SAE working on headlamp lens degradation

SubLGT

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SAE is also addressing the issue of headlamp lens degradation.

The [SAE] Headlamp Lens Durability task force is coodinating tests with different lens materials (polycarbonate, acrylic) with and without annealing, and different coatings, to get a handle on ways to bring headlamp lens durability more in line with the long service life of modern cars and LED headlamps.
 

Lynx_Arc

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SAE is also addressing the issue of headlamp lens degradation.

This is one thing that greatly concerns me.... when the plastic lenses cannot outlast a light bulb and costs 20x the price of a bulb someone didn't really give it much thought in engineering and manufacturing design unless they considered the profit from selling new headlights every 5-10 years on cars into their margins. Someone needs to start a business selling covers for headlamps to protect them from damage that are cheaply replaceable so instead of having to pay hundreds of dollars for new headlights you can spend $20 for a new cover every so often.
 
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GoMango

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This is one thing that greatly concerns me.... when the plastic lenses cannot outlast a light bulb and costs 20x the price of a bulb someone didn't really give it much thought in engineering and manufacturing design unless they considered the profit from selling new headlights every 5-10 years on cars into their margins. Someone needs to start a business selling covers for headlamps to protect them from damage that are cheaply replaceable so instead of having to pay hundreds of dollars for new headlights you can spend $20 for a new cover every so often.

I work at a body shop and many headlamp assys are in the $800-$2000 price range...if there was a lens available, what do you think they would get for that...??? It's ridiculous...
 
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Lynx_Arc

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I work at a body shop and many headlamp assys are in the $800-$2000 price range...if there was a lens available, what do you think they would get for that...??? It's ridiculous...
If they would design light assemblies in two parts.... the focusing/reflecting part and the lens cover part so when the lens or cover goes bad you don't have to pay for but a clear cover not an assembly that includes includes the light socket etc.
I sure miss the old Halogen sealed beam lights that cost from $10-$40 new and you could use an ice scraper on them without worrying in the winter months.
 
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LeanBurn

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If they would design light assemblies in two parts.... the focusing/reflecting part and the lens cover part so when the lens or cover goes bad you don't have to pay for but a clear cover not an assembly that includes includes the light socket etc.
I sure miss the old Halogen sealed beam lights that cost from $10-$40 new and you could use an ice scraper on them without worrying in the winter months.
I recall some Mercedes lamp enclosures are this 2 piece design you mention that come apart by design and you can buy replacement clear covers. It's a shame all companies aren't mandated to build them like that considering how many yellowed and frosted lamps are on the road today and their safety.
 

Alaric Darconville

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The problem is that often by the time the lens has degraded to the point where it's really bad or the driver really starts to care about it, he rest of the lamp is often not that great, either-- the bulb generates so much heat around the reflector area that the reflector itself starts deteriorating.

Perhaps when more vehicles start using LED headlamps this would be less of an issue, and then replacing the outer lens periodically would be a good thing.

But what we REALLY need is better standards and tests for lens/lens coating durability to that this isn't a problem in the first place.
 
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-Virgil-

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US regs do allow replaceable lenses, but only if the headlamp meets stricter requirements in terms of reflector durability. The idea being, a lens probably won't be replaced the minute after it breaks/fails, so water and dirt will get into the headlamp and the reflector will have to be cleaned before the new lens is installed. Therefore, replaceable-lens headlamps have to pass an inspection (no visible damage allowed) 48 hours after their reflectors are wiped with bug/tar remover (45% xylene, 55% petroleum base mineral spirits), or plain mineral spirits, or other non-water fluid as specified by the maker for the task of cleaning the reflector. And they also have to pass a test where the headlamp, without lens, is subjected to a 24-hour salt fog/spray, allowed to dry naturally for 48 hours, then the reflector gets cleaned in accordance with the maker's instructions included with the new lens, the new lens gets installed, and the reassembled lamp then must meet the photometric requirements.

So, makers have every incentive not to provide replaceable lenses: it requires that the headlamps be made with more damage-resistant reflectors and it requires additional testing, both of which add cost. It's much easier to get a good and durable permanent lens/housing seal than a removable and resealable one, which not only means extra cost but also extra warranty repairs (more extra cost). And repairable headlamps means fewer sales of replacement headlamps, which means less profit. All of that extra cost and reduced profit in exchange for nothing but the happiness of what is probably the vehicle's second, third, or fourth owner.

Headlamp lens degradation kills people. That's not an exaggeration, it's been proven, and NHTSA is aware of the proof, but hasn't done anything about it. Practically, lenses that are replaceable and/or adequately durable are the right thing to do. Economically, from the car/headlamp company perspective, not as much, at least not in the world we live in, where quarterly results and short-term shareholder value are about the only thing that matters.

With all that said, things are slowly getting better. SAE is working on figuring out what and how to specify in terms of better coatings, and LED headlamps are a lot easier on their lenses than halogen and HID, because with LEDs the lenses run much cooler (heat accelerates the degradation). Of course, LEDs also bring along their own new material-degradation problems, such as yellowing/opacification of optical materials used in close proximity to LEDs, but those problems are being effectively addressed, too.

It's fun stuff, all of it...and it argues pretty forcefully that the standardized sealed beam concept (leaving aside any particular implementation and just looking at the concept) was very close to optimal for vehicle headlamps.
 

Alaric Darconville

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It's fun stuff, all of it...and it argues pretty forcefully that the standardized sealed beam concept (leaving aside any particular implementation and just looking at the concept) was very close to optimal for vehicle headlamps.
When we consider all the maintenance that replaceable light source headlamps required in the '20s and '30s (bulb replacement with the right kind of bulb, very careful dusting of the reflector, replacing the gasket cord (not rubber! It outgasses and ruins the reflector), getting the reflectors professionally refinished), clearly sealed beams were the way to go and really ought to make a comeback.
 

Magio

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I think a replaceable headlamp cover is adding needless complexity with all those rules Virgil was talking about. Non-replaceable glass lens seem to be the simple solution to lens degredation, and with the cost of a lot of these new headlamps, whatever extra cost is incurred is gonna seem unsubstantial.
 

Lynx_Arc

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What about a sealed beam unit behind a clear lens assembly? That could be the best of both worlds as there would be little worry about reflector degradation and the sealed beam unit could be replaced and even upgraded as needed and the lens covering could also be replaced. It would mean a higher cost for the light engine if not LED but if LED the light engines could be more standardized making for less expense overall and easier testing as you would only need to test the sealed unit once and make sure the lens is optically correct.
 

Hamilton Felix

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Does anyone remember the Cibie Bobi headlight? The Bobi was a rule beater replaceable bulb H4 headlight for the American market. I don't recall if it was made in anything other than the 7" round size I had installed on an ambulance back in the 1980's. It met the "sealed lens and reflector unit" requirement of the time by having a clear "bubble" inner lens between bulb and reflector. If built to high quality with glass lenses and premium reflector, there's no reason a lamp like this could not last a long time. But if my foggy memory serves, that extra inner lens meant they never quite matched the optical performance of contemporary standard 7" Cibie H4 lamps.
 

-Virgil-

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Non-replaceable glass lens seem to be the simple solution to lens degredation

Glass doesn't cloud up like polycarbonate, but it does break. And many of today's complicated headlamp lens shapes are not possible to make in glass.
 

-Virgil-

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What about a sealed beam unit behind a clear lens assembly?

That's pretty far up there in terms of cost, too, not only because of extra parts but also because you can't just throw any old cover over a headlamp, you'd have to build an enclosure that would pass all the tests as far as water/dirt exclusion, vibration resistance, etc. Plus, when you have a lens in front of a lens, you're reducing the amount of light reaching the road.
 

-Virgil-

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Does anyone remember the Cibie Bobi headlight?

That solution (bulb chamber enclosed by a glass cup; space between outside of cup and inside of front lens sealed and filled with inert gas) was clever, and with additional development probably would have done a better overall job than the problematic system Ford and Sylvania came up with and NHTSA approved. The Bobi solution did have disadvantages (again, every time light hits glass, some of it doesn't get through), and the use of Helium as the inert gas was flamingly stupid -- Helium, being a very small atom, will tend to escape...witness Helium baloons getting smaller and smaller as days go by.

But this is late '70s, early '80s technology we're talking about; its time has passed.

I don't recall if it was made in anything other than the 7" round size

The Bobi was also made in the large rectangular 200x142mm size. There were several different variants of both shapes, in terms of lens optics. The American domestic sealed-beam industry cried foul and NHTSA kowtowed to them and "interpreted" the rule to require that a sealed beam not have a replaceable bulb. There was no safety basis for this determination, it was just purely to squash and block competition the American makers viewed as a nuisance/threat.
 

eggsalad

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I recall reading, and it wasn't terribly long ago but I can't remember the source, that manufacturers consider the useful lifetime of an automobile to be 10 years. So when cost is an issue, and it most always is, they design and engineer and build parts to have a useful life of not more than 10 years. That same 10-year period is all they care about parts availability for as well.

I would be surprised if SAE and/or NHTSA could either convince manufacturers to build better headlights, or convince Congress to legislate it, for anything beyond the 10-year period.
 

-Virgil-

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The average age of a vehicle on American roads is 11.9 years. That's the average age; over a quarter of them are over 16 years old. NHTSA knows this; it formed a central part of NHTSA's reason for denying a GM petition for inconsequential noncompliance regarding turn signal bulb failures.

Headlight lens and coating materials (not even the actual lenses themselves) have to pass three-year aging tests in Florida (humid) and Arizona (dry). Separate material samples are used for the AZ and FL tests. It's an open secret that better/more durable materials and coatings exist -- note that jet fighter windshields are also made of coated polycarbonate -- but they cost more, and since the only legal requirement is to pass those 3-year tests, there is no incentive for automakers to spend the extra money.
 
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