Friday, February 17, 2012

A new bicycle headlamp design: philosophy and rationale

In my opinion, contemporary bicycle light offerings have not kept pace with the demand for classically inspired bicycle components.  Companies like Velo Orange, Rivendell and now Compass Bicycles have fed demand for newly manufactured retro-styled components to update vintage frames as well as to equip the growing number of available lugged steel frames inspired by classic touring, randonneuring and racing bicycles.  These 'modern classical' builds can now be built with new handlebars, brakes, levers, rims, cranksets, saddles, stems, racks and fenders, all conforming to the new retro aesthetic defined mostly by Velo Orange and Rivendell.

However, contemporary headlight offerings that match a modern classical build are limited.  The best, and most popular option is the Edelux by Schmidt.  I have one on my 1970s Holdsworth Super Mistral and it is a great looking and performing light.  Its polished aluminum finish certainly agrees with the modern classicist's backlash against anodizing of any kind (here, the other major boutique player, Supernova, falls short).  The light is diminutive (85g!) and the hemispherical design is certainly better than anything else out there, vaguely reminiscent of the Soubitez 'golf ball'.   Still, in my opinion, it looks a bit out of place on a vintage or modern classical build.

Other contemporary offerings in the vintage vein include the Lumotec Retro and the recently introduced Classic from Busch & Müller.  The Classic is chromed and has a nice retro-looking selector switch, but on the whole I think it's one ugly duck.  The Retro is a little better looking than its younger sibling. I used to have one and it is just a Lumotec halogen lamp with a chromed plastic shell to retro-fy it.

After that your options are limited to a handful of cheap chromed bullet lamps from Taiwan or you can hunt down a vintage French headlamp, something I used to do with more enthusiasm before increased demand drove up Ebay prices.

I'm forever experimenting with upgrading vintage bike lights with modern LEDs and optics, but these efforts have led to me to conclude that the best option for a modern build would be a completely new lamp designed from scratch.  Something bright, elegant and weatherproof.

So, I designed one, hereby christened the 58A. 

Nº58A headlamp

This design references the elegant teardrop shape of the classic French lamp makers like Radios, Luxor, Soubitez and JOS, which were made of spun aluminum.  The lamp housing, bezel and bracket will be CNC machined and, of course, it will have a modern LED with standlight.

Nº58A cross section

Good thermal management is crucial to LED performance, so the LED is mounted on a large copper heat sink that transmits heat away from the LED through the lamp housing.  My design is for a dynamo powered lamp to begin with but the Cree XM-L can be driven up to 3A, so a battery powered version (with an external battery pack, unfortunately) is an option down the road.  The heat sink is very likely up to the task.  The reflector is, out of necessity, an off-the-shelf model designed for use with Cree XP LEDs. The beam is tightly focused but with enough spill to provide good off axis visibility in traffic.  I haven't done a detailed analysis of the beam shape but it reminds me of my Supernova's beam: round and symmetrical.  A reflector that produces an asymmetrical cutoff beam like that of the popular B&M IQ reflector is not available in the format I need.

Nº58A dimensions

The headlight is on the larger size, about 58mm (2.3in) at its largest diameter and 77mm (3in) long, though still smaller than classic French teardrop lamps such as the Radios Nº18 and the Luxor 65.  It's also quite hefty; based on volume and material density calculations, around 228g or 8oz.  Almost certainly too heavy for fender mounting (at least without a second set of stays), but fine for mounting on a front rack or fork crown.  The weight is due to a combination of thicker walls than traditional spun aluminium and the dense copper heat sink.  One advantage of the thicker CNC fabrication is that it shouldn't dent like old spun housings.

A friend of mine kindly put together a few photorealistic views in polished aluminium:

You can see the complete set here on Flickr.

Noticeably absent from my drawings is a switch. Finding a place for a power switch has been the most challenging design issue.  Vintage French lamps were almost universally bottle dynamo powered, precluding the need for a switch.  There isn't a compact enough selector switch available to mimic the switch of the old Sturmey Archer headlights.   I contemplated something similar to the clever magnetic reed switch used on the Edelux, but that design requires custom plastic parts.  In the end, I decided to go for a short actuator toggle switch with a splash proof boot. You can see its placement in the following renderings:

Shown is a switch with a flatted actuator, but I'll probably use a standard round actuator as it fits better in the boot and creates a better seal.  The seam between the lamp housing and bezel will be sealed with silicone grease and an o-ring will seal between the bezel and glass lens.

At the moment, I'm finalizing a quote with a prototype maker.  With a prototype in hand I'll be able to spend the spring and summer riding with it, running it in the shower, hitting it with a hammer, striking it with lightning, etc, etc.  Then, if there's enough demand, I might consider doing a small production run.  I'll post updates about the project here.   If you're interested, please comment below or send me an email (address at bottom of page).  I've even reserved a name for this putative enterprise: Bici Lux.


Anonymous said...

If you do wind up producing these would you also please consider having a bracket fabricated to allow these to attach to vintage headset mounted "Raleigh" style lamp brackets?

minisystem said...

Noted. The thought had crossed my mind. In fact, I just recently purchased an old Raleigh lamp bracket for my wife's Sprite. My design is a little on the rotund side and the stem bracket is designed to take the weight of the bulky old Sturmey Archer lamps. Could be tricky to fabricate as it would necessarily enter the realm of sheet metal bending rather than CNC milling.

I've also had a couple of requests to offer a version that can be mounted 'upside down' on front racks. This would involve moving the switch and holes for the wire to the opposite side of the bracket.

MT cyclist said...

Love the look of your prototype. I'll definitely be checking back to see your progress.
It's an exciting design and would be something that I'd be interested in purchasing.
Good luck.
Tom Howard

Anonymous said...

how do the wires enter the housing? It can be a challenge to keep the housing sealed at the point where the wires enter.
Or.. don't let anyone mount the light upside down.

For the switch.. the booted toggle is good. I'm trying to think of some way to use a simple booted momentary switch, but it's not coming to me.

Steve K.

minisystem said...

The wires are going into a hole that is just a tiny bit bigger than the wire diameter, so the tight fit along with a bit of silicone on the inside should provide a weatherproof, if not waterproof seal. Every dynamo light maker from B&M to Schmidt to Supernova explicitly state that their lights cannot be mounted upside down so I'd advise the same. With the prototype in hand I'll have a better idea as to how well this will work.

Everett Staley said...


JoeZG said...

Nice work . Keep on going.

Lenigas said...

Finding your project really interesting. However, as you add the functional elements to the base form the cleanness of your vision is getting lost. I would suggest revisiting how, where and why you puncture the bullet form. I don't know how to post sketches to the comments, but you can simplify the connections and solve the waterproofing at the same time.

Hope this become real, even as a prototype

minisystem said...

Prototype is currently being fabricated, so I'll know soon how much the switch actually impinges upon the form. Feel free to email me (address at bottom page of blog) with suggestions. I've already had someone else offer suggestions for improvements by sending me sketches, which were helpful.

Unknown said...

You're probably way beyond this, but: I wonder if you might have the headlight shell produced from thin sheet metal by the process of spinning? On one hand, it requires only very simple tooling, i.e. a lathe, a few slightly special tools and a male pattern over which the metal is formed. OTOH, it requires finding someone skilled in the operation, which is not very common. But it's an excellent way of producing shapes like paraboloids in small volume at low cost.