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Power Systems Talk about motors, ESC speed controllers, gear drives, propellers, power system simulators and all power system related topics

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Old 11-25-2006, 02:44 PM   #1
hauts
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Red face How to burn a speed 380

I just maidened another wing. For power it had a 380 motor with 25a esc from bidproduct.com. Dirt cheap parts. And then a 3s lipo because that's what I had, and Google told me it should be OK for a 380... you might guess where this is going.

The motors come with some 7 inch props but I put in a push-on Gunther of 6x something inches, those white props that should work great on 400 motors.

I was not sure if the plane would fly at all, in my hands it felt sorta heavy and I was not sure about the center of gravity. But it flew! Just fine! Got it in trim, flew a couple times around the field...

And then there was a smoke trail. First I thought my eyes were playing tricks, but also a loss of power became apparent. Motor off and safe landing, run to the plane to disconnect battery.

Well. The lipo got pretty warm but is OK, after cooling down there was plenty of volts left. Apparently nothing was destroyed except the motor. Some white wisps coming out of it, disgusting electrical-fire smell.

Must replace it with a speed 400 I guess.

Was the reason here too high voltage? Would throttle control have helped, or was the motor doomed from the start? OR does anybody think the motor might be defective?

I have tested these motors with 3s lipo before and they got pretty warm but did work, and produced nice thrust. That said, this was the first time I really flew one.
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Old 11-25-2006, 06:28 PM   #2
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In reply to your question re too high a voltage for a 380, yes a 3 S voltage is 11.2 volts which could push the amp draw higher tha a 380 can handle. Did you use a Whatt meter to check the amps youe motor was drawing?
It is always a good idea to check the amperage of a new motor/ESC/Prop combination before you fly to see if it is within the limits of the motor/ESC. There are a number of whatt meters in the market and an expenditure of $50.00 or $60.00 can save you alot in burnt motors, ESC's and Batteries.
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Old 11-25-2006, 07:16 PM   #3
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The only Speed 400 motor you can use with a 3 cell lipo is one rated for 7.2V- not the 6V motors. It's a maxed out setup that works very well if you keep it cool.

You can use a 6x3 prop or the spoon props that work so well with S400s- but never use a larger prop with a S400 direct- it lets the smoke out....

So when you buy one- buy a few more since they won't last long at this power level but you'll still get a hundred flights with it if you keep it exposed to the breeze.

I replaced the S400 in my Ascent every month or so when the motor was cooked due to lack of ventilation and this plane is an extreme example. Put it on a delta or anything else out in the breeze and its a hot setup that bridges the gap between Speed400 and BL motors with a lifespan of about one season (and replacement cost under $10) if you keep it cool.

Enjoy!
TW
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Old 11-25-2006, 08:23 PM   #4
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I would advise keeping the amp draw to 10 amps or less with a Speed 400 motor.
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Old 11-27-2006, 12:08 PM   #5
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I just replaced the motor with a small 1700 kv brushless and now the plane does limited vertical with the same six inch prop. No pics of the brushless setup yet, this is after the smoke came out of the 380.

I wonder if the prop being between the tailfins is somehow bad.

It is a Beetle slope plank. The first powered one I've seen. I love slopers for their crash resistance and good gliding ability, but have no slopes...

http://rcsail.com/beetle.htm

It also flies with a 4.75 x 4.75 prop (noticed after I lost the gunther propeller...) just with that it has almost too little thrust and getting up to speed takes some time.

Yeah, I guess amp/watt meter is on the must-get list.


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Old 11-04-2010, 09:24 PM   #6
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could someone please help me choose a battery for this speed-380 johnson battery because it runs well i just can't find a suitable battery
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Old 11-04-2010, 09:41 PM   #7
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Just FYI... a '380' is a "Speed 400"! If you want 3s then the 7.2v version is what you must use... with perhaps a Gunther (4.92x4.33) or a Zagi (5x5). You need a small 3s pack capable of delivering 10A-12A. (20C 600-800?).

You mention Johnson... then, if it has two flat sides, that motor is a "280".
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Old 11-05-2010, 12:27 AM   #8
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ok - i'm not entirely sure what motor it is: it's definitely a johnson and i think its a speed 380 because it matches the description of a 'speed-380' (at the bottom of the page) on this page http://www.robotcombat.com/store_motors_misc.html with the sizes and looks exactly like the one in the picture.

I built an rc car using this motor and tried to use a 8.4V 1000mah ni-mh battery taken from a hobbyzone supercub and it ran very well but the battery was drained in seconds, so im not sure what battery to use?

thanks for your help btw
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Old 11-05-2010, 10:34 AM   #9
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Unfortunately there are loads of motors of that physical size and they come in all sorts of different winds and voltage ratings. Unless you know EXACTLY what you have or can at least measure the current it's taking it could be anything.

But if "the battery was drained in seconds" that suggests that it's a very low voltage wind and you were seriously overpowering it. Maybe try it on 7.2V or 2S lipo starting with the smallest prop you can find and see how hot it gets.

Steve
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Old 11-05-2010, 11:19 AM   #10
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hmmm, i have a 3S lipo for 11.1V but ill probably burn out the motor, and I dont have a 2S, but I have researched and i'm certain it's the speed 380 from (http://www.robotcombat.com/store_motors_misc.html).
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Old 11-06-2010, 01:15 AM   #11
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Okay, so it is what would be equivalent to a 7.2v nominal Speed 400 (~2300Kv) as opposed to the stock 6v nominal Speed 400 (~2660Kv).. depending on how your car is geared, 3s might well be too much, if the amp draw on 8.4v is excessive!

Unless you were drawing more than the 8A-10A the motor is good for, a 1000mAh pack should have lasted 6 minutes or more.
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