from Fort MacArthur's website:
Carbon Arc Searchlight Facts
The first 60 inch Searchlight was made by General Electric in 1893
Searchlights were produced for military use from 1932 to 1944 at a cost of $60,000 each!
Lamp Type: Carbon Arc (no light bulb!)
Candle Power: 800 Million
Effective Beam width: 5' plus
Effective Beam length: 5.6 miles
Effective Beam visibility: 28~35 miles
Generator Power: 15 KWV nominal - 16.7 KWV max. (15,000~16,700 watts D.C.)
Powered By: Inline 6 cyl. "Hercules"
Flathead Engine
Generator Engine Fuel: Gasoline (can also be run using Kerosene or Gasohol)
Combined Weight: 6,000 pounds (3 tons, or the weight of 3 Ford Mustangs combined!)
The beam is made by 2 carbon rods, one positive and one negative, arching within the focal point of a 60 inch parabolic mirror. As the rods "burn" they are automatically fed into the light. The rods last approximately 2 hours and are then replaced.
The flame that is visible during the lights operation, is not actually the source of the light, rather, it is a by-product, produced as a result of the electricity arcing between the 2 rods.
The flame is the rod slowly burning away as it is fed into the light. The arc draws 150 amps continuously at 78 volts and burns at over 3,000 degrees Fahrenheit. The power is supplied by the D.C. generator which was designed specifically for this purpose.
Standing in the focused beam of this searchlight at full power would give you a second degree sunburn.
