Charles City Western 300

Some of you have been following along at home as we strive to understand and restore the carbon arc headlights on this locomotive.  See the submitted BLOG comments for some good information and discussion.

John Nelligan has researched and come up with some very good 'new to us' information.  I will repost his findings below.  Thank you John and Steve Kraus, for making all of us a little bit smarter.  Reading John's findings in light of Steve Kraus's comments makes sense.  The brightness of a carbon arc light device requires the positive electrode placement to be just so, to give maximum efficiency.  Reversing polarity with the DPDT headlight switch makes the other electrode the positive side, and it is now outside the optimum placement, making the headlamp seem 'dimmer' in that connection scheme.  The arc itself is unchanged.

Steve's experience is with lower voltage arc lights.  In the locomotive, the circuit receives a nominal 600 volts, but with the dropping resistance, the effective potential across the headlight is MUCH lower, after the arc is struck.  In fact, maybe VERY MUCH lower since ionized air in an established arc provides almost ZERO resistance.