VOR lamps with a stepped cutoff

hokiefyd

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This is probably more of a philosophical question, but I have noticed that some (most?) VOR lamps have a cutoff that is straight across. That is, there is no (or at least very little) distinguishing features of the cutoff; you can generally see where the hotspot or hot area is, straight ahead, and light bleeds off as you look to the sides, but the cutoff itself is very straight across. I've also seen some VOR lamps with a step to the cutoff, and I'm thinking of many Hondas in particular here...but also some Toyotas as I recall. My CR-V is an example, but current model Civics and the previous generation Odyssey with the round quad headlamps had a step cutoff as well. These are all VOR lamps.

I've read here before that a step in the pattern like this does not reduce glare to oncoming drivers. If that is the case, I wonder why they either:
a) wouldn't make the cutoff straight across, or
b) design them or mark them as VOL so that one can get left-side light further down the road nearer to the horizon.

I've also received advice here before that a VOR lamp with a defined step pattern like this CAN be aimed as a VOL lamp, potentially putting the top of the "step" on the right side above the horizon. This is exactly how the VOL projectors on our 2005 Acura MDX are: the left side would be aimed slightly below the horizon, and the top of the "step" on the right is above the horizon.

So again, given that, why do stair-step VOR lamps exist? There's a reduction in seeing distance to the left of center...there must be an "and on the other side of the coin..." benefit that I don't recogize.

Thanks,
Jason
 

-Virgil-

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I have noticed that some (most?) VOR lamps have a cutoff that is straight across.

Some VOR lamps have a straight-across cutoff, and some have a stairstep, and some have no discernible cutoff to the left of center. The defining characteristic of a VOR headlamp is that it has a cutoff at least 2 degrees wide, located at H-H (horizontal, not above or below), with at least 2 degrees of its actual width centered at 2.0 degrees right of center.

I've read here before that a step in the pattern like this does not reduce glare to oncoming drivers.

That's not true. The lower the top of the oncoming-traffic (left) side of the beam is below horizontal, the more it reduces glare for oncoming drivers.

why they wouldn't design them or mark them as VOL so that one can get left-side light further down the road nearer to the horizon.

This question seems a little confused. The defining characteristic of a VOL headlamp is that it has a cutoff at least 2 degrees wide, located 0.4 degrees Down from horizontal, and with at least 2 degrees of its actual width centered on 2.5 degrees Left of center. That does not regulate what the top of the beam pattern looks like anywhere else, such as on the right side of the beam; such regulation is handled in terms of intensity by the test points in the beam specification. There's nothing in this that would necessarily provide more left-side light nearer the horizon. A VOR with a flat cutoff can provide more left-side seeing distance, and a VOL can (but doesn't necessarily) provide more right-side seeing distance depending on what the top of the beam looks like to the right of center.

I've also received advice here before that a VOR lamp with a defined step pattern like this CAN be aimed as a VOL lamp, potentially putting the top of the "step" on the right side above the horizon.

Well, anyone can aim any lamp however they might get an idea to aim the lamp. That doesn't mean it's a correct or technically sound idea. There is no uniformity to where the left side cutoff is on a VOR lamp with a stairstep cutoff. It might be at 0.4° down like a VOL...it might be at 0.57° down like an ECE...it might be at 0.2° down...it might be anywhere, because the VOR specification does not regulate the existence or placement of a cutoff to the left of center, only to the right of center. The inverse is true of the VOL specification, which is why it is possible to design a VOL lamp that gives longer right-side seeing distance than a VOR.
 

hokiefyd

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I am certain that I have read before that a straight-across cutoff does not increase glare for other drivers compared with a stepped cutoff. Maybe I am confusing two different issues here.

You said that a "VOR with a flat cutoff can provide more left-side seeing distance..." That was more to the crux of my question...why wouldn't ALL VORs have flat cutoffs? The apparent answer is because those with the step down to the left reduces glare to oncoming drivers, which is not what I understood to be the case previously.

Here is the thread where we discussed the VOR/VOL aiming:

http://www.candlepowerforums.com/vb/showthread.php?357956-Good-(and-bad)-OEM-Headlamps/page2
 

-Virgil-

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I am certain that I have read before that a straight-across cutoff does not increase glare for other drivers compared with a stepped cutoff.

Yes, it does.

You said that a "VOR with a flat cutoff can provide more left-side seeing distance..." That was more to the crux of my question...why wouldn't ALL VORs have flat cutoffs?

To answer a question with a question, why wouldn't all VOLs have a 90-degree stairstep...or a 45-degree stairstep...or a 15-degree upsweep...or no right-side cutoff at all? It's all a matter of what the OEM wants (based on what they think will sell the most and/or get the best ratings in Consumer Reports) and what they and the headlamp supplier develop together.

The apparent answer is because those with the step down to the left reduces glare to oncoming drivers

Or because it facilitates whatever other aspects of beam structure and performance the automaker wants.
 

hokiefyd

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I think the VOL question is just as valid, yes. Our MDX's VOL lamps have a 90 degree stairstep cutoff, just like our CR-V's VOR lamps do. Why didn't Acura do an up-sweep to the right of center instead? It appears that there are a number of cosmetic components to the design of lamps in addition to the compliance issues. Thanks for the insight.
 

-Virgil-

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I think the VOL question is just as valid, yes. Our MDX's VOL lamps have a 90 degree stairstep cutoff, just like our CR-V's VOR lamps do. Why didn't Acura do an up-sweep to the right of center instead?

Longer seeing distance with a stairstep than with an upsweep. Picture a headlight beam thrown forward on the road: the steeper the angle upward from the left side cutoff, the longer the beam reach just to the right of the middle of the beam.
 
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