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Discussion Starter · #1 · (Edited)
Following on from this thread on road friendly light design I'm making a pair of lights for road use. The aim is to put more light on the road and less in the air than with the standard reflectors and optics we use. The way I'm doing this is by using half a reflector with the LED firing down into the parabola, best illustrated by the following diagram from the aforementioned thread:

Each light contains one XM-L and the pair operate together, with a single LFlex in one light driving both lightheads. The lightheads are made from 1.25 inch 16AWG aluminium tubing and are mounted beneath the handlebars to keep out of the way. Battery power comes from 4 * 18650 cells from DX.

After much trial and error here's the donor for the reflectors (my wife's old halogen bike light):


Here are (most of) the parts for the two lightheads


I've kept them as two lights for the sake of extra heatsinking per LED, and yes, for aesthetics! There's an additional heatsink on the bottom of the lighthead with the LFlex. Here's a mock-up of how the internal parts fit inside, although in reality there will not be any overlap of the two L-shaped sections. The LED is mounted on the inside of the main tube, firing down into the reflector.


Here is a further indication of how things fit together:


And finally here as a taster is a beamshot of one of the reflectors on a testbed. First shot is the control, second is the XM-L through a Regina reflector and third is with one of the cut reflectors from this build. All taken with (the equivalent of) the MTBR standard settings. Distance to the fence in the background is approximately 17 metres or 55 feet.

EDIT: Unfortunately the original beamshots have been lost for reasons only known to Imageshack. I've edited the other photos in this post but don't have the beamshots so will have to replicate them when I can.
 

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looking good and I'm happy to see the fruits of your efforts :)

it's a shame that there wasn't a way to have the LED and reflector all on the same piece of alu, so that you could make sure that the LED was in exactly the right place relative to the reflector (not saying you can't this way, just that it looks hard). It would also make the assembly easier too (something I can't overstate enough about sled lights) :) I'm looking forward to seeing how it all goes together!
 

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Nice!

I'm wondering if there would be a way to shoot some "oncoming" beam shots, to show what it looks like compared to the wide open beams to oncoming traffic. I'm getting the dim your lights flash from about 100' to 200' away.
 

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Discussion Starter · #5 ·
Thanks guys. Matthemuppet, I certainly hear where you're coming from regarding the LED and reflector positioning. In fact it's specifically because the reflector / LED position is so critical I've gone for this approach. The LED can be mounted centrally in the bar (that was easy enough, and has proved not to be too critical in testing). Next the L-piece with the reflector already attached can be slid in and epoxied with the light actually on to view the beam as you go, to ensure optimal positioning. That's where I am at the moment, LEDs in, reflectors epoxied to L-pieces and will probably position the reflector assemblies tomorrow evening.

I haven't yet been able to take photos from in front of the light - is something I'll do when they are finished. Next set of photos will come after the next bit of activity, hopefully at the weekend! And yes, the ideas are here for anybody to use.

Sent from my GT-I9100 using Tapatalk
 

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Discussion Starter · #8 ·
It could work offroad certainly, either as a helmet light or as part of a multi-optic main light. It doesn't provide much light above the horizon so you'd need some other optic or reflector to avoid overhanging branches - for example the silver birch on the right in the beamshot is almost invisible whereas it's quite clear with the Regina. However it does produce a lot of throw combined with nice spill on the ground. The throw is really because it's part of an approx. 50mm diameter reflector with a much larger focal length than the small 20mm Regina.
 

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The only problem is that we can't get these types of reflectors without ripping apart another light.
I have a model for a deep 10mm parabolic reflector in NX now. Next step is to get a program from that to cut it on the CNC lathe. If I get that going it would not be too tough to make bigger ones. Those could be cut in half for a result like the picture in post #1
 

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Discussion Starter · #11 · (Edited)
Lights now painted and (mostly) assembled. The reflectors are installed, LED wires potted and wiring complete. Still have to:
  • Cut out and glue in place lexan front covers
  • Affix LFlex to inside of light
  • Push switch through back cover and screw on waterproof cover
  • Fix back covers and cateye spacer mounts, and waterproof back cover with silicon

I'd quite like to put a small sheet of rubber in between the cateye spacer and the light for grip and waterproofing - do you guys bother? Also the biggest problem I have is in affixing the LFlex to the inside of the light as the adhesive on the thermal pad isn't strong enough and the wiring keeps on pulling it away. Do any of you have that problem?

The unpolished insides of the tube reflect a good amount of light wide to the sides, good for being seen from near side on.

Here's a shot showing the LED and reflector mounted inside the lighthead:


All wired up and functioning:


White wall beamshot on low.
 

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looking really sweat mfi :)

As for the Cateye spacer, I just rough up the surface of the housing and use a thin layer of Gorilla glue on the bit away from the mechanism (don't ask how I learned that!). Trim off any glue that expands outside the spacer, although if you're sparing that shouldn't happen. I've done that on 6 lights so far and they've all stayed put.

The thermal tape that comes with the lflex is supposed to bond better after 24h, after reading the lflex manual. Perhaps stick it on, clamp it down with something then leave it for a day? If that doesn't work which, fingers crossed, it will, you could always use a couple of screws either side if your housing alloys. Try the 24h wait first though.

BTW, did you assemble each light the same with respect to the focal length or are they slightly different for a composite beam pattern?
 

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Discussion Starter · #13 ·
Thanks for the advice matthemuppet. Yes, I guess a little glue on the spacer would be fine as it's not as though I'll need to take it off again. The mounting screw holds the back plate on and I was a little concerned about water getting in via the screwhole - have you ever had any problems with that?

The LFlex thermal pad is no more unfortunately, and I had the same problem with an Asaka thermal pad as well. I'll see if I can get some sort of clamp to hold things together whilst trying again. I'm a bit concerned as to what happens when things heat up as well - do they get less adhesive? At least I'll have the temperature cutout on the LFlex to protect it should it come unattached and therefore not have the heatsinking required.

I did contemplate having two different beams but ended up adjusting them both for optimal throw as the main aim is for road riding and seeing potential hazards at a distance, but usually dead ahead. :) The other option was to push the reflector in one ever so slightly further forward which gives a wider beam and more clearly defined cutoff, but lacks some of the intensity and throw. I even contemplated making one of the L-pieces moveable so it could be adjusted, but that would have required another hole in the casing (or two) for cinch bolts.
 

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Lights now painted and (mostly) assembled. The reflectors are installed, LED wires potted and wiring complete. Still have to:
Also the biggest problem I have is in affixing the LFlex to the inside of the light as the adhesive on the thermal pad isn't strong enough and the wiring keeps on pulling it away. Do any of you have that problem?
I had trouble on my first build. I've been using more flexible silicone covered wires and it's not as much of an issue.

Nice compact build btw- I may consider re-working some of my sled lights with this type of reflector depending on your final beamshot compared with a Regina or Laura CS optic.
 

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the screw(s) I use to bolt the sled and/ or spacer to the housing are always underneath the light, so they're a little less exposed, but I still put a thin bead of silicone sealant underneath the screw head so that it squeezes out the excess once it's tightened up

according to the manual and the testing George talks about, the adhesive bond gets stronger and the thermal conductance better after 24h and a few heat cycles, so it seems to do a better job with time.

as for the reflectors, I guess if you're getting as much spill as you need then going for throw makes the most sense, especially for a road bike light. I'm just worried that drivers will think that you're a BMW/Audi/Lexus/Escalade far away instead of a bike close to!
 

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Very nicely done!

Can I ask if the last shot in message #1 was taken when the reflector was outside of the square tubular housing .... maybe when it was just a test rig?

Would it be possible to repeat the garden shot with the completed light ...... and maybe even with just one of the heads lighting up the scene (or one head shielded/blocked off) to make the comparison fair?

The reason I ask is I'm wondering how much extra spill the housing creates compared with the really tight looking beam in msg #1.
 
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