If Your Servo is Acting Weird...

[DanWright]

Change it. My throttle servo has been playing up for a while now, but not enough to encourage me to change it. Until tonight.

ImageUploadedByTapatalk1362601834.731271.jpg

ImageUploadedByTapatalk1362601854.682425.jpg

ImageUploadedByTapatalk1362601816.335128.jpg

It's not been binding on anything just making some strange noises, yet after investigating, all the gears are fine and as they should be. Lucky I wasn't airborne, and no, it's nothing to do with the 3GX in the picture.

[dillwhacker]

Your servo caught fire and your first reaction was to reach for the camera!
Good man!

[DanWright]

Yea, what can I say... Lol

[RcRotaryMadness]

Jeeze, these Helis they just want crash, smash, explode and burst into flames at any moment! Not seen a servo just catch fire before tho.. thats a new one!

[cjcj1949]

There's a servo monitor you can get from JP that will check out the current taken by each servo. There's a good chance that you'll see an increased current draw on a servo that is finding life difficult, before it goes up in smoke. You can use it in flight to record max current.

[xygax]

Dont discount the 3GX just yet.... Ask yourself why when they are supplied in a kit they have to supply a larger bec on newer versions with later firmware revisions. ?? is it because the 3GX takes more current.. No it has no means of taking current but it is in control of the consumers the servos...

So for it to take more current what must it do waggle the servos more frquently than before... trust me its the only way.

And that in turn causes them to get / run hotter there is more work being done by the bridge that controls the servo motor it warms nicely probably to excess and lets out the magic smoke...

Now tell me the 3GX is blame free... put a scope on the output measure the pulse width and more importantly the jitter.... Only then will you know the true culprit.......................................

Enjoy your fire hazzard
Steve

[DanWright]

Ah I didnt know about that. Perhaps it did contribute to the problem, but as I said before, the servo was playing up before the 3GX was fitted so maybe it was enough to finish it of?
It would of need replacing anyway.

[bulldog5046]

i'll be attaching my watt meter to see just how much current the system is drawing when my ESC arrives.

But yes, i expect the update frequency of servo positions was increased, would make everything feel more locked in and cause higher current draw.

[cjcj1949]

This is what I meant.

J Perkins Distribution - Home

If you have any doubts about your system power supply you can check it on the ground by giving lots of collective and adding some extra load on each servo. You could also add a few extra amps to simulate the extra load your servos will get when moving the surfaces against air resistance.

[bulldog5046]

Yeah i have something similar:

Turnigy 2 in 1 Power Meter/Servo Meter 1.5 TFT

does battery and servo/receiver draw.

[bulldog5046]

As promised, here is the max amps I could draw on firmware version 2.1 with severe stick bashing on the bench.

image.jpg

And the same test on firmware version 3.0:

image.jpg

I also gave the heli a quick hover and the peak amps were 3.88. All of these values are over the continuous rating for the 3amp bec in the align 70a ESC which would probably explain the brown outs others have seen.

Not sure about burning out servos though.....

[cjcj1949]

Burning out servos can be caused by binding putting a larger load on the servo motor. This could be inside the servo due to bad gears or compression of the gear train caused by pressure on the plastic servo case, or externally due to residue on the main shaft causing high collective friction. If the current draw of each servo is checked in flight, it will detect some faults before they cause a crash.

The min volts value of 4.33 is basically fatal. The min voltage values on a rx or flybarless controller are regulated values. If the volts from a bec drop that probably means the bec is out of regulation and you can't then rely on anything working when connected to it.

Thanks for the Turnigy reference.

[bulldog5046]

The amount of stick bashing i could do with the Tx on the floor was significantly more than could possibly be achived in the air.

I'll aim to fly with the meter on and see how low the voltage goes. I suspect it wont get anywhere near 4.33 in the air. just for reference, 4.33v is still above the min working voltage for the Rx and 3GX, so there is no reason to suspect a brownout.

[DanWright]

I've got one on order now, along with a DS620 to replace the old throttle servo. Everything else seems to be working fine, and nothing else appears to have suffered any damage, apart from my ears from having a rollocking off my mother for messing with it in the lounge Mechanically, the servo seems fine, no binding gears, all shafts in it are fine, and the control rod and linkages wernt binding on anything. Perhaps it was just a dodgy servo from the start.

[moyesboy]

I understand how fitting a 3GX can make your cyclic servos work harder, and maybe the tail. Any flybarless controller will work the cyclic servos harder.

But the OP's burned servo was the throttle! THe 3GX will have no effect on that?

THe only question might be did it have a govenor or not. A govenor might play up and wiggle the throttle I suppose - I did manage to get a CSM one to do that once, but the align one seems pretty immune to doing that.

The throttle servo has the hardest stop to encounter as the linkage is short and direct and the carb has a hard stop with nothing to deflect and bend - so my guess is that at some time the throttle has had a poor adjustment and been hard against the closed or the open stop. When replacing the motor if you don't put the carb back exactly square its enough to change the throttle linkage adjustment...