@pd posted:In a chicken-or-the-egg type question, does pitting cause sparks, or does excessive sparking cause pitting? What does cause pitting in some electrical bits?
Enquiring minds...
PD
My understanding is this> Electrical Pitting is caused whenever there is poorish conductivity between two adjacent surfaces and by the removal of an electric current at a given location (one conductor rolling along another). Pick-up rollers are fair conductors but not perfect at higher currents such as are drawn by postwar AC motors.
The arc (electric current passing through a minuscule or larger air gap) causes pitting.
Carbon-dioxide molecules are atomized by the arc as oxygen burns off from the air. The residual hot carbon is mostly what leaves a black residue on the rails.
If I am mistaken, hopefully someone will be nice enough to correct me...
