With all the current interest in lighting I have decided to take it 'all the way' so to speak.
There has been a chap posting on the caving networks who crammed 3 Crees into an Oldham headset, I understand that he had heat problems, no kidding.
Anything overambitious put into a plastic or bakelite headset will have heat problems, however...
I just turned up an old Maglite C or D cell, years old with the batteries corroded in. Some work with a hacksaw, chisel and Stilson Wrench got it disassembled. I have salvaged the head, the partially corroded base cap, albeit with enough good thread left, and the forward part of the tube. There is an internal thread for the switch gear inside the tube, so on a cut down section of the tube the base cap screws in, the section of tube screws into the head, so in effect all I have is the head, well sealed and watertight.
A helmet bracket of an old Odham headset, a length of stainless steel bent at acute angle, and an 10 mm plumbing connector attaches my 'bracket' and provides a 'gland' for the cable to pass in. This is in a hole drilled into the base cap as there is nowhere on the head to do this because of the shape and because the tube screws in making a sort of double skin.
Although there are no electrics in it yet I tried for wear on my helmet, it felt OK. It does stick out more than the Oldham, but I considered this and the design of my bracket places it slightly lower than the Oldham.
I will be using external switches in a small abs box, 2 of them. One will control 1 Cree, the other the other 2 Crees giving me choice of 1, 2, or 3 Crees plus the intermediate settings. It should put out about 660 lumen. I shall mount the Crees on a piece of aluminium shaped to fit snug into the torch body so as to conduct away the heat. I shall also heat sink the drivers in the same way.
This one should work, and the choice of a single emitter for normal use puts it back into the realm of sense.
Will keep you all informed, and warn everyone in advance of anywhere I plan on using it.
My avatar is a poor likeness.