Wheels appear not to be conducting

[Overmod]

A poster new to the forums asks (on the Trains Magazine site)

While installing DCC lighting in one of my coaches, I found that the wheels do not conduct current at all. Apparently the wheels need cleaning/polishing. How do you usually do that?

I'd like to be able to refer him to past posts on the subject, but Kalmbach still can't get the site search feature to work.  So I repost it here for the 'best current advice' from the right community.

[gmpullman]

Many of the threads are ten years or more distant. There's this one which deals primarily with locomotive wheels but may have some useful tips:

http://cs.trains.com/mrr/f/88/t/265477.aspx

— and another:

http://cs.trains.com/mrr/f/88/t/188622.aspx

It would be helpful to know what the manufacturer of the car in question is. Perhaps it has metal wheels but no method of conduction the current to the inside of the car, i.e. Rivarossi or some Athearn models?

Good Luck, Ed

[khier]

Hello Ed,

I am the original poster of the question.

The wheels and axles are metal. There is no such a thing like plastic wheels in Europe. The manufacturer is Roco. The coaches come wired for internal lighting. I have several coaches of this type and they work perfectly. This one was bought second hand and is relatively worn. The wheels are definitely are not conducting current, i have checked that. The question is if there is a way to clean, or better said, polish them.

 

Regards

 

Walid

[York1]

Overmod

While installing DCC lighting in one of my coaches, I found that the wheels do not conduct current at all. Apparently the wheels need cleaning/polishing. How do you usually do that?

 

One of my N Scale passenger cars had trouble picking up the current.

I had a Q-Tip and alcohol, and had to gently hand turn each wheel while cleaning it with the Q-Tip.

It took a while, and I had to be careful with the alcohol and the car's paint.

It was successful, though.

[gregc]

Overmod

but Kalmbach still can't get the site search feature to work.

google   site:cs.trains.com cleaning metal wheels

[Overmod]

The first thing I'd do in the situation described would be to take a good multimeter with reasonably sharp probe tips and take a number of measurements across various parts of the car and the wheelsets.  You did not specify how you expect to get the electricity from the wheels to the car once 'they' conduct; you should do so explicitly, with pictures linked if you can.

Start by taking the wheelsets out of the trucks and measure (electrically) from each end of the axle to each wheel tread.  (With clean wheels this would also tell you which wheel is the insulated one for DC 2-rail).  If this gives zero at the typical multimeter test voltage (on mine this is nominal 9V battery) see whether the side of the wheel gives conduction (scratch a little if it does not) as this would give you differential diagnosis to the treads.  Similarly extend this to the contact patch between the axle and sideframe, if that is a conductive path on your model, or from any 'wipers' up to the car lighting or whatever you are trying to electrify.

One quick way to get the treads clean is to clamp the axle end in a suitable collet in a motor tool that has reasonable speed control, apply a suitable solvent to the tread, and rotate the adjacent wheeltread against something like a fiberglass scratch brush (mine is retractable and has a fairly small cylindrical tip) until it is clean of any 'dielectric' layer of schmutz that may have built up.  You can then use the usual slips and progressive polishing compound technique to polish the treads to good conduction.  (In my opinion cars should run with shiny tread patch and fillet contact area anyway, so this is not wasted effort)

After each pass, check your conductivity again, including tread to axle.  If you get good metal 'shine' on the treads, and have no wipers bearing on them at the 'tops', you may have insulation problems in the axle fit ... I believe a good 'truck tuner' or equivalent may be a reasonable first step (it will help other things, too).

[selector]

The multimeter tests are a good start to determine if the original wheelsets are installed or in a serious condition if original.  If the tires are badly oxidized and/or pitted, they're only possibly useful, especially after some cleaning.

The answer to your question really depends on what the surface condition is.  If covered, then a solvent or degreaser/detergent might clean them up nicely.  I would start with a Q-Tip and a floor cleaner liquid.  Or something like Goo Gone.  If tarnished, you'd need a metal cleaner, maybe a magnesium wheel cleaner and a scouring pad to help it to get back down to pristine metal after the compound has sat for maybe ten minutes.

If the wheels and axles check out, then there's a problem between the back faces of the wheels and the anchor points for the wires to the lighting components, or with the wire itself, or with the components that emit light.

[gmpullman]

khier

The wheels and axles are metal. There is no such a thing like plastic wheels in Europe.

The only reason I mention it, not knowing at the time what kind of cars they were, that Rivarossi, made in Italy, imported here by AHM, used to have metal treads and flanges on plastic hubs.

It would be possible for someone to assume the wheels could conduct current.

Cheers, Ed

[rrinker]

 There is a brass 'wire wheel' for a Dremel that I find works very well for polishing sheel treads. Do NOT use the regualr wire wheel, it will gouge the wheels.

 I used this on all my resistor wheelsets - After installing the resistors and painting the wheels, I use the soft wheel to polish just the wheel tread. A finger on the opposite wheel keeps the axle from spinning at a crazy speed.

                                         --Randy