# Origin of Black Dust?



## chuck n (Jan 2, 2008)

Over the years there has been some discussion of the origin and nature of the "BLACK DUST" that occurs in, on and around our layouts. Very fine grained brass from the grinding of the metal wheels of the engine and cars on the edge of the tail head has been suggested as one source and carbon from the arching between wheels and rails of engines has also been suggested. Yesterday I started an experiment to determine the composition of the black dust. I polished the top of my mainline with a green Scotchbrite pad and I followed it with a wet sponge to remove any dust on the top or the inside of the railhead.


I ran two engines for 2.5 hours each. My Aristo Mallet with a battery pack and my LGB Sumpter Valley Mallet via track power. My SV Mallet along with my Uintah Mallet are always causing a lot of arching and are the only engines that really need wheel cleaning on a regular basis.

After each run I wiped the railhead and inside with an alcohol wipe. I also did a Scotchbrite pass and following that cleaned the rails with a rag. I could not pick up any black dust after the cleaning.

Here are some pictures of the wipes after each run. I'm going to take them in to a lab so see if we can analyze the black dust.



















Chuck

PS The curves on my layout are all 10' diameter Aristo wide radius.


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## bnsfconductor (Jan 3, 2008)

Did you run any cars behind the engine or just the engine it self? 

Craig


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## BigRedOne (Dec 13, 2012)

Isn't 97% of the universe made up of dark matter?


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## chuck n (Jan 2, 2008)

Craig, I tried to limit the variables. The Aristo Mallet was powered by a trailing box car with the battery and REVO control. Both the battery car and tenders had metal wheels. Chuck 

PS here is a picture of the Aristo Mallet with the battery car pulling it's usual consist at one of Dr. Rivet's steam/spark ups.










There are 32 DM&IR ore cars in the train.


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## toddalin (Jan 4, 2008)

The lab will only find what you ask them to analyze for (e.g., metals, volatile organic compounds, oil & grease, etc.,). It could get expensive if you ask for the full gamut. I used to deal with these guys when I did hazarous materials investigations and tank removals.

Truesdail Labs


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## Greg Elmassian (Jan 3, 2008)

Why not run the sample through a mass spectrometer.... pretty easy to see the elements.... carbon or brass (copper and etc.) or steel (iron and etc.) 

http://www.sisweb.com/index/referenc/msservic.htm 

The proportions of the elements found will give you the answer pretty quick. 

You are not really interested the the levels or concentration in absolute measurement, just the composition. Makes it a lot easier.

Greg


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## chuck n (Jan 2, 2008)

As of now I don't know what magic machine we'll use: ICP-MS, SEM with detector, microprobe, or some other new tool that they have acquired since I retired. In all likelyhood it will just be a qualitative analysis. Carbon will certainly be there, because of the cotton swab used to collect the dust.


Chuck


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## Greg Elmassian (Jan 3, 2008)

Will be very interested to see the results... I'm betting on carbon from arcing... it's always been hard for me to believe it's ground up bits of metal, especially since the black dust has seemed the same for brass and stainless track alike. 

Greg


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## toddalin (Jan 4, 2008)

Posted By chuck n on 14 May 2013 06:07 AM 
Carbon will certainly be there, because of the cotton swab used to collect the dust.


Chuck


Not the way to do it.

Call the lab and discuss your plans with them, what you suspect the materials to include, and ask them what sampling media you should be using to obtain a representative sample. They may even provide it to you. You can probably forgo the chain-of-custody requirements.


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## chuck n (Jan 2, 2008)

The analysis is being done as a courtesy by a friend. The question is do we see copper and zinc (brass) or not? I wanted something soft with which to wipe the rails. I did not want to abraid the rails in any way. I could not think of anything I could wipe the rails with that did not contain carbon and was soft. I droped the swipes off this morning. All my track is brass. Chuck


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## Semper Vaporo (Jan 2, 2008)

They could measure a clean section of the swipe material and then subtract that from the measurements of the dirty sample. The difference is the content of the dirt.


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## Greg Elmassian (Jan 3, 2008)

Todd, in one reply you say you have to know what you are looking for (and imply high cost if you look for everything) 

Then a spectral analysis is suggested and you say this is not the way to do it. 

Given that we are not sure of what to look for (although a physicist would give you some great guesses, like copper, zinc, carbon, and whatever metals the wheels are made of) 

So what is the best way? You seem to have said no to both ways. 

Greg


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## Totalwrecker (Feb 26, 2009)

Posted By Greg Elmassian on 14 May 2013 07:49 AM 
Will be very interested to see the results... I'm betting on carbon from arcing... it's always been hard for me to believe it's ground up bits of metal, especially since the black dust has seemed the same for brass and stainless track alike. 

Greg 
All fine (dust grain size) metal particles are seen as black. This in not metal grindings of color. Finer. More like the thin surface scuff caused by a softer metal on a harder metal. Friction transfer thick. 

I'd go on, but judging by last nights ramblings I need a meeting of; On n On n On Aonoymous









John


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## Greg Elmassian (Jan 3, 2008)

Yeah John, I do remember that discussion... I have seen brass dust from abrasion on track, and it looks brass... but I don't doubt that finer stuff could look black. But my personal G scale experience has only been a much coarser "grind"... like drip coffee vs. espresso! 

Greg


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## toddalin (Jan 4, 2008)

Posted By Greg Elmassian on 14 May 2013 01:18 PM 
Todd, in one reply you say you have to know what you are looking for (and imply high cost if you look for everything) 

Then a spectral analysis is suggested and you say this is not the way to do it. 

Given that we are not sure of what to look for (although a physicist would give you some great guesses, like copper, zinc, carbon, and whatever metals the wheels are made of) 

So what is the best way? You seem to have said no to both ways. 

Greg 



My suggestion, from the start, has been to contact the lab, describe the situation, and ask them what you should be looking for and how to sample for it properly.


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## Greg Elmassian (Jan 3, 2008)

Sorry, what I took from you was a particular lab that seemed to do chemical detection of things, not mass spectroscopy. 

Further investigation does show they do indeed possess a quadrupole mass spectrometer .... the first page seemed to be chemical analysis only. 

Sorry again 

Greg


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## chuck n (Jan 2, 2008)

Todd:


I am just curious as to whether there are metals in the black dust. I talked to my friend this morning and he will be using either a ion microprobe or an SEM both of which are equipped with energy dispersive detectors. Either of these should be able to handle particles down to about 5 micrometers (microns).

Greg and I have been having this discussion for a while. I thought it was time to try to get some data. If you want to design a more suitable experiment, that meets your criteria, you are welcome to do it. I will be happy with the results of this regardless of how it turns out. 

I can see carbon (as part of plastic) coming from plastic wheels rubbing on the rails as they go around curves. Plastic is softer than brass or any other track material that we use. I have heard of LGB plastic wheel flanges being worn down. I haven't seen it, but it could happen on a layout being run continuously like in a store or restaurant and I haven't used plastic wheels for years. I do not see any other viable source for carbon. 

My problem with carbon, as a residue from arcing, is that it likes to burn and become carbon dioxide. The heat of the arc should, in my opinion, be sufficient to convert all the carbon and plastic to carbon dioxide and other oxides, like water and nitrogen oxides.

What appears to have been missed in this discussion is that in my original post I mentioned that one of the runs was done with battery power. There was no electrical current to or from the track. 

When I first ran the Mallet on battery several years ago, other engines on the track started to move, even though the power switch on the engine was moved from track to battery. Only after cutting the wires to the tender trucks was I able to stop the other engines from running.

John:

I agree with what you said recently and in the earlier earlier thread about the color of very fine metals. I mineralogy we have a test for minerals that is call a scratch test. It is a ceramic plate that removes a small amount of a mineral. The color of the smear can be used to help identify the mineral. Pyrite (fools gold) an iron sulfide, is bronze to gold in color when it is a crystal large enough to be seen with the eye or a magnifying glass. The scratch smear is black.

Chuck


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## Greg Elmassian (Jan 3, 2008)

Ahh, battery power, you're cheating ha ha! 

Well then carbon from arcing is out. Has to be metal from the rail or wheels. 

If the testing is reasonable, I'll have to send a sample in from my layout. 

Greg


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## chuck n (Jan 2, 2008)

I was just trying to cover the bases. I did state the battery in the first post. Not cheating, just careful. My thought is that the source for dust is wheels, track, or both. It all depends on your track and wheels. In my case I think that it is the track (brass) that is being ground down (slowly) because it is softer than the wheels. If you are using SS track the wheels may be loosing material. I have no idea as to nickel-silver track. Chuck


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## chuck n (Jan 2, 2008)

I just received the results of the analyzes of the particles on the wipes. Harvey was able to transfer some of the particles from the wipe to the machine (SEM with energy dispersive detector). The particles were 1 micrometer and smaller. Most of the particles contained copper and zinc (brass) a couple contained silicon and other elements consistent with weathered mineral material (dust from soil). This was probably picked up from the swipe contacting the ballast. He did not detect any carbon on or in any of the particles he looked at.

Both wipes, 1 and 2, had similar particles. Wipe 1 was after the battery run and wipe 2 was after the powered track run. 


Chuck


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## Greg Elmassian (Jan 3, 2008)

Hey Chuck, just pulling your leg on "cheating", next time I'll add a big smiley to know it's all in fun! 

Chewed up brass, wow, just after a few passes... so clearly from the track being abraded by the wheels (I think it's safe to assume the wheels on the loco were not brass, or did you check this?). I wonder if it would be a different "balance" on SS rail, i.e. the wheels would wear before the track... Is this affordable, maybe I could perform the same experiment on my SS track and with and without SS wheels. 

The funny thing is that my "black" seems a bit "greasy" and not "dry"... 

Greg


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## toddalin (Jan 4, 2008)

The detectors are so sensitive (typically parts per billion range) that you could take a wipe, go out and swab the track with some elbow grease, and they would find brass on it. This is not to say that there are not other materials or compounds in the dust that they just weren't looking for.


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## chuck n (Jan 2, 2008)

Greg, I knew you were kidding because of the "ha, ha". Not to worry. The analysis was gratis by a friend at a lab where we used to work before we retired. I think that I have used up my credits. The SEM with a detector is a fairly common piece of equipment in most geology departments. You might check around some of the Geology (Earth Science) departments in the LA area to see if some one has one and might be willing to help run some samples. If you can interest a high school student in this project it could be expanded into a neat science fair project. Visiting various layouts with different track and collecting and analyzing the dust, using battery and track power. The same engines should be used in all the tests. The Aristo Mallet still has shinny (original) looking wheels. I have no idea as to the metal used (help needed from someone). The LGB Mallet has plated drivers and the plating has worn through to the brass beneath. There is a narrow ring of brass showing on the tread. My dust also feels greasy. I think that is the result of the very fine grain size of the dust, just a guess. 

Chuck 

PS I ran the engines for 2.5 hours in each part. It was a lot more than a few laps. It was probably about 40 seconds per lap. 

A student through a school chemistry teacher might be able to gain access to a suitable SEM far easier that you could by yourself.


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## Greg Elmassian (Jan 3, 2008)

The mallet has "pot metal" drivers, with copper plating and some sort of silver plating on top.. (does not look right for nickel, but who knows), but for sure no brass. 

So pass 1 was mallet on battery? Was there any significant difference between pass 1 and pass 2? 

Greg


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## chuck n (Jan 2, 2008)

Greg:

The Aristo Mallet was on the battery. Other than using different engines, the runs were fairly identical, length of time and speed. 

If you have some scrap rail (SS) you might try to determine the relative hardness of your wheels and the rail. Find a sharp corner on the rail and see if you can scratch the back of a wheel. If it scratches, the wheel will probably wear relative to the rail. If it doesn't the wear will probably be on the rail. If the metals are of nearly similar hardness it will be hard to tell the relative hardness with a scratch test and both might wear nearly equally.

Another thought, we both agree that the dust feels greasy. Do you think that as the film of dust builds up, we could reduce further grinding because of the possible lubricating effect of the dust and we reach sort of a steady state where further removal of material is minimized?

Chuck


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## chuck n (Jan 2, 2008)

He zapped several different particles and only one particle was analyzed at a time. One would have to look a all the particles to be sure nothing was missed. That was not possible. For me the critical question is "Was there brass?" or not? The only heavy element that, if it was there might not show up, is Krypton. I was told that all elements with atomic weights equal to boron and higher could be detected. That doesn't leave too many out.

Chuck

PS other elements did show up. I didn't mention them because I didn't think it germain to the discussion: lead, magnesium, silicon, aluminum, potassium. iron, nickel, chromium, titanium, manganese. The critical elements for this discussion are copper and zinc.


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## Greg Elmassian (Jan 3, 2008)

The iron, nickel, chromium, silicon, manganese would make sense for the wheels, like the pilot and tender wheels which are plated steel.. but I assume that copper and zinc were far in the lead? 

The buildup being either abrasive or lubricative, interesting question. I would think abrasive... small particles of metal... but hmm... 

Greg


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## chuck n (Jan 2, 2008)

Greg, those elements could come from the wheels. Most if not all of those elements could also come from my ballast. I am using crusher fines from a local quarry. The geologic name for the rock is diabase. It is an intrusive rock which is chemically identical to basalt. For example, chromium and nickel are present in trace amounts in that rock type.

Chuck


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## Greg Elmassian (Jan 3, 2008)

I think you will find more chrome and nickel on your wheels, especially in light of the fact that you cleaned the rails first and it took very little time to make "black stuff" on clean rails. 

Greg


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## toddalin (Jan 4, 2008)

Posted By chuck n on 15 May 2013 01:55 PM 
Chuck

PS other elements did show up. I didn't mention them because I didn't think it germain to the discussion: lead, magnesium, silicon, aluminum, potassium. iron, nickel, chromium, titanium, manganese. The critical elements for this discussion are copper and zinc.





Maybe more germain than you think: 
*Q:* : Why do I get so much black soot on and around my welds when I use 5356 GMAW wire to weld 6061T6? 

*A:* The black soot actually is magnesium oxide. Magnesium content in 5356 is high (up to 5 percent). Some common base materials, such as 6061, also have relatively high amounts of magnesium—generally 1 percent.


When magnesium is vaporized by the arc’s heat and comes in contact with oxides, black soot forms. A proper gun push angle of approximately 15 degrees helps keep gas coverage at the leading edge of the weld pool, which reduces soot.


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## chuck n (Jan 2, 2008)

Todd, I have no idea about what you are talking about as it relates to my track or my experiment. I wouldn't know how to weld if I was given every thing needed and years to figure it out. Magnesium is a very common component in most naturally occurring material. I look on it as part of the natural background. This is not the place to discuss people's professional background. I am a little tired of your questioning my experimental design without knowing my background. Suffice it to say that I graduated with an undergraduate degree in geology in 1962 and have several other advanced degrees. Over my career I have been quite successful solving many problems. I even predicted the location of a mineral deposit that has more than $20,000,000,000 worth of molybdenum. Yes, that is twenty billion dollars.

Chuck 


Accept comments here as they are presented. It is fine to question results, but if you don't like the design of the study. Just say I disagree and do it yourself. Then we will have a discussion.


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## Greg Elmassian (Jan 3, 2008)

Todd, perhaps you made the same mistake I did earlier, I failed to read the OP's first post carefully. 

The first run was done on battery power, so no possibility of arcing. 

Greg


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## toddalin (Jan 4, 2008)

Posted By chuck n on 15 May 2013 05:01 PM 
Todd, I have no idea about what you are talking about as it relates to my track or my experiment. I wouldn't know how to weld if I was given every thing needed and years to figure it out. Magnesium is a very common component in most naturally occurring material. I look on it as part of the natural background. This is not the place to discuss people's professional background. I am a little tired of your questioning my experimental design without knowing my background. Suffice it to say that I graduated with an undergraduate degree in geology in 1962 and have several other advanced degrees. Over my career I have been quite successful solving many problems. I even predicted the location of a mineral deposit that has more than $20,000,000,000 worth of molybdenum. Yes, that is twenty billion dollars. Chuck Accept comments here as they are presented. It is fine to question results, but if you don't like the design of the study. Just say I disagree and do it yourself. Then we will have a discussion. 



I'm not calling anyone's background into question or even the methods. I am simply trying to get to the bottom of the "black dust and soot" issue.

You can't see the similarities between arc welding to micro-arcing at the wheels? Have you never watched your trains run in the dark?

My point is that trace quantites of some contaminants (including but not limited to magnesium) can also leave oxide residue when subject to arcing and their contribution should not be so easily discounted.

But it's you experiment and you can draw your own conclusions.


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## toddalin (Jan 4, 2008)

Posted By Greg Elmassian on 15 May 2013 05:34 PM 
Todd, perhaps you made the same mistake I did earlier, I failed to read the OP's first post carefully. 

The first run was done on battery power, so no possibility of arcing. 

Greg 

Right. Was that sample also run in the lab and did it prove to be the same? Could that have been residue off the wheels laid onto the track rather than vice versa? Most people who run batteries tend to let the wheels get a bit dirtier because it has no effect on performance so goes unnoticed.


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## chuck n (Jan 2, 2008)

Todd 

Both samples were run in the lab at the same time. Maybe a few minutes apart. 

The track was cleaned before each run. I ran the battery engine first, so that any possible contamination would be minimized.


The original question was carbon or track, in my case brass. There has been no discussion of other components derived from arcing. I won't deny there could be other elements freed through arcing. Just not carbon.


Chuck

In the OP pictures wipe 1 was the battery powered Aristo Mallet. Wipe 2 was the track powered LGB Mallet. Both wipes were analyzed.

There are examples out there of track heads being worn down by long term running.


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## toddalin (Jan 4, 2008)

Posted By chuck n on 15 May 2013 05:58 PM 
Todd 

Both samples were run in the lab at the same time. Maybe a few minutes apart. 

The track was cleaned before each run. I ran the battery engine first, so that any possible contamination would be minimized.


The original question was carbon or track, in my case brass. There has been no discussion of other components derived from arcing. I won't deny there could be other elements freed through arcing. Just not carbon.


Chuck


Actually, the question is what is "_the composition of the black dust_" regardless of if it is carbon based.


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## chuck n (Jan 2, 2008)

Most of the particles were copper and zinc with a little lead. Other particles had other elements. 


It is obvious that you do not like my experimental design. Go for it, design your experiment and have the dust analyzed. There is not much more I can say.

The experiment wasn't designed to look for other possible combustion products.


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## SD90WLMT (Feb 16, 2010)

Not to stir the pot here any further,.. But I do need to clarify one point, I'm not finding mentioned in this thread... 

I understand the rails were cleaned completely before each respective run was made... 

My ? is , were ALL the wheels also cleaned before their runs, so as not to introduce any old foreign material into the now 'sterile environment', and not bear any additional influence during the actual runs on the samples collected? 

Thanks Guys, great test BTW!! 

Dirk


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## chuck n (Jan 2, 2008)

Dirk, I checked the Aristo mallet and the wheels looked clean, so I did nothing. Because the LGBMallet always has dirty wheels, I cleaned its wheels with a Scotchbrite pad before running. Chuck


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