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-   -   Blow Up my Esc :3 (https://www.rcuniverse.com/forum/beginners-85/11693280-blow-up-my-esc-3-a.html)

Alexandros444 09-10-2021 02:01 AM

Blow Up my Esc :3
Hello, I am new to RC Planes, and just bought the parts off eBay to get started.
I have not the most experience with building, so my plane was a bit overweight. Around 1.2 Kg, or 2.6 pounds.
My Components are:

Esc 30A, short peak up to 40A, The Description said: Max Speed 210,000rpm for 2 poles BLM, 70,000rpm for 6 poles BLM, 35,000rpm for 12 poles brushless Motor if this is of any use.
Li-Po 3S 11.1V 30C
Motor A2212/5T 2450KV 280W

So I tried to gently increase the throttle, and it seemed to have enough power, but halfway through the Esc started to cheep and short after it just popped, with smoke and everything.
So I wondered why this is? I mean if I do the maths, since the motor is 280Watt and the Battery has 11.1V the maximum flowing Current should be 280W/11.1V = 25.2A.
This should be fine for the Esc, shouldn't it? :O
My Plan for next time would be to get a bigger Esc and also make a lighter plane. But will this be the right way ? Or do I need to change something different.
If you could help me, so I don't waste another Esc, I would be very glad, Tanks
Best Regards

Hydro Junkie 09-10-2021 07:37 AM

I've got a few questions for you:
  1. What brand are the motor and ESC
  2. Are the components all new, used or reconditioned?
  3. Was there a prop on the motor's output shaft when you were testing?
I wouldn't buy anything off Fleabay due to the very issues you are having. I would rather pay more at a reputable retail shop that stands behind what they sell than take a chance of losing my money on something cheap. Then again, I run gas and nitro fueled boats and planes and only use Futaba radio gear since I've never been disappointed by it

Alexandros444 09-10-2021 11:06 AM

Tanks, Hydro Junkie for answering. :)
I don't know which brand they have, but here are the Links: (I inserted a space after the h of https, because I'm not allowed to post links)
Esc: "h ttps://www.aliexpress.com/item/1005001676668972.html?spm=a2g0s.9042311.0.0.27424c %204dAl38mu"
Motor: "h ttps://www.aliexpress.com/item/4001196428994.html?spm=a2g0s.9042311.0.0.27424c4dA l38mu"
Battery: "h ttps://www.aliexpress.com/item/4001194059641.html?spm=a2g0s.9042311.0.0.56964c4d2 1oTpL"

I mean, yeah, those were the cheapest I could find. But I thought, if I crash or hit a tree, those would not be much of a loss.
I don't know if they might have been used, but wouldn't there be more negative feedback if their products wouldn't match the description ?
I bought a lot of small electronics from there and was satisfied most of the time, but sadly those are all different sellers.
Anyway, how much money would you suggest I should invest for each part?

And also, I would like to search for all possible other problems first, before going too fast to the ultimate "defect parts" conclusion,
so I can avoid making the same mistake with more expensive parts.

Yes, I tested it with a prop on.

Hydro Junkie 09-10-2021 12:21 PM

This is one where I think you're going to need to have someone that knows more than me chime in. Went to the first link you gave, only to discover the site is in German, something I can't read or speak

speedracerntrixie 09-10-2021 07:24 PM

The missing key to this puzzle is the prop. As of yet we don’t know what size was being used. According to my calculations the largest prop that motor/battery combo can use without exceeding the ESC amp rating is a 7x4.

Alexandros444 09-11-2021 03:51 AM

Oh, I'm sorry, I now changed them to English.

Alexandros444 09-11-2021 03:59 AM

Oh, thanks speedracerntrixie, this have to be it.
Because I used a 1045 prop, I guess it stands for 10x4.5, which would be way too large for what you said.
I thought, it would be fine to have a bigger one, because the motor said 280W and I assumed, that even with a bigger prop this power limit is not exceeded.
Where/How did you calculate it ?

speedracerntrixie 09-11-2021 05:41 AM

Since I have been flying electric power for about 20 years the calculation was done in my head. You can also download an app called Ecalc. The key to determining prop size is the motors KV rating. The KV rating is RPM per volt. In your case 2450 x 11.1 = 27,195. A very high RPM so a small prop is required. In fact your 10x4.7 will come apart at that RPM. If your ESC didn’t burn up you would have been generating more like 500-600 watts and pulling 50-60 amps. I would strongly suggest a different motor with a KV of around 1000 to 1200. That KV with the motor size of 22mm is much better suited for your airplane and should be just fine with the 10 x4.7 that is a suitable prop for your airplane type. I prefer the Dualsky brand of motors and ESCs, you can also find them on eBay but the Vendor Aloft Hobbies is where I buy mine.

This would be a good choice.


Alexandros444 09-12-2021 02:41 AM

Ok, tanks, that makes it a lot clearer.
I've had the same motor as the 2450kv, only with 1000Kv on it before, but it was not generating enough thrust, so I wonder if the motor you suggested, with 1000-1200Kv would be enough.
Is it only the Kv rating which you translate to thrust, or is there more to it?

speedracerntrixie 09-12-2021 05:58 AM

Yes there is more to it. Motor diameter and length play a part as well. If you notice, the motor I suggested is a little larger then the one you have. Typically for sport flying you want 100 watts per pound of airplane provided and this is also important that the airplane wing loading is not over 20oz per square foot. The wing loading is quite important, more then overall airplane weight. For sport flying we are finding that lower KV motors with larger props give better thrust. The airplane I fly the most has a motor that is only 220 KV but is also the battery is 10 cells. Most of the flight is done below 5,000 rpm with a 20x12 prop. The wing loading is around 18oz per square foot. If I knew more about your airplane I could narrow things down a bit better for you.

jester_s1 09-17-2021 07:49 AM

To get a little into the electrical theory that RC pilots really have to know-
For electric motors, RPM is determined by the voltage that the motor sees. It doesn't matter what the load is, only the voltage.
The motor, based on load, will draw whatever amps that are required to turn the load at the speed that the voltage dictates. Of course, as amp draw increases, voltage sags based on the combined resistance in the entire system. So RPM will drop a little with load because voltage has dropped due to the amp draw.
Important to understand though is that motors have (theoretically) unlimited power. They will keep drawing amps with load no matter how big the load is. Resistance in the system is the only reason a tiny 15mm motor can't turn a 20 inch prop at 30k RPM. The limits come from resistance, which goes up with heat and amp draw. The point is that motors don't self-limit- a 250 watt motor will draw much more than 250 watts if you load it and apply voltage to do so. And it will do it until something breaks. The same is true for ESC's. Most don't have an amp limiter, so they will provide what the motor is drawing until they burn up.
So it's vital to prop motors based on their specs.

Alexandros444 09-18-2021 12:49 PM

Thanks, that's good information to have. Only thing left, is to determine my ideal prop size and fitting motor.
My plane is about 1.2 Kg and has a wingspan of 1 m and the area is 14 dm² or 1400 cm².
Is there an easy rule for determining those, or do I have to go to eCalc and try getting some useful values out ?

049flyer 09-20-2021 06:52 AM


Some modelers buy “plug and play” airplanes where the system is matched by the manufacturer. Some modelers like to experiment and match components themselves, if you are this type of modeler you MUST use a WATTMETER. If you had plugged a wattmeter up to your plane and tested the system you would have discovered immediately that too much power was demanded from the motor and you would not have destroyed your ESC. A wattmeter is essential equipment for an E flight modeler.

jester_s1 09-20-2021 10:06 AM

You are probably seeing now why it's not recommended to try designing aircraft when you have never flown them. We'd have recommended that you go with a proven design with a proven power system that works well if you had asked before buying parts. That's what I'm still going to recommend- don't throw good money after bad by trying to make a faulty design work. Instead, look for plans for a plane that is good with the ESC and servos you bought and get the recommended motor for it. That way, you can learn RC flying with a plane that works properly instead of fighting with your equipment.

ktp344syz 11-05-2021 09:46 PM

How can you tell if the ESC engine is at the blow up limit sense? 11.4 volts and 1 ESC engine. 2450 kv to the ESC engine. Would reducing the volts to 7.4 volts still start the engine? Not sure about this part and how they calculate volts requirement to ESC engine.

jester_s1 11-08-2021 10:55 AM

Your motor (not engine) has specs for what voltage goes with the recommended props and what amp draw you should get.

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