My current light (as of October 2006) is home built, based on the Luxeon III Star design from Suzy at littlefishbicycles.
I didn't have access to the same tools as Suzy, so I modified the design to suit what was available. The main housing is from aluminium tube 40mm OD 3mm wall. The heatsink disc was turned from 10mm aluminium plate. The back disc is 3mm aluminium. Spacers are 25mm + 5mm. Lens is an L2-OP-005, giving 10 degree beam (5 degree half angle). This appears to be about the right beam width for a bicycle light. Front of the main tube housing has a 1mm rebate extending 3mm into the tube, into which sits the 2mm thick perspex front cover. I put a small amount of silicone sealant in the rebate, then pushed in the perspex. It hasn't fallen out yet. The heatsink disc is attached to the tube by two M3 screws and also by an M5 bolt used to mount the light. The mount is a handlebar bottle cage adapter, with one end cut off (the bit facing the rider) and the light mounted through the other end. The bike light can be fitted, adjusted and removed with a 4mm allen key.
The switch on the back is centre off, low power down (0.9W) and high power up (4.9W). These figures are the power output from the battery. The actual Luxeon III is running at 3.5W (3.5V, 1000mA) on full power. Running it at 1000mA shortens the life from 100k hours (700mA) to 10k hours (1000mA). Getting to 10k hours means riding in the dark for a year continuously, or 200,000km. I figure by the time the LED wears out, I'll make one with newer more efficient LED, or I'll be so blind with old age that it won't matter. On the 3.5AH battery I'll get about 8 hours on full power, 40 hours on low power, and half that on my lighter 9.6V 2400AH battery (made from 8 x AA NiMH solder tab cells).
Turning the two aluminium discs.
On the lathe I used the plate drive.
To this I screwed a wooden block (piece of MDF).
The spacer mounting holes in the two aluminium discs need
to be aligned, so when drilling the holes I held both pieces
together in the vice.
I then drilled holes at the same spacing into the wooden block,
tapped these and screwed the aluminium pieces onto it.
After the aluminium pieces were turned into discs,
the holes were in the correct place.
Mistake #1: I should have scribed the line between the mounting holes, and also the perpendicular. My marks were in pencil, which I lost during handling, making it harder to locate other things correctly.
Mistake #2: I turned the discs until they just fitted into the aluminium tube. The tube had been formed by extruding, which caused it to have longitudinal lines. This meant that the disc tended to bind on the fine ridges. I spun the tube on the lathe and removed the ridges with some fine wet and dry paper. The disc was no longer a snug fit. Clearly I should have cleaned up the tube prior to making the discs.
Turning the perspex cover:
I acquired the perspex from someone who had worked in the
plastics industry and had a collection of offcuts.
What was probably even more valuable was his advice on
how to work perspex.
When drilling (which I didn't need to do), don't use your sharpest drill.
A sharp drill will bite into the soft plastic and chase in like a screw.
You will get better results with a slightly blunt drill.
When turning on the lathe, similarly use a tool bit that is not sharp,
and which doesn't have too much bite.
The end of the tool bit should be relatively vertical,
not steeply angled back under the cutting edge.
The perspex came with a polyethylene protective film, which you leave on until the last possible moment. To hold the perspex on the lathe you put it betwen two pressure plates. I didn't have this system, so I clamped it between two pieces of wood. I used one piece of wood on the drive plate, then another piece of wood against the dead centre. A live centre would have been better, but since I only had a dead centre the solution was to lubricate it and apply a suitable amount of pressure. To make sure the perspex really didn't move, I put some double sided adhesive tape on each side before clamping it. This worked, but caused the protective polythene to come off when removing the tape. Next piece of advice was to take it slowly. If the lathe tool bit hits the work piece too hard, it will crack. Turning the perspex worked really well and was much easier to work on a hobby lathe than aluminium.
Mistake #3: I didn't take photos of the process. Sorry, you only get a written description.
First would be to use a Cree XLamp.
At the time I started building the light, the Luxeon III was the brightest available in the star mount that can be easily bolted onto a heatsink.
I did consider using the Luxeon K2, but it was only available in a emitter form, which requires you to reflow solder it onto a metal cored printed circuit board (MCPCB). I have neither reflow solder capability nor PCB manufacturing facilities, so I used the Luxeon III star. Current light output should be 80 lumens. Using a Luxeon K2 at 1500mA would give 140 lumens and a short life, or 100 lumens at 1000mA. The LuxDrive Buckpuck is only available up to 1000mA, so at the moment it isn't worth using a Luxeon K2 at the lower current. Luxeon K2 stars are now available from LuxDrive.
Currently the brightest and most efficient LED seems to be the Cree XLamp 7090 XR-E, so forget the Luxeon K2.
An upgrade of the bikelight is now planned as
Version 1.5
A new bike light with 3 LEDs is planned as
Version 2
2006-10-26