Thread Tools
Nov 17, 2012, 01:40 PM
Registered User
Cry_Wolf's Avatar
Help!

SK3 Motor losses power as soon as it starts


Hello everyone, I'm new to this forum and I wish I could have a better topic for my first thread but I really need help with this.

Well, I have an Aerodrive SK3 2836 1040kv with an 11 x 4.7 GWS type prop (a little bit heavier than a GWS) hooked to a AE 35A ESC and finally to a 3 cell 3000 mAh Turnigy NANO LiPo batt.

The math says that this setup should work correctly and push up to 1.2/1.3 kg. Problem is: The motor losses power and then regains it and this cycle takes up like half a second or even more, and it repeats itself again and again, making it impossible to go up because it losses power, stalling the plane and when the power comes back I'm at the exact same altitude.

I've tested using different props, batteries, ESCs and the problem is still there, that's why I think it's the motor itself. Anyways, as I'm no expert on this EP flight field I'm asking you guys.

I don't know if I explained myself well, please tell me if you need more information.

Edit:
Here's a video so you can understand what I'm trying to explain
SK3 Failure (0 min 5 sec)

The stick is all the way up till the end of the video (so that last power loss is still part of the problem)
Last edited by Cry_Wolf; Nov 17, 2012 at 01:59 PM. Reason: Added video
Sign up now
to remove ads between posts
Nov 17, 2012, 02:04 PM
Dude, I do fly all day long!
rcalldaylong's Avatar
I take it you've already tried a smaller prop.

a few things that can cause this:

#1Lipo isn't up to the amp draw (cuts out when drawing high amps)
I doubt this is the issue here. your 3000mah 3s should be fine.

#2 amp draw is too high for ESC and ESC is cutting power so it does not fry itself.
If you've tried a smaller prop then probably not it.

#3 there's a bad solder in one of the motor wires to ESC.
resolder just to be sure...or at least pull on it to make sure it's solid

#4 There's a break in the windings in the motor itself.
This would be harder to test, but you could do it. Take a meter and select AC. use a drill of some sort and spin up the motor. measure current coming from the motor (do wire 1 and 2, then 1 and 3, 2 and 3,) the measurement should be very close.

Edit (after seeing your vid)
Get a wattmeter. more than likely you're pulling too many amps and either your ESC or Lipo isn't up to the task. or if you have a huge ESC, try that.
Nov 17, 2012, 02:13 PM
Registered User
Cry_Wolf's Avatar
Quote:
Originally Posted by rcalldaylong
I take it you've already tried a smaller prop.

a few things that can cause this:

#1Lipo isn't up to the amp draw (cuts out when drawing high amps)
I doubt this is the issue here. your 3000mah 3s should be fine.

#2 amp draw is too high for ESC and ESC is cutting power so it does not fry itself.
If you've tried a smaller prop then probably not it.

#3 there's a bad solder in one of the motor wires to ESC.
resolder just to be sure...or at least pull on it to make sure it's solid

#4 There's a break in the windings in the motor itself.
This would be harder to test, but you could do it. Take a meter and select AC. use a drill of some sort and spin up the motor. measure current coming from the motor (do wire 1 and 2, then 1 and 3, 2 and 3,) the measurement should be very close.

Edit (after seeing your vid)
Get a wattmeter. more than likely you're pulling too many amps and either your ESC or Lipo isn't up to the task. or if you have a huge ESC, try that.
#1
I have a 3300mAh 4s LiPo of the same brand, the problem is still there

#2
ESC is 35A max, motor max is 28A, the setup -should- be drawing 26A at max load. Anyways, already tried with a smaller prop and the problem is still there.

#3
Will check that

#4
Will check that too

And I will also check the edited part. I have a Turnigy Trust 70A on my MQ-9 Reaper, will try with that one.
Nov 17, 2012, 02:26 PM
Registered User
Cry_Wolf's Avatar
Ok, stop everything.

I changed the receiver (as a random test) and that power loss isn't there anymore but after a 2 minute run at full throttle the motor almost fried itself.

Are those 2 separate problems?
Nov 17, 2012, 02:29 PM
I don't want to "Switch Now"
pmackenzie's Avatar
2 minute full power static run with little or no cooling is too long.
Nov 17, 2012, 02:36 PM
Registered User
Cry_Wolf's Avatar
Quote:
Originally Posted by pmackenzie
2 minute full power static run with little or no cooling is too long.
Well, I guess maybe. Flying it at 35C ambient with the cooling it has (I believe it's a good cooling) should be more than OK.

Thank you guys (Even when I still don't know why it worked with the other receiver)
Nov 17, 2012, 04:04 PM
Registered User
Dr Kiwi's Avatar
This from a contributor to HK: With a TP Slow Fly propeller 11x4.7 and 3s 2200mah 25C thrust 1150gr and 28A,

So you are right on the 28A [?optimistically] rated limit for the motor.. and since it is an 80g motor (using 3W/g that says 240W max).. you are really pushing it with that 11x4.7... over 300W at 35C ambient will surely fry it.
Nov 17, 2012, 04:56 PM
Registered User
Cry_Wolf's Avatar
Quote:
Originally Posted by Dr Kiwi
This from a contributor to HK: With a TP Slow Fly propeller 11x4.7 and 3s 2200mah 25C thrust 1150gr and 28A,

So you are right on the 28A [?optimistically] rated limit for the motor.. and since it is an 80g motor (using 3W/g that says 240W max).. you are really pushing it with that 11x4.7... over 300W at 35C ambient will surely fry it.
Time for a bigger motor I guess. Math says that a 10 x 4.7 goes up to 20A draw, which is less than the 27A that the 11 x 4.7 draws. That's enough to get the motor working at acceptable temps (but not enough to move my motor glider).

Again thank you guys for receiving me and answering my doubts.
Nov 17, 2012, 05:02 PM
Dude, I do fly all day long!
rcalldaylong's Avatar
Quote:
Originally Posted by Cry_Wolf
Time for a bigger motor I guess. Math says that a 10 x 4.7 goes up to 20A draw, which is less than the 27A that the 11 x 4.7 draws. That's enough to get the motor working at acceptable temps (but not enough to move my motor glider).

Again thank you guys for receiving me and answering my doubts.
Quite honestly if you didn't fry it after 2 mins of straight running on the ground, it'd be pretty hard for you to fry it in the air. I doubt you'll WOT all the way..and it'll unload some + you'll have airflow. I'd fly that setup and test to see how it comes down.
Nov 17, 2012, 05:58 PM
I don't want to "Switch Now"
pmackenzie's Avatar
Quote:
Originally Posted by rcalldaylong
Quite honestly if you didn't fry it after 2 mins of straight running on the ground, it'd be pretty hard for you to fry it in the air. I doubt you'll WOT all the way..and it'll unload some + you'll have airflow. I'd fly that setup and test to see how it comes down.
In a glider you pretty much run WOT, but only for 30 to 45 seconds.
Our club rules spec a maximum 68 gram outrunner for contests, and we all run about 250 watts with no problems.
If you run them on the ground for that long they get quite hot, but the prop unloading a bit in the air combined with the short run and everything runs fine.

But do yourself a favour - ditch the GWS style prop and get a folder

Pat MacKenzie
Nov 18, 2012, 01:34 AM
Registered User
manuel v's Avatar
An APC sf 11x4.7 has a limit of only 5909 rpm.
To 70% Of efficiency only need a motor of a Kv of 745 using 3slipo.

If the engine is sufficiently large and 1040 kV, this would turn with 3slipo to
about 8230 rpm and consume a few 30-32A.

With 4s lipo consume 55A 10850 RPM.

For an engine of this Kv is best to use propellers of type E.
As the APC E 11x5.5 to consume around 25A.

Manuel V.
Nov 18, 2012, 08:12 AM
Registered User
Cry_Wolf's Avatar
Quote:
Originally Posted by pmackenzie
In a glider you pretty much run WOT, but only for 30 to 45 seconds.
Our club rules spec a maximum 68 gram outrunner for contests, and we all run about 250 watts with no problems.
If you run them on the ground for that long they get quite hot, but the prop unloading a bit in the air combined with the short run and everything runs fine.

But do yourself a favour - ditch the GWS style prop and get a folder

Pat MacKenzie
I do 1 or 2 mins full throttle ascends, that's why I became concerned about the temperature, plus it's not a contest glider (Nor do I participate in contests), it's a 118" high performance thermal glider that we converted and added a motor to. It's quite a beast and it requires 2 or even 3 minutes at full throttle to get to the altitude we want it to be.

I'll try to get a folder anyways, but they are pretty expensive here.
Nov 18, 2012, 08:30 PM
I think I'm inverted. Maybe.
acetech09's Avatar
That pulsing often is a ESC's low voltage cutoff telling you that it's too low voltage. I helped a friend with that same issue a few weekends ago, turned out his pack had a dead cell. You said you tried multiple batteries, we did too. Turned out that all 3 of the Sky Lipos he had (all same order) were defective.
Sep 22, 2016, 05:03 AM
Registered User
Hi,

i'm going to use this motor to my thermic glider Deamon2000 with 10x6 prop and 40A ESC.
what's your idea?? please advice me is this good power setup or bad 1??
Sep 22, 2016, 09:04 AM
http://www.sgvhumane.org/
cmdl's Avatar
What is your current draw?
335 W motor: http://www.hobbyking.com/hobbyking/s...ner_Motor.html
1.76 lb glider: http://www.hobbyking.com/hobbyking/s...00mm_ARF_.html
190 W/lb: You don't need that much, look for a lighter motor. 120 W capable motor is about all you need.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold will be back up for sale soon as a running rig rc4life85 Cars - Trucks and Parts (FS/W) 0 May 21, 2012 11:53 PM
Discussion UM-T28 motor powers as soon as power is supplied Ste Hughes Micro Ready-to-Fly 3 May 19, 2012 11:22 AM
Discussion New WK-M: Every motor on the XA Hexa starts up as soon as it's powered up. brianshell Multirotor Drone Talk 8 Jan 15, 2012 03:11 AM
ESC (Griffin) goes to full power as soon as battery is hooked up? Andy W Vendor Talk 2 Mar 28, 2003 02:33 PM