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My setup uses a 5 watt hexagon LUXEON star with a NARROW collimating lens and a POWERPUCK.
I bought them from ATA (Alternative Technology Association)
The collimating lens has been removed from its supplied holder.
The hexagonal LED mount is bolted to some copper sheet with some brass screws. Bend the copper after drilling the holes but before mounting the LED base.
I forgot to put some heatsink compound on it first but it seems to be ok.
Copper is much better than Aluminum as a heatsink because it can move twice the amount of heat for the same thickness.
The copper sheet is just wide enough to accommodate the PVC tube. I've made the copper a bit long below the LED to give it more cooling area.
The lens housing is made from a short section of PVC water pipe, about 22mm or so.
The lens is glued to the copper with silicone glue. When it has set, carefully glue the lens into the PVC tube. The ridge on the lens sits on the top of the tube. You also have to cut a notch in the tube to allow for the aligning bump on the lens.
The distance of the lens from the LED is critical to get the correct focus of the lens. You want the lens to be just off the top of the LED. Experiment to make sure it's cut right.
Two small notches need to be cut into the bottom edge of the PVC tube to allow the wires to come out. Be careful when soldering the wires to do a neat job so you don't short out the leads on the copper heatsink. Excess glue helps to hold the wires in place, so they don't flex and break.
You don't need much glue as the plastic bits are very light, and you might want to take it to bits again someday.
The wiring is pretty rough 'cos I just sort of slapped it together to see how it works.
The POWERPUCK can be mounted away from the LED for a cleaner look.
It's fine for road riding on country roads. I haven't yet tried it on my mountain bike.
I use a 2 Amp Hour Sealed lead acid battery which should give me about three to four hours of light. The LED power puck consumption is about 6 Watts. Current drain is half an Amp.
I highly recommend a battery charger that uses a special charging chip designed for the type of battery you use. I can't stress this point enough.
My battery mount works well but I hope to make a proper mount for it (one day).
I recommend you put in a fuse (located close to the battery) and a switch. I use crimp type terminals to make the connections. The "live" side of any wire should have a female terminal on it, so that when you disconnect it, the live wire doesn't short to anything and burn out your battery and wiring.
I've simply taped my light on, but you can make a mount. My Tri Bars don't really have much room for mounting things, hence the tape.
make sure that brake and gear cables don't interfere with the light or the wiring.
This arrangement would be easily adaptable to a helmet light.
The battery.
A bit of extra copper to get rid of heat.
The LED is mounted just below my hands on the Tri bars.
I've taped the POWERPUCK on top of the copper strip.
Those arm rests are the BEST THINGS EVER.
The screws could be cut off a bit shorter.
From the rear.
My wiring needs to be tidied up.