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Old Feb 21, 2012, 06:40 AM
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Joined May 2011
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CW motors getting hotter than CCW motors

Hello everybody,
I finally started testing my heavy lift hexa today and I have noticed that the 3 CW rotating motors got much hotter than the other 3 CCW rotating motors. The setup is running Axi 2814/22 motors with APC 14X4.7, 25Amp plush ESCs with a hoverflypro. the total weight of the rig including the AV200 gimbal and the 2X14S 2650mAh batteries is 3.7KG.

Since I couldn't connect my flight logger system to the rig, I rewired all motors to a spare hitec optima receiver and set my Aurora 9 to my "esc programing" model which essentially outputs the throttle signal on all channels available on the receiver. I then connected to one battery through a power meter(other battery was on the frame but not connected to the distribution circuit) and did a very dangerous hover threshold "hand test" with this big monster. The hexa was lifting off and had significant lift thrust at about 34amp of power @ 15.2v(what was left in one of the batteries after the morning tests). So on average during hover, each motor is drawing about 6.5-7 amps @ 4S lipo level which is well within the range of the AXI motors as well as the 25amp ESCs.

What would cause certain motors(symetrically) to get significantly hotter than others when they are connected to the HFP? I set the ESCs to NiMH mode but with low timing and all are throttle range set using the same method described above.
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Old Feb 21, 2012, 07:08 AM
A man with too many toys
United States
Joined Feb 2001
17,624 Posts
Are you running low or medium advance?

Are all the ESC’s the same temperature?


.
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Old Feb 21, 2012, 07:18 AM
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Joined May 2011
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All on low timing. It was difficult to tell on ESC temp but I think the cw ones were slightly hotter, they were all warm. The motors however, especially one of the CW ones were much hotter than the other CCW ones.
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Old Feb 21, 2012, 10:29 AM
Sokratis
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Ελλάς, Κρήτη, Ηράκλειο
Joined May 2009
51 Posts
In the past i had the same problem..follow this instructions as George has write in previous post..recommend tilting the motors a few degrees in the opposite direction of the spin.and after a short flight check the temperature..if is still hot ..you must tilt in opposite direction..Sokratis
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Old Feb 21, 2012, 12:06 PM
Al Ducharme
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Orlando, FL
Joined Jan 2005
734 Posts
When CCW motors are a different temperature than CW motors there is an imbalance in the power causing one set of motors to work harder to maintain yaw. This is almost always because of 1. Need for ESC calibration. 2. A miss-alignment of the motors. They all need to be pointing exactly straight up.
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Old Feb 21, 2012, 12:10 PM
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Makes sense, it's just that they are all pointing straight up when visually examined, so I guess the issue is with a 1-2 degrees here and there and I didn't imagine it would make such a huge difference. I guess I have to use a tool to make sure they are in fact all straight. This is my first time using such large motors, do you think the low timing contributes to motor heat in general?
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Old Feb 21, 2012, 12:40 PM
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Just as a sanity check, I've just checked all angles of my motor mounts with a magnetic angle locator, and the interesting thing is that the only motor that has a major angle deviation is the one exactly opposite to the motor that got the hottest. This motor is tilted 4.5degrees in the direction of it's rotation(it rotates CCW and it's tilted 4.5degrees CCW), is this the actual problem? The rest of the motors are within .5-1 degree from the horizontal level of the board.

I would really appreciate any input here.
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Old Feb 21, 2012, 03:01 PM
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USA, FL, Winter Springs
Joined Apr 2006
3,066 Posts
Level is not the only requirement. Some motors may have a slightly higher or lower KV than the surrounding motors. I would adjust the tilt on your motors so that all of them are equal temperature.

Quote:
Originally Posted by IconFlyer View Post
Just as a sanity check, I've just checked all angles of my motor mounts with a magnetic angle locator, and the interesting thing is that the only motor that has a major angle deviation is the one exactly opposite to the motor that got the hottest. This motor is tilted 4.5degrees in the direction of it's rotation(it rotates CCW and it's tilted 4.5degrees CCW), is this the actual problem? The rest of the motors are within .5-1 degree from the horizontal level of the board.

I would really appreciate any input here.
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Old Feb 21, 2012, 07:55 PM
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USA, CA, Thousand Oaks
Joined Feb 2010
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Quote:
Originally Posted by IconFlyer View Post
Just as a sanity check, I've just checked all angles of my motor mounts with a magnetic angle locator, and the interesting thing is that the only motor that has a major angle deviation is the one exactly opposite to the motor that got the hottest. This motor is tilted 4.5degrees in the direction of it's rotation(it rotates CCW and it's tilted 4.5degrees CCW), is this the actual problem? The rest of the motors are within .5-1 degree from the horizontal level of the board.

I would really appreciate any input here.
Sorry can't be much help, I'm curious about the "magnetic angle locator," what is it, how do you use it and where do you get it?

I think CG might play a role as well as airflow.
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Old Feb 22, 2012, 11:53 AM
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USA, NY, Poughkeepsie
Joined Jan 2008
83 Posts
When I closely examine all the outrunners I own, it appears they are ported at angles to create max. airflow through the inside of the case for better cooling. I think running these motors in the opposite direction of how these are ported may reduce airflow and cooling effect, thus making one set of motors run warmer than the other set. Does anyone else feel this may be true?
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