10 replies to this topic

[Gary Donahoe]

Recently some others and I have come across new Top Secret Intimidator motors that will not start running unless the armature is manually spun. This is not an occasional problem, it happens every time the armature stops.

 

Could this be caused by excessive commutator timing or perhaps brush orientation? Is it possible that track running to better seat the brushes could solve this problem?

 

 

[Bill Seitz]

Motors that fail to self-start but run after the armature is spun usually have a dead pole. Typically that happens as the result of "burning/blowing" the motor, but in this case it sounds like a manufacturing defect where one of the pole windings has a bad connection at the comm or a broken wire. The motor will also not run at full rpm. Brushes or a dirty comm might be a cause, but that usually is a case where the motor won't start running until the voltage is cranked up or not at all, and then slowly. It's possible for excessive timing also, but I've yet to see a motor where the timing was so far off it wouldn't run. Brushes and timing also can cause a lot of arcing which is also visible with the motor running.

 

I believe this motor has an oval hole can. It is possible to orient the motor to get a look at the brushes. I regularly examine crimped endbell motors using a work light with magnifier. JK Products also sells an Otoscope for this purpose (an instrument for examining inside the ear canal also available from other sources and Amazon). If the brushes are broken or misoriented (not positioned squarely over the comm) that will be visible. Generally though, brush problems cause poor running or not running at all, not a self-starting problem.

 

Unfortunately, the most likely cause is the dead pole. It's very unlikely any additional break-in running or anything else the user can do will correct this problem.

[Gary Donahoe]

Thank you, Bill, for this information.

 

There are no obvious issues when looking through the oval can hole with geezer goggles and a bright light. After you get it running on a power supply it seems to run smooth and normal, but perhaps it needs more of a load to diagnose a dead pole. If it had a dead pole wouldn't it self-start when the commutator is rotated away from that pole?

[Eddie Fleming]

Just a question.

 

Could the comm be our of round and not making contact all round as it should?

[Gary Donahoe]

Eddie, when I turn the motor the brushes seem to run true, and following the comm.

[Hot Slots]

Its a common problem with that motor.

[Bill Seitz]

If the motor were not stopped on the dead pole comm segment, it probably does start to rotate, but as soon as it reaches the dead pole, it stops. The armature has to have some momentum to travel past the dead pole comm segment to one what works. A severe contamination that prevented the brushes from contacting a single segment, or some other ailment that causes the same thing would result in the same symptom, but I've never seen such condition. An out-of-round would need to be extremely severe and again not likely. Another possibility that I have experienced is a thrown comm segment, but that's going to cause more problems than just failing to self-start, and I've yet to see a new motor with a missing segment. Again, the reason a missing comm segment causes the same symptom is it's a dead pole. Dead pole is really the only practical cause. In manufacturing, if the wire insulating varnish doesn't get stripped clean where it connects to the comm tab or any other insulating contamination in the joint between comm tab and wire occurs, then a pole will be disconnected and this problem results.

 

Today, very few products receive 100% quality control inspection. Product integrity depends on manufacturing workmanship and process control. At best, only a small sample may be quality control inspected/tested. This allows defects to pass through to the customer unless the manufacturing process is near perfect. Some manufacturers rely on build process that is good enough to not create many defects and find it far cheaper to simply replace an occasional defective item that reaches the customer than to provide more quality control. Other manufacturers simply do not care about customers receiving defective products. That's the customers' loss. In this case, it's buyer beware.

[Ramcatlarry]

How is the magnet strength?  If the air gap is too small from shimming or crimping, that might contribute to the stall.

[Dave Crevie]

Didn't we have this discussion once before, involving the Pro Slot 4002FK? Seems it would not start after a track call or lane change. Anyone remember? I can't find it.

[MSwiss]

Dave,

That wouldn't apply.

 

The 4002FK has replaceable brushes. 

 

The Top Secret Intimidator is a true FK motor.

[Gary Donahoe]

Thanks to all for their input.

 

My quest to understand the cause of this problem led me to open the can. On inspection everything seemed as it should be. Next, I opened another Intimidator motor that had run 10 races and near the end of its brush life, and swapped armatures with the new motor. The spin to start problem followed the armature to the old can. I suspect Bill’s theory of a bad connection at the comm tab is the most likely culprit.

 

Just for the sake of curiosity I might have a go at trying to improve the comm connections.