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F550 flip of death
2696 11 2015-4-20
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kyrre
lvl.1

Norway
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Hi

I have been flying a Phantom for some months and decided to upgrade to a flame wheel f550. I have have assembled it by all rules possible and setting up the Naza M by the same setting as what worked for the Phantom, except the obvious settings that differ. Finally ready for the first flight after checking all the settings again. Doing the calibration dance ofcourse and then going for the first liftoff. All engines starting ok, all props going the right way, giving throttle to get it off the ground. Starts to lift but suddenly just flips over breaking a prop. Changed the prop checked all the directions again, my son tried to hold the drone while trying to giving throttle to see if it moved in a mysterous way, but it seemed normal. Down on the ground again, same procedure, and same result. Flipped over and this time it was one of the white arms on the left side that broke

Any ideas what that might be? What have I missed?

on gains I have set all to 75% to have a soft start.

Naza is dead center pointing the right way. GPS is mounted on top and offset should be correct. (6/3/-10cm), on the right side in the front.

I have a light gimbal attached, but no camera yet (luckily) and quadframe landing gear.


2015-4-20
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alansworld
Second Officer
Flight distance : 27434 ft
United Kingdom
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An instant flip like that definitely sounds like one or more props rotating in the wrong direction.  You probably need to check the rotation of the props on the side which flips downwards upon takeoff, but preferably check them all.
2015-4-20
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nig_smith
First Officer

United Kingdom
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As Alan has said, definitely check you have the correct prop on the right motor as it's easy to get two back to front  I know this as I've done it twice but thankfully spotted the error of my ways before applying power.

Regards

Nidge
2015-4-21
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kyrre
lvl.1

Norway
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Problem is fixed. Lesson learned is a classic one, do not believe any video on youtube. Motors were mounted the wrong order, thus the strange behaviour The order was from an assembly video, but it was opposite to the original order.

Now it is taking of ok. It is behaving a bit strange still, but made some changes and waiting for my battery and more daylight. Seems it is a bit wobbly. It hovers ok, but if I try to give more power or any other movement it is seems unstable, wobbling around. mostly controllable but had a couple of crashes, in soft soil. I will adjust gain and install new props and do calibration again before the next flight.  
2015-4-21
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nig_smith
First Officer

United Kingdom
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Great to know you sorted the problem, and never under estimate the power of the Internet to misinform.

Before you go about adjusting the gains ensure you have the hex balanced correctly about the CoG.

Regards

Nidge
2015-4-22
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kyrre
lvl.1

Norway
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Thank you Nidge!

Balance seems fine around CoG, but I guess it is always room for improvement
2015-4-22
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kyrre
lvl.1

Norway
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new test flight and now it seems better, but I think I might have bad soldering or a broken esc. the drone is nodding towards motor 5, the motor is not spinning up as quickly as the others. If I keep it hovering it nods every few seconds. Flying forward is ok, but flying backwards (less power to the nodding engine) it handles not very well and usually ends up crashing.
2015-4-22
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kyrre
lvl.1

Norway
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More testing (and killing props) done. One engine is stopping or "misfiring" it seems. Will have to look over the soldering, but could this be something like defective ESC or motor? Anyone with ideas?
2015-4-23
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nig_smith
First Officer

United Kingdom
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kyrre@kyrre.com Posted at 2015-4-24 02:42
More testing (and killing props) done. One engine is stopping or "misfiring" it seems. Will have to  ...

Quickest and easiest way to eliminate either the motor or ESC is to swap two motors, preferably two that rotate in the same direction, and observe whether the suspected motor is still exhibiting the sporadic behaviour or the original ESC is the course of the problem.
The ESC converts the DC input from the main board into three Separate pulsed voltages, separated in phase. These three voltages are then fed to the motor via the three wires. Because they are separated in phase they cause the motor to rotate, changing two of the three wires changes the order in which these pulses are received by the motor thus resulting in a reverse of the motor spin


Usually if a motor fails it's because one of the three windings have failed. In this situation the motor's rotation would be very erratic and appear to twitch back and forth.


The ESC is more complex than a motor and therefore the symptoms of the fault depend on which part of the circuit has failed e.g The input, the microprocessor and associated logic, the output FETs responsible for each channel.

Regards

Nidge
2015-4-30
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kyrre
lvl.1

Norway
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Hi. Some of the motors twitch both ways when I do a motor test on the naza. Is that a bad sign? Looks like the copper winding inside the motor is loose or disorganized some how.

I moved the motor on the arm I thought was the problem and it looked like the problem followed the motor. I disconnected two motors and reprogrammed as a quad and tried again. looked ok for a while den suddenly it dived into the ground. Then I switched ESC and again it seemed fine for a while, then suddenly committed suicide and dived into the ground again, breaking my third arm.

Starting to get really frustrated by this now. Will have to replace the arm now and then find a big field of grass to test some more.
2015-5-1
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q
lvl.1

Austria
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kyrre@kyrre.com Posted at 2015-5-1 23:05
Hi. Some of the motors twitch both ways when I do a motor test on the naza. Is that a bad sign? Look ...

a brushless motor going in different directions is a good indicator that one of the three coils (coil groups) is faulty.

the motor could also change its direction if the load changes in a low load condition. (in theory, haven't seen this yet but what you describe can be explained by that)

the fault could be in the motor, the connection to the esc or the esc.

I'd try a new motor and if that doesn't work a new esc.
2015-11-11
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DJI-Dave
Captain

United States
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"never under estimate the power of the Internet to misinform." Nidge


So true!
2015-12-8
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