My Versa wing caught fire!

[Arcfyre]

As the title said, I had just recovered my wing from doing a video flight, and was about to launch it for another loop. I punched the throttle and heard a popping sound, and all of a sudden there is smoke and actual flames eating the back of the plane! I quickly disconnected the battery and got the fire out. Looks like only minor damage, and obviously that ESC is toast. Any idea why that could have happened? I've heard of batteries exploding, but ESCs? It didn't get wet or anything.

 

[Chuppster]

Hmm. That looks like one of the cheap $6 ESC's from China. Here's my theories, in order of probability.

1. bullet connectors accidentally touched, causing an overcurrent condition that fried the ESC
2. ESC got hot and shorted itself out
3. motor got hot and shorted itself out

There is a chance your motor is toast to, but hopefully your receiver is fine. It's good that you unplugged it when you did. If you want to prevent this kind of thing from happening again, install a fuse rated at (max esc current * 1.25). That way, if you blow it again, you will limit the damage. Keep in mind this will shut down control of the airplane too, so be careful.

 

[Arcfyre]

Thanks for the reply! I'm (almost) sure the connections didn't touch, as I had them isolated with some electrical tape.

As for the ESC getting too hot I think you may be right. It's a cheap one, I'm guilty of that, but I had it mounted outside the wing in front of the motor to maximize air flow. The wing is black and today its pushing 90 so I guess it just wasn't enough cooling. Still surprised that it caught fire.

 

[quorneng]

What amps was the ESC rated at?
Do you know what amps the motor actually pulls at full power?
How many cells LiPo are you running?
Is the ESC rated for that number?

Cheap ESC are ok but are best used at never more than 75% of their max rated current and definitely only with their rated number of cells.

 

[Arcfyre]

Its a 30A ESC running a 3S Lipo. The motor is an 1135 kV and with the 8x6 prop pulls about 23A at full throttle.

 

[kilroy07]

Any idea why that could have happened?

Yup... I've seen this before (more times than I care to admit.)

You can see how I have overcome this issue here;
https://forum.flitetest.com/index.php?threads/are-escs-consumable-items.53742/

What I suspect (and have found) is not all "cheap" ESCs are created equal.
Some of the ones I have received are made of really questionable components, others on the other hand are quite good (especially with an external BEC.) Look for the ones with the readytosky label, if they just have a silver 30a sticker than are most likely the cheaper ones.

I have also noticed the solder on the cheap stuff varies, I wonder if maybe one of the motor leads developed a crack in the solder joint, this would start to heat up and cause further weaking the joint... finally causing a short.