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Testing some new brushes


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#1 Robert BG

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Posted 21 June 2016 - 02:49 PM

I came across some brushes that are not the usual Goldusts and Kofords and decided to give them a try. What would you guys recommend looking for? Also a way to test them back to back would be nice, too.
 
So far I just put a set in a old Pro Slot C-can I just rebuilt that isn't anything special other then it was one of my favorite motors from when I was a kid .All I did was add bearings, clean everything, and reassemble it. It's by no means a build like you see on here but I managed to use all my old parts except for bearings to put it together so I'm happy with it.
 
I'm sure it needs a zap but when I gave it a quick water break-in there was little if any brush material in the water and I actually ran it a little longer then most.
 
Could part of the issue be that the comm was too smooth? It was cut years ago so I just gave it a real quick polish with some 1500 grit to clean it up. I know it's not the best to do that but at times I'll give a comm two-three turns on a super fine grit if it's sat and it's never been a problem before.
 
Anyway they do seem harder then Goldusts but not by much and they have quite a bit of what felt like graphite in them from when I notched them for shunts.
 
I doubt I'll run them in my race motors but I'd like to have a cheaper option for play cars. $3-4 a pair is a bit steep especially if you slip and break one when doing shunts.
 
Would a harder brush be better in some cases? I'm sure the comms won't like them too hard but if it's a performance gain it might be worth it.
 
I'm sure I'll think of more stuff but its time to put another motor together.
 
Thanks.
Robert Fothergill




#2 havlicek

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Posted 22 June 2016 - 06:10 AM

Brushes are a funny thing... you can only use a particular brand and all of a sudden get a pair that run noticeably worse, like really noticeably worse. Other than that, BF and Goldust both seem to work fine, although I'm sure people have preferences.  
 

I doubt I'll run them in my race motors but I'd like to have a cheaper option for play cars. $3-4 a pair is a bit steep especially if you slip and break one when doing shunts.

 
The Parma 16D brushes may be fine for "play cars," but you'll need to radius them.
 

Would a harder brush be better in some cases? I'm sure the comms won't like them too hard but if it's a performance gain it might be worth it.

 
Maybe, maybe not. The problem here is that brushes will sometimes vary in hardness because of how they're manufactured. So, you may go with what you think is a little "harder" brush (there really aren't many choices from *common* sources), and still have some that are softer than what you thought was a "softer" brush. There was a time when racers/motor-builders hoarded "Mabuchi 36D pull-outs, saving the brushes and throwing-away the motors :), but that really isn't necessary since modern brushes are generally good.  The Mabuchi brushes seemed to be very consistent, and I never got a bad pair, so that made them reliable.

I guess what I'm getting at is, use either Goldust or BigFoot for the "good stuff" and be aware you might get a bad pair every now and then. For the "fun motors," just get the cheapest stuff you can find and see if they're OK for what you want to do. I don't know that there's anything more to it than that.
 

$3-4 a pair is a bit steep especially if you slip and break one when doing shunts.

 
Drilling the back-ends (if that's how you prefer to do shunts) is finicky and it's easy to ruin a brush until you get used to doing it. A simple vertical groove works fine and is less likely to break a brush (you can buy them with both vertical and horizontal grooves). For grooving, I just hold a thin cutoff disc in my fingers and carefully run it up and down on the back of the brush until the vertical groove is slightly deeper than the horizontal one. Pretty easy and safe.
 
-john


John Havlicek

#3 Bill from NH

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Posted 22 June 2016 - 06:59 AM

I agree with what John said about brushes, there isn't a good cheap way out. Brush density in the same lot of brushes is apt to vary and work differently. Too hard a brush may scar your comms, so unless you run old arms, be carefull what you use.

 

I'm one of those builders who "in the day" used Mabuchi "pull-outs." Today, I wouldn't bother because the aftermarket Goldusts and BFs are better. I also used to drill the brush back ends for shunts and still would. As the brush wore, I think it slid on the shunt wire. I never had a hung brush caused by a worn brush and shunt wires. I would also radius the corners and polish the brush faces on a piece of newsprint.


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#4 Koford fan

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Posted 22 June 2016 - 08:02 AM

i tend to use BFII on the plus side and Goldust on the negative side, works like charm!! 2.7xx on a blue King with 13.5(6) volt.

 

Using plastic endbell, not metal. (Sveslot rules, which follow ISRA).


Tom Blantern

#5 zipper

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Posted 22 June 2016 - 08:47 AM

What about Rocket (?) Boyington/Wittenauer shunted brushes in early '70s - advertised having some 60-70 or whatever % copper. I think I tried one pair and that was it...


Pekka Sippola

#6 Robert BG

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Posted 22 June 2016 - 09:01 AM

For now, I just notch them deeper for shunts but I'm not a fan of doing it this way. I've had hang-ups and issues from it in the past but when I used to drill them I had a small holder to hold the brush in place.

 

For now I'm going to keep the same Golddust brushes in my race motors but down the line I do plan on doing some back-to-back testing. One thing I would like to see is better life from my one motor set-ups. I've torn through brushes before a race was over in the past and although I doubt that is as much a problem these days I've still worn some down pretty fast.

 

As for this being a cheap way out, while they are a little less then others it's not by much. I honestly hope they perform on par but we'll see but as of now I'm quite impressed by the lack of arcing although more to follow from track testing.

 

I'm wondering with a more accurate meter than my Fluke would it be possible to test the resistance of them? If so has anyone tested the big name brushes?


Robert Fothergill

#7 Koford fan

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Posted 22 June 2016 - 10:10 AM

I just use dubic brush radius tool along with a voki brush slotter, works perfect.

Dubic brush radius tool

Voki brush slotter

 

I can file it down , it stops in the slot.

When adding shunt and springs it fits nice and angles are much better.


Tom Blantern





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