BL cogging - RC Groups
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May 05, 2012, 11:08 AM
Registered User

BL cogging

I smacked an eflite 400 BL into the ground yesterday; broke the prop and destroyed the plane. Now it won't turn freely; I think the term is "cogging" but at any rate it turns maybe 15 degrees, then a hitch, then 15 more. Have i destroyed it completely? If not, what do I do NOW?


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May 05, 2012, 11:20 AM
Wake up, feel pulse, be happy!
Piece's Avatar
Does it make any noise or notceable mechanical grinding, or does it just feel like the usual magnetic cogging?

Have you tried running it?
May 05, 2012, 04:03 PM
modisc's Avatar
Originally Posted by C₄H₁₀
Does it make any noise or notceable mechanical grinding, or does it just feel like the usual magnetic cogging?

Have you tried running it?
24 cogging per revolution (15 degree each), is normal for a 12N8P motor
May 05, 2012, 11:14 PM
Registered User
No noise; ddin't want to run until I was sure it wouldn't be hurt worse.

May 06, 2012, 06:35 AM
jackerbes's Avatar
If you have a multimeter set it for Rx1 and touch the probes together, you should see a low resistance of a fraction of an Ohm or so.

Check two motor leads with the probes and check all three pair combos (1-2, 1-3, 2-3). All should read about the same as the shorted probes and have steady values. It one is way higher or the numbers are dancing around you have a short somewhere and don't want to power it up. A shorted motor can kill your ESC if it is still alive.

If you pass that test and the motor will turn, short the three motor leads together. The cogging should become a little lighter and be the same all the way around.

At this point you have a chance that it is OK. Connect to the ESC and power up, if the ESC arms itself it is seeing a apparently normal motor connected. It it will not arm itself, there may be a problem. I would quit there and take the motor apart...

If it armed itself, open the throttle one click and close it immediately. If it ran momentarily and there is not heat or smells you may be OK. Try adding click one at a time and for longer periods check for smells and heat in the motor and ESC.

If the bearings are damaged you might not hear that until you have a prop on it that pulls a load on the bearings.

May 08, 2012, 04:46 PM
Registered User
Thanks for all the advice; I will file it away for future reference.

As far as this one is concerned, the ESC armed normally, but the vibration was not to be believed. Time to remove the connectors and wire, and toss the motor.


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