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Motor Temperature and Burn Out

Old 10-04-2011, 04:13 AM
  #1  
ryanstout
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Default Motor Temperature and Burn Out

I setup my 3dhs 41" edge a week ago running the recommended ESC, motor, and battery pack. However after testing the motor at full throttle for 1 minute, the motor started smoking and was really hot. It clearly melted some of the wires in the engine. 3dhs thought the issue was a short in the motor and quickly sent me a new one. However I have the new motor and after running it at full throttle for only 10 seconds the motor is very hot again.

Here's the setup:

Omega 72g 1100kV Motor
Hacker x40A ESC
Turnigy 1800mAh 3S 30C Lipo
12x6 APC E prop

I think I did a decent job on soldering on the XT60 connectors to the ESC, but is it possible somehow that is the issue? I'm also at 5k feet, not sure if that matters.

I'm not really sure what the issue is here. What kind of temperatures should the motor be running at. Do I need to get a watt meter to check the system. They recommend running at 320-380 watts. I'm new to this, but I think with the ESC it could run at: 444 watts, which might be too much? (40A x 11.1V = 444W right?) Any help here would be greatly appreciated.

Last edited by ryanstout; 10-04-2011 at 05:21 AM.
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Old 10-04-2011, 05:14 AM
  #2  
flydiver
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Exact prop size and make is critical to know.

YES! You NEED a wattmeter. To do this kind of stuff without one is almost like flying blind.

This is what 3dhs has to say about that motor.

Depending on your battery pack performance, either an 11x5.5 or a 12x6 prop is appropriate for 3D flight, where power bursts are relatively short and give some opportunity for cooldown. For sport applications where full throttle is used for long periods, a 10x5 prop is recommended.

Peak Amps: 40A
Peak Watts: 425W
Weight: 72 grams
KV: 1100

Most motors are not good for much more than 3w/gm of weight....so 425W is mostly fantasy. Anything you measure above 225W is mostly just heat. It's not doing you a lot of good.

If they are not entirely inaccurate the 11x5.5 is a THIN ELECTRIC (not slow fly) and for 3S. The 12x6 is for 2S ONLY. Notice that they even recommend 10x5 (again that's a thin electric) for prolonged throttle.

Rule of 'finger' for ALL electrics-if you can't put your finger on it, it's too hot. Motors that can't be touched after a 30 second WOT bench test are too hot. For 10 seconds...... WAY WAY too hot. The ESC does not force the electricity in. It is merely a pipe for the amps needed. The work is defined by the prop. The larger the prop, the more the work load.
At 5K altitude you should be able to run a bit larger prop. Not sure what the correction is but it's evident you are running too big a prop or something is not right with the setup.

FWIW it is common for retailers to over-hype their motors. If 3dhs is doing this they should get their act together better. They make a nice product and are well respected.

Disclaimer-I don't have any 3dhs planes, and am not personally familiar with THAT motor. Everything above is based on experience with motors and motor winding but is should be solid irrespective of the motor.

Side note: This shop doesn't make quite such exaggerated claims for the motor and adds a cautionary notepersonally I think even this shop is a bit over the top)

300watt continuous 400watt peak

NOTE: Please be sure to verify "your" power numbers with a watt-meter or power-meter prior to flying. Propeller recommendations are just that, recommendations, and power numbers will vary from user to user depending on various factors. The propeller recommendations listed will require throttle management and are not intended to be run at high throttle settings. Certain "high power" LiPo batteries will require an immediate change in prop. size to avoid over-amping the motor and causing a potential failure.

Last edited by flydiver; 10-04-2011 at 05:32 AM.
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Old 10-04-2011, 05:20 AM
  #3  
ryanstout
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Thanks, I forgot to mention, the prop is the recommended 12x6 APC E. It seems like that it shouldn't be that warm after 10 seconds.
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Old 10-04-2011, 05:22 AM
  #4  
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So when I get the watt meter, what should I be looking for? I was hoping to get away without one for now since it was all the recommended setup.
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Old 10-04-2011, 05:30 AM
  #5  
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check to make sure the correct timing is set on the esc.it may have high,medium,low and that would cause poor operation and possibly heat buildup.

+1 on the wattmeter,the most needed tool to see if watt your doing is ok.
stu

by the way....3dhs edge,very nice plane.
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Old 10-04-2011, 05:38 AM
  #6  
flydiver
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+1 on checking timing but I'll bet you haven't messed with it so doubt it's a problem.
A motor that gets hot in 10 seconds either has something wrong or is grossly over propped.

At 12x6 and you are using it on 3S you are over propped. So you ARE over propped. That's for 2S.
If thin electric (pointy tip) you are over propped.
If slow fly you are WAY over propped.

You don't NEED a wattmeter. All you need is a bunch of SMALLER props and your finger. Start small, run 'em 30 seconds at WOT. If merely warm, prop up. When the motor becomes hot to touch but not burning....STOP. You've found at least close to your prop.

But a wattmeter is WAY better and more exact. Even with a wattmeter I wouldn't use the specs provided, see below.

Hard lesson - de-rate ALL manufacturers and retailers specs on ALL electronics by 20% minimum, until proven otherwise. Yes ALL of them. You can always press the line but it's hard to un-smoke them once cooked.
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Old 10-04-2011, 06:22 AM
  #7  
kyleservicetech
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Originally Posted by ryanstout View Post
I setup my 3dhs 41" edge a week ago running the recommended ESC, motor, and battery pack. However after testing the motor at full throttle for 1 minute, the motor started smoking and was really hot. It clearly melted some of the wires in the engine. 3dhs thought the issue was a short in the motor and quickly sent me a new one. However I have the new motor and after running it at full throttle for only 10 seconds the motor is very hot again.

Here's the setup:

Omega 72g 1100kV Motor
Hacker x40A ESC
Turnigy 1800mAh 3S 30C Lipo
12x6 APC E prop

I think I did a decent job on soldering on the XT60 connectors to the ESC, but is it possible somehow that is the issue? I'm also at 5k feet, not sure if that matters.

I'm not really sure what the issue is here. What kind of temperatures should the motor be running at. Do I need to get a watt meter to check the system. They recommend running at 320-380 watts. I'm new to this, but I think with the ESC it could run at: 444 watts, which might be too much? (40A x 11.1V = 444W right?) Any help here would be greatly appreciated.
I looked up the specs on that motor. Funny they don't give one of the most important specs, that of the motor's winding resistance. Especially when it's so easy to measure with proper equipment. The winding resistance, along with the no load current has a direct bearing on how efficient the motor is in converting watts out of the battery to watts actually turning the motor propeller. (http://www.wattflyer.com/forums/showthread.php?t=59266)

A comparable Hacker motor weighs in at four ounces, and they rate it at 400 watts. http://www.aero-model.com/Hacker-Bru...30-16M-V2.aspx 1.5 ounces more than your motor, and near 2X the price. But you can run them at their rated specifications without concern. Running the numbers through www.motocalc.com, this motor will turn a 10X6 prop at about 9400 RPM, pulling about 330 Watts, and 30 Amps on a 3S LiPo. (I've got 7 of Hackers, all work well, one is being run at 20% over its rating, not recommended, but its been flying for several years.)

As others in this thread have indicated, look with suspicion any motor rated to run over about 100 watts per ounce of motor weight. This motor is rated at 425 watts on a 2.5 ounce motor. At 746 Watts per horsepower, that's over one half horsepower, for a 2.5 ounce motor. Not really realistic. That's 177 watts per ounce of motor weight. Its going to run hot, to the point of winding damage, magnet damage or both??? And its efficiency at 450 watts will likely be less than 50%, so most of the battery watts is just heating up the motor and its windings.

Also note running a motor at wide open throttle on the ground is the worst condition, in that maximum power, maximum motor heat loss, and minimum air cooling, since the model is not moving through the air. That's why hovering is going to really test your power system.

Remember, as compared to gas/glow engines, these electric motors are DUMB. They will happily turn over a propeller far to large for it for several seconds, or even minutes. Until the smoke comes out of the windings. As others in this thread have indicated, one of the best purchases you can make is one of those wattmeters. They are available from anywhere from perhaps $25 to double that for an Astroflight wattmeter. Most of them work well.

This is really no different than a common 120 VAC motor in your washing machine. Overload them for a few minutes, and they will run really hot, or burn up.

Last edited by kyleservicetech; 10-04-2011 at 06:59 AM.
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Old 10-04-2011, 06:51 AM
  #8  
ryanstout
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Thanks everyone for the info, very helpful. Also kyleservicetech, I was thinking that running it on the ground might cause more heat, but someone else had told me it didn't matter. So I think I'm going to try some smaller props and see how it does. If my LHS has a watt meter, I'll get one of those tomorrow and if not I'll order one online. I do think the first motor had a short, since it didn't take any time to start smoking, but hopefully now its just over propped.
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Old 10-04-2011, 07:00 AM
  #9  
NJSwede
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Welcome to Wattflyer!

1) As Stuart pointed out, this *IS* a nice plane. And she should know, because he's seen me flying mine! I love the plane!!!
2) You MAY be over propping. I'm flying mine on a similar motor with an 11x5.5 prop and it gives me plenty of power. I can do insane vertical rocket launches at full throttle.
3) The only way of really knowing is to check with a wattmeter. I would add an 11x5.5 APC-E prop to the order at the LHS. Check the watts and amp draw on the 11x5.5 prop first and if you're starting to get close to the maximum watt rating for your motor, I wouldn't even bother going up to the 12x6. You're just going to burn through batteries and wear out your power components. I'm running mine on a 380W system and there's no lack of power at all.... And it doesn't even get hot...
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Old 10-04-2011, 07:04 AM
  #10  
kyleservicetech
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Originally Posted by ryanstout View Post
Thanks everyone for the info, very helpful. Also kyleservicetech, I was thinking that running it on the ground might cause more heat, but someone else had told me it didn't matter. So I think I'm going to try some smaller props and see how it does. If my LHS has a watt meter, I'll get one of those tomorrow and if not I'll order one online. I do think the first motor had a short, since it didn't take any time to start smoking, but hopefully now its just over propped.
That's the issue with these brushless electric motors. I've got a Hacker A40-10L motor that weighs in at about 11 ounces. It puts out about one horsepower, and is doing about 88% efficiency per www.motocalc.com.

Compare that to a 3/4 Horsepower 120 VAC motor I've got that weighs about 20 pounds. You can run that 3/4 Hp motor at 1.5 Hp for several minutes before that 20 pounds of steel, windings and stuff get hot. But with our very light weight brushless three phase motors, they don't have much mass or weight to allow running them at 200% power for more than a few seconds. And as a result, they heat up real fast under overload conditions.

It's interesting, I hooked up that 3/4 Hp 120 VAC motor to an auto alternator years ago to run a brush type Astroflight 40 motor rated at about 800 watts or so. LONG before that Astro motor got to full power, that 3/4 Hp electric motor just stopped turning the alternator and stalled out.
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Old 10-04-2011, 07:07 AM
  #11  
ryanstout
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NJSwede, so when you say you're running a 380watt system, do you mean thats what things max out at when you run at full throttle according to a watt meter?
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Old 10-04-2011, 07:08 AM
  #12  
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Also, I've heard that wider props means more air over the control surfaces, does that matter for hovering and such?
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Old 10-04-2011, 07:15 AM
  #13  
NJSwede
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Originally Posted by ryanstout View Post
NJSwede, so when you say you're running a 380watt system, do you mean thats what things max out at when you run at full throttle according to a watt meter?
What I mean is that the system is rated for a max wattage. The motor is always the limiting factor since you usually go with an ESC that's a step up from what the motor will consume at WOT.

I'm using this motor:

http://www.headsuprc.com/servlet/the...80-Plus/Detail

As you can see from the table on that page, it draws 30A at WOT with a 11x5.5, which comes out to 330W, which is comfortably lower than the max wattage. This means I can fly at WOT for long periods of time if I wanted to. The specs don't list the draw with a 12x6 prop, but my guess is that it would put it around 400W (Denny can probably verify with his magical program), which means that I could probably survive short bursts of WOT, but constant WOT would fry the motor.

So the bottom line here is to try with an 11x5.5 prop. Mine cruises nice on 1/2 throttle with that setup and has unlimited vertical at about 3/4. At WOT it's a rocket.
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Old 10-04-2011, 07:19 AM
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Another thing, BTW: When you maiden your Edge, unless you're a really experienced 3D flyer (I'm not, that's how I know this), turn the rates WAY down! 50-60% on all surfaces with about 20-30% expo should be enough. It's an extremely snappy plane that does exactly what you tell it to, but it's pretty challenging on high rates. At least for a relative beginner like me...
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Old 10-04-2011, 07:22 AM
  #15  
ryanstout
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NJSwede,
Thanks, good advice. On my first 3d plane I started on high rates and very quickly realized that was a mistake. I've had a few 3d planes before, but I've got everything up for 50% and 25% expo on low rates.
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Old 10-04-2011, 05:35 PM
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Notice that Swede's motor is 102g (yours is 72) and his is rated 380MAX for 60 seconds > meaning if you keep that up like in a protracted hover you burn it up.

It does help to have air over the control surfaces. But a motor can only push so much. Propping it more won't make it push more. It's like hoping you can pull any size trailer with a compact car, just because a brochure says you can.
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Old 10-04-2011, 06:43 PM
  #17  
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One more thing .... none of these motors are meant to run WOT on a bench for 1 minute. There is not enough air moving over the motor and ESC. When you do a check with a watt meter, it only takes a very few seconds to get the reading.
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Old 10-04-2011, 11:09 PM
  #18  
ryanstout
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Thanks everyone, I got a 11x5.5E prop and a watt meter. It was pulling up to 500 watts with the 12x6E, but only did 350 max with the 11x5.5. I'm surprised to see such a difference, but it looks like I can run the 11x5.5 without many problems as long as I don't do WOT for a really long time.

Thanks everyone for your help.
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Old 10-05-2011, 01:36 AM
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Originally Posted by ryanstout View Post
Thanks everyone, I got a 11x5.5E prop and a watt meter. It was pulling up to 500 watts with the 12x6E, but only did 350 max with the 11x5.5. I'm surprised to see such a difference, but it looks like I can run the 11x5.5 without many problems as long as I don't do WOT for a really long time.

Thanks everyone for your help.
Yup
As you and many others have found, propeller size and cell count is critical on these electric motors. What might appear to be a minor change in propeller size, like from 12 to 11 inches can have a significant difference in watts to the motor. Likewise, going from 3 cells to 4 and the like.

Thats why those wattmeters are so useful on this stuff. First, to make certain you're not overloading anything. Second, to make certain you're making full use of the maximum safe power of your motor/esc/battery setup.
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