The following continuity tests were made in response to forum member Andreas experiencing a short circuit using graphite as lube for point rails with gapped PCB ties.
Following tests done with HO scale painted PCB tie with an approx. 1/32" gap, multimeter, Kadee graphite powder & Molykote Z dry powder lubricant:
Gap filled with graphite powder; no continuity across gap (open).
Paint lightly scraped from edges of gap until copper showing & filled with graphite powder; continuity across gap.
Graphite powder then brushed from gap; no continuity across gap (open).
Gap then filled with Molykote Z powder; no continuity across gap (open).
Though maybe well known I was not aware of the potential for short circuits using graphite powder in such an application. Other than during point rail lubrication it seems highly unlikely that enough graphite powder could find it's way into a PCB tie gap to cause a short circuit, especially if paint is intact at the gap, but "Murphy" is always ready to strike.
Regards, Peter
There must be a reason that motor brushes are graphite-carbon?
https://en.wikipedia.org/wiki/Brush_(electric)
I also use Molykote Z powder sparingly on the ties where the points slide. So far I can detect no discernable added resistance. I'm careful, too, to test any ballast materials I use for electrical conductivity or the presence of ferrite materials.
Regards, Ed
I have seen another instance where graphite accumulation caused a hard to find short - at the points of a turnout with a rectangular (points, pivot link and throwbar) moving point assembly where the pivot was direct metal-to-metal with the closure rails of a hot frog. Since continuous track cleaning was provided by a couple of John Allen slider cars no one ever vacuumed the track. Over the course of several years graphite (lube from axle journals) built up on the ties under the point, to the extent that the open point eventually shorted to the stock rail. Since the buiildup was heavy on one side but not the other, throwing the points to the little-used spur cleared the short.
The problem was cured in 30 seconds with a Shop-Vac nozzle.
If you had told the members of that club that you were going to lubricate the points with graphite they would have run you out of the building.
Chuck (Modeling Central Japan in September, 1964 - with un-lubricated, electrically dead open points)
We managed to set a tie on fire one time at the Clackamas club in Oregon. Someone doused a sticky switch point with powdered graphite, and the short was hot enough to set adjacent wood ties smoldering. This is why we find situation cards unnecessary during operations.
gmpullmanMolykote Z powder
Ed,
I can skin a mean wire, but 'lectrical theory and troubleshooting are not my strong suit.
I was lucky, happened to use Molykote Z to lube my point rails and throwbars, not that I knew better, but because I was aware of it's superior dry lubrication qualities.
Anyhoo' another gem of knowledge for ignorant yours truly to file away.
I once had a baggage car with brass trucks sqeaking as it ran down the track. I put a little oil in the journal and then added a little graphite. The combination bridged the axle insulation. It did not draw enough current to make a short but the oil got hot enough to smoke and make a realistic looking hotbox.
Mark Vinski