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Break-in of serated brushes?

Break-in of serated brushes?

Old 12-30-2003, 06:30 PM
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Default Break-in of serated brushes?

Running a stock motor.. how much should one "break-in" after a rebuild installing new serated brushes. The serations aren't going to last long - and breaking them kind of defeats the purpose of them to begin with?

Please advise..
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Old 12-30-2003, 06:44 PM
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well the main reason you are breaking in a brush is to fit the curvature of the brush to the comm. If they are not seated right, then you dont get full power.

for stock I do 2 volts for 7 minutes

mod, 3v for 3 minutes
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Old 12-30-2003, 06:47 PM
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Run-in the brushes seats them to the comm so that every corner of each brush is touching the comm, this will give you full power and alot less sparking(lost power). You can always re-serrate or replace the brushes if you don't like running them without serrations. I've had serrations last 2 weeks of racing in stock(including run-in), which imo is pretty dam good.
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Old 12-30-2003, 06:50 PM
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Originally posted by =MisFitz= NuKe
for stock I do 2 volts for 7 minutes
7 minutes is a bit much isn't it?
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Old 12-30-2003, 06:55 PM
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no, thats what we were doing at the On-road Nats in sedan, and at that voltage, it worked very well, also, going from 2 to 3 volts in this case is a lot, so it wasnt very hard on the brush. Kind of like going from 6cell to 4 cell
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Old 12-30-2003, 06:59 PM
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fatdoggy, no not really. It depends on the brush of course, but since stock motors are going to spin the comm (/arm) slower than modifieds, they take longer to break i, and when you combine that with the harder brushes that are sometimes used on stock motors, it could take that long. I like serrated brushes because to some extent when you are breaking them in you can look at the brush to see if the hood is aligned properly (even wear) and you can also tell how wlel the brushes are seating but looking at how deep the serrations are.

If you're running a softer brush such as the 766, 7 minutes would probably be too long, but with something like 767's, it could take 7 minutes.

Modifieds don't take as long because for the most part they use softer brushes - the 729 (quasar standup) is the same compound as the 766 laydown brush, which is also used in laydown mods such as the Kr. They also will spin the comm (/arm) faster, breaking the brushes in quicker.
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Old 12-30-2003, 08:19 PM
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i do not break in my serrated brushes. It usually says right on the package that they do not need to be broken in, and they usually put out more power when they are brand new(without break- in). I realize that they get dirty also, but even with a thourough cleaning after they have been broken in, they still dont put out the equal, or more amount of power that brand new, out-of-the-package serrated brushes do.
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Old 12-30-2003, 09:46 PM
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There isn't a brush made that doesn't need to be broken in.......if you don't break in your brushes, you are simply losing power and putting extra wear on the comm (unseated brushes at high voltages don't treat comms very well)

Later EddieO
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Old 12-30-2003, 09:59 PM
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I break in my monster stock with 767 brushes and green springs on both sides I use a 2 cell pack so its about 2 volts and it only takes 3 minutes for the brushes to seat. They are seated across the entire face of the brush. I do use a break in fan tho maybe that makes a difference putting the load on it. Some say not to use any load but for me Im not sure itll matter. My motors are fast and will go 6 runs before I can tell any significant loss in power. I race them with red green spring combo. It makes more torque if I use purple springs but it also wears twice as fast, 3 or 4 runs.
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Old 12-31-2003, 07:16 AM
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I ussualy visualy inspect my brushes every 2 minutes or so, while I break them in at low voltage... Some brushes can indeed take 7 minutes. Alot depends on the brush and/or the differance between the radius that is on the brush from the factory vs. the radius of the comm itself...


I already gave this 'secret' away once about a week ago, so I guess I have no reason to hold back now...

If I can, I really prefer to break in my brushes on a differnt armature then the one I will race. To do this, I would cutt the comm down on a second armature, so that the diameter of the comm on this stand-in arm matched exactly the same size of the comm on the arm I intend to race.... I don't really do this very often, but in my opion if you really want your motors comm and brush to be the best they can be.. this is the way to do it... Just make sure you get both comms exactly the same size when you do it...


If it's a modified motor, break the brush in at about 6 degrees timing rather then 36 or what ever you might actualy use in the race... this cutts down on comm wear during breakin...

(I've got lots of junk arms lying about... so it's not that hard to find a stand-in ussualy)
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Old 12-31-2003, 08:48 AM
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I do my motors (stock and 19 turn) for 300 seconds at 5 volts.

Did somebody say that the 766 is softer than the 767? I think its the other way around.
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Old 12-31-2003, 11:11 AM
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767 has more silver content than the 766... I beleive.
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Old 12-31-2003, 12:19 PM
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more silver = softer brush.....??
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Old 12-31-2003, 12:35 PM
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Reedy has never said which brush has more silver, but its pretty common knowledge that the 767 (and its siblings the 768 and 769) is more abrasive than the softer 766, which seems to have more lubricating properties to it.


Later EddieO
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Old 12-31-2003, 03:17 PM
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more silver= harder, in most cases.
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