Why bother?
With Cree 3W LED torches avaialable on EBay or even Tesco (£10!!!) that run for 2 and a bit hours on 2900mAh rechargeable batteries, there is little economic sense in building LED lights. Of course, there’s always just ‘because’… might even build 3 of them into a super head torch myself.
BTW, I can vouch for these torches – I’ve ridden offroad and a decent speed with one as my only light source when I smashed my HID lamp, and to be honest I didn’t miss it that much. A little more of a focussed beam, with a bit more penetration would be nice for road work, but I’ve seen a lot of LEDs and think HID is still better if you need that.. I’m happy to save the money and go a little slower 🙂