Update: Removing Blackening from Metal Wheels and Other Resistive Wheel Set Information

Model Railroader Layouts and layout building
1

Does anyone know of a method for N-scale wheels, such as Micro-Trains? I need to add resistance across the wheels for block detection but the blackening on the treads is an insulator, at least according to my multi-meter.

Help would be much appreciated.

Thanks,
Bruce

2

If you are talking about the black gunk that accumulates on the wheels and looks like dirty gum spots on sidewalks, there are lots of solutions but they all lead to the same result. You have to get it off the wheels to improve electrical contact and avoid derailments.

One way to do it is to use a small screwdriver blade to scrape it off. It comes off pretty easy using that method, but if you are not careful, you risk leaving scratch marks on the wheels.

Another way, and my favorite way if the black gunk is on locomotive wheels, is to wet a white cotton cloth with 70% isopropyl alcohol and lay the wet cloth on a section of powered track. Hold the front or rear wheels of the locomotive on the wet cloth and apply power. Within a second or two, the wheels will be bright and clean, free of the black gunk. Then, reverse the operation and do the other set of wheels.

Rich

3

Thanks Rich,

Actually, I’m talking about the black (more a kind of dark bronze) finish applied to metal wheels. It acts as an insulator. As an experiment, I scraped some off of a wheel and the metal underneath was conductive. In order to activate the block detectors (Dr. Bruce Chubb’s Optimal Detector) you need conductive wheels with an insulated axle, across which you add a resistor or resistive paint.

Unfortunately, scraping off the finish scratches up the wheels, which will make them dirt collectors and might otherwise affect rolling.

Regards,
Bruce

4

I do not have direct experience with the new blackened metal wheel sets from Micro-Trains…

But… in HO scale using a brass brush in a Dremel rotary tool is the ticket.

-Kevin

5

Thanks, Kevin.

Figuring a way to hold these tiny wheelsets will be a challenge, but I’ll give this a try.

Regards,
Bruce

6

Dunno, seems like a bad idea to me. How do you keep the wheel in round?

Rich

7

For HO I have a pair of pliers that is almost exactly the right width to hold HO wheelsets for nearly the entire axle. For N, perhaps needlenose?
Dave Nelson

8

I removed that blackener from the treads of Kadee wheelsets using a brass wire brush in a motor tool. Simply leave the wheels in the trucks and use a gloved thumb or finger to prevent the wheel from spinning at the same speed as does the wire brush. It takes only a few seconds per wheel.

Wayne

9

You might think about chucking the axle end in a collet, or the tread or flange gently in a chuck, and turning the wheel treads or backs you can reach against a thin wire brush or something else ‘yieldingly’ abrasive. Many years ago the thing I used for treads was a retractable ‘pocket’ glass-fiber cleaning brush, which as I recall was sold to clean typebars – probably too coarse for modern stuff, but still possible.

If you have to use any particular force, just clamp the tool that’s turning the wheelset, and push something reasonably smooth 180 degrees away from the point on the tread or back you’re ‘cleaning’ with your other hand to balance things.

One of those very small ‘anodizing’ electroplating rigs used to put colors on jewelry could have polarity reversed with some chemicals and used with a ‘spun’ wheelset to clean, polish, or brighten just the contact patch with the rail.

10

Never been an issue. The brass wire wheel is soft. A steel brush could be an issue.

You barely need to touch the wire wheel to the model wheel to get the black off of it. There is not need to be agressive with the wire brush or use any pressure.

-Kevin

11

When I have to dress a wheel tread, I use my thumb (left hand) against the other metal wheel (same axel) to add drag while dressing up the metal wheel’s black tread with a Dremal Tool and soft wire (brass) wheel in my right hand, (you must pick the correct speed ‘‘SLOW’’ that works for you) (WEAR EYE PROTECTION) this is done with the wheels in the trucks. DO NOT LET THE WHEELS SPIN FAST, SOMETHING LIKE THE PLASTIC AXEL POINTED END OR SIDE FRAME WILL MELT.

The way I hold the Dremal Tool, as the wire wheel spins it is throwing crud/loose wire wheel wire right at you. (WEAR EYE PROTECTION)

I missed Doctorwayne’s above reply. I will just add this, wear eye protection.

If you have trouble holding the car, truck, wheel and the Dremal Tool try this. If the trucks are fasten to the car body with a screw, I can’t remember if it’s a screw or push pin, remove the screw and truck and fasten the truck to a board with a small wood screw, snug the truck down then the truck will not move/swivel. Then clean the wheels.

12

Thanks Wayne,

Emphasis on gloved, I’m sure! Have you ever had occasion for the brush to slip and damage the truck frame?

Regards,

Bruce

13

Thanks, Kevin.

Regards,
Bruce

14

Thanks, PC101.

One question: would you recommend wearing eye protection?

Regards,
Bruce

15

As I follow this thread, a question comes to mind. Why does Micro trains blacken the wheels in the first place if the blackening interferes with conductivity?

Rich

16

Beats me, Rich.

I ordered some Fox Valley resistive wheelsets, which tend to be out of stock everywhere, but when they arrived the tiny surface mount resistors–probably 0201 size–had popped off about half of them. I have some resistive paint I plan to use for those, as I do not have the means to reattach the resistors unless I can find some conductive glue somewhere.

I just purchased some Intermountain wheelsets on Ebay. The pictures showed them as un-blackened, but we’ll see when they arrive. I’ll try the resisitive paint on them, as well.

But I still have lots of brand-new Micro-Trains wheelsets I’d like to put into service.

Regards,
Bruce

17

This is only an issue for model railroaders with block occupancy detection.

I suppose Micro Trains believes they will satisfy more customers with blackened freight car wheels than they disappoint with poor conductivity.

When I was in N scale, all the freight car wheels from Mirco Trains were black plastic. They did not conduct electricity worth a squat.

-Kevin

18

I just find it weird that a manufacturer would purposely coat their wheelsets to the extent that it interferes with electrical conductivity. I don’t get it.

Rich

19

I wonder the same thing. I used HO Scale Intermountain wheelsets for the base of my resistor wheel sets. they are blackened brass but it doesn’t seem to interfere with the electrical properties of the brass.

I scrape off teh coating on the back face of the wheel and on the axle where I mount the 10Kohm resistor so the conductive paint has a good place to bond and make good electrical contact. I test every wheelset before installation with a DVM on the wheel tread to make sure I get the correct resistance across the wheelset.

As for answering the OP question, I chucked up a blackened metal wheelset I had laying around in my drill and hit the tread with a bit of 600 grit sand paper and it tool blackening off real quick. If you are worried about a pitted surface you may try a 800+ grit sandpaper or maybe even some steel wool.

Here is what I used. The wheelset is this case had a plastic axle but it was really easy to just wrap sandpaper around just hte tread in this case.

20

It’s probably much more expensive to mask the wheels before plating than to plate the whole thing.

I work for a semiconductor company, and at first I was surprised to learn the lengths we go to in order to shave ¼¢ per unit cost in manufacturing. Of course, these parts sell by the millions, but if you scale for low-run production, then an extra 50¢ per wheelset is huge.

But then, you almost never see a railroad car in regular use that does not have wheels with shiny steel treads and oxide-red discs.

Regards,
Bruce