XA Hexa build...

GGoodrum

Member
I got tired of not being able to deal with the low frequency vibrations on the VC-600-X8 setup, so yesterday I moved everything over to an XA hexa frame. This uses the very stiff ABS arms used on the X450, which is similar to DJI's F450 Flamewheel design, but in a hexa "X" orientation. Where I was able to grab the end of one of the X8's arm, and twist it about 15 degrees, these arms don't move at all. This is a very solid setup, so hopefully, this platform will not have an unmanageable vibe problem.

Eventually, the plan is to use a Naza on this setup, but since I can't seem to find anyone who has these yet, I decided to just go ahead and use the WK-M setup. This WK-M is still destined for my Cinestar 6, but it still needs quite a bit of work before it will be ready to fly. I have to sort out a power distribution solution, to the ESCs, and figure out how/where to install the WK-M bits. In any case, I need something to fly, and I spent literally weeks trying to get the X8 there, and I now know those efforts were futile. The design is just too prone to vibrations, and the coaxial configuration just makes it worse. I think I'm done with coaxials. :black_eyed:

The XA hexa frame looks like it was designed for a WK-M. :) The extra electronics plate has a cutout in the middle that just fits around the WK-M IMU. Also, there is another small plate that snaps into the two tubes that are used to attach the landing gear and camera gimbal, that when turn around, makes a perfect platform to hold the WK-M's GPS mast. Until DJI fixes the gimbal drifting/wandering issue, I'm using a v1 XA FC/AHRS combo, just to drive the gimbal servos, so I have the FC mounted on the plate with the GPS mast, and I stuck the AHRS on top of the WK-M's IMU.

The gimbal is not shown, because I'm still assembling it. It is the MC6500PRO unit that CNCHelicopter sells. I've seen a few videos of a WK-M - equipped XA hexa, with this gimbal, and it seems to work. This uses a mechanical reduction in each axis, and they have supposedly "tailored" the servos to this application. I think the "secret sauce", however, is that they use rotary-type dampeners, in each axis, which will smooth out the small movements, and help take up any play in the linkages/servo gears. We'll see. :nevreness:

I still need to tidy up some of the wires, etc., and then I'll be ready to do a quick test flight. Then I'll finish up the gimbal, and get it installed. I'll post some more pics after I get the gimbal mounted.

My hope for this is that I will finally have a stable video platform for my GoPro 2. I can then get back to trying to finish up my CineStar 6 build, which I' need to do before Christmas, as I'm hopeful Santa is bringing me a new NEX-5N. :)

-- Gary
 

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GGoodrum

Member
I finished the MC6500PRO gimbal, and got it mounted. I also tidied up some of the wiring, and got the two 4s-3300 packs mounted. AUW, with the packs, and the GoPro2 is 5lb 14.9oz/2688gm.

I still need to redo the Assistant settings, for the WK-M, and setup the gimbal gains on the XA FC, which I will do in the morning. Then it should be ready for its "maiden" flight. Actually, maiden might be the wrong term here, as most of the stuff on here has already flown. :) Sorta like a "born again" virgin. :highly_amused:

-- Gary
 

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GGoodrum

Member
Because of the drifting/wandering of the gimbal servo outputs on the WK-M, which shows up as jitter and/or "jello" in the video, I decided to make use of a Xaircraft FC/AHRS combo, that I wasn't using, just to drive the gimbal servos. DJI is still working on a fix for this issue, so this is my workaround.

-- Gary
 


GGoodrum

Member
I've not had a chance until late this afternoon to do a test flight, and ran into a slight snag. I forgot to reverse the motor direction on the three clockwise rotating motors. :shame: When these were on my X8, the motors are flipped 180 degrees so you don't need to reverse the motors. I had a brain freeze, and forgot. :) Anyway, when I fired it up, it just sat there, and made a bunch of noise. :highly_amused: Anyway, it started getting dark, so I decided to try again in the morning.

I was able to do a quick video of how the MC6500PRO works. It works great, as long as you don't go farther than about +/- 30 degrees in the roll axis.


I added some LEDs, to make it a bit easier to see the orientation.

More tomorrow... :)

-- Gary
 

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