RC Fan Chris

I was flying a scratch built plane the other day, and right after I landed, the ESC and motor both died. Outside temp was 65 ish degrees, slight wind. ESC is (was) a Swift 50 A model, and the motor was a rather generic 2217/8 brushless motor, rated at around 25 or so amps. The reason why the ESC rating is so high is because the first one I got didn't work for whatever reason so the LHC gave me the swift to replace it. Anyway, I was flying the plane for several minutes, full throttle the first minute or so to gain altitude and do some quick stunts, then throttled back to around 50-60% the rest of the way, with some quick shots of full throttle every minute or so. Towards the end of the flight, the motor cut out very briefly, which I thought was for LVC. So I gave a tiny bit more throttle to get to the landing strip, then cut the throttle and landed quite nicely. Only then, after a second after touching down, a small could of thick white smoke came out the front of the plane, followed by a short white and orange flame. panic mode was engaged because I thought the LiPo was going to burst, but I found that the ESC and motor smelled kind of nasty. The spot where the black motor wire connected to the ESC board was blackened, and two poles of the motor were also black. That black wire came completely off before, but I resoldered it before this flight. The motor was burning hot, the hottest I've ever felt it. Finally, I checked the LiPo's voltage: 11.5 volts. Well above the 9 volt cutoff. LiPo wasn't even warm, btw. Ive been keeping an eye on it since, but it seems to have survived ok.

So, some questions: why exactly did this all happen? Did the ESC or the motor cause the smoke and flame? What caused the motor to cut out during flight?

kyleservicetech

Hey Wisconsin! What part of WI are you located? (I'm from South East WI).

Looks like you need to buy one of those wattmeters such as the Astroflight wattmeter. A number of different wattmeters are available, they will pay for them selves the first time you DON"T burn up a motor/ESC/battery. Another option would be to buy a Sears Craftsman digital AC AND DC clamp on ammeter #82369 for about $60. More $$$$ than a good China import wattmeter, but will do the job. Note that other clamp on ammeters such as the Harbor Freight units are AC only, and don't work on our DC power circuits.

As for overheating, a very rough indication is to rate the motor at 100 watts per ounce of motor weight. So, a 2.8 ounce motor would be fairly safe running 280 watts. That would be assuming you're using the right number of LiPo cells on it.

If your motor can handle 280 watts at 11 volts, that would be Amps equals watts/volts, or 280/11 or about 25 Amps.

pmullen503

Unless this was massively over propped, I'll bet you had a short. Probably where the leads exit the motor. The short was intermittent, depending on temperature or a wire being moved in flight. The first ESC didn't work because the short wouldn't allow it arm.

"That black wire came completely off before, but I resoldered it before this flight."

Another indication that something was wrong. Leads don't spontaneously desolder themselves.

It's not a bad idea to secure the motor leads to the frame shortly after the exit the motor so they don't move around. Where the windings come together into the motor leads, and exit the motor is the most likely spot for shorts or breaks to occur.

I'm in Fond du Lac, WI........

Beemerider

Electronics run on smoke. You let the smoke out.

RC Fan Chris

Prop was an 8 by 6. The leads coming from the motor were pretty secured going to the ESC, since they went through a smallish hole in the firewall. That black lead always was the troublemaker though.

Btw, I'm in Baldwin wi.

pmullen503

Were you running that on 3s or 4s? On 3s you are conservatively propped. (I run a Turnigy version of the same size motor with a 10x5.

That motor is not rated for 4s. So, if you were running that with a 8x6 on 4s you were over that motor's rating.

kyleservicetech

Fond du Lac, I was just at your recent fun fly, had a real good time there. It was pretty windy though, my wind meter over-ranged at 25 MPH. Even still, a lot of people were flying. Put 7 flights on my giant electric Big Stick model.

dahawk

RC Fan,

Former Wisconsinite here too but have been in TX a long time. ! Go Packers ! You're not the first to experience the "magic puff." Sounded like an intermittent short as P Mullen suggested based on the description of the motor sputtering and the fact that this wire had been re-soldered along the way ? Could there have been solder spatter making a cross connection? Or just an overload, but it seems like you had plenty of amp capacity in the esc.

Good Luck. Wish I could make to Oshkosh this year !

-Hawk

RC Fan Chris

Sorry, the prop is actually a 10 by 6. I used to have an 8 on there before, I think, then bumped up for more thrust. LiPo is a 3 cell 2200 mAh.

RC Fan Chris

I checked the ESC again, and sure enough, the dang black terminal was completely off the circuit board. Not sure if that came off before the incident, or if the incident caused it to come off.

Rodneh

"That black wire came completely off before, but I resoldered it before this flight."
What you said, perhaps that is where the problem came, a defective solder joint causing a short. It was probably intermittent until the slight shock or vibration occuring on landing made it a permanent short.

pmullen503

Most likely a short in the motor that took out both of them. Poor quality from the factory or mishandling the motor leads, or possibly a defective ESC with an internal short. No way to know at this point. Time for new motor and ESC.

Certainly wasn't over propped and the ESC was over sized.

RC Fan Chris

Does it matter much if the ESC is overqualified? I just got a 36 castle ESC, btw.

ron_van_sommeren

Bad connection/wire/soldering can cause high currents, explained after Whenever a motor just quivers back and forth:
http://www.rcgroups.com/forums/showt...0#post18461017

Do you have pictures of your fried controller?

Voltage ratings are pretty much useless. A motor can handle any voltage as long as max.rpm and max. current are not exceeded. Volts jolt, current kills.

No problem. The ESC does not push current, the motor/prop/battery combination determines current at WOT.