Few people realize that all 60 inch Carbon Arc Searchlights are all 60 years old or older.  Ten thousand were made, mostly ending up in Europe for WWII. One guess puts the surviving number at about 2500 worldwide, but a recent survey taken in 2004, indicates that this number is more likely in the hundreds. Having been stored out in the elements for over 60 years has taken its toll most of them.
These lights were built by the General Electric, and Sperry Gyroscope for the U.S. Military as Anti-Aircraft Searchlight Units. Their original purpose was to aide World War II anti-aircraft gunnery crews in spotting enemy aircraft during night-time air attacks.  These lights have not been built since 1944.  They no longer had a military use after the war having been replaced by the invention of radar.  The lights were sold off to civilians who created the night Outdoor Advertising Searchlight Industry.  The Outdoor Advertising Industry has slowly been phasing out these old searchlights in favor of the more portable, cost effective multi-beam spotlight units.  A step backward in the effective use of lights in the Outdoor Advertising Industry. Before W.W. II, the motion picture industry used their studio spotlights for their movie premiers, so yes, we are  stepping backward, and using them again.  One day, the opportunity to see a real W.W.II carbon arc searchlight will disappear into history, only to be replaced by an inferior, second-rate alternative to the real thing.

Source: Taken in part from an article in the Lighthouse Digest February,2001  Mt.Lowe's Search Light The Most Powerful in the World.

Photo Courtesy : Jake Brouwer

---

1904
The Largest Searchlight

The worlds largest searchlight Type B.C. Form "A", was originally built by General Electric Company for a fair in Russia, but the deal fell through.  When Edward Gardner Lewis built the Woman's Magazine Building in University City Missouri in 1903, he aquired,  and included this massive 80-inch searchlight on top of the building as a means of attracting people attending the St. Louis World's Fair just a short distance away.

By the 1970's there was on longer a source for the  2 1/2 inch carbons that were required for this light.  Mr. Hughes of "Lite A Rama Searchlights" in the St. Louis area, was contracted to convert the carbon  arc assembly to a more modern type that used the more common sized carbon rods.
In 1961, Mr Hughes installed a W.W. II General Electric 1942 searchlight arc assembly, and an automated control box was retrofitted into this big light.

The building has since become the University City, City Hall. This light is still a operating searchlight and is used for special events.  The light sits on an elevator platform in the attic of the dome. When it is to be used, the operator has to manually crank open the roof doors. The two roof doors slide open from the center. Once open, the elevator is raised to the top of the roof by electric motor, or by hand crank.  The power supply generator for this light was originally located in the basement, and is now replaced by a 3 phase rectifier unit.  With a 6'glass mirror, this light should be seen for over 50 miles buy it is in need of maintenance, and today you would be  lucky to see it for more than 1 or 2 miles.
Bill Kaufman, son of the University City Mayor in the early 1960's, has been the operator of this light since he was 14 years old in 1960.
Learn more about this beautiful building at this web site.... http://history.ucpl.lib.mo.us/test/home.asp

Heinrich Beck - The Life Of An Inventor
http://www.becklaser.de/hbeng/hbeckframeset.html

A History of Searchlight Development & Use
http://www.skylighters.org/searchlights/index.html

GENERATOR:
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) 26 gallon capacity
Under searchlight load burns about 2.6 gallons per hour
Combined Weight: 6,000 pounds (3 tons, or the weight of 3 Ford Mustangs combined!)

THE HERCULES JXD ENGINE
The engine used to power the GE and Sperry generators was made by the Hercules Engine Company who supplied nearly a million engines to the US military and allied armed forces during 1941-1945. Hercules engines were used in Jeeps, 2.5 and 5-ton trucks and generator sets.
The JXD version of the Hercules engine used in searchlight power plants is a straight six side valve gasoline engine. The engine displacement is 5240cc (320 cu in). It is rated at 110hp @ 3000rpm
The engine uses about 2.6 gallons (10 litres) an hour when running the searchlight.
1hp = 0.75 KW so the engine is capable of putting out 82.5 KW at 3000 rpm
The generator runs at 1250 rpm and power output is approximately proportional to RPM therefore the engine output power at 1250 rpm would be about 35KW
The generator output is 15KW (max 16.7KW). Under normal running conditions the light runs at 93 volts (at the generator terminals) at 150 amps @ 14KW
The efficiency of a typical DC generator is 75%. That would require 20 KW of engine power when there is 35KW available at 1250rpm. The whole design of the searchlight power plant is very conservatively rated since it is idling along at less than one quarter the rated power of the engine.
The searchlights cost $60,000 in 1940. Using inflation figures from 1940 to 2005 - that is equivalent to $830,000 in 2005 - no wonder they are such a magnificent piece of machinery!

THE LIGHT
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 ARC. The rods last approximately 2 hours and then are 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 arching between the 2 rods, and burning the carbon. 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.

THE ELECTRIC MIRROR

The National Carbon Company had manufactured Carbons for searchlights and other carbon arc lights since 1892 in Fostoria Ohio.  They stopped making carbons forever in 2002. There were three reasons for National's decision to close down their carbon rod manufacturing. Declining sales (the arc carbon business was small compared to other product sales, loosing money), a few of the key Engineers that had the background and knowledge have since retired (one passed away a few years ago after retirement but he had been consulting up to just before his death), and the equipment was getting old, some dating back to pre W.W. II.   At one time carbon rods were the biggest selling product being produced at the plant employing over 1200 people. At the end, there were only about 200 employees involved in the production of carbon rods..

Learn how carbons were manufactured by the National Carbon Company... HERE

  Recipe for the inner core.
  19,4 kg petroleum coke or pitch coke.
  6,3 kg carbon black.
  1,3 kg boracic.
  27 kg luminous addition ) 20 kg. cerium fluoride  6,73 kg cerium oxide.  0,27 kg cerium borate.
  9 kg. pitch.
  4 kg. tar.

  Negative carbon 24 mm.
  Recipe for the mantel.
  35 kg. ground electro graphite.
  10 kg. natural graphite of Passau.
  5 kg. carbon black.
  12 kg tar pitch.

  Recipe for the inner core.
  33 kg. natural graphite of Passau.
  4,5 kg. carbon black.
  15 kg tar cake - green once rolled.
  7,5 kg sulpher.
  13,0 kg pitch.
  1,5 kg. heavy oil.

Learn How Searchlights were used during W.W. II, click... HERE

My Searchlight Hobby Page, click... HERE

General Electric 1942A Searchlight that I restored, click HERE

Jim Mulligan's Restored 1942 GE Searchlight & Generator
http://www.skylighters.org/photos/mulligan/
htp://www.skylighters.org/photos/plaque/plaque.html

Fort MacArthur Museum in San Pedro California's 1941 Sperry Restoration.
http://www.ftmac.org/sperryproj.htm

Restoration of a  British 1939 Mk1 150cm Anti-Aircraft Searchlight in the U.K..
http://www.projectoraa150cm.co.uk/

Skylighters 225th AAA Searchlight Battalion from W.W. II
http://www.skylighters.org/mainmenu.html