(Photo: Mercedes-Benz)
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"Two lamps fed by either petroleum or electricity are essential on the mudguards. These small lamps are quite adequate in
city traffic to comply with police regulations, large headlamps would only be a hindrance in city traffic as they dazzle both
horses and people. Electric lamps with a switch on the mudguard are effective; there are 4- and 8-volt versions which are
connected to one or two batteries. These lamps are not adequate for country journeys at night, however. It is advisable to
mount two headlamps on the front of the frame, to the right and left of the radiator, and these are best powered by electricity
or compressed acetylene gas carried in steel flasks."
This is a quote from The Modern Automobile, circa 1914, which was regarded as a standard reference for automobile design in
its time. Even then, engineers were faced with the need to illuminate the roadway without blinding oncoming drivers. During
this time in automotive history, lighting was often provided by a combination of electric lights and gas lamps (petroleum
or acetylene). In 1908, a mechanism was invented that used a lever operated cable to "dip" the gas flame away from the focal
point, resulting in the first high/low beam switch.
Electric lighting was restricted by the batteries of the era, until Bosch developed the first dynamo powered headlights, fitted
as an accessory to cars of the age. Electrical systems were not mature enough to make electric lighting practical until the
1920s.
(Photo: Ford Motor Co.)
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In 1924, the "bi-lux" bulb was invented, a twin filament bulb which contained the low and high beam in one reflector and producing
two distinct lighting patterns. This was the standard until the mid-1960s when the halogen bulb was introduced.
Not only did bulb technology reach new levels, so did reflector technology. New computer designs allowed smaller housings,
acting more like a projection lens rather than a mirror reflector. This allowed designers to precisely focus the lighting
pattern for better nighttime visibility.
The next major improvement in lighting was the development of the xenon bulb, which uses xenon gas in a quartz shell, with
some trace metallic salts added. A short 28,000-volt discharge results in a plasma arc between the lamp's electrodes. This
arc is stabilized at about 85 volts and takes the place of the filament used in other designs.
RESTORATION (Photo: Pete Meier)
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This design produces twice the light at 35 watts as a halogen bulb does at 55 watts, resulting in less electrical load for
the car to carry. Due to the intensity of the lights, these systems generally are coupled with self-leveling headlight units
that constantly adjust the lighting pattern relative to the road, vehicle load, acceleration/deceleration and road inclination.
In 1999, bi-xenon lighting was introduced, meaning that xenon bulbs generated the light source for both the main (high) and
dipped (low) beam.
