Micro-Arcing,..... Metal vs Plastic wheels


B

beiland

Well-Known Member
I believe that it's established that its the micro-arcing that creates the black gunk we get on our model railroad wheels. So a few questions came to mind this morning:

1) Does this arcing occur to same degree using metal wheels as plastic wheels?

2) Does the arcing occur, at all, using plastic wheels,... a non conductive material?

3) Is the black gunk we find on the plastic wheels just a deposit from another source, or a result of any type of arcing?


Other than for improved reduction in friction, is there other compelling reasons to switch all of our plastic wheels to metal??
 
Brian -
Micro-arcing doesn't create the black gunk, it contributes to its formation.
1 & 2 - There is no arcing with either metal or plastic wheels. Arcing only occurs when there is electrical conductance in play, such as locomotives. And it normally only occurs when there is a break in conductivity, uneven track, extra wide gaps between rails, dirt deposits on track, etc.
3 - Plastic wheels, being non-conductive, pick up a static charge which then attracts dust and dirt, which in turn gets compressed into the black gunk on the wheels. Some of this in turn re-deposits itself on the track, which besides being spread around, causes places where the loco wheels have a momentary break in conductivity which causes further arcing. The arcing pits the track which traps dirt and dust, thus compounding the problem.
I have converted almost all of my 800 freight cars to metal wheels, and I have noticed that they don't get any black gunk on them. I rarely clean track, but I have a Woodland Scenics "Dust Monkey" on every caboose for dust control. I also run trains at least five days a week which in turn keeps track cleaner.
Others may have different results.
 
I agree with Willie on the electric contact, or poor electrical contact as the primary cause for the black gunk on the wheels. The locomotive wheels causes micro-arcing which deposits the gunk on both wheels and track.

But, in regard to plastic wheels, I think the composition of the older plastic and plastic like wheels also causes the black gunk as the wheels slowly broke down over use and age. The newer wheels are not as likely to cause any problems, but I like Willie, like to install metal wheels on my rolling stock.

I'm trying a method to use Track Magic as a rail cleaner in a yard and lead and then apply graphite very spareingly on the "sides" of the rail and this is reported to reduce the build up of the deposits. Joe Fugate on Trainmasters Videos showed a demo of this method.

I too like the Woodland Scenic Dust Monkeys to control dust, but they alos remove any liquid cleaner that you may have applied to the track.

Greg
 
What is the gunk?

JoeF

The black gunk has been chemically analyzed by a modeler who is also a chemist.

It consists of mostly: metal oxides, dust, and oil residue — in that order.

But it’s mostly metal oxides that form from micro-arcing when you run trains.

Essentially, a micro-arc “fires tiny lightning-like energy” at the metals in the rail and wheels, combining the metal alloy molecules with oxygen, and exploding the molecules off into a non-conducting gray-black oxide coating that builds up on the rails and wheels.

Dust and oil residue also get attracted to the electrically charged rails and wheels. Blame the electricity in the rails for most of the black gunk, in other words. If the rails were not powered, all we would get is a little dust for the most part, with maybe a little cleaning solvent or oil residue.

Black Gunk be Gone
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I also found this comment in that discussion

Plastic Wheels - Don't Use Them
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Plastic wheels are going to cause problems with dirt collection to the wheel tread. They are considered tribogenerators, where electrons are stripped off the plastic while the wheels roll down the rails. This effectively makes them capacitors with a positive charge. This charge attracts the dirt around your railroad. The longer you run plastic wheels, the more often you will have to clean the gunk collected on the wheels. It's not going to change.
Replace all your wheelsets with metal wheels. There are many benefits: 1) they will not generate a charge and therefore won't collect dirt, 2) they are heavier and will lower the center of gravity of your rolling stock, making them track better and stay on the rails better, 3) they are easier to adjust to the proper gauge and will stay in gauge. Plastic wheels may not be in gauge and may not be adjustable to the proper gauge, and 4) the metal wheels make a nice "clickity-clack" as they pass across rail joints.
Once I changed mine, I NEVER use plastic wheels and seldom clean the track. I never have to clean the wheels on the rolling stock or engines.
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