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Post by dopey190 on Jun 6, 2013 21:29:35 GMT 1
I recently put this motor in my cub, hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=19038 I liked the extra power that came with it, I tried to hand launch the plane this morning and it went straight down on its nose. It has lost i would say about 75% of its power. Its a new motor, and after my few flights with it the motor wasnt hot, but the esc has been pretty warm. I have been using a 30 amp esc, and a 10/6 prop and a 1300maH battery. On the HK site it suggest to use a smaller prop, but its all I have. |
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Post by Crazy Horse on Jun 7, 2013 12:24:16 GMT 1
Hmmmm,
I think this could be one for Flydiver? He is the font of knowledge for all things Supercub, (and probably much more besides).
I have a thought or two on this but would not like to muddy the waters, being respectful to those who know far more than I regarding these matters.
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Post by flydiver on Jun 7, 2013 20:34:48 GMT 1
First suspicion, you put the prop on backwards. This is the easiest if you did this. It's amazingly common.
If you did this pay attention to the rest of this because you are courting disaster.
People considering upgrading the motor need to pay attention to these concepts. If you don't, it can bite you.
2. per motor specs:
Max Current (A) 28; 9x5 > 25.2A with 1310g Thrust
You are using a 30A ESC and a larger prop. Like most newbies I would guess you don't have a wattmeter, and are working in the dark. There's a good chance you are over both the motor AND the ESC capabilities and have partly fried something. The ESC is more likely than the motor.
3. Stock battery? 1300mA = 1.3A > 1.3A x 15C= 26A MAX that battery is capable of. Of course that's baloney and it's only capable of about 18-20A. Since you are likely pulling over 30A with that setup you may have killed the battery also. You would need a 20C minimum, and a 25-30C would be better (assuming those specs aren't made up) in 1300mA size to feed that motor properly. A larger battery would be better.
Lesson - you may have ruined a new mod because "its all I have". Kind of harsh to do that for a few dollar chunk of plastic. Details matter in flying.
Get a wattmeter and learn to use it or continue to pay the price in fried electronics.
Note - degrade ALL Chinese specs by 20% unless PROVEN otherwise. Even some mainline products like Rimfire motors have bogus specs.
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Post by iandhunt on Jun 7, 2013 21:24:12 GMT 1
I agree with fly, if your ESC is getting "PRETTY WARM" than it is possible you could have cooked the ESC. I would also be highly suspicious of the motor going bad since the ESC seems to be the sacrificial lamb in the setup. I had to learn the hard way that using the 10X8 prop on the stock cub electronics was stressing the whole system out. My ESC had a failure and it spent 2 months in a tree until the tree had an unfortunate chainsaw accident.  The more (i.e. larger) prop you have means you require more power to spin the prop. This requires more draw on the electronics and as you may have found out this can KILL electronics that are not rated for such a high AMP draw. Lesson learned I assume. This hobby is about making mistakes on cheaper planes so when you buy the bigger and better ones down the road these "rookie" mistakes are non existent. I truly hope you don't drain your bank account before you get there though! |
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Post by flydiver on Jun 7, 2013 21:34:05 GMT 1
I agree with fly, if your ESC is getting "PRETTY WARM" than it is possible you could have cooked the ESC. Warm is OK, hot is not. Linear ESC work by using resistors to pull the voltage down to 5v for the servos and RX. Resistors make heat. They actually work HARDER at low throttle than at full throttle since the voltage will be higher at low throttle. But that's on the BEC side. The ESC side is where the 'specs' you read about are, like 30A in this case. You should try to have a 20-30% margin OVER the TOP/MAX current motor draw. In this case he's right on the edge IF he propped right. He appears to have propped wrong. That's almost a guaranteed disaster. Switched ESC use electronics to pull the battery voltage on BEC down. They run cooler and more efficiently. You seldom see them in ESC smaller than 40A though as they are more expensive. So in this case he has a linear BEC (may or may not be an issue), inadequate ESC, too many amps from over propping > not good. The BEC side has NOTHING to do with the specs on the ESC side. Best to think of them as 2 separate devices that are sharing the same space, because they are. You Spektrum users especially need to pay attention to the BEC side once you get over 3 servos and 3S or you risk Brown OUT and disaster from a different problem. |
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Post by dopey190 on Jun 13, 2013 3:31:53 GMT 1
First I will check the prop, I ordered a 40a esc from heads up, smaller props, and a bigger battery. I do not have a watt meter yet, but will get one in the near future. Thanks for your help everyone. Also from what iamhunt said, about the motor, would it have gone bad aswell? Or do you think its more of an esc issue? I will test it when the esc comes in, dont want to have to get another motor.
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Post by flydiver on Jun 13, 2013 4:00:47 GMT 1
Think of the power train as a chain...everything connects. In every chain there is a 'weak link'. Doesn't matter as long as the weakest link is sufficient for the task. But, if you overstress it, THAT link breaks. So, depends entirely on the individual components and how they interact. You can damage any one of them, even a couple of them but you generally don't destroy them all.
In your case it seems likely the ESC was the weak link. It blew and saved the motor....probably.
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Post by dopey190 on Jun 13, 2013 20:30:46 GMT 1
Guess I will find out soon if it will work, Once again thank you FlyDiver.
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Post by dopey190 on Jun 17, 2013 23:47:24 GMT 1
It was definitely the esc. The prop was on correctly, and the planes flies great now, however, the new 40a esc is still hot to the touch.
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Post by flydiver on Jun 18, 2013 0:08:03 GMT 1
It was definitely the esc. The prop was on correctly, and the planes flies great now, however, the new 40a esc is still hot to the touch. Sure - you probably bought the LINEAR BEC. It uses resistors. Resistors get hot. There's nothing necessarily wrong with that, just understand what you are getting and know the properties, and limitations. Read the specs. Learn what they mean. |
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