Car makers intentionally creating a safety hazard?

[PoorManQ45]

Alright, this is about headlights.

We all have seen, and probably own, vehicles with foggy headlights.

We know that UV light causes an oxidation to occur on the outer surface of the acrylic. Initially from the factory there is a coating on the lenses to protect them from UV light. This coating typically lasts between 3 and 5 years. This coincides with most "bumper to bumper" warranties(headlights being covered).

Vehicles used to be manufactured with glass lenses. Glass does not exhibit the same oxidation as acrylic and will stay as clear as the day the car rolled off the lot for pretty much as long as the vehicle is on the road.

When manufacturers made the decision to switch to acrylic what were the factors? Weight? Cost? Reoccurring costs(repair/replace)?

The thing is, the DOT has regulations on how many lumens a bulb of a given type must put out. There is an established minimum and maximum range.

The beam pattern is also regulated to cover a certain distance and a certain angle.

What is NOT regulated is how many lumens must come out the front(OTF) of the headlights. This allows manufacturers to basically do as they please when it comes to lens material.

The problems are two fold
1: Ultra Clear glass is capable of 98~99% light transmission. Acrylic maxes around 92%.
2: Acrylic is affected by UV light when not coated. This causes oxidation. When the lens oxidizes the light transmission decreases(can't find a %).

These two issues make Acrylic an inferior and potentially unsafe choice for headlights.

The safety issue with acrylic is due to the clarity issues with the lens. The light transmission starts lower then glass, and decreases over time. This causes the OTF lumens to become lower and lower. The light output will eventually decrease to the point that proper illumination of the road surface is not provided. This can cause all sorts of issues for a driver with said lighting issues. They'll be unable to see obstacles far enough ahead to avoid them, difficulty illuminating pedestrians, visibility to other drivers is decreased, and the headlights are easily overrun at speed.

So, what it comes down to is:

Why are manufacturers not held responsible for this obvious safety flaw in the design of their illumination systems?

[scotty-2-forty]

[youtube]http://www.youtube.com/watch?v=XF2ayWcJfxo&ob=av2e[/youtube]

Just another way that manufacturer's try to take more of your money down the road.

[Dattebayo]

Weigh out the other obvious hazards involved with glass in an area that is prone to being smashed.

[Jesda]

Glass FTW.

[PoorManQ45]

Weigh out the other obvious hazards involved with glass in an area that is prone to being smashed.

What sort of additional hazards are you referring to?

The only thing I can think of is the debris on the ground will be a little sharper when you destroy a headlight.

How does that compare to not being able to see the road properly?

[takethewall]

No.

I love my glass headlight housings.

[Dattebayo]

Brien, it's not as bad as you think. The fact that you don't even have a percentage for acrylic after 6 years means this whole thread is moot.

A loss of even 10% isn't going to make enough difference unless you have a sight problem to begin with.

[fiznowler]

I just assumed it(acrylic) was cheaper to produce and needed to be replaced more often. Thus the factory gets a double win on parts sales. Glass is by far superior for headlights IMO.

[Jesda]

Brien, it's not as bad as you think. The fact that you don't even have a percentage for acrylic after 6 years means this whole thread is moot.

A loss of even 10% isn't going to make enough difference unless you have a sight problem to begin with.

The average car on the road is 9 years old. That's more than enough time to turn the lenses into this:



Its as bad as you think.

[Dattebayo]

The reason for the plastic going opaque like that picture above is from the coating that is put on it, not the plastic itself. I think the information got switched around somehow... It can be buffed out easily, so it's not the crazy "safety hazard" that Brien thinks it is. There have been many threads on how to get rid of it on this board for years now.

I would consider it part of normal maintenance.

[PoorManQ45]

The reason for the plastic going opaque is from the coating that is put on it, not the plastic itself. I think the information got switched around somehow... It can be buffed out easily, so it's not the crazy "safety hazard" that Brien thinks it is. There have been many threads on how to get rid of it on this board for years now.

I would consider it part of normal maintenance.

Incorrect. The issue occurs when the factory coating wears off.

The oxidation does indeed buff out easily. The problem is that it will then return much more quickly even when properly clearcoated.

This is an issue that never occurred with glass.

You seem to support acrylic. Can you give me a few of the negatives about glass that you were talking about.

Thanks.

[Jesda]

The reason for the plastic going opaque like that picture above is from the coating that is put on it, not the plastic itself. I think the information got switched around somehow... It can be buffed out easily, so it's not the crazy "safety hazard" that Brien thinks it is. There have been many threads on how to get rid of it on this board for years now.

I would consider it part of normal maintenance.

Its a hazard.

Its a hazard.

Its a hazard.

[Dattebayo]

Its a hazard.

Its a hazard.

Its a hazard.

I'm sorry, what was that again?

Incorrect. The issue occurs when the factory coating wears off.

Well that's not what my mommy told me. She said it's because the coating goes bad and starts to break up. She also said if the actual plastic were getting opaque that it would be much more yellowish. There are compounds that you can put on new headlights to prevent this from happening.

You seem to support acrylic. Can you give me a few of the negatives about glass that you were talking about.

Thanks.

I never said I support anything. Glass is better, but the current DOT standards don't allow for the extra "sharpness", as you put it, in accident debris.

[Jesda]

[youtube]http://www.youtube.com/watch?v=YgJffiGHz7M[/youtube]

[PoorManQ45]

Incorrect. The issue occurs when the factory coating wears off.

Well that's not what my mommy told me. She said it's because the coating goes bad and starts to break up. She also said if the actual plastic were getting opaque that it would be much more yellowish.

I'll take a picture of one of our cars when it gets home. The haze is indeed very yellow.

You seem to support acrylic. Can you give me a few of the negatives about glass that you were talking about.

Thanks.

I never said I support anything. Glass is better, but the DOT standards don't allow for the extra "sharpness", as you put it, in accident debris.

Sorry, you just seemed to be in support of acrylic.

What do you mean DOT doesn't allow for "sharpness"? I was referring to when the glass explodes on impact(just like acrylic does).

[Dattebayo]

I'll take a picture of one of our cars when it gets home. The haze is indeed very yellow.

Well too bad you didn't take care of it like you should have. Now why don't you go blame the government?

I was referring to when the glass explodes on impact(just like acrylic does).

It's not the same thing at all.

[PoorManQ45]

I'll take a picture of one of our cars when it gets home. The haze is indeed very yellow.

Well too bad you didn't take care of it like you should have. Now why don't you go blame the government?

Wow, you're a little sour there Dave.

The whole point is that the issue should not exist in the first place!

I was referring to when the glass explodes on impact(just like acrylic does).

It's not the same thing at all.

Agreed. The acrylic doesn't break into as many pieces. But hell, windows break into tons of pieces. Mirrors do too. Why not change them out for acrylic? I mean, they're lighter and would be safer in an impact!

Who cares about clarity, right?

[Jesda]

[youtube]http://www.youtube.com/watch?v=Y1a_ikfUico[/youtube]

[93coupe]

Since when are you concerned about safety hazards, don't you park your vespa on the sidewalk?

[Dattebayo]

Windows and car mirrors are made from another kind of compound other then glass.

[AppleBonker]

Pretty sure windows are safety glass. Been to factories where they are made.

And they don't replace them with acrylic because polymers don't tend to fail in the same manner as safety glass (breaking into tiny bits).

[PoorManQ45]

Pretty sure windows are safety glass. Been to factories where they are made.

And they don't replace them with acrylic because polymers don't tend to fail in the same manner as safety glass (breaking into tiny bits).

Windows break into a lot of pieces

[youtube]http://www.youtube.com/watch?v=gIibknMJUhs[/youtube]
[youtube]http://www.youtube.com/watch?v=uAp-y9CsLr4[/youtube]
[youtube]http://www.youtube.com/watch?v=5XrMAF-0AcI[/youtube]

[93coupe]

Now there is a job for you, Brien.

[PoorManQ45]

Now there is a job for you, Brien.

I do have an awesome announcer voice!

[Dattebayo]

Brien, re-read what Adam said again.

[AppleBonker]

re-read what?

[PoorManQ45]

Windows and car mirrors are made from another kind of compound other then glass.

i missed this post.

They're made of tempered glass.

Interesting note I just found when reading. Tempered glass that's used in windows will break into small cubes. Plastic/acrylic breaks into sharp jagged pieces.

So then... Why no glass headlights again?

[Dattebayo]

Tempered glass with a special coating on it to keep the cubes from spreading out in a crash. We've come full circle now. Are you happy?

[AppleBonker]

Uh, tempered glass is glass. They're the same material, it's just in the heat treatment. That's like saying a frozen hotpocket is something completely different from a cooked one.

Edit: based on the comment about a film to keep them from spreading, the cooked hotpocket in the above analogy is now on a plate.

[Dattebayo]

It's not the same glass as "glass". Tempering the glass removes gas bubbles from inside and makes it more able to absorb shock by purifying the chemical structure.

The plate is also made from a similar compound as that on the acrylic plastic.