tcs

This was a bit of a COVID social distancing project.

So, I wound up with this new-in-box 1978 Sturmey-Archer Dynohub. I found out why it was still new-in-box: it was 36 spoke American but with a 90mm OLD (British roadster). Yeah, I had to swap out the axle, which was an adventure. Anyway, I spoked it up in NOS 27" rim, shod it with a 'handmade in Germany' Conti and spun on some axle wing nuts.

Well, then I had this quirky 43 y.o., 1.8W dynamo (magneto) hub. Might as well hook a headlamp to it, right? I had an old B&M Lumotec 3W halogen in the 'Big Box of Parts Under the Workbench' so I wired that up. As you can guess, with a 27" wheel spinning @ neighborhood speeds I could almost make out the beam it threw onto the pavement. Phthphth.

So I did a little state of the industry review and ordered a B&M OneFive LED. Yeah, baby, that's what I'm talkin' about - it's no IQ-X, but it throws a nicely shaped, very useable beam of bright white light.

steelbikeguy

always nice to get an old piece of gear back in use again! Especially something as classic as the Dyno-hub!

The old incandescent bulbs were really weak when compared to the early LEDs. It's amazing that we were ever able to feel our way through the darkness with them. Using a 3W bulb at about half power means that the light output will be down to a tiny fraction of what it should be, so no surprise that it looked awful. Glad that a modern LED light was able to operate acceptably from the Dyno-hub's modest output!

Steve in Peoria

tcs

The B&M OneFive LED headlamp is allegedly optimized for the 1.5W dynamo hubs that Shimano and SP make these days, and I'm giving it a trial mating it to a hub rated at 1.8W 43 years ago. I'm told the old Sturmey Dynohubs can acceptably light up low to medium lumen LED headlamps rated at 3W, but won't give you everything you paid for if you've got one of the big German photon cannons mounted on your bike.

znomit

I run an eyc off a 1.5W hub on my commuter. I don't think the onefive was available back when I set it up. The slow speed flickering would drive me nuts climbing hills at night but actually is probably beneficial for visibilty in city traffic.

steelbikeguy

I didn't know that there were headlamps rated for that low power. I wonder if it still meets German standards?
I'd be surprised if the standard LED headlamps would perform noticeably worse than the 1.5W headlamps. A 1.5W headlamp could be smaller and cheaper than a standard 3W version, due to the lower voltages and/or currents, and the reduced amount of heat to get out of the LED. ...and it would still be hugely better than the old incandescent Lumotec that I still have in my parts box!

Steve in Peoria
(I really do need to get rid of some of my old stuff)

znomit

I assume there are fewer poles in the low power dynamo so lights designed for them might need a larger smoothing capacitor.

Tourist in MSN

Last summer I met someone that had a 1960s or 70s vintage Raleigh three speed bike with dynohub and vintage light. He had installed a LED flashlight bulb in the light but he complained that at slow speed it flashed. I commented that it could be improved with a rectifier because his LED bulb likely only worked on half of the AC cycles, but I think that the term rectifier was something he was not familiar with. If you wanted to try your vintage light again, an LED flashlight bulb plus rectifier might be an option if your interest was closer to bike restoration that gave you more light than the incandescent bulb that you tried.

I will try to remember that phrase for next time I am behind the wheel at night and am blinded by some moron that thinks his strobe light makes the world a safer place.

tcs

Yep, apparently, the industry convinced the StVZO folks a dynamo (magneto) hub driving an LED @ 1.5W can put out plenty enough light to meet the standard.

"The intention was to encourage the use of smaller, lighter and cheaper low power dynamo hubs in place of the less reliable sidewall generators that were still found as OEM on most German utility/town bikes."

The StVZO standard was written around filament bulbs, but the world has left filament bulbs behind. Dynamo hubs are (and always have been) current sources, not voltage sources, and modern lamp driver electronics regulate the voltage across the LED. Some smart girls and boys explained to me with a series of graphs, equations and circuit diagrams I didn't quite follow that's why an old 1.8W Dynohub™ can light up a modern 30~40 lux "3W" LED headlamp just fine.

tcs

Just for grins I put an LED blub in an old Boy Scout flashlight. I got plenty of photons, but because an LED isn't suspended above the reflector the way a filament is, the flashlight put out kind of a goofy beam.