dead motor?

[miky94]

hi all,
after a crash (but on the other side) a motor doesn't spin anymore, I checked and there isn't continuity between power in wires and the esc outputs, but also there wasn't continuity between one wire of the motore and the others two so I saw that it broke off on the side of the motor, I soldered it as you can see in the image and now there is continuity between all three but the motor still doesn't work as you can see in the video. it doesn't have black burn marks, doesn't seem crooked and manually spins like the others, is it dead?
thank you

 

[wafflejock]

You can get motor twitches like that if have a shaky connection on one of three of the phase wires. To eliminate chance of it just being esc that is shot can always swap two motors but I would put my bet on motor just needs replacing, luckily only like $10-20 a pop.

 

[miky94]

yes I tried but it is the motor, in the long waiting for a new one do you think it is worth to try rewiring it? I soldered the broken one but I don't know if I did it right

 

[wafflejock]

I suppose it couldn't do any harm and could learn some in the process but can't say I've ever done it myself. There's a few vids on youtube of a guy who designed and 3D printed his own fairly large electric motor but might be helpful as a high level guide (imagine can find some diyers who have rewound their own motors on the smaller scale too but imagine that can get tedious, usually there is a motorized tool that helps wind the motors for our quads)

 

[wafflejock]

Found the video I was thinking of, again maybe better to find something more size appropriate but what a motor

 

[miky94]

yes I'm trying to learn something on youtube
in the image you can see the broken wire, I took off half turn of winding because it was too short, but as it is insulated copper wire I don't know how to test the solder joint

 

[wafflejock]

Think ohm meter/multimeter in resistance measuring mode is probably best bet to check for connection and low resistance (if low enough and multimeter isn't precise enough will just read as 0 if low ohms and connected, or usually -- if no connection). If bad solder connection won't see connection in continuity mode or resistance mode. When trying to get enamel off the enamel coated copper used for windings I've had some luck with the aspirin and solder iron method but make sure have really good ventilation (do outside cause stuff put into the air is super nasty and toxic from what I gather). Other options are acid (have not tried myself) comes with obvious risks or using razor and time to scrape it off the copper. Problem is if you scrape enamel off two wires near each other when looped it will short across there (hence the enamel coating to keep the current flowing around the coils)

 

[miky94]

I reconnected the broken wire of the motor and now on another esc it works!
but if I wire a working motor on the other esc it behaves like in the video, no chance to repair the esc?
if i have to replace it, an higher current and higher voltage rated esc would be more durable? or in that case would it be dead too?

 

[wafflejock]

Yah replacement is the way to go for esc that's damaged, repair on esc requires working the whole pcb with hot air rework station and finding the mosfet(s) or other component that failed. I still somewhat prefer individual escs because easier to replace one if only one burns out but 4in1 board does make for a cleaner build. A higher current capable esc is a little less likely to blow since if the motor/prop gets stalled/blocked the current can spike out as the esc continues to try and spin the prop I have found the mid-range or slightly more expensive than cheapest possible tend to be a lot more resilient when it comes to escs.

 

[miky94]

as I heard that 4S ESC is a little close to the edge and the motors are 6S rated I bought that 6S ESC for future upgrades even if probably I'll have to buy a 6S rated FC
but in this case I think the motor wire broke and then the ESC burnt, I don't think the bigger ESC would have survived anyway

 

[wafflejock]

Yah if there is a straight short then the mosfets on the esc will likely fry regardless but if just caused by a stall/current spike then escs with better mosfets can handle it better (also caps and other passive components arranged properly can help dissipate spikes in current or voltage)

 

[wafflejock]

Generally a component like esc with higher voltage rating just had caps and mosfets with higher voltage rating too but the amp rating is separate spec on all the components on the esc and the esc spec is based on weakest link in terms of max voltage and current allowed before something frys in one way or another.

 

[holtneil]

Hi if you go 6cell you don't have to change FCB you may buy a Bec we use these on helicopters all the time , we have only in the last few years got high voltage servos and FBL gyros