Author Topic: I've blown something - or - stupid question part 2 (Read 1926 times)

John Hammonds · « **on:** November 05, 2008, 05:57:01 PM »

Hi All,
Been a bit quiet due to redundancy but now back in full time employment so got busy again with my 30 year old Flightstreak and finally got it ready for it's maiden flight. Hope the image shows up.

I've been playing around with props etc trying to get a static run of around 270 watts on my watt meter and seemed to get it about right when the motor suddenly stopped (Nowhere near the low voltage cut off and amps well within the ESC ratings) and then began "shuddering" for want of a better word. Disconnecting everything and starting from scratch just results in the shuddering. The arming beeps indicate all is well. I only have one ESC, motor, battery pack at present so can't try substitution, The battery takes a charge and the cells are well balanced so what have I blown ESC or motor? I'm guessing it's the ESC (A cheap "Robotbirds 60a") but would prefer an informed guess before I replace it, probably with a CC 45 (Which I should have bought in the 1st place). Or could it be my JMP timer?

Apart from that electric is great, I can even lock myself in the spare room and run the engine up with no complaints about the noise, (Just try that with an LA46).

Thanks in advance

TTFN
John.

Dennis Adamisin · « **Reply #1 on:** November 05, 2008, 06:51:02 PM »

uh oh, that sounds like what happened to me when I overloaded and cooked a motor. Look for burnt windings and that sickening smell.

At 270W where is that relative to the sustained rating of your motor? Also, does the wattage at full throttle exceed the peak rating of the motor?

Mark Scarborough · « **Reply #2 on:** November 05, 2008, 09:38:57 PM »

One further comment, if you did run it very much static on the ground, its a good possiblility its toasted, they just dont cool on the ground, no to mention that they draw much more current when sitting still.

Richard Grogan · « **Reply #3 on:** November 05, 2008, 11:50:45 PM »

Quote from: John Hammonds on November 05, 2008, 05:57:01 PM

Hi All,
Been a bit quiet due to redundancy but now back in full time employment so got busy again with my 30 year old Flightstreak and finally got it ready for it's maiden flight. Hope the image shows up.

I've been playing around with props etc trying to get a static run of around 270 watts on my watt meter and seemed to get it about right when the motor suddenly stopped (Nowhere near the low voltage cut off and amps well within the ESC ratings) and then began "shuddering" for want of a better word. Disconnecting everything and starting from scratch just results in the shuddering. The arming beeps indicate all is well. I only have one ESC, motor, battery pack at present so can't try substitution, The battery takes a charge and the cells are well balanced so what have I blown ESC or motor? I'm guessing it's the ESC (A cheap "Robotbirds 60a") but would prefer an informed guess before I replace it, probably with a CC 45 (Which I should have bought in the 1st place). Or could it be my JMP timer?

Apart from that electric is great, I can even lock myself in the spare room and run the engine up with no complaints about the noise, (Just try that with an LA46).

Thanks in advance

TTFN
John.

John,
I would first disconnect the motor leads from the ESC and check the ESC output with an DC voltmeter (DCV). If you have no DC voltage, the ESC is either fried or has a fuseable link that popped. If you have good DC out, then its your motor.The shuddering you described kinda reminds me of AC being applied to the DC motor(bad ESC), or one of your windings in the motor has opened up(bad motor).
Hope this helps..
Richard

Alan Hahn · « **Reply #4 on:** November 06, 2008, 08:11:25 AM »

Richard,
I am not sure that a sensorless brushless ESC can be tested with a voltmeter (I think this is a brushless setup). It needs some back EMF feedback from the motor coils (the set that are not energized) to know when to switch the power. I might be wrong of course.

My guess is that there is a bad connection or short somewhere. Check your connector solder joints to the motor to make sure they are good. Doesn't hurt to check the battery connectors either, just in case the issue is too big a voltage drop across a poor connection. If it is a short, it is probably inside the motor. Might take a peek inside to make sure it looks nominally ok.

Mike Anderson · « **Reply #5 on:** November 06, 2008, 12:09:16 PM »

The 60amp ESC that he mentions is for brushless motors, so there is no DC voltage
on the output of the ESC - the motor is fed voltage pulses and the "commutation"
is handled by the computer in the ESC.

If the motor is shuddering or trying to run, then there will obviously be some kind of
signal on the motor leads and trying to determine if the ESC or the motor is at fault is going
to be a real challenge with just a voltmeter.

The quickest and easiest way for most would be to try and borrow a working ESC
(and or a known good motor), just to plug in and try. Hopefully, John has someone
(maybe even a local hobby shop would have something setup that you could plug
your components into??) that can give him a hand.

(My own first guess would be the motor - after all, if you are trying to ramp up to only
270 watts, it's doubtful if you blow a 60 amp ESC. Not impossible, of course, but
less likely to be the fault than the motor is ...)

Or like Alan mentions, possible cold solder or poor connection -

John Hammonds · « **Reply #6 on:** November 06, 2008, 02:15:55 PM »

Thanks for the replies, I removed all the connectors and re soldered did them to try to eliminate and possible connection problems. Still the same result. The full set up is a 3s1p A123 pack (9.9v) with the previously mentioned Robotbirds ESC and a Scorpion 3014-16 motor (Rated at 600w / 43 amps continuous), all controlled by a JMP timer.

I wasn't paying that much attention to the amps draw at the time but I think it was around 28 amps and I was about 90 seconds into the run. I was running an APC 10X7 electric prop. Thinking back I do recall the prop wash getting warm just before it died. I have also noticed on subsequent attempts the "arming tune" although telling me everything is fine is much quieter than before and the sound comes from the motor not the ESC.

is this normal? The timer seems fine in as much as it follows the programming sequence of zero revs for 30 seconds before attempting to run the motor. Slowly working through my stock of 30 year old planes the next one to get my attention will be my old Goldberg Buster currently home to a Copeman tuned MKIV Oliver Tiger, which I had planned to re equip with the same power train as the Flightstreak so I guess a comparable ESC or motor would not go amiss. I had been slowly increasing the prop from an 8X6 originally through a 9X6, 10X5.5 trying to get somewhere near the magical 150W per pound for as long as I could. I had only done 2 runs per night and after each run both the ESC and motor were only "warm" as they were when it all went belly up. Also the ESC talks to the programming card as normal. I'm heading towards thinking it might actually be the motor and as that's the cheapest option I will probably try that 1st, I'll also go ask my friendly model shop if they will allow me to connect one of their motors up to the power train. (I guess any cheap old motor would prove the point, just in case it's the ESC which has somehow destroyed the motor). I'm suprised doing static runs could have such a detrimental effect on the components, especially in a profile set up but I guess you live and learn.... Slightly out of pocket but still as keen as ever, thanks for the replies. It will be about a week before I get a chance to visit my local shop as I'm off for a mucky we.. erm romantic weekend away with my beloved but I'll get back into this next week.

Final question, Is there a magic formula I can apply which might indicate from a static run what I should see in the air as far as Amps/Watts/rpm etc are concerned?

Thanks again.

TTFN
John.

Alan Hahn · « **Reply #7 on:** November 06, 2008, 04:08:06 PM »

Quote from: John Hammonds on November 06, 2008, 02:15:55 PM

<snip>......

....... I have also noticed on subsequent attempts the "arming tune" although telling me everything is fine is much quieter than before and the sound comes from the motor not the ESC. is this normal?

......<snip>

Final question, Is there a magic formula I can apply which might indicate from a static run what I should see in the air as far as Amps/Watts/rpm etc are concerned?

Thanks again.

TTFN
John.

John,
Yes it is "normal" for the sound to come from the motor, it is the ESC pulsing the motor that causes the windings to vibrate. I have noticed that the sound volume depends somewhat on how I have mounted things, and sometimes sounds a lot quieter than others. So I am not sure if you can make a whole lot out of that.

I find that with the props I use and the fact that I use governor mode, that static watts tend to be the highest watts I get during the flight (during the vertical maneuvers). Level flight tends to be about 2/3 or so of the peak values. I don't think you are using governor mode .

I have used a similar motor (Scorpion 3014-16--but hand wound) on my Electric SuperClown. As I recollect, I am using the same APC 10-7 TE prop running at about 8600rpm and am pulling about 200 watts in level flight and ~300 watts peak. I'm flying just less than 5.0s laps on about 58 foot lines (need to look that up to be sure), and that feels pretty good.

Crist Rigotti · « **Reply #8 on:** November 06, 2008, 05:30:28 PM »

John,
Figure about 20% more wattage will be drawn on the bench than in the air at a given rpm. I find that it is less than 20%, somewhere around 15% from what I have found. Running them static gets them heated up real fast, especially at flight rpm and props.

John Hammonds · « **Reply #9 on:** November 07, 2008, 04:10:19 AM »

Thanks for the info, Not had chance to get to my local shop but spoke with an electrician friend this morning and we tested the continuity of the motor. It looks like there is a short between 2 of the phases. Just ordered a new motor and I guess this one will be put aside until I feel confident enough to try my hand at re winding it.

I think I have a ballpark figure now for some air time so hopefully the next post will relate to my 1st successful CL flight for 30 years and I don't end up taking it all home in a shoe box.

Thanks again

TTFN
John.

Alan Hahn · « **Reply #10 on:** November 07, 2008, 08:27:36 AM »

John,

The 3014 motor is terminated in a "Delta" configuration. That means that you will always have a connection between all phases! However check to see if there is a short between any phase (doesn't matter which you choose) and the stationary part of the case.

The wires coming out from the motor are actually the same wires as used in the winding, They are all soldered together at the bullet connector. Scorpion uses many strands of a ~30 gauge wire (15 strands on the 3014-16), so if you would look into the bullet connector (but don't!!!), you would see a total of 30 wires soldered together. In a 12 tooth motor, any one continuous wind is around 4 teeth making 6 sets of wires after all is wound (or 3 legs). Then to make the final termination (DELTA), one end from each leg is combined with the end of another leg to make three outputs. The net result is that all output wires then are connected in one way or another. Another mode of termination is the "WYE", but even that one will show a continuity between all three outputs. The only way to look for shorts between legs is before the termination into WYE or Delta is made. Since the resistances are so low for these windings, it is difficult (but not impossible if you have the right setup---and I don't) to look for resistance differences which would show up if there was a short.

In a motor like a Scorpion, NEVER cut the wires coming out of the motor (before the bullet connector). The main reason is that if you did that, you would then need to strip the enamel off 30 little teeny wires in order to resolder them back to the bullet connector. Again this is not impossible, but it is a major PITA!

So I am trying to think if you have any other options.

Take off the propeller, and see if the ESC can spin the motor. I don't expect this to actually work, but it would allow you to hook up to a smaller ESC (and not burn it out) to test the motor out.

By the way, I use a CC Phoenix 35 on my Nobler and it is just fine. On the SuperClown I am using the Phoenix 25. I mention that because it is cheaper than the 45A version. Of course if you want to move up to bigger planes, then the 45 might be a better option.

Mike Anderson · « **Reply #11 on:** November 07, 2008, 10:25:15 AM »

Delta or Wye - there is always a connection from any phase to each of the other phases IF there are no open windings. Nevertheless, it sounds to me that the problem is most likely in the motor and if it turns out to be the case, I would first check with your Scorpion dealer (or Lucien at Innov8tive, directly) and see about warranty service - it sounds as though you were running well within the limits and there is a two year warranty. Lucien has been extremely helpful to many of us.

Also, there is little chance of harming a motor/esc by bench-running it. Yes, the cooling might be slightly less efficient, yes you will be drawing somewhat more current than if in flight, but unless you are considerably over-loaded or over-voltage, you'll be well within the safety zone of most setups. A sixty amp ESC is plenty of overkill (even a cheap one), for a 300 watt setup.

Since you were running an "E" prop, we can even pretty much rule out vibration causing what I call a "rotor crash", where vibration-caused bending loads allow the magnets to strike the stator - I've only had that happen when using heavier propellors.

It sounds as though you just had the misfortune of a random failure, whether ESC or motor.

Richard Grogan · « **Reply #12 on:** November 07, 2008, 12:06:21 PM »

Testing a Brushless Motor--Somewhere I read that you can test a brushless motor by jigging up the motor on a teststand, hooking a drill up to the prop shaft and locking the drill on a set speed. Then measure the phases with an AC voltmeter. They should all be the same voltage, providing the drill speed isnt fluctuating. Be careful not to shock yourself! I suggest doing it at the lowest rpm the drill will lock on.
Sounds reasonably easy.

Alan Hahn · « **Reply #13 on:** November 07, 2008, 02:28:23 PM »

Quote from: Richard Grogan on November 07, 2008, 12:06:21 PM

Testing a Brushless Motor--Somewhere I read that you can test a brushless motor by jigging up the motor on a teststand, hooking a drill up to the prop shaft and locking the drill on a set speed. Then measure the phases with an AC voltmeter. They should all be the same voltage, providing the drill speed isnt fluctuating. Be careful not to shock yourself! I suggest doing it at the lowest rpm the drill will lock on.
Sounds reasonably easy.

Yes, that's a god idea--that might show if it all three phases are basically equal. If they are, then it isn't the motor.1000 rpm would give an output somewhere in the 1-1.4V range (don't remember my "rms" stuff exactly!) You do need to put your DMM into AC mode as you mention. However don't short the leads together while spinning. Also be careful that you don't damage the bearings, so the motor should be soft mounted--not rigidly fixed to a table.

Want to see something interesting? Unhook the three motor leads from the esc. Flip the prop and note how easy it rotates. Now short the 3 leads to each other and try the same flip. In the first case you are making voltage, but no current (output power=0). In the second case you are actually flowing current at a voltage so are outputting power. Also be careful that the back of the blade doesn't slice your fingers in the second case!

correction added above---a 1000kV motor would give about 1-1.4V @1000rpm, not 10-14 V. Need to think a little more before typing!

Richard Grogan · « **Reply #14 on:** November 07, 2008, 02:47:41 PM »

Quote from: Alan Hahn on November 07, 2008, 02:28:23 PM

Yes, that's a god idea--that might show if it all three phases are basically equal. If they are, then it isn't the motor.1000 rpm would give an output somewhere in the 10-14V range (don't remember my "rms" stuff exactly!) You do need to put your DMM into AC mode as you mention. However don't short the leads together while spinning. Also be careful that you don't damage the bearings, so the motor should be soft mounted--not rigidly fixed to a table.

Want to see something interesting? Unhook the three motor leads from the esc. Flip the prop and note how easy it rotates. Now short the 3 leads to each other and try the same flip. In the first case you are making voltage, but no current (output power=0). In the second case you are actually flowing current at a voltage so are outputting power. Also be careful that the back of the blade doesn't slice your fingers in the second case!

A little off-topic thought:
You know, its too bad they don't come out with a brushless motor with an auxillary set of coils(acting as an alternator) that could be used to run a onboard DC charger to keep the LiPo cells topped off! Now THAT would be something! You could fly until you get too tired!But, the weight of an 3-5 amp charger could be prohibitive!

Mike Anderson · « **Reply #15 on:** November 07, 2008, 03:23:16 PM »

Quote from: Richard Grogan on November 07, 2008, 12:06:21 PM

Testing a Brushless Motor--Somewhere I read that you can test a brushless motor by jigging up the motor on a teststand, hooking a drill up to the prop shaft and locking the drill on a set speed. Then measure the phases with an AC voltmeter. They should all be the same voltage, providing the drill speed isnt fluctuating. Be careful not to shock yourself! I suggest doing it at the lowest rpm the drill will lock on.
Sounds reasonably easy.

Good idea - Not much danger of shocking yourself at 1000RPM/volt or so - unless maybe you use a dentist's drill.

Alan Hahn · « **Reply #16 on:** November 08, 2008, 08:14:28 AM »

Quote from: Richard Grogan on November 07, 2008, 02:47:41 PM

A little off-topic thought:
You know, its too bad they don't come out with a brushless motor with an auxillary set of coils(acting as an alternator) that could be used to run a onboard DC charger to keep the LiPo cells topped off! Now THAT would be something! You could fly until you get too tired!But, the weight of an 3-5 amp charger could be prohibitive!

I always thought it would be a neat idea to add a brushless motor to the tail of the plane with a prop. Then when you were flying, the airstream through the rear prop could keep the lipo charged up--never have to come down!!

Mike Anderson · « **Reply #17 on:** November 08, 2008, 02:25:04 PM »

Quote from: Alan Hahn on November 08, 2008, 08:14:28 AM

I always thought it would be a neat idea to add a brushless motor to the tail of the plane with a prop. Then when you were flying, the airstream through the rear prop could keep the lipo charged up--never have to come down!!

Perpetual motion machine #364204859090 - better apply for a patent before someone else beats you to it.

Author Topic: I've blown something - or - stupid question part 2 (Read 1926 times)

John Hammonds

I've blown something - or - stupid question part 2

Dennis Adamisin

Re: I've blown something - or - stupid question part 2

Mark Scarborough

Re: I've blown something - or - stupid question part 2

Richard Grogan

Re: I've blown something - or - stupid question part 2

Alan Hahn

Re: I've blown something - or - stupid question part 2

Mike Anderson

Re: I've blown something - or - stupid question part 2

John Hammonds

Re: I've blown something - or - stupid question part 2

Alan Hahn

Re: I've blown something - or - stupid question part 2

Crist Rigotti

Re: I've blown something - or - stupid question part 2

John Hammonds

Re: I've blown something - or - stupid question part 2

Alan Hahn

Re: I've blown something - or - stupid question part 2

Mike Anderson

Re: I've blown something - or - stupid question part 2

Richard Grogan

Re: I've blown something - or - stupid question part 2

Alan Hahn

Re: I've blown something - or - stupid question part 2

Richard Grogan

Re: I've blown something - or - stupid question part 2

Mike Anderson

Re: I've blown something - or - stupid question part 2

Alan Hahn

Re: I've blown something - or - stupid question part 2

Mike Anderson

Re: I've blown something - or - stupid question part 2