Cause of motor stoppage?

Midflight and lower starboard motor just stopped. Disarmed, re-armed, still same thing. Landed safely. At home, hooked up to diagnose, system arms up and runs just fine all motors happy as can be. WTF could be causing this?

I have a batch 3 unit and earlier this summer I developed a short in the throttle cable. One of the symptoms was that it would disarm…another was only some or none of the motors would run when I re-armed it. I am in the process of building a new cable with 24ga silicone wire and shielding tape and will post pictures in a day or two of the process. It took me a while to figure out what had failed.:slightly_frowning_face:

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If it is just one motor, you can most likely trace it to an ESC issue. Either the PWM connection could have vibrated and very briefly disconnected (unlikely), or the ESC could be going bad from voltage spikes. Are you using external capacitors next to your ESCs?

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I do not have anything in there that is not stock, other than anti-spark battery connectors.

Also, that would suck if it’s already going bad, it only has about an hour of flight time on it.

The longer your internal wire harness is, the worse the voltage spikes will be in your system. This can be remedied by shortening wires as much as possible AND adding external capacitor banks at each ESC.

If you have an oscilloscope you can check the intensity of your voltages spikes at different throttle ranges.

My internal wires are as short as I could make them. I do not have an oscilloscope. Is there a definitive article or example here that shows how to/where/what kind to install?

Here a post from my dad about how he accomplished it:

Thanks for this! If this is indeed something routinely problematic to the point of burning out your ESCs in their early lives, why is it not something that is mandated in the assembly of the kit?

Personally I think they should be part of the kit. However, I didn’t have issues till I started using 6 batteries. How many batteries are you using? Have you cut down the leads on the batteries? I cut mine in half.

The speed controllers are made for RC aircraft and have capacitors inside to handle the wire length of the typical application. Because the ESCs are mounted on the arms for better cooling the wires end up being too long. Paul probably hasn’t personally had this issue but this forum is a good place to learn stuff like that.

Using 4 batteries. Leads on batteries are just slightly shorter than stock, since I replaced the ends with spark-stoppers. Seems like if I make them any shorter I will have difficulty getting all of them hooked up. They’re short enough that they don’t threaten the props. If I cut anything off, I might be able to shorten them by an inch but I wouldn’t want to lose more than that.

I ordered a bunch of capacitors and will be making your mods, worst case is that they are redundant.

Just curious, what would a burned out ESC behave like? Would it operate at all?

Have you weighed the wires? It seems like if they’re heating up as much as everyone is saying that it might be worth doubling them up.

Regarding the poles on the capacitors-- do you think they really need solder, or would they be OK being needled into the wire and held in by the pressure of the wire and insulation itself?

I’ve had an ESC stop mid flight and work again after rebooting then just happen more and more frequently till it didn’t work anymore. That was before I had extra capacitors.

I had another one do that and after inspection I found I had a bad solder joint on the caps I added. I fixed the joint and haven’t had problems with that ESC since.

It is hard to solder the middle of a wire like the because the heat is drawn out in two directions but I recommend solder over just needling it in.

Not sure what you are referring to but the only time I had wires get hot was when I used only 2 bonkas with 10awg leads.

I fly with 6 bonkas now and nothing gets hot.