at your flying weight and work your way back into the specs you need - then find a motor and prop combo that you feel good about. For example, above you mentioned that you want to fly at 24 pounds. 24 pounds is just under 11,000 grams. If your SJ is a coaxial configuration you will probably need to add 10-15% for the loss of efficiency of the stacked motors vs flat motors. This puts your hover thrust in the mid 12,000 to 13,000 range. To make the math easy, if you need 12,000 grams to hover - divided by 8 motors used - you need 1500 grams per motor. Now, find a motor and prop combo that gets you 1500 grams of thrust (or more) at 50% throttle. There are other small things to consider such as if you are using the stock mixer on the A2, all the bottom motors spin one way and all the tops spin the other way. Because of the motor inefficiency on the bottom, it will take a little more thrust for your motors to hold your altitude while you hover and yaw one direction opposed to the other. Also, in wind, when you are pitched into the wind to hold position some of your motors are working more than the basic hover throttle to hold you in position. If you are holding in the wind and yaw you again will require more power than basic hovering in ideal conditions. For things like this, consider getting more than just the minimum you need to hover at 50% in perfect weather. Also, as most of us learn over time, we generally make our rigs heavier and not lighter. Getting some extra headroom in the beginning makes sense for that reason as well.

    Next, ask around about other people's experience with published motor specs to make sure the motor and prop combo you pick will give you the real world performance you are expecting. Different manufactures probably use different approaches to motor and prop testing. Certainly altitude, temp, etc can all change the performance of your system. Andy, and others have been testing motors and props as well and have some data you could compare.

    Then, if you want to determine your expected flight time, total your amp draw and divide it into the amp hours of batteries you intend to fly (less a comfortable safety cushion). Here is another example: If you were to fly the Tiger 4120s, at 50% throttle you would be drawing 8.4 amps per motor * 8 motors = 67.2 amps. If you were flying 20,000mah of batteries - or 20 amp hours you could draw 20 amps for an hour, 40 amps for half an hours, etc. So in this scenario we divide 20 by 67 and get .298. That is the fraction of an hour we could fly using the full 20,000mA. If you were to fly each one down to 20% remaining capacity you would just divide 16 (20amps * 80%) by 67 and get .238. To get that in minutes, multiply .238 * 60 to predict just over 14 minutes of flight time. Again, variables like MK active braking that returns charge into the batteries could change this, you will not fly at an even amp draw per motor your entire flight, etc. This just gets you in the ball park according to the manufacturer specs.

    Hope this helps you find what you need and put your hard earned money in the right place.
     
  20. Alex Smart

    Alex Smart Member

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    ECALC.jpg Hi Michael,
    First of all, many thanks for your extence and detailfull post, thanks for your time!

    At this moment I have to make a quick move and my unbudgeted position is :

    A)The 4120 465kv look like the proper choice, but does that mean that I have to change ESC also?At the moment I`m running 40A T-M. and could n t aford changing both.

    B)4014 400kv with 15x5 look like they could deliver just enough at 55-60% throtle on the basis of a 20% loss, and I would have to change esc or props.

    Do you fly DJI? would you concider a custom mixer with MK basis?

    I´m framing your post and will read over 100 times before I purchase the next chopper ahahah!

    Again, many thanks,

    Alex[/quote]
     

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