Need some guidance on 8-rotor build

Hey guys, my group is interested in using a multirotor aircraft for near surface remote sensing (earth science applications). We'd like to have the most flexible and versatile platform. For us, this means high payload capacity, reliability, and versatility with respect to configuration. The ArduCopter stuff is particularly appealing to us as it offers the greatest flexibility for mission planning, development, etc.

We are interested in building a CineStar 8 but using ArduCopter electronics (APM 2.5). From my forum searches I see that many people have done similar things, so I know this should be possible.

I'd appreciate some guidance on several things (my background is not in RC electronics):

* What motor/prop/ESC/lipo configurations will give us the best payload capacity/flight time balance? I've used the eCalc online tool, but most of this goes way over my head (I know that I will need to grasp it fully before we continue, but I don't know where to start!)

* How to expand the APM 2.5 outputs so that all 8 motors can be controlled in addition to stabilizing a camera gimbal? Is there another way to stabilize/control the gimbal without expanding the outputs?

* Assuming that we have an airframe, is my checklist here close to complete for the whole build?

  • 1x APM 2.5+ w/ GPS and Power Module
  • 8x motors w/ prop mounts
  • 8x ESC
  • 8x props
  • Rx/Tx pair (Graupner MX12 or similar)
  • Power distribution solution (like the homemade Deans rings)
  • Battery(s)
  • Misc. items? additional cables, hardware, etc

And for adding on a controllable 3-axis gimbal

  • 1x 3-axis gimbal (FreeFly or similar)
  • Rx/Tx pair for Gimbal
  • Lipo for gimbal power
  • Camera/sensor triggering solution

The ESCs are a particular mystery to me. I played around with the eCalc tool and couldn't figure out the proper ESC to use for the AXI 2828/12 motors (for example). I kept getting errors indicating that the max current was greater than the battery could supply. So, any additional information on how to select batteries/motors/ESCs would be very much appreciated (including just pointing me to the relevant literature).

One more question: Can the gimbal/shutter controls be integrated into a flight plan from the Mission Planner? It appears that they can, but I don't know what is involved to get that capability.

Thanks in advance!

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Replies

  • Josh, you also have to take into account the pilot. ;)

    Half the questions in your list hint that there's not a single guy with multicopter experience in your group. While the APMs are potent flight controllers, they don't have an error forgiveness variable that you can dial down as you gain experience. And as I'm looking at a $3000+ wish-list, your first mistake might be a costly one :)

    You'll need at least two more machines before you can safely operate the Cinestar8:

    - One very small and cheap quad, maybe a WLToys v929/939, with lots of spare props and parts. Once you can fly that miniature thinghie for a couple of minutes with it's front facing you, you're OK for the Cinestar :) 

    - One diydrones quadcopter with the FC that you'll use on the bigger octo, to learn tuning, P/I/D values, connections and general operating procedures. Also the do's and dont's at way lower expenses.

    Either that, or hire a seasoned drone pilot.

     

  • Developer

    Josh,

    I will try to help:

    1. Propellers - APC 14x4.7 SF, you need 4 pusher and 4 regular

    2. ESCs - Any 60A opto, like hobbywing

    3. Motors - AXI 2826/12 or equivalent. I have some used ones available here: www.rcgroups.com/forums/showthread.php?t=1808801 Please note you would have to change out the regular length shafts for the short shafts that are included. I also include the radial propeller mounts.

    4. Batteries - Either 4S or 5S. I fly 4S

    5. I believe the APM 2.5 supports 8 motors and stabilized gimbal without modification

    6. Radio - I use a Spektrum DX8 but Graupner makes good stuff too.

    7. These guys make good power distribution boards for large octos: Power Hungry Systems

    8. 3-axis gimbal might be overkill.. depends on what you are looking to do. You can also just use the yaw of the copter with a 2x. Probably not as smooth of video though.

    Hope that helps!

    Cheers,

    Adam

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