New Kato Mikado 3rd run engine

[peteski]

I have never seen a coreless motor using carbon brushes.  Some have a small black (rubber?) price glued to them ,but that *DOES NOT* contact the commutator and it is probably some sort of vibration dampening device.  The metal fingers still contact the commutator.

 But the largest coreless motor I ever dealt with was I think 16mm diameter.

[Point353]

I have never seen a coreless motor using carbon brushes.  Some have a small black (rubber?) price glued to them ,but that *DOES NOT* contact the commutator and it is probably some sort of vibration dampening device.  The metal fingers still contact the commutator.
But the largest coreless motor I ever dealt with was I think 16mm diameter.

It would appear that Canon coreless motors are available with either metal or carbon brushes:
https://prec.canon/en/products/coreless.html

[narrowminded]

I have never seen a coreless motor using carbon brushes.  Some have a small black (rubber?) price glued to them ,but that *DOES NOT* contact the commutator and it is probably some sort of vibration dampening device.  The metal fingers still contact the commutator.

 But the largest coreless motor I ever dealt with was I think 16mm diameter.

The largest I fooled with in this way was, I think, 8mm.   6, 4, and 3.2mm were my main focus.  And recollection says it was a 6mm that was rated at 6v and had the carbon brushes.  It's been a while so...

The blocks I saw added mass, a heat sink at the point of contact, and as I recall it was a carbon block, approximately cube shaped, with all of the evidence of wear that you would expect on a motor brush.  With it questioned whether the finger was under or over the contact point with the commutator I now don't recall absolutely but also don't find that it would really matter as far as it's being a heat sink at that point.  I have relayed to the best of my recollection what I observed, what worked well and what didn't work well, and my deductions as to why.  I am satisfied that the information relayed is understandable, logical, and useful in the practical sense if not 100% accurate in all of the gory details.  Maybe some day it will help someone with their project.

[narrowminded]

Interesting thing about the piece of large brush material attached to the brushes in the higher-voltage-rated motors.  Are you sure it's because of the higher  voltage and not just the simple fact that those motors are also probably going to draw more current through the brushes and generate more heat?  I think the purpose of the brush blocks is that they keep the brush fingers and commutator cooler under heavier currents.

That's pretty much my take on the matter.   

[peteski]

While we have strayed way OT here, I would like to clarify this.  I think I misunderstood you guys.  Are you guys saying that the carbon (or whatever that black square attached to the springy metal finger brushes is) is not in contact with the commutator?  Then that sounds like what I have observed.  Whether that thing is vibration damper or a heat sink, it is not a brush! To me a "brush" is the part which is in direct contact with, and passes current directly to the commutator.

[narrowminded]

While we have strayed way OT here, I would like to clarify this.  I think I misunderstood you guys.  Are you guys saying that the carbon (or whatever that black square attached to the springy metal finger brushes is) is not in contact with the commutator? 

No, that's not what I said.  I said pretty clearly that my recollection is that it was the brush in contact with the commutator.  When that was questioned I acknowledged that maybe my recollection was faulty (I don't think so because that detail might be noteworthy, but...) but even if it was just attached to the backside of the brush contact it served the practical purpose of a larger brush which is larger because it has to handle more current, therefore more heat, so the larger brush is larger to handle the heat of the higher current and therefore is functioning as a conductor but also by its mass, its own heat sink, even if not given that title with all of its honors and privileges.   Did we just go full circle?

[peteski]

Did we just go full circle?

I think we have (and it is not the first, nor last time). 

[mike_lawyer]

Pictures of the offending loco disassembled:

[mike_lawyer]

I removed the decoder and set everything up for DC, and the locomotive works great - even in both directions! 

[ns737]

they did a nice job of hollowing out the weight . I put the decoder in my mikado the same way but did not reuse the weight. its the same mikado you sold me the tender and drawbar.

[ns737]

was the decoder ok?

[peteski]

they did a nice job of hollowing out the weight . I put the decoder in my mikado the same way but did not reuse the weight. its the same mikado you sold me the tender and drawbar.

I have contemplated taking a mold of that white-metal weight and casting it in lead, for some extra mass.  But probably not worth it,

[mike_lawyer]

was the decoder ok?

I have not tested the decoder yet.

[mmagliaro]

I have contemplated taking a mold of that white-metal weight and casting it in lead, for some extra mass.  But probably not worth it,

I tried that.  It's not.  There is even a post somewhere buried in Railwire that I showed with photos.  I think you only pick up about 2g by doing it, so I abandoned that idea and just cobbled together a weight made from pieces of tunsten all glued up and ground down with diamond Dremel tools to shape it so it would fit under the shell.  I remember now.  I think it was in my NP 2-8-2 W-5.

[djconway]

I have contemplated taking a mold of that white-metal weight and casting it in lead, for some extra mass.  But probably not worth it,

A gram or two here or there makes a difference, keep it balanced over the drivers.