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Old 12-05-2002, 04:33 PM   #16
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Default Every little bit helps

Bubbaicm;

I'm of the belief that EVERY little bit that you can do to refine your Cars and Equipment, just gives you that much of an edge over the average person. I spend HOURS each week getting my cars ready for the weekend battles and it shows by almost always being in the Top 3 spots in the "A" main. Right now I'm new to electric racing, so any extra edge I can get on the competition helps.
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Old 12-06-2002, 06:01 AM   #17
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There use to be a good FAQ on motors and brushes on the Team Orion site which did a pretty good job at explaining everything (much better than I can!)....I just had a look and not all parts of the FAQ appears to be complete.

If I remember correctly there was some mention of cut brushes for running 1/12 to reduce amp draw and increase rpm (these were not cut brushes for timing changes) for max amp draw you run full face brushes.
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Old 12-06-2002, 07:30 AM   #18
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Default Re: Brush serrations and power

Quote:
Originally posted by popsracer
DTM;

See this is why I asked. Not having a Dyno yet, I am wondering what produces more overall power. Serrated brushes or Full contact brushes. I've heard theories that the serrations actually allow MORE current to the Com, while others like yourself claim that a FULL contact brush makes more power.
An electronic engineer told me, that brushes cost 15% power due to friction! This is a plus for the serrated brushes, since the contact area are smaller. On the other hand, the bigger the contact area are, the more amps get through. So it's an comprimise whatever you do. But depending on track layout, the transmission in your car, your driving style....

And then there are brushes, where you cut a little of the end. The result is less contact area AND sligthly timing adjustment.

In "Racer", july issue 1999, theres an article about brushes. If you like, I can scan it and send it to you. But I only got this issue and it's part 6 in motor tuning.

As far as I know, these timed brushes are legal.
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Old 12-06-2002, 07:42 AM   #19
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pops every little bit helps but we caught some poeple cheating tryingto get that edge.these guys were taking a sodering iron
laying it across the coms heating the shaft sofingthe com. lock pins then taking pliersand twistingthe com to turn upthe timing,finaly someone put up the protest money and we started
to unwind it correct #of winds??????? opon closer inspetcion we noticed cracks in the epoxy over the com lock pins..........................DQ forthe rest of the day .now when he is legal and fast people ???????? his motors. this was hard to detect unless the motor was opened and inspected . I personaly like stock racing, and building stock motors .it will always be a challange to make stock motors run faster


Cole couldent have said it any better

Last edited by bubbaicm; 12-06-2002 at 07:44 AM.
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Old 12-06-2002, 09:41 PM   #20
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Default Cheating son of a.........

Bubbaicm:

What made everyone feel that these guys were cheating? I suppose a twisted Com would also show up at the Com tabs too with the wire being pulled to one side.
Some peoples desire to win is greater than their desire to play fair, but this goes for everything in life. I'm NOT talking about cheating. My edge is putting that 10% extra attention to detail in what I do, that most people tend to ignore or overlook.
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Old 12-06-2002, 09:52 PM   #21
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Default Fuller Brushes

Cole Trickle;

I understand the theory of full face vs serrated, but was hoping someone would have a definitive answer about what was actually bettter on the track. I have also read some theories about how the serrations allow the current to flow more readily to the Com. (can't remem. where)
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Old 12-07-2002, 05:56 AM   #22
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pops one of the reasonswas he was too fast for only being in the sport for only six months when the veterian racers are getting blown away after putting years of work andtime in these motors
plus the person he hangs with has been known to do anything to win also caught cheating questions do come upabouthow he got so fast so quick so tired of being dusted we(the other drivers) put up protest money to check and unwind his motorat least if the motor was leagal he wouldnt be running that motor any more. but that's when we found the cracks in the com lock epoxy and your right the wire was streched on the tabs. we also found people were cutting the 24 degree timing notch on motors and cranking up the timingsome to 40 degrees only the round can motors. i hope this helps u police the ceaters at your track.
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Old 12-07-2002, 08:32 AM   #23
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Default Re: Fuller Brushes

Quote:
Originally posted by popsracer
Cole Trickle;

I understand the theory of full face vs serrated, but was hoping someone would have a definitive answer about what was actually bettter on the track. I have also read some theories about how the serrations allow the current to flow more readily to the Com. (can't remem. where)
Current flow more readily? Never heard of that before....

Which is better? Depends. for me, it's quite simple. This is because that for me all parameters draws in the same direction: Torque. The tracks I'm running, are mainly tight and technically. My drivetrain are quite heavy. And my driving style demands for torque. So I simply needs torque.

What are your needs? RPM or torque? You cant get both. Basically, you get torque or RPM. You can get a little more RPM's, but it will (almost) always be at the cost of torque. And vice-versa.

If you need more RPM's, I'll suggest you'll try another trick, than serrations. It's about drilling a small hole in the brush at the side which touches the comm. This way you'll reduce contact area and get the advantage of more consistent performance, since the drilled hole dont wear out, like the serrations.

A couple of other tricks, (that you might already know - but I dont know what you know ):

* Softer springs on brushes also reduce friction.
* Center the winds inside the can, so they are in the strongest part of the magnetic field.
* Ensure the bearings are monted correct. If one are a little off-direction, it makes too much resistance to the axle.
* Charging at higher amps, means more punch.
* If belt cars, run the belts as loose as possible - without belt skipping (makes a huge difference)
* Discharging NiCd's to zero volt, means lower IR which equals punch. (use an equalizer, to avoid voltage reversing).
* Less toe-in in the rear raises speed. But the car may be too nimble.
* Use good connectors and thick wires. Big difference.
* If you got plenty of grip, use smaller wheels/tires. Reduce rotating mass.
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Old 12-07-2002, 09:12 AM   #24
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Default Cavity Brush

I find that a cavity brush (Reedy 769) with the serrations worn away runs very similar to a serrated brush (Reedy 767) still running on the serrations. I get more punch out of the corners with a reduced area brush. I remove the serrations on an old motor and then break them in on the race motor so that the first run will be a good one.

The advantage of the 769 is the surface area in contact with the comm is constant for its lifetime. You can use it until it gets too short.

A 767 will loose most of its serrations and become more like a full face brush after 3-4 runs. Then if you like running on the serrations most guys will replace the brush.
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Old 12-07-2002, 10:57 AM   #25
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Default Thanks guys

Everyone;

First of all, I would like to thank everyone for their intelligent replies to my questions.

John Stranahan;

I've read about the cavity helping power and now you have explained it so I understand the reasoning better. Will the Cavity reduce the torque output any?
Thanks.

Cole Trickle;

I'm running a Monster Stock right now. It has SO much more power/punch than my P2K2 it is unbelievable. Though I think that the P2K2 may just be a DOG motor. I could go to a little larger wire at the speed control (14 ga now) but everything else is at least 12 ga and nothing is getting warm as to indicate too small of a wire size. If I buy a new ESC (smaller) then I will definitely go the larger gauge wire. All of the other tricks I know about.
Thanks.

Bubbaicm;

There are 1 or 2 guys that are ALWAYS way faster than the rest of us on the straights, but their driving skill really isn't Superior. So it always makes one wonder. Thats the whole idea of stock racing that the motors are supposed to be fairly equal and driving skill/set-up is what usually wins the race.

Thanks all,

Last edited by popsracer; 12-07-2002 at 11:00 AM.
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Old 12-07-2002, 12:37 PM   #26
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Popsracer-It's a funny thing about torque. Changing it does not do what you expect in an electric motor.

For example if you use heavier motor brush springs, most people think you get more torque. They notice more punch out of the corners. In fact what you get is more RPM and less torque. This gives you more POWER at higher amps and gives the motor more punch out of the corners. I have good dyno data to verify this.

I expect a similar effect for the cavity brush. I get more punch out of the corners. I get more power at 40 amperes with a reduced area brush on a CE dyno. I don't expect that this is from more torque. I have not done a set of dyno runs with brushes of different contact surface area (different size holes) to verify this in concrete form.

I your car is faster than the guys running fast laps, on the straight, it's probably because you are not geared quite right for fast lap times.

Last edited by John Stranahan; 12-07-2002 at 12:41 PM.
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Old 12-07-2002, 01:29 PM   #27
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Default Brushes and Gearing

John;

So it is your belief that a cavity brush will produce more power for a given motor rpm, is that corrrect?

I have no problem keeping up in the corners, but by the midlle of the straight I am getting passed (sometimes). If I adjust gearing to improve top speed then accelleration suffers. This was with my P2K2. My Monster Stock motor seems MUCH better overall.

Thanks,
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Old 12-07-2002, 01:46 PM   #28
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It is my belief that a cavity brush will produce more power under heavy load, coming out of the corners. I don't guarantee higher speeds on the straight because the motor is drawing fewer amps there due to the high motor speed.

Funny thing about gearing is that most people think that you get the best top speed with taller gears (a larger pinion) Not neccesarily so. A car will develop top speed when its motor produces more power at its top speed. This requires the perfect gearing rather than taller gearing. My cars are usually faster than other cars on the straigh in stock, but I use lower gears (smaller pinion) than they do for the most part. 7.09 with a P2K, 7.55 with a P2K2 on a Losi XXXS with rubber tires at ReflexRC in Houston, which is a tight indoor asphalt track. Motor is setup with 769 brushes serrations removed and Trinity black overhead springs (9 oz) with the arms bent so they aim 180 degrees apart from each other. After a couple of races you need to rebend the springs or get new ones. Trinity may have discontiniued this spring and has a green (9oz) spring to replace it. Don't know how the arms should be bent on the green spring. When I run out of Black Ones I'll measure the actual tension of the green ones. When you use the black springs bent this way it will apply about 8.5 ounces to a digital balance while pushing the brush on a cutdown endbell onto the balance.
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Old 12-07-2002, 04:41 PM   #29
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Default Usefull information

John S;

See this is what I would call usefull information.
I had been running 7.20-7.40 FDR in my Pro-3 with the P2K2, but it was just so slow. Everyone kept saying GEAR-UP,GEAR-UP, so I did and the motor just had ZERO punch. I tried every tuning trick around and nothing would work.
I finally broke down and bought 2 Monster Stocks and the difference is amazing. I'm going to drill the brushes and try a droping down a tooth on the pinion for tomorrows race.

John, I really don't know how to Thank You enough.
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Old 12-07-2002, 05:07 PM   #30
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Default brushes

anyone need brushs i have all kinds
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