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DJI › DJI Naza H question.
10-23-2013 04:56 AM  4 years agoPost 1
Harpy

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Columbus, Oh

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Didn't know if anyone could help with a setup question. I am setting up the unit and wanted to get a good mechanical swash plate level at mid stick pitch. I get everything perfect using a little sub trim, but when I turn the unit off and on it always seems to start the servo in a slightly different position throwing off my mechanical level off. Is that normal? Been holding off on finishing the software setup till a have a constant mechanical level.
Thanks,
Jim

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10-29-2013 03:21 AM  4 years agoPost 2
Joel Rosenzweig

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Marlborough, MA - USA

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Do you mean you're using sub-trim in your TX? Or are you referring to the servo trim via the Naza software?

You do not want to use sub-trim in your radio. Use the Naza servo trim in the assistant for these adjustments.

Provided your Naza is not shifting every time you turn it on, your swash should seek the same initial position every time you turn it on, and it has initialized. Of course, if your TX cyclic sticks are actually noisy (say you have dirty pots) then you might be getting position error due to that. Normally though, no, the swash should not seek a different position each time you start it up.

If you haven't performed the advanced sensor calibration on the Naza yet, go ahead and do that, and see if the swash settles, too.

Joel

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11-15-2013 04:13 AM  4 years agoPost 3
Harpy

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Columbus, Oh

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Thanks Joel,

I didn't have the unit taped down yet, so some of it may have been do to it shifting. I haven't performed the advanced calibration yet either.
The other thing I can't figure out is the Cyclic Pitch section. They recommend 6.5 degrees, but I am around 9 degrees with the slider all down to 40. Any way to fix that? It's kind of a Frankenheli Has a Smart Models 700 rotor head on a Chaos 600.

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11-15-2013 07:42 PM  4 years agoPost 4
Joel Rosenzweig

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There are two items you can adjust to reduce the cyclic pitch range. First, adjust the collective pitch travel using the slider on the previous setup screen. I forget exactly what it is labeled, but I can look it up if you can't find it. That slider, when adjusted, controls the travel volume, and directly impacts cyclic pitch. If after adjusting that slider, you still cannot get the cyclic pitch lowered far enough, then you will have to use shorter servo arms.

DJI does say to use 6.5 degrees of cyclic pitch, but I found that is far too high for every helicopter I've setup, and I've setup a lot of them at this point. I tend to run 4.0 to 4.5 degrees with excellent results. When I go higher than that, the heli tends to oscillate wildly in ATTI or ATTI/GPS mode when given stick input.

Feel free to try 6.5 in your application. Just make note of it, and if it doesn't behave properly, you'll know to lower your deflection.

Joel

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11-16-2013 03:46 AM  4 years agoPost 5
Harpy

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Columbus, Oh

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Thanks again Joel. I'll shoot for 4 degrees. I played with the collective mix, but it made no difference to the Cyclic Pitch it always went to 8.5 on measure. I don't know if a factory reset would help.
Dropping the arms makes sense. I am just not certain on how to adjust the elevator linkage in front of the swash.

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11-17-2013 01:24 AM  4 years agoPost 6
Joel Rosenzweig

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I'm not sure why you don't see a change in cyclic pitch when you change the "collective mix" on the "MIX" tab. It is true that it is not directly changing your cyclic pitch, but rather, it is a significant ingredient in the equation that is used to compute the total cyclic pitch range.

When I setup a heli, I have to visit and revisit the MIX tab slider and the cyclic pitch slider as I adjust them, because it's all ultimately related.

Either way, if you don't get the adjustment range you need when you adjust the "collective mix", and when you decrease the cyclic pitch slider all the way down, then your primary option is to reduce the size of the servo arm radii. You'll need to adjust all swash plate servo arms to the same length when you do this.

If you can't adjust the servo arms for some reason, then you could adjust the location of the ball ends on the rotor head grips to reduce the mechanical advantage. Depending on your rotor head, this may require you to do some machining.

Another option, is to use a smaller diameter swash plate... so see which option is most appealing to you and go with that.

Joel

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11-17-2013 03:11 AM  4 years agoPost 7
Harpy

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Columbus, Oh

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Thanks Joel, I really appreciate the explanations its been a great help. I played with around with the "Collective Mix" again and can get it down to 1 degree at full stick, so I am not pegged out there. I'll play around with it again tonight then start exploring some of the options you laid out. Again thanks for all the good info.

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11-19-2013 01:31 AM  4 years agoPost 8
Harpy

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Columbus, Oh

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I replaced all 3 servo arms and I can at least get to 6.2 degrees now. Not sure if the newer Align 600 swashes are more narrow than the older N type. Be nice to get a little more reduction, but I am happy to be at 6.2. Thanks Joel.

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