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Old Aug 23, 2012, 07:36 AM
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United States, MI, Rochester Hills
Joined Aug 2012
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F550 +Naza-M not able to take off. Really unstable

I posted this in an old post of mine but I guess I should start a new thread because it's a different matter...:

Ok, here is the last update from this all...
I bought all the components:
-DJI F550
-Naza M+GPS
-Graupner props
-5.8 Ah 4S LiPO
-X468 landing gear+gimball

I assembled it all, no problems at all. I already have a Futaba 9F and a corona Rx

Set up the Naza. After 1000 videos about it, seems easy, many options I leave them as default.

Set up the Tx. Make sure I get at least the main modes on the switch, some Exp, travel end points, etc

Correctly assembled props, CCW on 1,3,5 and CW on 2,4,6. I check and they all blow downwards

OK, lets go. I start it all. CSC and motors idling. Give it some throttle and the hexa just wants to tip over the front side. I try many times and always the same behaviour.

I check the Naza. It's completly flat and stable on the bottom board. Lets try trimming it. Ok, I push the throttle enough to see a trend to take off (from one leg of course) and start touching the trim downwards. The trim in this Tx is really delicate, but anyway I cannot find a point where it stays stable in the middle, either it wants to tip over the front, or wants to tip over the back. So I don't dare to make a real take off, for sure I'm going to break a prop on the ground.

I even try to take off trying to correct the behaviour with the ail/elev stick, really slightly, but there's no way to find a middle point, I end up hitting the ground.

I recorded a video of it. You will see the first 2 attempts are working only with throttle. From there the next one I was trying to correct the leaning with ail/ele but it was impossible to keep it flat. Shouldn't it be able to take off by itself with few help anyway?

First test on F550+Naza, something's wrong here... (0 min 47 sec)


FC is in the middle of the bottom plate with the Motor outputs facing frontward, the GPS (although not needed yet at this point) is pointing to the front. I checked the directions of the sticks and it's clear that moving the right stick forth/back/right/left get the same trend on the hexa, but it is unable to stabilize itself...

Any suggestion?

Thanks!
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Old Aug 23, 2012, 07:45 AM
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Joined Mar 2012
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The one thing you did not mention is, are the motrs turning the correct directions. Just because you fill air moving under them does not mean there turning the correct way.
I take a piece of paper and draw arrows the direction it should move.Take off all the props and slip paper over motor shaft.Start motors then stop them.As the paper slows you will see if they are spinning the right way.
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Old Aug 23, 2012, 07:49 AM
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United States, DC, Washington
Joined Dec 2007
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The motors in the front should be rotating such that hitting a piece of grass will feed it inwards towards the center of the quad in forward flight, not push it out, like the ravenous buzz saws of death are trying to feed the flight controller while in forward flight (Front left clockwise, front right counter-clockwise). That's the way I think of it at least, and I might have had too much coffee.

Then the motors diagonal from each other should be rotating the same way.

Check that those are rotating the correct way first.
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Old Aug 23, 2012, 08:04 AM
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Quote:
Originally Posted by machina View Post
The motors in the front should be rotating such that hitting a piece of grass will feed it inwards towards the center of the quad in forward flight, not push it out, like the ravenous buzz saws of death are trying to feed the flight controller while in forward flight (Front left clockwise, front right counter-clockwise). That's the way I think of it at least, and I might have had too much coffee.

Then the motors diagonal from each other should be rotating the same way.

Check that those are rotating the correct way first.
You are right, I'm pretty sure I double checked the direction as well (135 ccw and 246 cw right?), but it won't hurt checking again tonight.
Anyway what I feel is something in the control is getting wrong "sensing", just by idling I can hear really different speeds in the motors, so when it starts to lift, it's clear some of the motors are pushing double than the other.. that's why it tips over. What can be causing that?

Thanks
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Old Aug 23, 2012, 08:07 AM
I never finish anyth
United States, TX, Houston
Joined Jan 2012
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Video is private.

Tipping before getting airborne is either you handing on some grass or not giving it enough throttle. You have to kind of gas it to get a multi up and out of prop wash.
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Old Aug 23, 2012, 08:07 AM
I never finish anyth
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Are you taking off in ATTI mode?
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Old Aug 23, 2012, 08:08 AM
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Kingdom of Sweden, Dalarna County, Sater
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No that should be alright. It's the same on my F550, three of the motors seem to run at a higher RPM than the others at liftoff. The other motors eventually catch up.

I'm not sure what it could be. If you haven't done so already, pick it up, hold it over your head and test the inputs. You can feel if it's moving the right way or not. If you take off in ATTI mode then you need to quickly go to 60% throttle, let it take off on its own then you can go back down to 50% throttle to keep it steady. Otherwise it'll just bounce around and not gain altitude.

Also, the video is set to 'private'.
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Old Aug 23, 2012, 08:09 AM
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the 1M$ question... did you calibrate escs ?
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Old Aug 23, 2012, 08:26 AM
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United States, MI, Rochester Hills
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Thanks everyone for the interest. Some answers:

1.-Not trying to take of in atti, just in manual (check the light, first blink ir red)
2.-Changed the video to public, sorry
3.-Honestly Im scared to try to really lift it hard... I guess it's gonna tip over hard
4.-It's not grass, just my basement. Now that the video is public you will see. I won't do more serious take off attempts in the basement but wanted to check its attitude indoors first
5.-I didn't calibrate the esc's. Supposingly the ones that came with the F-550 kit were pre-calibrated.
6.-I already checked it's attitude. I put a hand over the top holding it, throttle it up a little bit, and moving right stick to front/back/right/left I feel the same push in the hexa in the same direction.
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Old Aug 23, 2012, 08:42 AM
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Kingdom of Sweden, Dalarna County, Sater
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The DJI ESCs can not be calibrated.

It looks like everything is spinning the right way, when you touched the ground I could see which way the props were spinning. Don't know what to tell you. Sometimes you need to get off the ground fast, also, tall landing gear can make these things a bit unstable when taking off. I've used landing gear on mine once, but I HAD to take off quickly because it was very unbalanced.
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Old Aug 23, 2012, 08:49 AM
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Ok, if no one finds anything wrong, or any typical mistake in the assembly (I think I read hundreds or advises, FAQs, etc before) I'll cross my fingers and take it to the park and push it HARD....:-)
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Old Aug 23, 2012, 08:56 AM
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What you could do is pick it up, hold it over your head, throttle up to just over hover level then check all the inputs and also move it around to see if it resists your movement. If it responds to your inputs, if it tries to hold whatever angle you hold it at or move it to and if it doesn't go crazy. Then it should be OK. Try that first before you push it 'hard' and send it flying at yourself or others. My advice up there was probably not the best. :P

You can do this indoors too. Just hold it by the landing gear and you won't be anywhere near the props. Or let someone else hold it.
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Old Aug 23, 2012, 09:06 AM
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Quote:
Originally Posted by WiseDuck View Post
What you could do is pick it up, hold it over your head, throttle up to just over hover level then check all the inputs and also move it around to see if it resists your movement. If it responds to your inputs, if it tries to hold whatever angle you hold it at or move it to and if it doesn't go crazy. Then it should be OK. Try that first before you push it 'hard' and send it flying at yourself or others. My advice up there was probably not the best. :P

You can do this indoors too. Just hold it by the landing gear and you won't be anywhere near the props. Or let someone else hold it.
Sounds good, I'll do it tonight.

Anyway, should I try to take off in ATTI mode or manual mode? I am trying it always in MANUAL mode, is that right.

Yesterday it was idling in MANUAL mode, I switched it to ATTI and the freaking thing lifted off and hit the wall, why did it raise the throttle just by switching to ATTI? Was that expectable?

Thanks!
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Old Aug 23, 2012, 09:09 AM
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What throttle level were you at? Over 60% and it'll rise automatically. 40% and down and it'll sink slowly. It should not take off like that. Now, mine did shoot for the sky once when I switched to ATTI. But that was right after I changed to new motors, but after switching to manual and then ATTI again it worked fine. I think it needs some time to calibrate itself.

I always take off in manual mode. Full throttle on 4S, EVERY TIME! I do it because it's seriously fast on 4S and it's fun to do it in front of crowds. People are always amazed by the performance. I guess they haven't seen any Warthox builds yet.
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Old Aug 23, 2012, 09:22 AM
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Maybe I'm just being a pussy trying to check slowly and I should just give it some real throttle (I move around 40-50% maybe), but from the behaviour I see at low throttle I'm guessing it's going to crash suddenly as I takes off quickly...
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