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What is a "conductive lubricant" and why do I care?

5093 Views 12 Replies 8 Participants Last post by  Mike O
There's a thread on another forum that brings up a good FAQ that bears repeating, and actually has information for newbies and experienced modellers alike.

So here goes another "Techno-Greg" thread.

I think at one time or another we have all heard of a "conductive lubricant". Wow, that sounds great!

It seems to make sense that if you have power pickup on an axle, a lubricant that was ALSO conductive would be a great thing. Well it COULD be.

First: let's talk about what is REALLY conductive or not.

In the model train industry, I only know of ONE product that is plastic compatible and says "conductive" on the outside. That's LGB "conductive paste" in the red and white tube.

This stuff is NOT conductive. I don't care what the tube says. Put an ohmmeter in it. Yes I know it has graphite in it. But it's not solid graphite, but little particles in suspension in a nice grease. Not conductive. Period.

There are other "conductive" products, that are NOT plastic compatible. Aristo has one called "Electra Lube". It's actually somewhat conductive, not enough to help anything (more later), but it is documented to destroy certain plastics, notably the first generation of Aristo truck sideframes: //www.aristocraft.com/vbulletinforums/showthread.php?t=5686

There are "conductive lubricants" that are kind of a light oil/clear fluid. They are not conductive either, but it does not matter, they eat plastic, and say not for use on plastic. They are more like "tuner cleaner" in a light oil base.

There are also real conductive lubricants with copper, silver, or gold in them. They are VERY expensive, and do conduct electricity. They are not normally plastic compatible. The danger here is they spread everywhere, so even if it did not attack the plastic sideframes, it has the potential to create short circuits on insulated wheel sets, and many other parts. Just not practical to use. (This stuff is often used in electrical wiring and large high current wipers in moving equipment).

Then why are people calling something conductive when it's not?

This is because the best thing you can do to keep metal surfaces conductive is to keep them from oxidizing. Just as oxidized brass rail does not conduct well, virually any oxidized metal surface does not conduct well.

So, if you put grease in your LGB rail joiners before assembling, water and air cannot get in, and it keeps the joint conductive. Basically any grease will do. In the auto industry, when we had rotors and distributor caps, what grease was put on the contacts? Silicon grease. It's a wonderful dielectric, i.e. insulator, by itself.

But wait! how can this work, I put an insulating grease on my axles? How does the electricity get through?

This is the part you have to understand. It actually takes a VERY SMALL patch of "clean metal" to make electricity flow. On a round axle, the actual contact "patch" is very small, but on that very small part, the pressure is very high. High enough to make sure the metal parts touch.

So all you need to do is keep the metal clean, unoxidized.

What's the bottom line?

Use the appropriate lubricant for your axle bearings, grease or oil, use grease on wipers or rail joiners. You can still use the contact cleaner and lube stuff on your motor commutators, but use it sparingly.

The bottom line is the electricity WILL get through, just keep it clean and oxide-free.

Regards, Greg
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I tried the silicon grease from Active Electronics in the motor blocks of an Aristo-Craft FA-1. It quickly turned to oil when agitated or warmed and ran out. LGB grease seems to be somewhat similar when used on the worm and pinion gears in motor blocks. Labelle appears to be the only plastic compatible grease that will cling and not melt.

The silicon grease is handy for lubricating the moving parts on side frames however. Even when wiped off the silicon seems to leave the plastic surfaces slippery.

My pet peeve is the dirty black grease USA Trains uses in the bushings of their diesel truck bushings. It gets on your hands, clothes and anything else you touch. The first thing I do clean the axles and bushings, and add some clean white Labelle grease.
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