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Types
When most people picture a spotlight, they picture a GE or Sperry 60-inch Carbonarc model. These were produced in the tens of thousands during World War II at a cost of $60,000 each. Modern functioning models have been revamped, but they still use the same technology of the ones WWII soldiers used to spot enemy planes. The companies produced the searchlights from 1932 to 1946. GE spotlights and searchlights are similarly constructed.
Head Components
The actual lighting portion of the searchlight contains a 60-inch mirror and lens, two Carbonarc rods, a thermometer and the outer housing assembly. Attached to these are positive and negative assemblies, allowing the light to shine in any direction. Beneath is the swiveling assembly, which allows it to have a full rotational range of movement. Other parts of the head include insulation material, reinforcement plates, lockwashers, screws, nuts and support pieces for the head.
Assembly Parts
Each of the assembly parts is made up of many smaller parts. For example, the positive head assembly contains castings, springs, studs, brushes in both upper and lower sections, nose plates, insulation against heat and water and many screws, washers and nuts. The other assemblies are constructed in a similar way with many small pieces held together with fasteners. There are also many miscellaneous parts not attached to the assemblies. These include the motor and various ring, shaft drives and electrical parts--such as resistors.
The Carbonarc Rods
There is a flame evident when the searchlight is engaged that some people assume is responsible for the beam of light. Actually this flame is produced as the two carbon rods arc to one another, causing them to be consumed in flame and creating the bright light that is reflected off the mirror and intensified by the lens. The rods are completely consumed after about two hours.
History
Searchlights have been used since times of antiquity. In ancient Egypt, The Pharos Lighthouse in Alexandria was used. Evidence suggests that even this searchlight was powered by carbon rods. Thousands of years later, in 1872, carbon arc searchlights were heavily employed to defend the coast of England. However, it was in WWII when the allies employed groups of soldiers to spot nighttime Axis bombers that the lights were most heavily used.