# two different brushes?



## Grampa Ho (Feb 25, 2009)

Been working on these things for over 40 years now and came across an interesting oddity. I have numerous JL's and was testing one last night. It seems that a certain combination of brushes pushed this thing to a very new level, as in major speed increase.
I put a JL domed brush in the front and a worn AW silver in the back and the darn thing picked right up after having no luck improving the quality of performance in my usual ways. 
What's with that?
I changed the brushes to the opposite sides and it was a dog again. 
Plate and arm are all in sync, no measurable difference, even changed arms and the results were the same.
Could this chassis have that much variance to produce this effect?
It got to be supper time so I did not get to try this experiment on any other chassis, but I am going to pursue this a little more. 
Anyone else notice or have tried this?

Rich


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## slotking (May 27, 2008)

the front brush is the power brush, so generally more tension there can provide more speed. the silver brush provide better conductivity than copper and that may up the speed you need.

als the brush tension comes into play!
the 1 thing that helps there is the VRP SRM tool! lets you know where you are on tension and make change to test, then go back to the tension that offers the best speed.

I would think if you found a big silver brush like the 1 in the front, it would even be faster. 

My other tip, try some slottech brushes and see how they work!
per my dyno testing on many cars they are the best! When my fellow racers tried them, they became the brush of choice hands down.


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## slotking (May 27, 2008)

forgot to add, when testing if a car need more tension, i take the idler gear out, place car on my vrp dyno with the bottom exposed, and slightly press on the brush spring, if i hear the arm speed up, I know I can add tension.


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## Grampa Ho (Feb 25, 2009)

I am aware of the tine tension, but for the front brush to be the drive brush, that, I don't understand. Why would the front be the dominate one? 
Last night I switched out the brushes for brand spanking new silver domed and it was a dog again. I did find that an afx mag brush worked better than the used aw silver flat brush that I did use in the rear brush hole. 
Experimentation.....trial and error and what should make sence and what accually works might be a whole different thing.
Ah the joy of this sport can drive ya crazy :freak:
Rich


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## slotking (May 27, 2008)

the front(left side) brush is the power brush, it a lot more evident in inline cars, after a few races, if you take the brushes out, you will notice that left brush worn more than the right brush.

you can see this with shoe tension as well, upping the shoe tension on the left shoe will provide better speed than upping the right shoe.

So I normally run more tension on the left side to add speed.

with the new brushes, try putting them back in, let the car break in 5volts for 30min to an hour. or just run it for around for 10-15 min and see if that makes a difference.


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## Ralphthe3rd (Feb 24, 2011)

Hey Slotking, about your advice for shoe spring tension. I notice that on some of my T-Jets and A/FX, that the left shoe gets more arcing-pitting than the right side. Is this because the shoe tension is too light, or is it because I'm unloading the tension when racing on my Oval, and the left side goes to full shoe extension(I just use standard style AL shoes). BTW- some of my cars that are set-up alot lower, do not exhibit this arcing damage to the left side shoe.


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## slotking (May 27, 2008)

normally I see arching from tension being to light.

When racing my fray cars, sometimes I do not have enough travel and the stutters in the turns because one of the shoes is lifting. but I do not get burns from that. 

travel such a fine point! having enough to not stutter in the turns, but restricting enough not to have the car push out in the turns! that changes as you go from track to track!:freak:

I do not race ovals so could the burns be from consistent lifting? maybe
but I would think it more like road course racing and from lack of tension. Is your car losing power in the turns? if not it would most likely be the tension.

btw
I mostly adjust my t-jet shoe tension by slightly bending the rear hook up or down. if it need drastic changes, I swap between my Champ springs


JMHO


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## clydeomite (May 5, 2004)

My experiences have show that if you can see arcing in a pickup brush it is because of resistance between that pickup and the delivery of the current. What i am trying to say is there is usually a dirty spot ( brush hangar or corrision between plates) that doesn't allow full current to be delivered to that motor brush. As a side note this is the positive side of the power supply as well.
Clyde-0-Mite


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## slotking (May 27, 2008)

that could be it as well, but most often if I see a burn spot, I can increase the shoe tension and it goes away.

most of the tracks I run on are kept clean
and i keep my electrics clean as well


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## Grandcheapskate (Jan 5, 2006)

Ralphthe3rd said:


> Hey Slotking, about your advice for shoe spring tension. I notice that on some of my T-Jets and A/FX, that the left shoe gets more arcing-pitting than the right side. Is this because the shoe tension is too light, or is it because I'm unloading the tension when racing on my Oval, and the left side goes to full shoe extension(I just use standard style AL shoes). BTW- some of my cars that are set-up alot lower, do not exhibit this arcing damage to the left side shoe.


Check out this thread....

http://www.hobbytalk.com/bbs1/showthread.php?t=295508


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## slotking (May 27, 2008)

some great info there!
and more things to try! 
I do find some tracks at times are problems no matter what!
but I would i can fix the problem at let 80% of the time with a shoe adjustment. and that also work at times with problem tracks as well. 

I run a wiz track, not sure if the rails are the same as max??


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## Ralphthe3rd (Feb 24, 2011)

Hmmm...ok, thats alot to think about, and I'm going to check out that thread link in a minute. As for my arcing problem, my rails are clean, my electrics are clean, and I don't lose power in my turns unless I'm lifting an inside wheel and it's about to roll....but I usually drift the tail around the corners. But I do believe that my tension maybe too light. But I used to worry about too strong a spring tension, and bouncing the front end under hard acceleration, which btw- used to be a problem on my stock JL/AW Tuffies, but I cured that with lower spring tension by swapping out to NOS A/FX Shoe springs and/or weighting the front ends. But what puzzles me is, why some cars do it, and some cars never burn their shoes-no matter what brand I use- even plated JL/AW shoes. But I've noted something else, when I run these same cars (that are plagued with left shoe arcing) on my Drag Strip for dozens of passes, the shoe isn't arcing anymore, and grinds itself smooth again.....hmmmm.
PS- I only run on plastic sectional track, my oval uses Tyco/Mattel track, and my full 1/4 mi length Dragstrip is using Marchon.


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## slotking (May 27, 2008)

yeah
these are fun!! we get to try to figure why 1 car works and another does not!11:freak::freak::freak:

what I found is that I can take the perfect shoes/springs on car ! and put them on car 2 and get 1 or more of the following:
1> the shoes do not move freely
2> to much tension 
3> to little tension
4> who know what the heck is happening!

Aurora worked very hard to make sure no chassis is ever the same as another!:tongue::jest::jest:

one of the 1st things I do when putting shoes on a car (inline or pancake) is after I make sure the shoe is flat on the rails, I put on the vrp dyno, then I push or pull the shoe. if the dyno reading increase, I keep tweaking the shoe till the dyno reading stays the same.

Now i can drive it, to check for speed(increase tension), check for handling (decrease tension or restrict travel), check for arcing (more tension generally).


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## copperhead71 (Aug 2, 2007)

Very informative slotking!!!


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## Grampa Ho (Feb 25, 2009)

so tell me, how did we get from brushes to shoes and springs on this thread?


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## slotking (May 27, 2008)

left turn on lipton ave!
:wave:

nothing new! it happens all the time!


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## Grandcheapskate (Jan 5, 2006)

There was a discussion on SCI concerning getting the right combination together for a pancake chassis.

http://www.slotcarillustrated.com/portal/forums/showthread.php?t=59505

But as I said in post #29... 



> Okay...So here's what I am taking away from this discussion...
> 
> To build a good pancake chassis, you take parts, any parts, and spread them on a table. Then, while wearing ceremonial flowing black robes, you perform some voodoo, black magic and chant the mystical passages found in the sacred tomes.
> 
> You then put all the parts together and see what happens.


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## slotking (May 27, 2008)

yeah good thread and nice that you could link to it without getting yelled at like what would happen on SCI.

Why I like this BB and other that allow links!


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## AfxToo (Aug 29, 2003)

There's probably more truth in the flowing black robe theory than you might think. This is not because of a lack of solid science behind how these motors and brushes work. Rather it is because there are so many variables involved including the most important ones, i.e., we want these things to go fast and operate effectively over a wide range of speeds and loads and ambient conditions. Setting up a brushed motor that runs well and has long brush life within a narrow operating speed and load is a non-trivial task. Achieving the same thing with a race car is much more challenging and we usually compromise on the motor life and brush wear side of the equation for pure racing performance. 

I would say that your best bet to achieving repeatability is to build to the same set of measurable parameters every time and measure everything you can including, brush length (height), brush tension, brush material, brush angle, brush free play, shoe tension, shoe material, shoe angles, motor timing, motor winding type, motor winding resistance, motor magnet strength, motor fore-aft spacing, motor bearing tolerances, motor current versus voltage curves, motor speed versus voltage (or equivalent dyno readings), motor temperature versus load, test track performance, etc., and keep a record/diary of what worked well under certain race conditions and try to at least start every race with what you consider a deterministic setup. 

Of course once you start running your car the brushes wear which changes the brush tension and possibly brush angle, the commutator starts filming up which changes brush friction, the motor temperature rises which changes motor winding electrical resistance and brush friction (for better or worse depending on brush material), the motor timing changes due to armature induced current, which may cause increased brush sparking, which changes brush effectiveness and wear ... and brush tension, the motor fore-aft movement causes the brushes to contact different parts of the commutator and motor bearing tolerances change the brush angle and the brush contact patch (especially in a pancake motor), free play of the brushes in their holders changes brush angle and the brush contact patch and may even cause the brushes to wobble, and so on and so forth. 

With so many variables and dynamics it's no wonder the black robe theory exists. The best you can hope for is to narrow the range of deviations by building to as narrow a set of tolerances as you possibly can. Otherwise you're constantly stumbling upon something that works magically under some random set of conditions but lacks repeatability or reproducible positive results.


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## alpink (Aug 22, 2010)

*what HE said*

yeah-yeah, what AFXToo said .... I think!
:roll:


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## slotking (May 27, 2008)

no not at all!
Aurora cars where not only 100% American made (hong kong sticker was placed on for political reasons) the car was precision made!

all t-jet parts are identical unless you got a Russian clone that the commies distributed to bring done this country!

them are the facts jack!:wave::tongue:


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## Bill Hall (Jan 6, 2007)

Great post TOO!

In a perfect world it would hang on the wall above every slotter's bench.


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## Ralphthe3rd (Feb 24, 2011)

BTW- back to my Hi-Jack  A little update on my Left Shoe arcing/pitting problem on a few cars. Well..... I took some of the advice, and I stretched the left spring a tad to give it a bit more tension, but also, at the same time I switched my left side shoe to a Slottech that I enlarger the hanger window to give more travel(for my non-lowered chassis), and BAH-Zing-Ga ! No more arcing and/or pitting on that side shoe...thanks Guys !
PS- I also did another little experiment on a few cars, and that was to replace my JB Front brush with a Taller Wizzard Brush, and those cars gained some speed. Granted, it may have just been from the resulting stronger brush spring tension afforded by the taller brush, but that's my results....YMMV


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## TGM2054 (May 14, 2011)

OK!..... Now I gotta get a black robe?...... Is there any certain chant that works better than another?
Actually thanks for all the great advice, I've picked up a lot of good stuff from this tread.


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## slotking (May 27, 2008)

I will say this:
despite all the variance with all the parts from t-jets to AW cars there are the same basics. 

Once you understand those basics, you can generally improve any of the cars. may may not make all of the the same speed or super fast, but you can make them better.

I have improved cars for a good number of people but I am not as good as others who can get even more out of their cars.

I have not come across a car I could not make faster even though they still may be slower than what I want.


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## Bill Hall (Jan 6, 2007)

*One thing at a time!*

Nawwww....no black robe...mines a red and black plaid affair.

After re-reading the thread starter, the brushes were worn and or the comm springs were fatigued. Installing different parts that were serviceable made it better. It aint voodoo. Replacing NWI's (normal wear items) and periodic adjustment is a matter of course. Improved performance shouldnt come as a surprise, it is the expecation.


The reason we go from "brushes to springs" is that... 

... ya gotta actually learn the relationships of the parts within a slotcar's individual sub-systems. Then recognize how changes affect both that individual sub-system, the immediately related sub-systems; so you can finally determine what effect it has on the platform as a whole.

The trouble always starts when we (builders) exceed or ignore the operational range of the sub-system's surrounding parts by making changes that dont compliment the existing package or neglecting to meet the normal service requirements. If the parts dont play nicely together we create additional undesirable conditions on top of the diagnostic problem we had in the first place.

Real magic occurs when a slotter can finally just let go of preconceived notions and unreasonable expectations; so they can then hear what the chassis is really saying. This only occurs through repeated building, careful attention when testing; and most importantly remembering what ya learned for next time. 

The reason the ancients preached the fundamentals and build protocols is because there's no magic, only proof, truth and probablity.


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## Boosted-Z71 (Nov 26, 2007)

Bill Hall said:


> The reason we go from "brushes to springs" is that...... ya gotta actually learn the relationships of the parts within a slotcar's individual sub-systems. Then recognize how changes affect both that individual sub-system, the immediately related sub-systems; so you can finally determine what effect it has on the platform as a whole.


So very true, and many times a small re-positioning or tension change on the brush/spring makes all the difference in the world, but you have to tweak and listen to the results to determine if you gained or not.

Boosted


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## Grampa Ho (Feb 25, 2009)

you must understand this was a new chassis with the original domed brushes in it and that on a whim heard about this trial and error brush thing and tried it. as for if or what it does in an older aw chassis, tried it on 2 of them and same results.
as for sounds, I have motors that sound like a dentist drill that do not go as fast as some that sound like a mutt. the mutts sometimes are my fastest cars.


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## slotking (May 27, 2008)

that's a small part of what I was implying, just not providing details.

brush spring tension
shoe spring tension
brushes, new, used, oil soaked or dry, brush composition
gear mesh, gear slop
axle/arm shaft/gear shaft friction or slop
do the holes of the gear plate & chassis line up
are the axle holes level

then you get into motor testing! 
I use a tach to test each motor while in different chassis because the magnets make a big difference. and how the same mags can work differently in each chassis.

so once you know the basics, improvement is repeatable


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## Grandcheapskate (Jan 5, 2006)

TGM2054 said:


> OK!..... Now I gotta get a black robe?...... Is there any certain chant that works better than another?


There are certain chants I use which cannot be repeated on a family oriented board. While these particular chants often cast dark and evil spirits at the ancestry of the chassis, they often do nothing to improve the performance. However, some chassis have been known to cower in fear at the prospect of certain annihilation and respond positively.


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## jobobvideo (Jan 8, 2010)

does a corrugated-face framing hammer scare them into submission? you know with the threat of soon becoming infield diorama fodder...or worse tell them they will get put on the display circuit for fans to take pics next to them at the all major sponsors events and never run again...crush or caress you be the judge


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## Boosted-Z71 (Nov 26, 2007)

Grampa Ho said:


> as for sounds, I have motors that sound like a dentist drill that do not go as fast as some that sound like a mutt. the mutts sometimes are my fastest cars.


I was trying to say that in whatever testing methods you use, you have to very carefully pay attention to the results of all the little tweaks performed to wring every last drop out of these T-jets, Your correct sound, while an important observation trait is not the end all be all of tests. I prefer measuring, rpm, amp draw, and voltage drop all with an applied load on the chassis, similar to the drag of the car on the track. Of course the track is the truest test method, Track results will not lie, a dog will be a dog, and a speed demon will be a speed demon, at least for a little while, My experience has been with T-jets they all change with time as well:wave:

Boosted


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## Gary#8 (Dec 14, 2004)

The domed (AFX style)brushes in a ThunderJet 500 chassis will wear out the AutoWorld silver com plates very fast compared to stock flat style brushes. The taller brush on the positive side, front (left drivers side of car) is what gives more speed/power, more tension as Slot King said.


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