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[HauntedMyst]

I've only used the plain brushes, but in the store I seem them with serated faces, a line down the middle, even an H face. Whats the benefit of these? I am running a Chrome Stock motor.

[HauntedMyst]

Joe,
Great info! I do have a question though. My motor uses laydown brushes. It sounds like what you are suggesting is in the second image? The ones at my store are full face or like the top image.

http://albums.photopoint.com/j/View?u=324108&a=11577336&p=53895404


BTW, thank you for taking the time to explain all that!

[ 09-07-2001: Message edited by: HauntedMyst ]

[Railman]

Haunted, We run the cut like figure C. The other cut I like is similar to the H cut, figure A, except it's just a small V instead of a rectangular cut. The tip of the v's at the center are only about 1/16" apart. The slot in figure C can vary from 1/32" to 1/16". I prefer to keep it small for trucks. No need to cut it deep. A deep cut will increase the brushes resistance. I wouldn't do the B cut. You are running this in a stock motor...right? The Figure C slot would be parallel with the arm shaft, like I said in the previous post. The other option that some like is to drill a hole in the center of the brush. We've done it also, but I still prefer the slot or V, because I think they cool better. Keep in mind there is no perfect way to do these cuts, but it's the experimenting that's part of the fun for me.
Joe

[Railman]

HM, For the most part, the different cuts will reduce friction. The serrated ones will beak in much faster, & in fact many top racers will tell you they don't break them in at all. I think that the serrations are so shallow that the current still arcs over to the com, while reducing the contact/friction area, sort of a floating current. The different type slots have different theories behind them, but like I said above, it has mostly to do with reducing friction, & to a degree cooling. A horizontal slot (parallel with the arm shaft), will also give more pressure on the leading edge of the brush. That's where the big amp draw happens, along with the most wear. Since there's less meat at the center of the brush, it forces more pressure on the other two areas. The only thing about slotting is that it works better with lower (more reduction) gearing...ya gotta let'm spin. Slotted brushes can't quite give the amp draw of a full face, but I like the way they run when geared right. They will run cooler, last longer, & give better run times with a cut. This is due to the brush's leading edge making better contact, & reduced arcing at that point. The verticle cuts I'm not that familiar with. We have played around with them, but they seem to have limited uses, & don't make sense for offroad racing. Having said all this, what we generally run is a serrated high silver Trinity E brush, can't remember the number right now. We either run a small slot all the way across, or a v cut on each side. It works especially well for buggies. Trucks are more apt to run full face serrated brush's, but it depends on driving style & gearing preferance. You can easily do these cuts with a small hobby file. Most shops carry an assortment in bulk for about a buck or two each. I got a set of 8 or so from Harbor Freight for $4. If you take your time it's easy, but my boys don't seem to have the patience for it. Start with just a small line, inspect, & then cut a little more. It does take a little practice to keep them centered. We also use a serrator kit that will also cut slots with a dremmel wheel. Thats what my boys use mostly, but I prefer the small file v cut. Hope this helps. ;)

If I'm not clear enough let me know.
Joe

[HauntedMyst]

Thanks Joe!