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Old Oct 27, 2013, 12:16 AM
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dji Phantom compass position

Does the compass have to be in a specific location or orientation? I purchased a set of the helio type landing skids for the phantom but it will not fly right with them installed. As soon as it lifts off it starts drifting sideways and nothing I do corrects this and it only gets worse and I have to cut power to land as it's to out of control to land. I put back on the stock skids and it fly's just fine.

The only thing I can think of that would cause this is the position or orientation of the compass. I trued to put it similar to the way it was on the stock skids. I don't think the composition of the carbon fiber tubes would be a problem but I don't know for sure.

Any one have skids installed and flying successfully or any ideas what might be causing the problem?

Thanks
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Old Oct 27, 2013, 12:24 AM
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ya, the compass position is super important.. has to be in a similar position as it was on the stock legs..

even a degree or too off and it will cause flying problems..
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Old Oct 27, 2013, 12:30 AM
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Yes it absolutely does. What you experienced is the "toilet bowl effect" or TBE stemming from compass mis-orientation. You can fight it with stick input but it's hard, and within a few seconds it can get away from you.

In short, look at the compass mount on the stock landing gear. IIRC it should be on the back left leg, with the flat metal plate of the compass module facing the back right leg. If you change the position of the compass, or the leg it's mounted to, you MUST replicate the position it's in while stock (square to the ground, cable coming out the top, metal plate facing towards the right).

I switched landing gear and inadvertently put the compass on the back right leg, and it took me a while to realize it was the compass causing the crazy TBE.
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Old Oct 27, 2013, 01:16 AM
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Originally Posted by ElGuano View Post
You can fight it with stick input but it's hard, and within a few seconds it can get away from you.

.

Man does it ever ...and being new and inexperienced doesn't help. At least now I know what it is and can deal with it....I hope. I assumed that recalibrating it would compensate for it's new position/orientation ...my mistake.

The configuration of the new legs the way they are it's not possible to get it orientated as it is on the stock legs. So I will need to make some kind of pad that allows me to duplicate the orientation it's in on the stock leg, correct.

Thanks
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Old Oct 27, 2013, 05:26 AM
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Originally Posted by Sundance2013 View Post
Man does it ever ...and being new and inexperienced doesn't help. At least now I know what it is and can deal with it....I hope. I assumed that recalibrating it would compensate for it's new position/orientation ...my mistake.

The configuration of the new legs the way they are it's not possible to get it orientated as it is on the stock legs. So I will need to make some kind of pad that allows me to duplicate the orientation it's in on the stock leg, correct.

Thanks
Yea, those landing gear are cool, but they don't provide a buffer to put the compass back in the same spot. It's why I don't put them on
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Old Oct 30, 2013, 03:17 PM
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First, thanks to Sundance for asking about the same exact issue I've been having, and thanks to everyone else for clearing it up. I just added an aftermarket landing gear (http://www.heli-world.com/detail.aspx?ID=11420) and lost flight stability almost immediately thereafter. I was also worried that the carbon fiber legs might be causing it, but I see now that even though I'd mounted the compass *close* to the original location, it was still about 2" off horizontally.

After reading this thread and poking around a bit with my phantom, I think I may have a workaround that I'll try later today if I have the time: taking one of the original phantom landing gear and cutting it up so it just forms a post for mounting the compass. I'll post pics if it ends up working
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Old Oct 30, 2013, 09:44 PM
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I look forward to hearing how this works.

Would be nice if one of these company's selling all the 3D printed stuff for the Phantom would make a little mounting pad for the compass.

Something else that would be nice is if these &^$% selling this stuff would be a little more up-front and honest and say hey you need to modify the compass location to make this thing fly instead of selling it knowing full well your Phantom will not fly unless you do.
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Old Oct 31, 2013, 01:10 PM
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Update: repositioning the compass as I described went off without a hitch, pics of the results are below. However, I haven't had a chance yet to do a test flight with the nasty weather today.

It only took 15 min or so with a Dremel to get this to work, including the time spent shortening the rear metal mounting shaft that connects the main landing gear plate with the Phantom. It isn't the prettiest solution, and I'll probably paint the piece black or something to make it less obvious, but it seems like it should accomplish exactly what I need
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Old Oct 31, 2013, 01:23 PM
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Originally Posted by Sundance2013 View Post
I look forward to hearing how this works.

Would be nice if one of these company's selling all the 3D printed stuff for the Phantom would make a little mounting pad for the compass.
Many aftermarket landing gear do--the Simensays options all include compass mounts. Other makers do as well. I guess it all depends on whether the gear is custom made for the Phantom or just kind of retrofitted from a generic design.
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Old Oct 31, 2013, 01:34 PM
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[QUOTE=PhunkeeQuad;26516754]Update: repositioning the compass




Looks OK to me and I don't see why it wouldn't fly normal.

Just wondering, do the skids show in frame when you do video (assuming you are using
a GoPro)?
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Old Oct 31, 2013, 01:53 PM
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Originally Posted by ElGuano View Post
Many aftermarket landing gear do--the Simensays options all include compass mounts. Other makers do as well. I guess it all depends on whether the gear is custom made for the Phantom or just kind of retrofitted from a generic design.
Yeah, the one I'm using was originally engineered for the 450/550 and they just added some extra-long screws and shafts in the rear to retrofit it to the Phantom.

I honestly hadn't seen the Simensays gear (and other goodies), thanks for the tip! I haven't given up yet on making the gear I have into everything it should have been, but when I hit that point I'm sure I'll be trying out the folding gear!
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Old Oct 31, 2013, 02:10 PM
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Originally Posted by Sundance2013 View Post

Just wondering, do the skids show in frame when you do video (assuming you are using
a GoPro)?
Hero 3 black edition, and it's pretty easy to keep them out of the frame. Even on wide, I can keep them out if the camera is horizontal. Switching to med gives me a lot of range to tilt down before they appear.
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Old Oct 31, 2013, 09:54 PM
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Didn't know about the Simensays ones when I purchased. Wonder if they sell the compass mount by it's self?
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Old Oct 31, 2013, 10:22 PM
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Originally Posted by Sundance2013 View Post
Didn't know about the Simensays ones when I purchased. Wonder if they sell the compass mount by it's self?
they do not and I don't think the angle would be quite right regardless.. his compass mount is designed for the angle of his legs..

maybe you could make something out of Instamorph or something similar..
http://www.amazon.com/InstaMorph-Mol.../dp/B003QKLJKQ
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Old Feb 16, 2014, 02:19 PM
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Compass location

Based on my experience what matters is just the orientation of the compass which must be similar to phantom. The wire should be on the top and it should be facing right.

Here's the video of how stable it is after mounting the compass inside my quadcopter and fixed the toilet bowl effect.

DJI Phantom compass relocation for new custome frame (1 min 8 sec)


I didn't take a video of yawning but still works very good.
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