# Build thread - double XM-L road lights



## mfj197 (Jan 28, 2011)

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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## mattthemuppet (Jul 16, 2004)

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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## phburns (Sep 30, 2008)

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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## mrradlos (Sep 3, 2010)

That looks very good! :thumbsup:

Could you take a photo, that shows the mounted XM-L inside the tube with the reflector in position? If you don't mind I would be interested to copy your design?


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## mfj197 (Jan 28, 2011)

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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## mattthemuppet (Jul 16, 2004)

that makes sense. Seems like a pretty neat way to make sure you get the beam you want. It doesn't matter how many times I measure something, it always ends up slightly off


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## Ofroad'bent (Jul 10, 2010)

Hmm, intriguing beamshot! It might actually work well offroad too, if tilted up a bit.
Nice take on the sled design.


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## mfj197 (Jan 28, 2011)

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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## HuffyPuffy (Jun 9, 2008)

This is cool, and the beam has a nice cut off, not a crisp line which seems to mess with my night vision more than this feathered cut off. The only problem is that we can't get these types of reflectors without ripping apart another light.


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## Vancbiker (May 25, 2005)

HuffyPuffy said:


> 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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## mfj197 (Jan 28, 2011)

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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## mattthemuppet (Jul 16, 2004)

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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## mfj197 (Jan 28, 2011)

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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## Ofroad'bent (Jul 10, 2010)

mfj197 said:


> 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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## mattthemuppet (Jul 16, 2004)

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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## mfj197 (Jan 28, 2011)

Here's some photos of the completed lights on the bike.


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## phburns (Sep 30, 2008)

:thumbsup: Nicely done!


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## HuffyPuffy (Jun 9, 2008)

It's a very clean looking light, and well thought out design, looks great!


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## *JP (Nov 23, 2011)

Those look great.


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## Bobblehat (Dec 1, 2007)

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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## mfj197 (Jan 28, 2011)

Bobblehat, the last shot in the first post was indeed done with the reflector outside of the light housing. I'll try and get a comparable beamshot from one completed lighthead as you mention, and ideally also some in the target environment (i.e. on road). The beamshot won't be quite comparable as the road reflector is now behind lexan whereas the regina reflector wasn't, but it should be close enough. I'll also try and take some oncoming shots too.

The beam penetration and width isn't really affected by the housing, as that light was projected from the reflector anyway. It may have an effect in the nearfield however. I do find that the illuminated inside of the tube makes me very visible from the front three-quarter view, as you can see from the above pictures.

Yesterday riding home one cyclist I passed commented that he had to get my lighting setup. He said he thought from the light pooling around him that I was a car. I haven't been flashed by any drivers either. :thumbsup:


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## Khrystyan27 (Jul 3, 2011)

I know it's been a while since nobody posted here, but can you please provide more nightshots of the light?

Some of the photos aren't working any more.


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## Khrystyan27 (Jul 3, 2011)

Message for the OP.

Do you still have this light?


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## mfj197 (Jan 28, 2011)

Khrystyan27, my apologies - I haven't been to the forum for a while. Sorry to see some of the beamshot photos aren't working any more. 

I do still have the lights; indeed they have been permanently mounted on the bike since I made them. Is that a couple of years ago now? They are in use pretty much daily through the winter months. The only change I've made is I've ditched the custom battery pack and just use a Magicshine one with its charger - far easier. 

I never took beamshots of the final lights. I'll try to take some soon, at least here in the garden. It's not yet dark for my commute and I have a 1 month old son who, together with his 2 year old sister, is demanding quite a lot of time! 

Michael 

Sent from my GT-I9100 using Tapatalk 2


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## Khrystyan27 (Jul 3, 2011)

Hi!

First I need to thank you for your reply.

There's no rush at all, take those photos whenever you can.

I want to do the same project but using just one XM-L powered by my dynamo hub.


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## borrower (Feb 26, 2011)

Just a wild idea about beamshots... if you could catch it on a really foggy/rainy night and shoot the beam from the side, it might give a really good idea of how the beam cuts off.


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## Khrystyan27 (Jul 3, 2011)

Good idea.


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## mfj197 (Jan 28, 2011)

borrower said:


> Just a wild idea about beamshots... if you could catch it on a really foggy/rainy night and shoot the beam from the side, it might give a really good idea of how the beam cuts off.


Nice idea. It'll have to be a foggy night - I went out tonight in the pouring rain that we have at the moment and it didn't really show off the cutoff. All that happened was I got wet! Incidentally I do have the centre of the beam pointing straight ahead so it catches the mirrors of cars I may be filtering through, but the cutoff either side prevents it shining into the eyes of incoming traffic. Unless I'm filtering up the middle...

Michael

Sent from my GT-I9100 using Tapatalk 2


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## Khrystyan27 (Jul 3, 2011)

If it's not too much for you, you could try to make a set of pictures on a normal night (no rain, no fog, pitch black), and another set on a foggy night.


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## Khrystyan27 (Jul 3, 2011)

Anything new?


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## mfj197 (Jan 28, 2011)

Sorry, nothing new Khrystyan27. I'll try and get beamshots, both from behind and in front, when I can. As the days close in I ought to be able to get some shots in mist too.

Michael


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## Khrystyan27 (Jul 3, 2011)

Still no nightshots?


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## mfj197 (Jan 28, 2011)

No, my apologies Khrystyan27. I've been away from home for most of the last month and am away again this week - and the evenings I have been home have been busy with my wife and two kids, one of whom is 11 weeks old so it's all a bit hectic! I can't do any this week but should be able to next week as I'll be cycling on the commute.

Michael


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## Khrystyan27 (Jul 3, 2011)

Ok, thx man.


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## mfj197 (Jan 28, 2011)

And now I find I'll be in Dubai for 2 weeks as of this Saturday! Apologies - I'll put beamshots and a head on comparison up when I can.


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## mfj197 (Jan 28, 2011)

*Update and beamshots*

It's been far too long since I updated this thread, but with all the foggy weather recently I've finally been able to get some useful beamshots to show the cutoff as per borrower's excellent suggestion. The lights are now on another bike and are mounted above the bars rather than underneath.

Here's a shot showing the cutoff and reach of the lights (close to MTBR standard settings but not exact)








Here's another one, this time with (equivalent of) MTBR settings.








That's all well and good, but what are the lights like compared to a standard flashlight? Well, here's my little helmet mounted flashlight as a comparison with the same settings. It's advertised as 230 lumens and yes, it is on!








But what about from the front? The light on the left is my helmet flashlight as above (230 lumens) and the lights on the right are on the bike (2,000 emitter lumens).








The bike mounted lights are a bit brighter from the front (compared to the flashlight) but the difference is as nothing compared to the difference in visibility provided - which is quite literally night and day. I haven't been flashed at all by other road users, whereas if I had a pair of XM-Ls with standard reflectors I'm sure I would have had a few irate drivers.

Finally another shot from the side - and yes, I've recently made a decent rear light too!








I'll try and get some normal beamshots at some point although I'm away on business again at the moment. I've a P7 flashlight somewhere that I might be able to use as a comparison.

Michael


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## brad72 (Jun 12, 2009)

That has turned out really well and looking at the beam spread from the rear light it is clear to see how well the cutoff on the front light works.


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## mfj197 (Jan 28, 2011)

It's worked out well and the great thing is it gives more light focussed on the ground where it's needed and much less above the beam where it's not.

The most difficult part was finding a suitable reflector to cannibalise. It had to be a complete parabola (or as close as possible) as the LED fires down into it - it has to focus the beam from both in front of, and behind, the focal point. Therefore none of the thousands of LED flashlight reflectors would work, as they don't have any parabola behind the focal point (they don't need to as an LED in its normal orientation only projects forward). In effect these lights are pointing an LED downwards from the same location as a flashlight normally has one pointing forwards.

Finding a reflector from an incandescent lamp these days isn't easy!


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