Bicycle light beam shaper

[Cyclothesist]

Has anyone had any success making a beam shaper for a battery LED cycle light? I have a collection of good bike lights but with a torch-like beam profile. In theory it should be possible to deflect the light beam to a lower and wider profile using a stick-on fresnel lens. Has anyone tried this with success and if so what did they use please?
It would be particularly useful on my Moon Meteor Storm Fog to have a dipped and a high beam.

[mattheus]

Has anyone had any success making a beam shaper for a battery LED cycle light? I have a collection of good bike lights but with a torch-like beam profile. In theory it should be possible to deflect the light beam to a lower and wider profile using a stick-on fresnel lens. Has anyone tried this with success and if so what did they use please?
It would be particularly useful on my Moon Meteor Storm Fog to have a dipped and a high beam.

Such lenses have existed for a while to make Magicshine lights a wider profile/pattern (don't think I've heard of making them lower)

I don't think they are switchable.

[Cyclothesist]

Has anyone had any success making a beam shaper for a battery LED cycle light? I have a collection of good bike lights but with a torch-like beam profile. In theory it should be possible to deflect the light beam to a lower and wider profile using a stick-on fresnel lens. Has anyone tried this with success and if so what did they use please?
It would be particularly useful on my Moon Meteor Storm Fog to have a dipped and a high beam.

Such lenses have existed for a while to make Magicshine lights a wider profile/pattern (don't think I've heard of making them lower)

I don't think they are switchable.

The 2 LEDs in the Moon Meteor Storm Fog are switchable, and as they're side by side one could be beam shaped and tbe other not.

[freiston]

I had a Fenix bike light with a supposed shaped beam (by virtue of a fresnel lens on the upper part of the full lens) but it was hopeless - too bright too close to the bike when angled down so as not to dazzle other road users. I made a visor for it out of a piece of coffee tin - long and curving down towards the front - it was better but still far from good - pictures of in this thread where there is discussion relevant to this thread. I tried to kid myself for too long before ditching it and going for a StVZO dynamo light.

Saying that, I do have a Cateye HL-500 with a fresnel lens in it, that I bunged an LED "converter bulb" in - it has a decent beam pattern for road use but the lens and reflector are not torch style round but more rectangular - I put some beam shots in this post but they're at a perpendicular wall from a short distance, so they don't give a good idea of the road beam. So I reckon it is possible to get something useful with a fresnel lens, certainly at lower power, but I'm not confident that it'll work with something round and high powered, without scattering too many photons into the eyes of others whilst keeping it useful on the road.

[andrew_s]

In theory it should be possible to deflect the light beam to a lower and wider profile using a stick-on fresnel lens.

All the stick on fresnel lenses I've seen for bike lights just spread the light left & right, but do nothing to the vertical spread, so as far as anti-dazzle is concerned, or light of the road directly ahead, it's the same as turning down to half power.
Basically, one reflector/lens and one LED means one beam pattern, with the only control being power.

If you are willing to rig up an arrangement to manually flip a fresnel lens across the front of the light, a sort of dip would be possible. You'd still have a round torch style beam, but it would be aimed closer.
If you want to try it, I'd suggest a section cut from the edge of one of those wide angle view stick-ons you occasionally see in the back window of a VW Camper or similar, arranged to give as near horizontal ribbing as can be managed.
It's far simpler to just twist a bar-mounted light down though.


To get car-style main beam/dip beam lighting, you are going to need to switch between separate LEDs.
Such lights do exists for bikes, most commonly as e-bike lights powered off the bike battery, but there's also a very expensive Supernova separate battery light (M99 mini), and B+M (IQ-XL) and SON (Edelux USB-FL) have announced dynamo versions for next year.

[Cyclothesist]

Thanks for the replies. I am not looking to fit a mechanical beam dipping device, not sure where some of you got that idea from, but it's an interesting steam-punk style concept. The Moon Meteor Fog has 2 LED emitters in 2 reflectors side by side (see pic). The 2 leds are switchable so you can have either on or off or both on and at infinitely variable brightness within their range. One LED is standard white, the other is yellow-white. The yellowish beam does definitely penetrate further in fog and drizzle (standard Scottish cycling weather) with much less back scatter. A lens to dip the yellowish beam only would allow me to switch between 3 options - dipped yellow only, white only, and dipped yellow plus white full power.
I think andrew_s' suggestion is worth experimenting with. I'll give it a go and if it's worthwhile report back.

[st599_uk]

I have a Raveman light that creates an STVzO-esque T-shaped beam with a vertical cut off.

That's done with a Fresnel looking element on the lens.

[mattheus]

I have a Raveman light that creates an STVzO-esque T-shaped beam with a vertical cut off.

That's done with a Fresnel looking element on the lens.

Looks interesting ... <googles ...> The CR1000? ~£80 is reasonable for a well-made light in that format.

From your pic it looks like a clever reflector is also used to produce the beam-shape. I think.

EDIT: oh dear; it's got 6 modes, and two of them are flashing. <sigh ...>

[Brucey]

round, torch-like beams usually comprise a bright central region [from a parabolic reflector] with a wider beam which is emitted directly from the unshielded LED. You can of course steer the whole thing a few degrees using a fresnel type lens, but as pointed out already, this still leaves any oncomers in the second part of the beam, and close up, any unshielded emitter of reasonable power is likely to be too bright. Personally I reckon anything over~1W and unshielded is likely to be too bright.

[Bmblbzzz]

The Exposure Strada has two emitters of which one supposedly acts like a dip beam and the other like a main. I don't think it's entirely down to beam shape though, one is also more powerful than the other. And it's expensive! but well made.

[st599_uk]

round, torch-like beams usually comprise a bright central region [from a parabolic reflector] with a wider beam which is emitted directly from the unshielded LED. You can of course steer the whole thing a few degrees using a fresnel type lens, but as pointed out already, this still leaves any oncomers in the second part of the beam, and close up, any unshielded emitter of reasonable power is likely to be too bright. Personally I reckon anything over~1W and unshielded is likely to be too bright.

The CR1000 has a pretty sharp cut off vertically. There is a road.cc test on Youtube showing how it is less dazzling than most other makes as a cyclist rides towards a driver in a car.

This is the beam shape that Road.cc measured for it

[PH]

I have a Raveman light that creates an STVzO-esque T-shaped beam with a vertical cut off.

That's done with a Fresnel looking element on the lens.

Looks interesting ... <googles ...> The CR1000? ~£80 is reasonable for a well-made light in that format.

For an extra £25 you get the superb Trek Commuter Pro RT, with high and low beam, the latter has a very distinct cut off.
https://www.bikeradar.com/reviews/acces ... ht-review/

https://www.tritoncycles.co.uk/accessor ... F8QAvD_BwE

[edocaster]

round, torch-like beams usually comprise a bright central region [from a parabolic reflector] with a wider beam which is emitted directly from the unshielded LED. You can of course steer the whole thing a few degrees using a fresnel type lens, but as pointed out already, this still leaves any oncomers in the second part of the beam, and close up, any unshielded emitter of reasonable power is likely to be too bright. Personally I reckon anything over~1W and unshielded is likely to be too bright.

The CR1000 has a pretty sharp cut off vertically. There is a road.cc test on Youtube showing how it is less dazzling than most other makes as a cyclist rides towards a driver in a car.

This is the beam shape that Road.cc measured for it

That's not bad at all for a forward facing LED and what looks like a fairly small lens-to-LED size ratio. Some will quibble and say the brightest area should be concentrated closer to the cut-off, but optimising that part is hard, and the further benefits (better 'throw') are debatable in real-world situations.

[Bmblbzzz]

I have a Raveman light that creates an STVzO-esque T-shaped beam with a vertical cut off.

That's done with a Fresnel looking element on the lens.

Looks interesting ... <googles ...> The CR1000? ~£80 is reasonable for a well-made light in that format.

For an extra £25 you get the superb Trek Commuter Pro RT, with high and low beam, the latter has a very distinct cut off.
https://www.bikeradar.com/reviews/acces ... ht-review/

https://www.tritoncycles.co.uk/accessor ... F8QAvD_BwE

The Trek light seemed interesting until I got to "Run time on full beam is claimed to be 1 hour 30 minutes." Obviously you'll get more on low beam, but it's only going to be any good for commuting or short night rides. Reminds me why I've had a dynamo for several years.

[Brucey]

...... it is less dazzling than most other makes as a cyclist rides towards a driver in a car.....

That's not bad at all for a forward facing LED.....

i agree but until we know what it was compared with, we can't be sure that it wasn't just the best of a bad lot.