SYMA X13 hovers at low throttle but flies faster forward and left as throttle is increased

[Mike Westwood]

Hi Everyone,

I'm very new to all of this, the truth is when I bought my nephew a Syma X13 for christmas I couldn't resist buying myself one as well (which I had to give him when I flew his off into the distance almost immediately, but fortunately it made it back)

I'm finding it very difficult to fly and I've read all instructions regarding pre flight sequence, trim, resetting trim, resetting gyros, etc.

I think nailed the behaviour down to the fact that as the throttle is increased the aircraft tilts more and more with the front left corner down and goes hairing off in that direction. The pitch/roll becomes so severe that the controls are unable to compensate for it, so it has the ironic effect that as it gets higher it becomes impossible to control. Most entertaining for spectators but not so much for me.

I've watched videos of people hovering the X13 and moving up and down while barely even touching the pitch and roll controls.
My understanding is that remaining at a (more or less) stable position within it's capability is exactly what the controller is supposed to do based on feedback from the gyros, but as I said I'm new to all of this so maybe my basic assumptions are wrong.
I've tried both indoors and outdoors and the behaviour is identical every time.

I have access to a high speed camera so I will try and set up a test, video it and upload it here if that would be at all useful and is allowed on this forum.

Thanks,
Mike

 

[Jackson]

My understanding is that remaining at a (more or less) stable position within it's capability is exactly what the controller is supposed to do based on feedback from the gyros

Well assuming the unit isn't faulty, constant micro stick adjustments of older tech quads is pretty much a fact of life.

 

[Mike Westwood]

Fair enough and it's a very cheap unit, but its not possible to compensate using the stick, it doesnt have the range. With the stick pulled full back and right it still flies forward and left. If I let the stick centralize it flips over.

 

[Jackson]

Could simply be bad. I'm assuming you've crashed it hard. How do the props feel when you just spin them by hand, any differences?

Take a good look at the gears, it doesn't take much (a grain of sand etc) to throw things off. Do the pinion and gears mesh nicely?

 

[Mike Westwood]

Thank you for your responses, I will check it out.

Once again, I'm new to quadcopters, but I am familiar with electronic hardware design, software development and to some degree control theory.
What puzzles me is that I would expect that whatever problem exists in this case, eg, faulty rotor, motor, mechanical linkage,etc, the controller would be able to mitigate it by slowing down the back right rotor. I realize as I say this I am ignoring a degree of freedom and possibly a whole level of complication, as the resultant rotational (yaw) effect would need to be cancelled out. Perhaps I should keep my thoughts to myself.

 

[Jackson]

What puzzles me is that I would expect that whatever problem exists in this case, eg, faulty rotor, motor, mechanical linkage,etc, the controller would be able to mitigate it by slowing down the back right rotor.

You're expecting too much from a board that probably cost <$2 to make. A gritty gear/bearing, slightly bent shaft and it's all over.

 

[Mike Westwood]

In case this info is useful to anyone, here's what happened...

I ended up with two of these aircraft, one properly broken but with useable parts.

On the "good" one I did the following

1) Dismantled and checked the mechanical components. Found nothing obviously wrong.
2) Replaced the motor most likely to be faulty based on the symptoms. No luck.
3) Rotated the board and motors by 90 degrees in the airframe. This would show if the problem was related to the board and motors, or the mechanics, ie, airframe, shafts, gears, rotors, etc. The problem followed the electronics. The symptoms were identical.
4) Replaced the pc board. This fixed it!

My conclusion is that there is a problem on the bad board, either electronic or with the software. What's interesting is that I'm fairly sure it was fine when I first flew it (out of the box), implying that the problem was caused subsequently either by a crash (resulting in a poorly soldered IC being knocked lose, perhaps?) or something else.
I have a strong magnet around which I use to catch or find dropped screws... I wonder if proximity to this could have screwed up the sensors on the board?

Mike

 

[Rick M]

Glad you sorted out the issue, Mike. For future reference, another thing to watch for is a hair wrapped around the prop shafts. When flying indoors the micro and nano quads are famous for picking those up, and it can really screw up their flight.