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Thread: MMP Sensored, randomly started to cog terribly.

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Old 07-28-2014, 11:13 PM   #1
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Default MMP Sensored, randomly started to cog terribly.

So I have a MMP, I was running a Novak 13.5T motor in sensor only mode. Worked GREAT for about 1.5 months. Packed it up last Sunday for a trip to visit family, tried to run it Thursday, cogged like a sensorless system.
Funny thing is, when I unplug the sensor wire, it doesn't work at all. So at least some of the sensor had to be working. I figured the motor went bad, since it is an old Novak motor.

I caved in and bought the motor I wanted from the start, Tekin Roc412 2300Kv. Got here today, and it's still doing the exact same thing.

Better explaination of symptoms: Very bad cogging (stuttering) and very poor low speed performance. Sudden onset while not being used. When I quit running it on Sunday it worked fine. Turned it on Thursday and it wasn't working correctly.

I called Castle, the guy started off trying to blame my servo, so I unplugged it. Then tried to blame the radio, so I changed Tx/Rx. Luckily he didn't try to blame the motor since I already told him this is the 2nd motor, and it's brand new. Changed all the settings in the Castle Link, tried TONS of firmwares.

Finally, I reverted back to a much older firmware, plugged in the battery, and it worked even worse. Motor just made some noise with throttle applied. Thought that was odd, reached down, and the wires were warm...after about 3 seconds. Immediately unplugged the battery, and cussed out the ESC in frustration.

Figured I would ask here for any input before I waste money sending it in to castle (MAN! their repair prices have skyrocketed recently....).

Leaving town for a day, so it will be a bit before I get back on. I'm also a little worried about even plugging the ESC back in after what happened at the end...
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Old 07-28-2014, 11:59 PM   #2
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Default Re: MMP Sensored, randomly started to cog terribly.

I had mine do the same thing in my short course truck. I even replaced all the wires just in case. I had been running this motor/ esc for a couple years. I replaced it with a pro4 hd and rx8 in the SC truck. But I would look for the traxxas version of the mmp on ebay. About $64 shipped vs the $75 from castle.
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Old 07-29-2014, 02:29 AM   #3
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Default Re: MMP Sensored, randomly started to cog terribly.

My very first suspicion when getting that cogging would be that the sensor wire cause the problems. Those wires are weak and glitches are common.

Assuming you replaced the sensor wire with the motor then that's not to blaim in your case.
The ESC seems to be the problem, and if it's just two months old it should be a warranty issue.
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Old 07-29-2014, 02:53 AM   #4
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Default Re: MMP Sensored, randomly started to cog terribly.

Quote:
Originally Posted by Olle P View Post
My very first suspicion when getting that cogging would be that the sensor wire cause the problems. Those wires are weak and glitches are common.

Assuming you replaced the sensor wire with the motor then that's not to blaim in your case.
The ESC seems to be the problem, and if it's just two months old it should be a warranty issue.
ditto to this
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Old 07-29-2014, 07:23 AM   #5
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Default Re: MMP Sensored, randomly started to cog terribly.

Thanks guys, it's not the sensor wire. That was my original suspicion on the Novak motor, since the sensor wire is permanently attached to the endbell. But the Tekin motor came with a new sensor wire, and I even had a spare in my tool box that I got in a trade. No improvement. Though when I unplug the sensor wire entirely it fails to work at all.
As for the possibility of a warranty repair, I bought the ESC used but new, was in original packaging, and had never been soldered to.
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Old 07-29-2014, 08:10 AM   #6
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Default Re: MMP Sensored, randomly started to cog terribly.

Quote:
Originally Posted by Brainanator View Post
Thanks guys, it's not the sensor wire. That was my original suspicion on the Novak motor, since the sensor wire is permanently attached to the endbell. But the Tekin motor came with a new sensor wire, and I even had a spare in my tool box that I got in a trade. No improvement. Though when I unplug the sensor wire entirely it fails to work at all.
As for the possibility of a warranty repair, I bought the ESC used but new, was in original packaging, and had never been soldered to.


Mine did this, Go into the castle link software and make sure you're set to sensored, not smart sense, then go and change your start power from low which is default to high, it should stop.
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Old 07-29-2014, 08:16 AM   #7
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Default Re: MMP Sensored, randomly started to cog terribly.

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Originally Posted by Brainanator View Post
... Though when I unplug the sensor wire entirely it fails to work at all.
That's fine, as the ESC is set to sensored only.
In SMART mode it should run fine (with some cogging) without the sensor.
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Old 07-31-2014, 08:35 AM   #8
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Default Re: MMP Sensored, randomly started to cog terribly.

Changing start up power to high decreased cogging, but it will still do it. But now it just takes off like a rocket with the smallest amount of throttle input. As soon as the green LED on the ESC comes on it shoots across the room...Throttle is calibrated correctly. 0 expo on radio with linear throttle curve on ESC.
So frustrating considering it worked great when I turned it off Sunday, and it didn't work worth a crap when I turned it on Thursday. I guess that's the nature of the hobby.
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Old 07-31-2014, 11:00 AM   #9
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Default Re: MMP Sensored, randomly started to cog terribly.

My setting are sensored only, default deadband, start power high, linear throttle curve with 10% minimum. Works great though I do run 4s. I would call Tekin and ask if the motor has any advance timing set from the factory. The old redline I run did.
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Old 07-31-2014, 11:13 AM   #10
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Default Re: MMP Sensored, randomly started to cog terribly.

Same issue with 2 different motors, one of which worked great last weekend.
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Old 07-31-2014, 11:41 AM   #11
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Default Re: MMP Sensored, randomly started to cog terribly.

I just ripped apart my SC truck and found the rear diff pinion bearing completely trashed. I think that is what might have been causing my issues. I did buy a new rx8 and HD pro 4 so I need to try the old. Combo in something else.
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Old 07-31-2014, 02:32 PM   #12
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Default Re: MMP Sensored, randomly started to cog terribly.

When I hard the motor out I checked all the gears by hand. Everything is super smooth. Wish it were something as easy as a diff pinion.
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Old 08-06-2014, 02:34 PM   #13
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Default Re: MMP Sensored, randomly started to cog terribly.

Ended up buying a new MMP from Amazon. Cost me $5 extra over the repair fee charged by Castle. Really sad to see the days of affordable repairs are gone. Was a huge selling point for me. I knew that if my Castle stuff ever broke I could get them fixed for about half of the price of a new one. Now you just save $5 and waste weeks waiting for it.

I will keep this shoddy one on hand, the issues I'm having won't be an issue on a non-crawling RC.
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