Sturmey Archer headlight Cree XM-L power LED upgrade

Raleigh Superbe's Sturmey Archer headlight. Photo by lowercase design

I really like the Sturmey Archer lamps that equipped later model Raleigh Superbes.  The older Raleighs (and other English 3 speeds) seem to have come with a variety of different lamp styles over the years.  My best guess is that when the Superbe hit North American shores in full force in the late 1960s and throughout the 1970s, Raleigh/Sturmey Archer had standardized their lamp offerings, which resulted in the now classic chromed bullet head lamp and tail lamp.  This version of the lamp set is what I see most commonly on the streets of Toronto, as well as in Flickr feeds.  They aren't especially rare and certainly don't show the craftsmanship and quality of the earlier French lamps, but a Sturmey Archer light set can still command  prices of well over $100 on Ebay.  They can even occasionally be found as a NOS.

The output from the incandescent bulb is rather pathetic.  This is mostly due to the low output from the Sturmey Archer Dynohub that typically powers the lamp, possibly exacerbated by the seemingly low quality of the reflector.  Halogen replacements are available from Reflectalite, but even these are rated at a rather paltry 18 lumens.  I tried upgrading the bulb with an screw base LED replacement, but found the output rather disappointing. I even went to the trouble of making a custom screw base power LED mounted on a copper heat sink.  This produced a big floody beam, but the flimsy bulb holder that mounts the bulb in the reflector probably wasn't up to the task of supporting the extra weight of the power LED's heat sink.

So, back to the drawing board.  To start, I thought I'd replace the flimsy stamped bulb holder with a copper heat sink.  The reflector is made of coated metal, so it shouldn't have any problem with carrying the weight of the heat sink, which can be wedged into the opening in the reflector in the same fashion as the original bulb holder.  This time I decided to use the super high output Cree XM-L, which is rated at 290 lumens @ 700 mA.  As in my previous designs for the Cree XPG, a nub pokes through the PCB so the LED's thermal pad can be soldered directly to the heat sink. Something like this:

Design for Sturmey Archer headlight heat sink

Looks a bit like a top hat. Here it is machined in copper:

Copper heat sink for Sturmey Archer headlight power LED upgrade

It flares out a tiny bit where the bottom of the pillar meets the rim.  Here's the heat sink with a Cree XM-L soldered on to it:

This is how the original bulb holder fits in the reflector:

and here is the copper heat sink mounted in the same opening:

Copper heat sink mounted in reflector of Sturmey Archer headlight

It fits very snugly in the reflector and doesn't feel like it's going anywhere.  A dab of Loctite wouldn't hurt though.  The LED sits low in the reflector, about where the original bulb's filament would be.

Sturmey Archer headlight with Cree XM-L power LED upgrade on copper heat sink

Coupled with an upgraded LED bulb for the rear lamp and a Dynohub magnet upgrade, a modern and powerful dynamo system emerges.  It will eventually even be possible to add a standlight and flasher.  The lamp is still a victim of its original optics, which obviously aren't nearly as good as the highly optimized optics of modern bike lights, but the high output of the Cree XM-L does result in a bright, floody beam.  Certainly enough for cruising around city streets in relative safety and quite possibly enough to illuminate a poorly lit country bike path.

I'm thinking of making this LED upgrade available, along with an LED upgrade for the matching taillight.  Let me know if you're interested either by commenting or by emailing me directly (bottom of page).

The XM-L can be run at up to 3A to produce a whopping 943 lumens so a battery powered retrofit could produce an impressive amount of light, although it remains to be determined if the heat sink would be adequate.  That would require some performance testing.