# Buildup on Negative Rail



## Grandcheapskate (Jan 5, 2006)

Hi Guys,
I have noticed that I get more buildup on the negative rail and shoe of all my cars as opposed to the positive side. The negative side is wired directly to the track with the positive side going through the controller. Each lane has it's own power pack and is wired seperately.

I know I'm going to get buildup from an unrectified power source, as well as from arcing. But the negative side always shows more blackening. This has become more noticeable as the summer humidity cranks up.

Why more buildup on the negative side?

Thanks...Joe


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## martybauer31 (Jan 27, 2004)

Check the flux capacitor, it probably isn't getting 1.21 gigawatts of power... Are your cars hitting 88 MPH?


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## NTxSlotCars (May 27, 2008)

Squeaky wheel gets the grease?


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## Hornet (Dec 1, 2005)

Add more shoe tension to that side


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## AfxToo (Aug 29, 2003)

> Why more buildup on the negative side?


This is a naturally occurring phenomenon that has been known about for many decades (it was a very big deal back when telephone switching circuits were based on electromechanical switches) and is known as "fine transfer" or "material transfer." If you really want to understand the theory behind "fine transfer" there are some PhD level white papers and thesis dissertations on the topic, which is still subject to different interpretations and conflicting theories. Need sleep inducement? 
http://www.lib.ncsu.edu/theses/available/etd-04292008-102452/unrestricted/etd.pdf

From a practical standpoint, seeing this effect on your shoes is an indication that you are getting a pretty good non-arcing connection at the pickup shoes. If your shoes were arcing you would encounter what is known as "course transfer" and you would see material build-up on the positive shoe. Increasing the shoe tension on the negative side will help scrub off some of the material build-up. 

When the humidity is increased there is less potential for arcing and the fine transfer effect becomes even more noticeable. But at higher humidity you also see corrosion due to electrolysis because of the electrolytic reaction between the different metals - shoe and rail. So there are multiple things going on at the same time. I seem to recall that the ideal relative humidity for electrical devices is is the 45% to 50% range.


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## Grandcheapskate (Jan 5, 2006)

Thanks AFXToo. As much as I would like to spend an evening reading a PhD level white paper, I will take your word on the technical electrical explaination.

Bottom line - it's normal, expected and not much you can do about it. I don't want to increase shoe tension because that just leads to "shoe hop".

Thanks...Joe


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## NTxSlotCars (May 27, 2008)

a form of electro plating?


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## WooffWooff (Dec 23, 2009)

*Maybe a solution to the negative side build-up....*

...would be to reverse the direction. That might clean the the one side, while starting the build-up on the other rail? I haven't noticed it having an effect on car performance, but I lightly clean the rails 3-4 times a year (need it or not, LOL), with a train track rail cleaner that looks like an eraser, I think it's made by "Life-Like" and called "Rail-Brite" or "Brite-Boy"..........wooff


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## SwamperGene (Dec 1, 2003)

Whatever the actual reason, using stainless steel cleaners when cleaning the rails seems to keep it at a minimum. The stuff they sell at WalMart, Weiman's I think it is, works great and seems to rejuvenate plastic track nicely as well. :thumbsup:

Steve Medanic has a great article about it here, in my own use I've found it works well on any types of rails.


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## joegri (Feb 13, 2008)

swamppa g that was a very informative read! just tonite i did a trak cleaning and rail cleaning. the lil cars went much better now my mind is thinkin bout a chunk of marble. i used a piece of this stuff to sand drywall not very impressed.now i gotta hunt around for a trophy, i,ve never won any. thanx for posting the good stuff !!


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## Grandcheapskate (Jan 5, 2006)

SwamperGene said:


> Whatever the actual reason, using stainless steel cleaners when cleaning the rails seems to keep it at a minimum. The stuff they sell at WalMart, Weiman's I think it is, works great and seems to rejuvenate plastic track nicely as well. :thumbsup:
> 
> Steve Medanic has a great article about it here, in my own use I've found it works well on any types of rails.


 Okay...one more thing to put on the shopping list.

Thanks again Gene.


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## Grandcheapskate (Jan 5, 2006)

I have a theory and I want to throw it out for discussion.

As the title of this thread suggests, I always get more buidup on the negative pickup shoe than the positive shoe. This goes across all chassis types on my track.

My track is wired with 16 ga. speaker wire. Speaker wire as you know has two internal wires, one for the left channel and one for the right. When I wired the track, I used both internal wires as a single wire. So if I understand correctly, the wire should perform as if it were larger than 16 ga.

The negative wire goes directly to the track and the positive wire to the controller. There is no brake wire. I use old Aurora Russkit controllers, mostly at 60 ohms although I just repaired two of them and put in 100 ohm resistors.

Now here's my question. The Russkit controllers use 22 ga. wire. I imagine this is a choke point on the electrical flow. It doesn't matter the rest of the track uses larger wire as a chain (or electrical circuit) is only as strong as it's weakest limk - in this case, the smaller wire of the controller.

I am looking at replacing the internal wire of the Russkit with the same size wire as the rest of the track, but until I do that, could the fact that the controller has smaller wire in any way contribute to the buildup on the negative rail?

Thanks...Joe


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## alpink (Aug 22, 2010)

let us observe an automotive battery in a car ....
one terminal always corrodes more that the other.
which is it?
.....
.....
.....
and is that because it is ALWAYS attracting molecules of the other polarity, especially from moisture in the air?

please correct me because I am often wrong.
but voltage flows from positive to negative while amperage flows from negative to positive?
probably have that half bass ackwards anyway.
for drag tracks, I wire the positive as my common directly to the rails and the negative through the controller stations, placing one fuse inline on that positive common.

but I digress. there are many reasons one shoe corrodes and attracts dirt before the other and it mostly has to do with direction of atoms flowing from one molecule to another.


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## smalltime (Jun 3, 2006)

Hornet said:


> Add more shoe tension to that side


+ 1000%:thumbsup:


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## LDThomas (Nov 30, 1999)

*You got it...*



NTxSlotCars said:


> a form of electro plating?


 
Just like an electro plating process, the current flows one direction and the deposits go the opposite direction. Current flows out of the negative rail and the deposites go onto the negative rail.

By adding pressure to that shoe, you simply wear off the coating at the same rate it is deposited - thus a clean shoe/rail. Simple and easy solution.


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## Grandcheapskate (Jan 5, 2006)

I guess I am wrong in what I was thinking. I was supposing because the positive wiring was not as robust as the negative wiring (due to the 22 ga. wire in the controller), electrons were flowing freely to the negative shoe but then some had nowhere to go because they could not all fit through the smaller positive wire - thereby depositing themselves on the negative rail/shoe.

Joe


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## alpink (Aug 22, 2010)

*wire dimension*



Grandcheapskate said:


> I guess I am wrong in what I was thinking. I was supposing because the positive wiring was not as robust as the negative wiring (due to the 22 ga. wire in the controller), electrons were flowing freely to the negative shoe but then some had nowhere to go because they could not all fit through the smaller positive wire - thereby depositing themselves on the negative rail/shoe.
> 
> Joe


Joe,
is there a wire in the whole of the schematic for track, controllers, etc .... smaller than the armature wire?


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## Grandcheapskate (Jan 5, 2006)

alpink said:


> Joe,
> is there a wire in the whole of the schematic for track, controllers, etc .... smaller than the armature wire?


 No. The track is wired with 16 ga. (doubled) and the internal wiring of the controller is 22 ga. But then read my story...

Here's something which happened to me a while ago and made me think the smaller controller wire is a problem. I have two of the original Aurora electric lap counters. One of them I got used and it would never be able to go over 9 because it would not turn the 10s digit. I thought it was because the gears inside the lap counter were worn, but turns out it was something else.

If you are not familiar with this lap counter, it used an isolated piece of 9" straight which was self powered, one wire connected directly to the power pack the other went through the lap counter. The lap counter was triggered when the car made the connection between the two rails.

Back in the late 60s and early 70s, I had my track wired using a thin single strand bell wire (who knew any better?). Same for the lap counter. Even after I put my track back up in the late 1990s I used that thin wire for the lap counter and gave the lap counter it's own power pack. The lap counter still could not turn the 10s digit. Then one day I changed the wire and used the 16 ga. speaker wire. All of a sudden the lap counter worked!

The only reason had to be using larger wire for the lap counter. The wire of the armature was the same, yet the lap counter was obviously getting more power. So I don't know if the wire size of the armature is the limiting factor in the circuit, which is the point I think you are trying to make.

Plus, if the armature wire was a limiting factor in the electrical circuit, why would you not just wire your whole track with 36 ga. wire if that was the size of the wire used in the armature?

Thanks...Joe


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## SDMedanic (Apr 21, 2011)

Rewiring the controllers wont help. As many have indicated it is material transfer associated with current flow from track to car and from car to track. This is why (all things being equal ) one pickup wears and the other burns (grunge buildup). Increasing the spring pressure on the burn shoe helps.


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## ajd350 (Sep 18, 2005)

LDThomas said:


> Just like an electro plating process, the current flows one direction and the deposits go the opposite direction. Current flows out of the negative rail and the deposites go onto the negative rail.
> 
> By adding pressure to that shoe, you simply wear off the coating at the same rate it is deposited - thus a clean shoe/rail. Simple and easy solution.


+1

Simple, and it works. 

You don't need to crank the pressure up any more than it takes to solve the issue. Also, if there is metal deposition from the rail on that shoe you must sand it ALL off or it will continue to return no matter how much pressure you have. Look at the shoe under a magnifier. If you see any sign of streaks or flecks, get them off. Finish off with 1000 or higher grit sandpaper.


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## Grandcheapskate (Jan 5, 2006)

Hi Guys,
Thanks for giving me the solution to the problem. 

However, in my mind I still do not understand how the size of the wire inside the controller cannot have an effect on your total track wiring. If you wire your track (power supply to all jumpers) with 16 gauge wire but there is 22 or smaller gauge wire used inside (and outside) the controller, how can that not be detremental?

The controller is part of the whole circuit and if the controller has a smaller "pipe" than all the other parts of the circuit, how can it not restrict the flow of electrons? If you were to change all the wiring on your track to 22 gauge from 16 gauge, wouldn't that have a negative effect on the amount of current the wire could carry?

I still want to experiment with changing the wire inside the controller to at least the same size as the track wiring and see the result. If you believe that the size of the controller wiring has no effect on load capacity, then I ask this question - would changing the wiring of your controller to the same gauge wire used in the armature (34-38 gauge) make a difference? If so, why?

Thanks...Joe


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## LDThomas (Nov 30, 1999)

The controller is SUPPOSED to limit the power to the track. That is its job. At full power, it should bypass the smaller wires.


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## cwbam (Feb 8, 2010)

Electricity is a lot like flowing water.

Volts & Amps compare with 
Pressure (psi) & Gallons/minute (gpm)

yes the armature wire is very small (also shoes rail ect.....) 
(just like small 1/2" pipe to sink)

A power supply with some AMPs really is like a big tank water supply on top of a hill.
For every foot of wire, length of track (rail), its size, its type of metal, ect...
limits the flow of electricity. compare to a 3 story house the lower floors have more 
power/ water.


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## Gerome (Sep 25, 2011)

Which side is the negative side for t-jets?


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## slotcarman12078 (Oct 3, 2008)

The negative side is (on a US car) the passenger side. Looking at the bottom of the chassis, the front brush is the positive, the back brush is the negative.


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## Grandcheapskate (Jan 5, 2006)

LDThomas said:


> The controller is SUPPOSED to limit the power to the track. That is its job. At full power, it should bypass the smaller wires.


Not true. At full power the controller bypasses the resistor, not the controller wires.

Let's assume at full power a controller completely bypasses the resistor. So for this discussion remove the resistor from the circuit. There is still a wire going from the power supply to the controller and then from the controller to the track. If the wires to and from the controller are smaller than the wire used in the rest of the track wiring, how can that not have a limiting effect?

As CWBAM points out, electricity is like (though not exaclty like) water in a pipe. So if the "pipe" inside the controller is smaller than the rest of the "pipe", does not that limit the "flow" potential of the entire system to the potential of the smallest "pipe"?

Thanks...Joe


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## slotcarman12078 (Oct 3, 2008)

The smallest wire in the whole circuit is the armature wires. And not only are they the smallest, but they're also loaded with bends plus the wire's natural resistive qualities. Running the juice through them is what makes the corresponding pole on the arm magnetic that is attracted to the front magnet, which in turn makes the motor turn, but only about 1 6th of a revolution.

Since HO motors have 3 poles, it isn't just the front magnet doing the work. When the motor turns a certain amount, the brushes activate in reverse charging the pole approaching the back magnet. The juice goes back and forth between arms and magnets keeping the arm spinning. Hypothetically, a pancake isn't a 3 cylinder engine. Think of it as a 6 cylinder.


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