First some background - a couple of years ago I built a dynamo light using W bin Luxeon III LEDs - 4 wired in series to run off a Schmidt hub. I used the manual switched voltage doubler circuit from that top man Martin, and Optics from Carclo. Being only for on-road use I selected the 4 degree optics to get the highest light intensity on the road. The LEDs were mounted in a 2x2 arrangement on a large heatsink bent so that the optics projected the light about 7 degrees apart - the result was that 15-20m in front of the bike the light was exactly where I wanted it on the road. The set-up worked pretty well, and the dynamo Solidlights (which a lot of people here in the UK are using) looked pretty dim by comparison.
Anyway, I recently got hold of some samples of un-mounted Cree XR-E LEDs (P4) and compared the light output to the Luxeon III. Despite the datasheets predicting that the Crees would only be slightly brighter, it turns out that the integrated light output of the Crees (as measured in an integrating sphere) is about 2.6x that the the Luxeons at 350mA to 500mA. So, what I want to do is to replace the Luxeons with Crees, but with minimal disruption to the mechanics of the light (that being the hardest bit to do in the first place). I've ordered some star heatsinks from DealExtreme onto which the Crees will be surface mounted, but I can't use the 26mm Carclo optics that worked so well before.
So, to come back to the title of this post, I would be interested to hear people's recommendations for the best optics (lens or reflector) to use with Cree XR-E to give the narrowest beam spot (without having to go to aspherics), but which are be compatible with a start mount (I am assuming the ones I have ordered are the same size as the Luxeon ones).
Thanks for your help.
Anyway, I recently got hold of some samples of un-mounted Cree XR-E LEDs (P4) and compared the light output to the Luxeon III. Despite the datasheets predicting that the Crees would only be slightly brighter, it turns out that the integrated light output of the Crees (as measured in an integrating sphere) is about 2.6x that the the Luxeons at 350mA to 500mA. So, what I want to do is to replace the Luxeons with Crees, but with minimal disruption to the mechanics of the light (that being the hardest bit to do in the first place). I've ordered some star heatsinks from DealExtreme onto which the Crees will be surface mounted, but I can't use the 26mm Carclo optics that worked so well before.
So, to come back to the title of this post, I would be interested to hear people's recommendations for the best optics (lens or reflector) to use with Cree XR-E to give the narrowest beam spot (without having to go to aspherics), but which are be compatible with a start mount (I am assuming the ones I have ordered are the same size as the Luxeon ones).
Thanks for your help.
The adhesive pad was also too small to hold the thing on, as most of its useful area was off the sides of the star. 
The thing just wasn't designed to be used. I really hope the Cree versions are better.
