Creating track dirt for testing

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Someone
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Creating track dirt for testing

Postby Someone » Fri Nov 26, 2021 8:59 am

Does anyone know how to artificially create track dirt for testing, because I want to test different Track cleaning methods without having to wait for track to get dirty.
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Bigmet
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Re: Creating track dirt for testing

Postby Bigmet » Fri Nov 26, 2021 10:25 am

Truly, the answer is to give as much of your stock as possible a very extended run on a track circuit.

I tested what 'track dirt' actually was back in the early 70s, what with having access to a very comprehensively equipped materials analysis laboratory. This was from a nickel silver rail, mostly metal wheeled stock layout. What did I find? The 'dark stuff' proved to be largely metal oxides in very fine particulate form, dominated by copper oxide. What was gumming it together was a mixture of organic stuff, probably lubricant residues and plasticisers.

Even knowing this, I cannot suggest a means of replicating it, nor of applying it to the railhead, to properly represent what actually happens when model trains are operated; which is what you need for any test validity.

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Bufferstop
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Re: Creating track dirt for testing

Postby Bufferstop » Tue Nov 30, 2021 11:31 am

In my experience artificially created dirt never works on any level; it doesn't look right, doesn't produce the same problems and is usually far too easy to clean up.
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muggins
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Re: Creating track dirt for testing

Postby muggins » Tue Nov 30, 2021 5:30 pm

Bigmet wrote:...The 'dark stuff' proved to be largely metal oxides in very fine particulate form, dominated by copper oxide.


It's a long time since O-level chemistry, so I have now given up trying to work out how on earth we start with metallic copper as a constituent of the nickel silver track and we end up with an oxide of copper *word censored* on top of that track. Did you ever work out the means whereby the one turns into t'other?

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Bufferstop
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Re: Creating track dirt for testing

Postby Bufferstop » Tue Nov 30, 2021 8:55 pm

The loco wheels and the track are like your car battery terminals and the connectors clamped to them, if the air (which will have some moisture) can get in there you'll get electrolytic action! That will turn copper into copper oxide. At least that's how I understand it.
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Re: Creating track dirt for testing

Postby Bigmet » Wed Dec 01, 2021 1:22 pm

muggins wrote:...how on earth we start with metallic copper as a constituent of the nickel silver track and we end up with an oxide of copper ... on top of that track. Did you ever work out the means whereby the one turns into t'other?

In addition to the above, keep in mind that this is 'micro' action. It's the working of the wheels on the rails that exposes the metals in the alloy to Oxygen, which is second only to Fluorine as an oxidising agent.

What I would surmise from having looked at this type of process on the materials our team was paid to analyse, and for which purpose we were generously provided with state of the art instruments; is that the oxidation occurs 'instantly' any bare metal is exposed to atmosphere. What happens thereafter depends on factors such as the volume of the metal oxide compared to the metal, and the tensile strength and adhesion of the oxide compared to the alloy structure in which it forms. The end of this is that the copper oxide detaches most easily from the rail alloy under the mechanical action of wheels on the rails to become the major metal oxide constituent of the dirt I sampled.

I didn't think at the time to look at the oxide particulate size and its size distribution: very, very, small, probably dominated by sub micron size particles would be my guess. Very sloppy of me as we had a world class microanalyst available...

Edited to eliminate a 'quote' error.
Last edited by Bigmet on Wed Dec 01, 2021 4:11 pm, edited 1 time in total.

muggins
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Re: Creating track dirt for testing

Postby muggins » Wed Dec 01, 2021 2:53 pm

Cheers Bigmet. By sheer coincidence I've just been sent a link to this awfully long-winded video which purports to explain the science of track cleaning ...https://www.youtube.com/watch?v=nXH1_ZU ... sUnlimited

I'm still undecided as to how much of that is kosher. As I said earlier, it's an awful long time since O-levels ...

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Re: Creating track dirt for testing

Postby Bigmet » Wed Dec 01, 2021 4:15 pm

Yes, I just failed my 'O' level 'Watching Tedious Video'.

Eliminate dirt causes from wheels, mechanism and track. Hard metal wheels and rails only, carefully applied minimal lubrication.
Operate very regularly.
Clean railhead periodically, period determined by experience. Back of hardboard does all that is required.

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Re: Creating track dirt for testing

Postby luckymucklebackit » Thu Dec 02, 2021 12:18 pm

An interesting discussion, and so far nobody has mentioned what used to be thought as the number one enemy of clean track - the traction tyre!

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Re: Creating track dirt for testing

Postby Bigmet » Thu Dec 02, 2021 2:35 pm

That's a straightforward choice, abandoning the traction tyre is part of dirt prevention as far as I am concerned.

The rail dirt problem broadly falls into two categories:
All metal wheels and rail layout;
Polymer wheels and plastic track component layout.

My own current experience is restricted to the first of these.


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