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Electric motor shutdown?

Old 03-21-2010, 10:55 AM
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dieFluggeister
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Default Electric motor shutdown?

I have recently developed a problem in my setup that has worked well until now.

I have a BM2408-21 (1750kv) Outrunner.

When connected to any of my ESC's (which are 15A and 25A) the motor will start turning, then shut down. I can reset it by moving the throttle to 0%, but can never advance the motor past about 10%.

Batteries are fully charged, have more than enough C rating, and I have tried operating on both 11.1v and 7.4.

With a watt meter attached and the motor is started, voltage only drops 0.2v and the motor pulls a max of 14W at 1.2A before it shuts down.

What could be happing here guys?
Old 03-21-2010, 11:53 AM
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dignlivn
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Default RE: Electric motor shutdown?





Is the ESC arming ?

Are you using a BEC ?


Bob
Old 03-21-2010, 11:59 AM
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dieFluggeister
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Default RE: Electric motor shutdown?

Thanks Bob,

Yes, the ESCs are arming just fine and both of them have BEC. I am testing the motor using two proven ESCs and getting the same result with each.

Edit - Oh and I am watching the voltage from the batts during testing and they do not dip below 11V at any time.
Old 03-21-2010, 12:05 PM
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dignlivn
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Default RE: Electric motor shutdown?




Is the motor brushed or brushless ?


Doesn't sound like the LVC is shutting it down.

Bob
Old 03-21-2010, 12:10 PM
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dieFluggeister
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Default RE: Electric motor shutdown?

Its a brushless (albeit cheap) outrunner of +/- 150W. Good performing motor until now.

Dimension: Ф30.6*62
Max Efficiency: 80%
Length : 6.5cm
Diameter : 3.5cm
Weight : 72 g
Working voltage : 7.2-12.6v
Shaft Diameter : 2.9mm
Battery : 2-3 LIPO
Speed constant : 1750 rpm/v
Propeller 2 LIP09 x 4 / 3 LIP08 x 4



Update - I got it to run inconsistently without the prop, so I started checking bearings. I found that the shaft was out of true ever so slightly, and there was side-play in the bearings only enough to make it give a tiny 'click' when moved. End play was about 1mm. Neither of the bearings sounded like they were gritty or turned poorly. When I put a spot of lithium grease on them and reassembled the motor, it ran for a short time on full throttle and then shut off again.

Could these issues be explained by the small amount of bearing play I found?
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Old 03-21-2010, 03:29 PM
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dignlivn
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Default RE: Electric motor shutdown?





I suspect the Motor going bad.


Just for kick, reverse 2 wires and see if it
will run backwards at full power.


Bob
Old 03-21-2010, 06:38 PM
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Default RE: Electric motor shutdown?

Hello gents, I am having a similar problem. I recently got an ARF TW 748-1 F4U Corsair, I put a AX 2308N brushless 1800kv motor with a Turnigy Sentry 18a esc all running on an 11.1v 1800mAh lipo and a 9x4 prop when I go to full throttle wih prop installed it makes a loud sqweel and the motor stops when I retard the throttle and then push it up again the motor works fine till full throttle is applied, without the prop installed the motor runs fine, is this too much of a load for the esc to handle? Also can you tell me when they talk about a motors poles is that the number of magnets the motor has? When a motor is installed should it be kept inside the cowling of the plane or is it OK for it to stick out a bit. When I mounted the motor on the stick mount it seems as though the stick mount is a little too long and the motor sits outside of the cowling a bit not too far but it does stick out. I know this is alot of questions but I am new to this and I want to make sure I am doing the right thing when I attempt to fly this plane after I learn the basics on a Hobbyzone mini supercub and then move on to the fullsize supercub. Thanks!
Old 03-21-2010, 09:00 PM
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dieFluggeister
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Default RE: Electric motor shutdown?

Well I talked with 'the guy' at my local hobby shop. He was of the opinion that the very small play I have detected is causing problems with the ability of the motor to sync. I greased the bearings and I got the motor to go to WOT for a short time then the same problems reappeared. I am guessing since I had bent the shaft with a hard landing slightly and that eventually lead to a failed bearing. I could replace the bearing and shaft, but the cost is nearly the price of the motor itself. Therefore I think this motor is headed for the trash bin. I wish I would have detected that shaft sooner. From now on I'm balancing my props regularly and checking the squareness of the prop after every session!
Old 03-21-2010, 09:52 PM
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jimmyjames213
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Default RE: Electric motor shutdown?

this will happen if your solder connections arnt good enough (motor cant get enough current)
Old 03-23-2010, 09:27 AM
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dieFluggeister
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Default RE: Electric motor shutdown?

Well, I am glad you posted Jimmy! As I was removing the motor to unceremoniously throw it in the trash, I took some time to pull the bell housing off and inspect the contact points inside the motor. To my amazement one of the leads was hanging on by one or two wire strands underneath the shrink tubing. In fact it came apart in the process of my inspection.

I took some time and resoldered it as best I could, and low and behold, it ran just fine. I dont know how much more life I will get out of it, but it learned me a good lesson. thanks for your posting.

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