I have just bought the ArduPilot Mega 2560 Full Kit... plus the Triple Axis Magnetometer HMC5883L. I should have it built over the weekend.. then i'm off to a my mates machine shop, and i'll make the splitter plate for the lower frame onto which i am going to fit the Ardupilot. the magnetometer i'll put on the tail as suggested. I am going to use my X-cell Razor 600E. For those that dont know its around the 50 size nitro heli.

Do i need to buy any other sensors i.e. the Sonar... i can fly a helicopter all day long but this is my first time flying one with stabilisation so any tips would be gratefully appreciated.

If this works well then i am going to try and use it on my x-cell gasser. i can get up to 20 minute flights with this. But i think for the time being a battery 600 is the way to go.

i'll post some pictures when i have it all together.



Setup Instructions

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I've got a 600, and it mounted under the tail, just behind the frame on a custom subframe.

I don't think the GPS has to be fully out from under the blades.  We've never seen that to a problem, but we have seen motor magnetics cause problems for the compass.

 I figured it would be iffy mounted underneath because it was so close, but I thought the radio tray might be far enough. Do you know if anyone has had problems with it mounted on the tray?

If not, then then the same question applies for the mag. Will I need to replace the APM with one that doesn't have onboard mag, or can I use an external mag and have the software bypass the onboard?

We should probably update the wiki page to point out that people want the APM2 without the GPS and compass on it.  Those should be purchased separately and put on the tail...although I agree with Robert, it's not been proven that it matters if it's under the blades.


When it comes to mounting the main APM itself, I think putting it between the body and the landing gear is the best place.

Why do you prefer mounting underneath? I've read some of the older conversations on the topic, and things to consider, and I gave it some thought.

There were a couple of reasons I decided on using the radio tray. If I'm not understanding right, please set me straight. I'm certainly not married to any of my justifications here.

The first is that flying the stock setup, I had the gyro mounted directly under the rotor shaft in a little space in the body, and a trusted friend said that that spot tends to suffer from vibrations messing with the gyro. I figured similar mounting for the APM might do the same.

The second is for the aforementioned placement of the onboard mag and GPS, getting away from the motor, and putting the least stuff possible above it without using external GPS. That reason may be invalidated if my GPS tends to drop out where it is.

The third was for weight distribution. While radio tray placement normally makes it back heavy, I'm also strongly considering getting a nice little camera and gimble, and mounting it on the front of the copter, a bit like the electronics pod on the nose of an AH-64 Apache. I figured if it looked cool enough, I'd even get an Apache body kit and go the whole 9 yards. XD

Hi chris, My APM is directly under my rotor shaft and have had no issues. But my GPS is mounted out on the tail and the mag on the horizontal Stab. I did have my GPS under the main blades, but then a few people were talking to me about multipathing, although i never really had a chance to test that. I moved mine to give the GPS the best chance possible. The mag if its near the main motor or lipo then you will need to move it, or at least test it thoroughly . Also make sure that what ever you mount it on is solid.

Next noob question regarding the camera. I've seen the 3DR pitch/roll gimble, but I was wondering if there's a good setup out there that will let me swing the camera around and use the camera to track ground coordinates all Predator style. If anyone knows anything small enough to go on the TRex, that's the next direction I plan to go.

There is no way of searching the thread/discussion which is a shame.

Correction.  There is no good/effective way of searching. ;)

You can search in the forum, but not by thread.  And when you search in the forum, you are not guaranteed to actually find all the results you should.

Chris, go to page 84 of this thread. There you see my 450 setup. I mounted the GPS almost into the shaft ;) Kidding. But it is totally close and with wooden blades, I have no issues with the GPS. The mag is more sensitive. Although I wonder how the GY401 gyro works in HH mode. It should have a mag as well? And it sits much closer to metal and all the electronics.

No, I really doubt a HH gyro has a mag.  They just have REALLY good accelerometers/gyros and a dedicated I/C that does nothing but try to hold the tail.

I'd like to see some examples of how good a HH works so I can compare how I've got mine now.  It's very good.  At least as good as the Flymentor I had.

Just look for the 3D guys like Alan Szabo or Curtis Youngboold and you might get an idea how rock solid good gyros are.

This isn't really relevant for 2 reasons:

1) We are not intending to fly like that.  I would rather have precise control, rather than hard and fast control.  For all I know, they could have the gain dialed way up, and the thing wags in a hover, but you can't see because it's never not moving.

2) Obviously these guys are incredible skilled on the cyclic.  Maybe they are incredibly skilled on the rudder too, and are compensating for the mistakes the gyro is making.

What I need is a video, a really clear video, close up, of a heli in hover.  Is the tail wagging *at all*?  Then, stab the collective to the top, does the nose move at all?

I'm cautious because I try to be pretty precise in my descriptions of what I'm seeing.  It happens all the time where somebody says "nope, I have no problem at all, it's perfect".  Then I show them what I'm working on, the problem I'm describing and they exclaim "Oh!  That?!  That's nothing!  Yeah, mine does that but it's normal.  It doesn't get any better than that."


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