Are your headlight lenses getting cloudy?

Discussion in 'General Motoring' started by Rick, Sep 2, 2005.

  1. Rick

    Steve Guest


    Hardened toughened glass, and in a STANDARD FORM FACTOR (or three) so
    that every car made can use one of maybe 3-4 standard lamp designs, all
    of which work well and can be kept in stock on parts store shelves.
    Instead of a custom lamp design for every different car model, some of
    which work OK and some of which barely work at all, and NONE of which
    are sitting on the shelf down at Joes Parts Shack when you need them.

    ;-p
     
    Steve, Sep 6, 2005
  2. Want to bend your mind further? Compare these two isoscans:

    http://dastern.torque.net/Photometry/Cibie_CSR_Iso.jpg
    http://dastern.torque.net/Photometry/2C1_L.jpg

    The top one, we've already been through. It's a low beam generated by a
    5-3/4" round headlamp that takes an H1 bulb producing 1500 lumens. The
    beam contains 687 lumens. System efficiency = 45.8 percent.

    The bottom one is a low beam generated by a 5-3/4" round headlamp with a
    halogen burner producing 620 lumens. The beam contains 298 lumens. System
    efficiency = 48 percent, slightly more efficient than the lamp above.

    I don't imagine you have to have too much experience at reading isoscans
    to look at these two and tell me which is the more effective headlamp in
    terms of lighting your way at night!
     
    Daniel J. Stern, Sep 6, 2005
  3. Rick

    Bill Putney Guest

    Heh heh! To me it looks like a topographic map of New Orleans about now!

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
     
    Bill Putney, Sep 6, 2005
  4. All the light is ultimately absorbed and converted to heat.
    Neither infrared nor any other form of EM radiation is heat, but all
    EM radiation with longer wavelengths than X-rays is converted to heat
    when it is absorbed.
    Lumens are not a unit of energy; they are a unit of luminous flux.
     
    Matthew Russotto, Sep 7, 2005
  5. I don't follow. If I put my hand in front of an infrared bulb, I feel
    heat. If I don't do this, the infrared waves keep traveling until they
    find something to heat or dissipate? Is this like a tree falling in the
    woods - is a sound still made?

    And I'm wondering about the x-rays. When someone gets burned by x-rays,
    is that because the x-rays then are not passing through but being
    absorbed instead? It is literally possible to burn someone with x-rays?
    Or not? I guess with lead, does it ever get heated when it absorbs
    x-rays, which it does, yes?
     
    treeline12345, Sep 7, 2005
  6. Rick

    Bill Putney Guest

    Your other points are well taken, but to figure usefulness of a bulb, I
    think that measuring light output (even if it later gets converted to
    heat) for wattage input is definitely a measure of its efficacy.
    Certainly you can see that.

    If it getting converted to heat later means you can't count light energy
    produced as its output, then you could say the same thing about any
    mechanical enrgy expenditure too. Take, for example, a cooling fan. A
    certain percentage of the wattage put in immediately goes to heat up the
    fan motor, the rest goes to moving air - and that is the efficacy (or
    efficiency if it's energy in per useful energy - energy converted to
    moving the air - out) of that fan motor - the energy of moving the air
    around compared to the wattage put in. But - guess what - eventually
    that air quits moving. WHY? Firction. Unltimately the energy that got
    transformed into moving that air gets dissipated as heat (friction) of
    that air motion - that's what sops the air from moving once you turn the
    fan off. Are you saying that therefore you can't count the very useful
    and intended motion of that air in its efficacy/efficiency simply
    because eventually it gets turned into heat?

    Same with the energy of burning fuel to move a car. Eventually it all
    gets eaten up by friction (bearings, tires, brakes) and turns to heat.
    Yet we don't say the efficiency of a car is zero because all the energy
    released from the fuel eventually ends up as heat. Pretty much that
    that is not immediately converted to heat (heating up the coolant,
    block, various other engine parts, and air moving thru the radiator)
    that goes into moving the vehicle is what gets plugged into the
    efficiency formula as the output - even though ultimately it alll gets
    converted to heat.

    So - you're off on this one point. Your other points I think are valid.

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
     
    Bill Putney, Sep 7, 2005
  7. Rick

    fbloogyudsr Guest

    That's not really a very good analogy, Bill. ALL the output of
    a light bulb is electromagnetic radiation - visible or infrared light.
    SOME of the (heat) energy from a IC motor is converted to
    physical work (acceleration of the car).

    That's why "efficacy" is a better term than "efficiency", as it essentially
    measures the PROPORTION of the output in the visible spectrum.

    FYI, one reason that fluorescents aren't 100% "efficacy" (if you
    will ;->) is that most emit some portion of their output in the UV
    portion of the spectrum (usually a pretty small amount, some
    more than others. That's why many are behind diffusers of one
    kind or another.)

    Floyd
     
    fbloogyudsr, Sep 7, 2005
  8. Rick

    Jack Guest


    My '92 Explorer had the best headlights I've ever seen, and my '99 is
    only slightly less impressive.

    Of course, the '92 Explorer did catch fire and burn up, but that was
    after I owned it, at about the 150,000 mile point. I don't think it got
    any more TLC after it left here.

    Even the '99 Explorer's lights are about 200% better than the crappy
    lights on our '97 Sebring convertible. The convert's have not yellowed,
    either, though come to think of it I don't even know if they are glass.
    It mostly just sits in the garage. It's got 15,000 miles on it since we
    got it new in Sep '96.

    The '99 Explorers "fog" lights, make pretty good corner lights -- the
    Sebring's might as well not be there. The beam is so low and narrow they
    only illuminate stuff you're just about to run into, or over.


    Jack
     
    Jack, Sep 7, 2005
  9. Rick

    Nate Nagel Guest

    The problem with all the vehicles you claim have great headlights is
    that they piss *everyone else* off. Ford trucks/SUVs in particular I
    find to be painfully glaring when following me, the low beams still have
    enough stray upward light that I can't even glance at my rear view mirrors.

    nate
     
    Nate Nagel, Sep 7, 2005
  10. Rick

    Steve Guest


    Which EVENUTALLY gets converted to heat, either when you step on the
    brakes (flat land) or eventually travel back downhill to the same
    elevation you started at and step on the brakes.

    I think its a pretty good analogy. Yes, EVERYTHING that causes a
    conversion of energy will ultimately just result in a slight increase of
    the entropy of the universe, whether it be turning on a light bulb,
    driving a car, or the solar radiation from a star. But in the interim
    period, you can distinguish between a "useful" output (the visible light
    portion of the spectrum as it emanates from a light bulb filamant) vs a
    sort of "direct to waste" output (the thermal radiation from an
    incandescent lamp).
    And they also put out heat- feel a running fluorescent tube. You can
    keep your hand on it (unlike an incandescent lamp of identical input
    power) but it is warm. And the ballast gets warm as well.
     
    Steve, Sep 7, 2005
  11. That's true, but secondary. The problem with the vehicles he claims have
    great headlights is that they *don't*. I hesitate to imagine what-all
    headlamps Jack has driven behind to have such low standards that the '92
    and '99 Explorer headlamps, both of which are objectively poor, are the
    best ones he's seen. He mentions a '97 Sebring, and that's certainly got
    bad lamps.

    But y'know, if you've been eating dirt all your life and somebody offers
    you a bowl of grass clippings, you'll probably say the grass clippings are
    the best food you've ever tasted!
     
    Daniel J. Stern, Sep 7, 2005
  12. Rick

    DTJ Guest

    Three great responses. :-D
     
    DTJ, Sep 8, 2005
  13. Rick

    Bill Putney Guest

    It's not an analogy. It is another example.

    Yes - so you restrict the measruement of output to what is useful -
    visible light. If IR is not useful to you in the application, then it
    is part of the lost (wasted) energy. What's so hard about understanding
    that concept.
    AND ULTIMATELY ENDS UP AS HEAT WHEN ALL IS SAID AND DONE. THE CAR
    ULTIMATELY STOPS DUE TO THE KINETIC ENERGY (ENERGY OF MOTION) BEING
    CONVERTED INTO HEAT BY BRAKES, BEARINGS, TIRES, AIR. IT IS A FACT. If
    a car moves from one point ot another (coming to rest) without a net
    change in elevation, 100% of the energy that was extracted from that
    fuel ended up in the environment as heat - a law of physics.

    The ***ONLY*** exception to the above is if at the end of the trip, the
    car is higher level (elevation) than when it started - THEN - THEN AND
    ONLY THEN - is some of the energy not converted to heat - it went into
    producing the technical term called work (the change in elevation -
    force over distance). But when it comes down to the height at which it
    started, it needs that much less energy from the fuel (and ultimately
    heat) to get there.

    Here's something for you to thnik about: regenerative braking.
    That's a good thing. Efficiency is used in a similar way.

    Another thing to think about: An engine on a dynamometer. The
    efficiency would be the energy measured at the output of the crankshaft
    compared to the energy in the fuel. The dynamometer measures this
    output at the crankshaft by putting a brake on the crankshaft that it
    turns against (that's why it is called "brake horsepower"). The energy
    produced at the crankshaft is turned into heat. A car moves, but the
    same amount of energy is eventualy converted into heat by all the
    friction that eventually brings the car to a stop (either gradually, or
    more quickly by use of the brakes).
    Plus they generate some heat. So if the desired output is visible
    light, then everything else is disregarded in any kind of efficiency or
    efficacy measurement or calculation. However if the desired goal is
    for the bulb to produce heat and not light (a heat lamp), then the light
    is considered waste energy and is not considered as useful output, but
    the heat is. IOW - The if heat is the desire, then an incandescent bulb
    has high efficacy or high efficiency, but a flourescent has low efficacy
    or low efficiency. If visible light is the desire, then the opposite is
    true. What's plugged into the equation depends on the desired effect.

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
     
    Bill Putney, Sep 8, 2005
  14. Rick

    Bill Putney Guest

    Thanks Steve - I posted before I got to your post.

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
     
    Bill Putney, Sep 8, 2005
  15. Rick

    Bill Putney Guest

    As long as someone doesn't say that because the light ultimately gets
    absorbed as heat you can't count it as output in efficacy or efficiency
    calculations - which is what some are erroneously saying. The measured
    output is the light *before* it converts to heat by being absorbed by
    air and/or some object. Otherwise you'd say there was zero output - and
    you don't.

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
     
    Bill Putney, Sep 8, 2005
  16. Rick

    C. E. White Guest

    Is there a publically available headlight comparison?

    Ed
     
    C. E. White, Sep 8, 2005
  17. They keep travelling until they are absorbed. It's possible they
    could make it into interstellar space and keep going indefinitely, but
    not really very likely.
    Yes. However, X-rays are different in that they can do more than heat
    a substance. They can also tear electrons away from it; this is what
    makes them ionizing radiation.
     
    Matthew Russotto, Sep 8, 2005
  18. All fluorescents produce UV. Most is absorbed by the phosphor
    which then emits visible light. The diffuser is just that; it won't
    appreciably reduce the residual UV output.
     
    Matthew Russotto, Sep 8, 2005
  19. Rick

    fbloogyudsr Guest

    IMO, you're defining the closed systems in differing ways/methods,
    which invalidates your analogy, and methodology.

    Looks like I'm not going to convince you, so I'm done.

    Floyd
     
    fbloogyudsr, Sep 8, 2005
  20. Rick

    Jack Guest

    A lot of very mundane cars, just like everybody else except the esoteric
    gurus here, of course.

    Now you've made me want to see if I can even remember all the cars I've
    owned, let alone the ones I've driven in the past ~50 years. Let's just
    say...a lot. But the 92 Explorer's lights were the most satisfying. Hey,
    I LIKE it when they put a lot of light everywhere, and I got very few
    complaints.

    Of course sitting up high in a 4x4 will put the lights in a smaller
    vehicle's rear view mirror, so I stay further back at night stops.

    Maybe my lights are adjusted properly, and I don't usually drive over
    100 mph -- suppose that could be it?


    Jack
     
    Jack, Sep 8, 2005
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