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Old 11-18-2006, 03:16 PM   #1
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Default Brushless TC Help Needed!

I run a T2 with a GTB and Novak 13.5 brushless motor on rubber tires on carpet. I have been hearing a noise that sounds remarkably similar to a belt skipping when squeezing the throttle from a dead stand still to full throttle. The car also seems to hesitate a bit when i hear the noise. Once the car is up moving, i no longer hear the noise when cycleing the throttle. I have taken the car completely apart and can find no mechanical issues with the car. A further point of interest is that a friend was running the same car, tires, gearing and motor and was noticeably faster in the straights than I was. We both have 4200 batteries with very good numbers, but mine are only 2 cycles old whereas his have several cycles on them. The only other variable is that he was running a LRP Sphere Competition speed control. My questions are 1) could the motor be "cogging" if so, what is the cause of this? 2) due to space constraints the large diode that is hooked to the speed control is touching the motor. Could the heat from the motor have damaged the diode and be causing this issue. Any help or similar experiences would be greatly appreciated since I am out of things to try.

Scott
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Old 11-18-2006, 03:40 PM   #2
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You say it sounds like belts skipping, have you tryed tightening them to see if that helps?
Also make sure your diffs are adjusted properly.
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Old 11-18-2006, 04:22 PM   #3
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It's very common for diffs to slip because of the massive torque brushless motors generate, especially from a standstill. Try tightening your diffs a bit and see if that helps with the problem.
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Old 11-18-2006, 04:51 PM   #4
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I just picked up the Losi Brushless XXXT RTR. It uses the SS 10.5 E.S.C / SS4300 combo. So far, I've run 4 packs through it. It is acting up the same way you describe yours. Mine is also acting like a hung brush. Once I get it going everything is fine. If I come to a complete stop for a few seconds, pull trigger and I get no throttle response. At this point, if I give it a little shove it will work fine. At first I suspected my Nomadio Sensor...I was thinking that the time it takes to "connect" might be interfering somehow with programming the E.S.C. When I got home from practice today, I put the stock Jr radio in, and it still acted this way. I now suspect the motor is the problem. Anyone with any kind of BL experience have a clue/suggestions, your input is much appreciated.
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Old 11-18-2006, 05:18 PM   #5
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I did tightened the belts a notch to make sure that wasn't the problem and the problem still persisted. I also installed a brand new 13.5 which did not cure the problem either. Has anyone had this experience with the GTB? I guess that's next on my list to replace.
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Old 11-18-2006, 05:34 PM   #6
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You have a bad motor. Thats what they call cogging. You have to send it in to Novak and get it fixed. I had 2 of them do the exact same thing. Now they run great
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Old 11-18-2006, 05:41 PM   #7
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they make a up graded rotor that will correct that, mine does that but only from a standing start and only clicks a few times, it runs great otherwise so it doesn't concern me. novak says you can try advancing the timing to correct it also.
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Old 11-18-2006, 07:21 PM   #8
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thanks guys for all your help, I do have a couple more questions:

1. What causes the cogging? Is this just a manufacturers defect?
2. How do you increase the timing? Is this harmful to the motors?
3. Which upgraded rotor works on the 13.5? is it the same as the 4.5, 5.5, etc? Is this the "sintered" rotor?

Thanks again for all your help.

Scott
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Old 11-18-2006, 07:30 PM   #9
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cogging is usually caused by a bad sensor in the motor or one of the sensor wires going to the speed controller has a poor connection. to increase the timing loosen the 3 screws on the wire end of the motor and turn the black ring with the grooves on it opposite of motor rotation. The 3.5 rotor is the correct replacement. Timing shouldn't make the motor cog
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Old 11-19-2006, 03:40 PM   #10
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I have had a similar problem with the 5800 SS version. Mine is quite old-3 years or so.
It was a bit slow to accelerate and had a noise like you describe, also was causing a bit of glitching on the radio and getting very hot.
I thought it sounded alot like an industrial brushless servo motor, when the gains and limits are not adjusted properly/or filthy dirty.

I stripped the motor down, cleaned out all the dirt from inside the windings with motor spray. It was filthy! Put a new bearing in the front also, it is now running "as new-perfect". I would describe the difference to be like an old 27 turn with 30 runs on it to a newly rebuilt motor.

I would suggest to take the motor apart reasonably frequently to prevent this build up, dirt and dust can make their way inside the open mounting bolt holes. Carpet dust is especially bad for this.

Regards,
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Old 11-19-2006, 05:08 PM   #11
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Quote:
Originally Posted by Matt Dall
I have had a similar problem with the 5800 SS version. Mine is quite old-3 years or so.
It was a bit slow to accelerate and had a noise like you describe, also was causing a bit of glitching on the radio and getting very hot.
I thought it sounded alot like an industrial brushless servo motor, when the gains and limits are not adjusted properly/or filthy dirty.

I stripped the motor down, cleaned out all the dirt from inside the windings with motor spray. It was filthy! Put a new bearing in the front also, it is now running "as new-perfect". I would describe the difference to be like an old 27 turn with 30 runs on it to a newly rebuilt motor.

I would suggest to take the motor apart reasonably frequently to prevent this build up, dirt and dust can make their way inside the open mounting bolt holes. Carpet dust is especially bad for this.

Regards,
If anyone is planning on returning a motor under warrenty do not use motor spray to clean it. Paperwork that comes with the motor warns not to do this, could possibly damage the electric"s inside the can.
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Old 11-19-2006, 05:48 PM   #12
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Quote:
Originally Posted by Robd347
If anyone is planning on returning a motor under warrenty do not use motor spray to clean it. Paperwork that comes with the motor warns not to do this, could possibly damage the electric"s inside the can.
Granted, point taken; do beware of this!
If the motor is new, or you want to try and get a warranty on a 2 year old motor then send it back.

If you take the risk and don't mind to tinker;
Most specific electrical cleaners should be acceptable, as they are used to clean the circuitry of electronic components far more sensitive and expensive than a simple hobby motor! Remember that "brushless is not new technology" just new to RC.

Do be aware that common solvents like shellac or acetone can dissolve coatings on wiring circuits.

Regards,
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