by Alan Blay
Originally from “ON SOLID GROUND”
Fifty years ago, the auto industry converted from a two-headlight system to four headlights with the introduction of the new 1958 models. The 1958 Corvette was restyled around a design that incorporated the new quad head- lights. Four headlight styling, though, made its debut on the 1957 Cadillac Eldorado Brougham. Like the 1953 Oldsmobile Fiesta styling of next year’s features, the same idea was exhibited in 1957. For $9,000, the price of many new homes, the “horseless carriage of quality” could be purchased, incorporating 1958 styling and engineering features.
From an engineering standpoint, the quad headlights were designed to offer improved low beam illumination. From 1940 to 1954, headlamps offered by GUIDE Lamp Division (the GM Bulb Company) were a bulb in a bulb Sealed Beam. Low and High beams were two different filaments, reflected from the shiny backing through the reflector focus. The 1955 redesign had 40 watt low beam filaments mounted above the reflector focus. This was a compromise. And the problem is that you can “outdrive” your headlamps. In essence, the low beam illumination distance is less than your nighttime reaction time and breaking distance at 40 MPH.
In quad design, the outer lamps are designed for low beam 50 watt at reflector focus. The high beams of 37.5 watts are designed below low beam low beam reflector focus, for the outer lamps and at reflector focus for the inner lamps. The focus point is in the center of the lamp glass cover. Since low beams are used most of the time, the outer lamps address that priority, and upon high beam actuation, the inner high beam lamps are below reflector focus when high beam filaments are on, used for “body light”. This avoids foreground illumination.
The quad system was first produced in the late 1930’s when the Buick Y job was developed. It was shelved due to war and Postwar automobile shortages, then revived with the Motorama fervor. The weakness of the two bulb system propelled the quad system into the spotlight. Overcoming the problem of one filament, the high beam is designed this way to provide a hot spot for aiming.
Originally, the idea was to use two entirely separate pairs of lamps…two for high beam and two for the low beam. The plan was discarded after some testing as it was found to be inferior to the system adopted (two double filament bulbs on the outside, two single filament bulbs on the inside) for two reasons. First, the single filament bulbs in the wattage desired for the high beams were two much in respect to the reflector focus. Second, was a safety issue. In icy weather a lit headlight generates enough heat to prevent icing up the light. In a separate two and two system, switching beams may mean little illumination from iced over headlights.
Back in 1958, headlamp courtesy was more paramount than today. With the advances in illumination technology over the past 50 years, many drivers have little regard for other motorists with their blue headlamps of intense illumination. In 1958, the Chief Engineer of GUIDE Lamp Division, Robert Falge, said you needed to illuminate anything on the road, plus shoulders and allowance for rises and dips in the road. Should we give drivers the lighting they want, or what they can best see by? Even in 1958, drivers had all 4 headlamps lit, discourteous to other motorists. Compared to today’s Flame Throwers, it was just a minor inconvenience.
Reference: Popular Science, August 1956 “Why Cars Are Going To Four Headlights”, pages 65-69.