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Headlamps Glued / Tailamps welded , Cut-offs

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  • Headlamps Glued / Tailamps welded , Cut-offs

    Hi All,

    Does anybody know why Headlamp is glued and tailamp is welded...
    I reckon its because HL has some sensitive parts (like aiming,PCBs etc) which may get badly affected and may non-functional if subjected to vibration welding...Makes sense?

    Why do we need different types of low-beam cut-off pattern? (Flat, Notch & Step) and how do we achieve these cut-offs patterns? Only through optics??

  • #2
    The basic goal is to provide as much distance lighting (and sides) as possible without blinding oncoming traffic. In a projector, the maximum intensity at different angles are governed by the reflector & lens optics' shape and location relative to the light source (e.g. HID arc or halogen filament or LED emitter). For angles where no light is allowed, a shield blocks the output. The shape of the shield drives the cutoff pattern; a slope will cast a (negative) slope shadow, a step will cast a step shadow. The thickness variation on the shield's edge can also affect the cutoff pattern. A nub somewhere between the reflector and the lens can also affect the cutoff pattern (like some single emitter LED low beams).
    Jul 2012 ROTM (3-way quad headlight) ; Sep 2015 ROTM (custom muli-lens 7" fogs)

    3-way quad wiring; foreground limiter; squirrel finder;


    • #3
      Thanks for the reply Satrya, So in essence you're saying the cut-off is achieved by combination of reflector optics, lens optics and Shield (when present like in bi-xenon)...


      • #4
        Yes. This is a simplified illustration of a projector. The main components are:
        (1) Light source, depicted as a point light source by the yellow circle. For halogen filaments, it is a almost straight filament material that is mostly brightest in the middle and gradually getting dimmer on the edges. For HID, it is an arc that is mostly brightest on the edges where the electrodes are, and less in the middle. For an LED emitter, the pattern is very directional.
        (2) Reflector bowl, depicted as the thick red surface made from an ellipse. Original old projectors use a strictly 3D version of this, i.e. an ellipsoid. Modern day projectors have a more complex shape that changes focal length in the 2 axes, as well as have more than one reflector facets. The reflector bowl picks up as much light from the source and redirects it to the lens.
        (3) Convex lens, which collects light sent by the reflector bowl and further redirects it to maximize distance reach while achieving other objectives as well.
        (4) Shield, not shown. Without the shield, you can see that some of the rays may point to directions that can blind oncoming traffic or create intensity beyond what is allowed in some directions. Having a shield is an easy solution for this limit, at the expense of wasting light.
        Jul 2012 ROTM (3-way quad headlight) ; Sep 2015 ROTM (custom muli-lens 7" fogs)

        3-way quad wiring; foreground limiter; squirrel finder;