How far from the center of gravity can a NAZA M v2 be safely positioned?

[Steve_in_NJ]

I am building a QAV500 v2 frame and am considering putting my whopping battery on the same deck as my NAZA M v2. This would mean that the NAZA will need to sit forward of the CG. I have read varying opinions about placing a FC anywhere other than at the CG; what are the facts about it?

Thanks!
Steve

 

[AndyPG]

Hi Steve, The TBS Discovery has it placed about 2.25" forward of the CofG as standard so I guess a little more wouldn't hurt. How far forward are you thinking?
My measurement is to the centre of the Naza.

Andy.

 

[Steve_in_NJ]

Hi Steve, The TBS Discovery has it placed about 2.25" forward of the CofG as standard so I guess a little more wouldn't hurt. How far forward are you thinking?
My measurement is to the centre of the Naza.

Andy.

I am still building the unit - I have to jury-rig my gimbal/gopro/bracket onto the front of the thing. Only then can I place the battery and see where the CG is going to land. The QAV500 v2 comes with 35mm standoffs to create the space between the top and bottom decks; to fit the battery I will add 25mm M/F standoffs to them for a total height of 60mm. Once the gimbal is in place I can pile in the various DJI bits, place the battery as far toward the center as reasonable, find the CG and see how far away the NAZA must sit. If it's all too much I can hang the battery from below as with my last build, but I would rather enclose it.

Here's my last build. All the guts are coming out of this and going into the QAV500 frame.

 

[Rainman]

I swapped my Naza out of an F450 and put it into a TBS Discovery but then put it back again. I found that the CoG on the Disco made it toilet-bowl like a ***** and it required a fair bit more setting up and mucking about to make it fly correctly. I know some people love them but my own experience wasn't great and I just put everything back into my F450 frame. Yup it's untidy compared to the Disco but it just more stable because everything is uniformly positioned. Personally, I'd have it on the CoG and nowhere else.

 

[AndyPG]

Hi Rainman.
If the Naza was in the correct position as shown in the TBS manual and the Naza gain settings are set to the recommendations in the TBS manual and the CG was correct, it should fly like a dream.
Mine is all per manual and it is rock solid and has never even looked close to even a single toilet bowl swoop.
I guess the effect might be down to other hardware variables on your particular setup.
Its all part of the fun.
Keep experimenting.

Andy.

 

[Motopreserve]

I thought the toilet bowl effect was more about the GPS puck not being directed to the proper declination.

 

[jbrumberg]

"I thought the toilet bowl effect was more about the GPS puck not being directed to the proper declination."- Motopreserve

That is my understanding as well. There are quite a few "magnetic deviation finder maps" to be found on the internet. Here is one:

http://www.magnetic-declination.com/

 

[Steve_in_NJ]

I swapped my Naza out of an F450 and put it into a TBS Discovery but then put it back again. I found that the CoG on the Disco made it toilet-bowl like a ***** and it required a fair bit more setting up and mucking about to make it fly correctly.

As others have said here, the biggest reason for the toilet bowl effect is the NAZAs lack of ability to compensate for "magnetic declination" - that is, depending on where you live on the planet, your GPS puck needs to be rotated a certain number of degrees left or right. It could be a little or a LOT. Last year I learned of this when I noted that my quad wanted to fly on an angle - like a car with bad alignment. I am in New Jersey, so in my case twisting the puck 12 degrees to the left fixed it. Look at the map below for the adjustment YOU will need to make. This one is for the USA. If you are somewhere else on the planet, here's a page that describes the phenomenon more authoritatively than I can, and gives a calculator... http://ngdc.noaa.gov/geomag/declination.shtml

Note that this map changes a little each year!

I found this bit of info which summarizes the fix: "...If your location has a POSITIVE declination then turn your GPS to the RIGHT the number of degrees of declination for your area. If your location has a NEGATIVE declination then turn your GPS antenna LEFT the number of degrees of declination for your area..." That line came from this page. The part that talks about magnetic declination is halfway down the page. Take a look! Best of luck.

Another question re your TBS setup: In the assistant software, did you plug in the distance from the NAZA to the GPS puck on the X, Y, and Z axis, in cm? I don't know what the impact is of NOT doing that is, but it can't be good.

 

[Wothrline]

I have a Discovery with AerialMob arm extensions (73cm cross), DJI E800 motor kit, Feiyutech 3D Mini gimbal, 6S 8000mAh LiPo and DJI Naza M V2 FC.
Also been thinking about CG, MC and where the FC is positioned. It flies very well and is a great model to handle, but can it be better...
MC = ModelCenter, looking from arm to arm is located way back on the model and there's just no space for FC to be mounted.
CG = Center of Gravity is located approx 6cm front of MC.
FC = Flight Control center is positioned just under 2cm in front of CG.

My gain setting at the moment is Pitch 115, Roll 115, Yaw 75, Vertical 95

GPS is positioned on a pole at the right rear arm mount with GPS setting X = 6cm, Y = 4cm and Z = 12cm

 

[cootertwo]

 

[FerdinandK]

Already three year ago I had an ecilop frame where the Naza was positioned 14cm (x,y +10) off the center. It flew great.

From my point of view, if the basic gains are dialed in, the ACC only needs to do corrections. If your Basic gains are too low the copter already flies with the ACC, in this case it is of advantage if the Naza is in the COG

best regards
Ferdinand

 

[Wothrline]

Have watched this several times before.

I opened the Discovery today and relocated the FC about 4cm towards MC and that gave me a position 2cm behind CG and slightly less than 4cm in front of MC.
Will be interesting to see if this will improve anything in flight and if Gain can be changed for a more aggressive setup.
GPS location changed to X = 2cm, Y = 4cm and Z = 12cm

Maybe an already great machine will be even greater to fly!