Many cars now have 2x2 headlamp layout in front somewhat like this
Oo === oO
IIRC, the bigger lamps are for dipped beam and smaller ones for full beam.
Why the smaller ones are used for full beam? What is the advantage of having 2x2 layout instead of both headlamp/dipped beam within a single lamp assembly?
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>> What is the advantage of having 2x2 layout instead of both headlamp/dipped beam within a single lamp as
Each lamp has a fixed focus. No need for dual filament bulbs or dipping mechanisms, just relays to turn one set or the other on.
My VW 411 had four headlamps, all the same size, with the inner ones doinf main beam and the outer ones with the extra sidelight bulbs. The advantage in those days was that the units were standard round units, much cheaper than these special shaped things. The whole system is simpler, cheaper, more repairable and more effective.
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AFAIK the dipped beam headlamps need to spread the beam wider whereas the high beam are more like spotlamps and in conjunction with the dipped beams providing the spread of 'near' light can be optimised as such. they can therefore be smaller but the main reason is merely styling.
With a single conventional headlamp there are 2 filaments in the bulb, AFAIK only one is lit at any time so the high beam filament has to provide both the spread of light and the spotlight function simultaneously and is more of a compromise. Also there is less light being thrown onto the road.
Many HID arrangements actually only use a single bulb for both functions, the smaller 'spotlights' being ornamental or DRLs, these have shutters on them to change the light pattern when on high beam, the brighter beam meaning that they're less of a compromise than a single lamp dual filament halogen arrangement. Some HID installations retain the separate halogen driving lamps to provide for high beam and lamp flashing instead of having the shutter arrangement.
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>>Why the smaller ones are used for full beam? What is the advantage of having 2x2 layout instead of both headlamp/dipped beam within a single lamp assembly?
Fashion. And as ever it goes in circles.
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>> >>Why the smaller ones are used for full beam? What is the advantage of having
>> 2x2 layout instead of both headlamp/dipped beam within a single lamp assembly?
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>> Fashion. And as ever it goes in circles.
Very likely. There's a (tiny) advantage in dual-filament bulbs, in that each filament is incandescent or hot all the time
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>> Fashion. And as ever it goes in circles.
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I seem to remember some pre-war cars had an electric motor to physically dip the drivers side headlight.
I can't see this coming back in to fashion!
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>> >> Fashion. And as ever it goes in circles.
>> >>
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>> I seem to remember some pre-war cars had an electric motor to physically dip the
>> drivers side headlight.
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>> I can't see this coming back in to fashion!
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My 1947 Triumph Roadster had that. The left-hand reflector was tilted by an electromagnet, which also operated a contact extinguishing the right-hand lamp.
Stags and 2000s used the 2+2 layout in the 60s and 70s.
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>>Stags and 2000s used the 2+2 layout in the 60s and 70s.
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By default I had a Triumph 2000 and the headlights were truly awful. By far the worse lights on any car I have ever driven. The car was an auto and totally gutless but I was never happy driving it at night on country road so just as well it was so slow.
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That's the price you pay for an automatic. My manual + overdrive was very fast, and incidentally had excellent lights.
If you had been meaning the Roadster I would have agreed. A single 36 watt bulb in a tarnished reflector was hardly adequate in a car that claimed to be a sports tourer. Mind you, the lamps looked impressive in daylight - 10 inch polished chrome on stalks mounted betwen the front wings in front of the radiator.
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Dipped and main beam layout - Armel Coussine
