On May 7, 12:41 pm, SMS wrote:
Prisoner at War wrote:
Not sure how I'd prevent their being blinded, anyway: I couldn't
predict it, could I? But I'm sure the two HIDs I'm considering have
some kind of optics which should mitigate such circumstances. They
better, anyway, for $600!!!

In reality, the optics on the higher end bicycle lights are excellent.
It's not a wild unfocused beam such as on the old 2 D cell battery
headlights of the olden days. The quartz-halogen lights are typically
using MR lamps, which are very good optics with matched, mirrored
reflectors.

The optics of MR lamps are excellent for their primary intended use:
track lighting, to properly display paintings on walls, or to give
supplemental or decorative lighting inside houses and buildings. For
those applications, you want a soft, even, radially symmetrical beam
pattern.

The optics required for road use are entirely different. Park your
car in front of a wall and examine the shape of the headlight beams on
the wall. Rather than a radially symmetrical beam, you have a
precisely tailored beam shape. The most notable feature is the
horizontal cut-off plane, with bright light below that plane (to land
on the road) and dimmer light above that plane (to prevent blinding of
other road users). There are legal requirements - at least, in many
countries - governing the shape of the beam.

Most bicycle and motorcycle HID lamps also use MR11 and MR16 type lamps,
as it's become the super-standard for high-end lighting.

AFAIK, motorcycles are subject to the same legal beam requirements as
other motor vehicles. Certainly, my BMW has a beam shape that's
tailored as precisely as my car's lights. I seriously doubt any
radially symmetrical HID lamps are used as original equipment on
motorcycles, but I'm willing to look at properly cited evidence to the
contrary.

Now it's true that aftermarket light sets have no road-tailored
optics. Those are the ones installed by irresponsible hot-rodders,
the ones that blind oncoming traffic.


One of the big advantages of the MR system is that the bulb is aligned
precisely with the reflector at the factory. One problem with the lamps
where you replace the actual bulb is that you have to align the bulb by
trial and error (not even possible on the cheap lamps with threaded
bulbs, and a hassle on the higher end lamps with a bulb that can be
rotated for proper alignment).

Statements like that make me wonder about SMS's experience with
lights!

Bike generator headlights use flange-mount bulbs. The flange-to-
filament distance is precisely controlled. When replacing a bulb, the
flange sits against a precisely placed shoulder. The shoulder has a
protrusion, and the flange has a matching notch, so the bulb fits only
in it's precise orientation. No trial and error is necessary. In
fact, it's not even possible!

You really have to look at them to evaluate them. Do any have a metal
mounting bracket to the bike? How rugged is the wiring and the switches?
How much will battery replacement cost? How much is a replacement
lamp? Most of these systems use the MR11 Welch Allyn HID lamp, which
costs close to $90, and you definitely want to have a spare.

IOW, add $90 onto the already exorbitant cost of the HID set you're
considering.

Through all this, I think it's good to remember that motorcycles
travel legally up to 75 mph. Their headlights are designed for such
speeds.

Using that light output for a bicycle is as inappropriate as using
motorcycle wheels on a bicycle.

- Frank Krygowski