Most articles on special lighting gear appearing in BMWCCA publications deal with creating a rolling blowtorch. Such systems are costly, vulnerable and impractical 90% of the time. The most effective improvement in night vision is the conversion from sealed-beam to quartz-iodine headlight units.
In standard sealed-beam lights, a tungsten steel filament is vacuum-sealed in a molded glass reflector/lens combination. The reflector portion is surface silvered prior to installation of the filament. The vacuum seal reduces internal heat, extending filament life and preventing the shell from cracking or melting. As the filament burns, it sheds small, heat-blackened particles. These particles have a positive electrostatic charge and are immediately drawn to the negatively-charged reflector (and, to a lesser extent, the lens). Headlight efficiency progressively drops and the filament wears thin. By the time the filament quits from malnutrition, the darkened reflector and lens have robbed the unit of 70% of its initial output.
The quartz lamp has. neither quartz filament, lens nor reflector. The tiny envelope surrounding the stainless alloy filament is made of optical-grade quartz. Because the melting point of quartz is many times that of glass, and because the high-strength filament can produce far more heat (and, therefore, brightness) than the tungsten filament, total light output can be dramatically increased.
The quartz bulb (itself a sealed beam) is filled with an iodide gas. The iodide ionizes the particles cast off from the filament and reverses polarity from positive to negative. These particles are therefore repelled by the reflector and attracted back to the filament, where they continue to burn. The end result is a life expectancy approximately three times that of a sealed beam. In that time, the quartz lamp unit will lose but 5%-10% of its original brilliance. Bromine and halogen gases are sometimes used rather than iodine, but iodine has proven to be reliable, relatively low in cost and capable of providing long filament life.
Better construction comes with the superior luminance and durability of the quartz unit. Accurately-formed metal reflectors have super-brilliant reflective surfaces. Bulbs are located with high accuracy and held in place by elaborate tensioning devices. Lenses are molded of lead crystal that which costs a king's ransom as stemware and fluted with exceptional precision.
The lens designer working with quartz lighting has more freedom than one restricted to tungsten lights. To obtain maximum efficiency from the low relative output of a sealed beam, the light must be concentrated in a narrow block pattern and aimed directly at the road but a short distance in front of the car. The result is excellent brightness in those two blobs of light. Precious little light is cast ahead and to the side, however. The quartz headlight has been designed to provide a wide sweep with extra right-side intensity and a center-to-upper-right sweep. The effect of immediate road-surface illumination is not as noticeable, but side vision is improved drastically and quartz headlights reflect back what is on the road, not the asphalt itself.
There are several options open to owners of BMWs employing both twin 7" headlights and quadruple 5 3/4" lights .
Plug-in a single-bulb light employing dual filaments through a single reflector. They are commonly called H4 because of use of the H4 quartz lamp configuration. Wire-in: a twin-bulb package employing separate reflectors for the H1 (low beam) and H3 (high beam) lamp designs. The only available twin-bulb unit at this time is the Marchal "Amplilux." Bosch has a light employing two H1 bulbs, but it is presently available only in Porsche recessed mounting buckets. Robert Bosch Corporation has not said whether this light will become available for other applications.
Cutaway drawings of the H4 and Amplilux lights are shown in Figures 1a and 1b, respectively. Both could be called "The Paradox," for operation is the reverse of what would be anticipated. The low beam is actuated by the upper filament (or bulb in the Amplilux) and employs the upper portion of the reflector. Conversely, high beam uses the lower filament (or bulb) and exits from the lower portion.
In both the H4 and Amplilux, a series of shields are employed to precisely control the shape of the beam. These baffles vary in design and placement according to the theories of different manufacturers.
Another paradox is that the horizontal spread of the light is controlled by vertical fluting. This employs the technique of refraction the bending of light rays as they pass through media of different density.
The high beams in both H4 and Amplilux units are unencumbered by the shields. The H4 emits light from the entire reflector area. The Amplilux concentrates its high beam through the secondary reflector and a non-dispersant, clear lens. When the high beam is selected, the filament or bulb for the low beam is extinguished. This is a disadvantage in the Amplilux, as the spread beam is eliminated for the narrow beam piercing the blackness. The Amplilux only may be wired to maintain low beam operation when the high beam is selected. This will be explained further on.
Next month, 5 3/4" conversion options will be discussed, including their wiring and a comparison of the 7" and 5- 3/4" units currently available.
Author: Nelson Barnes