agmetal

I have an early version of Sturmey-Archer's DynoHub, the GH-8. It puts out a nominal 8V 0.15A (1.25W).

A datasheet for the hub says that it should be used with a headlight bulb that matches those numbers, and if a taillight is to be used with it as well, it should be 1.5V 0.15A (0.225W)

A friend and I did some testing last night with a couple bulbs we had on hand, as well as some plain resistors, and found that there's a significant decrease in efficiency when we used a bulb (or resistors as a dummy load) that didn't match the impedance that the generator was expecting.

Frustratingly, there doesn't seem to be much out there for bulbs that will actually work, particularly with the taillight. However, I've found myself with a bunch of questions.

I found some NOS vintage bulbs for sale that appear to be the correct thing for the headlight, that say 6-8V on the package. This led me to discovering "trade numbers" for these bulbs, and I'm a bit confused about those. I see bulbs numbered 40 and 133 that have the same specs as each other, except for the shape of the glass envelope. The NOS vintage bulbs I found are also listed as being trade #40 , but the ones I'm finding available new are only listed as 6V or 6.3V, as opposed to the 6-8V of the NOS bulbs. Does this mean that I'll risk blowing them out? Also, how much does the shape of the envelope matter when we're talking about a bulb that'll be getting put into a fixture with a parabolic reflector?
Here's a current #40 bulb: #40 MINIATURE BULB E10 BASE, T3 1/4 M SCREW 6.3V .15A .5CP,2FMR6,#2FMR6,#40, 40, #40 BULB, #40 MINIATURE, #40 LAMP, #40 MINIATURE LAMP, #40 MINIATURE LAMPS, #40 INDICATOR, EIKO# 40694,6240-00-019-3146,#6240-00-019-3146

For the taillight, the closest specs I've been able to find on a currently-available bulb is #458 https://www.interlight.biz/light-bulb/458

The spec sheet for the hub lists 1.5V 0.15A for the taillight, the 458 is 1.5V 0.2A. Will this work?

I also found an LED bulb that claims to be compatible with #40 and #133 and AC power....but does that mean it'll work with the 8V output from the hub in question? https://www.ledlight.com/e10-screw-b...led-light.aspx



EDIT: Before anyone asks - yes, I realize that this will be underpowered compared to a modern light, but I specifically want to use this particular hub because it's more period-appropriate for the bike.

Tourist in MSN

I can't answer your bulb questions, but the terminology you are using suggests to me that you understand calculating things like watts and ohms, etc. Thus, I assume you are knowledgeable about electrics. Have you considered adding a rectifier to the circuit and trying a LED flashlight bulb in your vintage light? Some of the LED flashlight bulbs out there can take a wide voltage range. The light would flicker at low speed, but that is not really a big deal.

A couple months ago I met someone riding a vintage Raleigh DL-1, he had a Sturmey Archer dynohub on it. And he had put a LED flashlight bulb in his vintage light. But he said his has a very bad flicker at low speeds. I was surprised it worked at all because he did not realize that an LED bulb should be used on DC, but I think his hub was putting out AC. I suggested a rectifier to him, but I have not seen him since then.

For taillight, I have no suggestions.

When I used a sidewall bottle alternator with incandescent bulb, I put a pair of zener diodes on it to drain off higher voltage that would blow out my bulbs. I think I used 8 volt diodes, but that was a 6 volt system at normal biking speeds. If you start blowing out bulbs you might consider adding some diodes.

unterhausen

led bulbs should work fine with that dyno. Incandescent lights are a lot trickier to match. It's possible putting a zener diode in parallel would help longevity.

fietsbob

generally head light wattage is a draw marching the output.

noglider 

Some have had success using an old Dynohub to power modern LED lights. The nominal power output of the old hub isn't sufficient in theory, but in practice, it is.

agmetal

I've heard this before, but remember that I'm using an 8V 1.2W hub, not a 6V 1.8W hub. When my friend and I tested it with one of the bulbs we had on hand, the bulb (rated for 6V 3W, I believe) barely came on at all

noglider 

Aha, good point.

znomit

The Voltage/Wattage specification is based on a resistive load (like a bulb). It doesn't really apply to a LED load.

Dynamo LED Light Systems for Bicycles (electronic circuits)

steelbikeguy

this detail caught my eye... with a taillight bulb rated for 1.5V and the same amperage as the dynamo, it implies that the taillight is wired in series with the headlight. This differs from the current practice of wiring the taillight in parallel with the headlight.

Very interesting, to me at least!

As for the other aspects, I can only assume that someone has been working on the same problem. For the more common dynohubs, I've heard of folks using the Reflectalite led bulbs in the flanged package.
LIGHT BULBS FOR CYCLE LIGHTS
Their website says that the models that are used with Dynohubs are no longer available, though....

Good luck with your search.

Steve in Peoria

PaulRivers

Just wanted to point out the other reason is because incandescent bulbs didn't last - 1-2 years before it burned out under ideal riding - less than that other times because incandescent bulbs are fragile.

An led-equivalent bulb would probably be the best way to go for that reason.

Sorry I don't have a specific suggestion.

Steve B.

Over driving an incandescent lamp with higher voltage than specified greatly shortens lamp life. Driving a 6 volt lamp at 8 volts is a 1/3 increase, so expect an increase in light output and color temperature (whiter/bluer) as well as a lot less life.

The envelope and size only matters in terms of heat. The filament generates X amount of heat and needs to work in either a vacuum or a quartz glass envelope that has a high pressure halogen gas inside. The glass envelope standard A lamp you use at home has a roundish shape to allow the glass to tolerate the heat of the filament. A quartz halogen lamp (think of an architectural MR16 lamp) has a much smaller glass envelope as the quartz glass can better tolerate heat and pressure.

One major issue for a dynamo hub generator is can it generate enough voltage to power an LED lamp ?. LED's typically need at least 5 volts DC to operate and will use a driver to control the current going into the lamp. 6 volts may well be enough and as the LED array is typically a low current users, a dynamo might work. Problem is variations in speed and voltage may cause the lamp to flicker on and off, where as an incandescent will just dim up or down..

Tourist in MSN

When I commented above that I think I used 8 volt zener diodes to protect my incandescent bulbs, keep in mind that it is an AC alternator, so I wanted to trim off the peaks of the sine wave. If I had bought 6 volt zener diodes, my average AC voltage would have been cut to well below 6 volts.

An alternator will put out more power the faster it turns. In my case the zener diodes were not for normal use, but for going down a hill when I was going a lot faster, that is when you burn out the bulbs.

These alternators are simply that, an alternator and nothing else. The more current you draw, the lower the voltage will run. And the opposite happens too, if you draw almost no current then the voltage will climb. I have no experience with a vintage Sturmey Archer alternator (I assume it is an alternator, not generator), but I can say that when I have no load (only a multi-meter that draws almost zero current) on my modern dynohub, going down a hill at 25 mph it puts out over 30 volts. But if I try to suck too many watts out of it for powering something, the voltage will plummet.

Modern LED headlamps designed for dynohubs have over-voltage protection built in. Once I am up to about 8 or 9 mph, my headlamp is as bright as it is going to get, but it won't burn out on a hill either. But the old incandescent bike lights offered no over voltage protection.

rhm

Several years ago I got a couple of the little LED bulbs that have the same screw base as old incandescent bulbs, and used them in GH6-powered head and tail lights. The result was disappointing. The led light source was weak and poorly placed relative to the parabolic reflector, so the light was dim and very uneven.

I have had better luck putting together my own led "bulbs" using the base of a burned out bulb, a star led with its correct lens (collimator), solder and epoxy.

The experts will tell you you need a bridge rectifier &c, but I'm no expert. I simply wire the headlight and tail light in parallel (not in series) with opposite polarity. The headlight and taillight flash alternately but it's not annoying.

I've done this both with GH6 dynohubs and a "MK II" dynohub (from 1939?) which is, I think, the 12v version. As you've anticipated, the light is not up to the standard set by modern manufacturers like BuM but it's far better than any incandescent bulbs I've tried.

Trevtassie

The bridge rectifier will help increase light output in some cases. If you imagine AC as being a wave form with half the wave about 0 volts and half below, a normal LED, being a diode which acts like a one way valve, will cut off the bottom half of the voltage. A bridge rectifier effectively "flips" the wave below 0 to above 0 so you end up with a series of bumps. But a lot of LED globes or star LEDs have a bridge rectifier in/on them anyway, so polarity doesn't matter when used with DC, so they work OK with AC too.

steelbikeguy

pics??

One of my projects that is waiting for some spare time is a slightly higher grade of this same idea. My hope is to have two white LEDs in series with some half decent heatsinking. This would provide the same nominal 6V drop that an incandescent would, and allow the LEDs to be aimed into the reflector, which ought to produce a better beam.
My expectations are pretty low, though. Still, it would be interesting to see how far I could take the idea.

As far as bridge rectifiers, it wouldn't be hard to put wire up four diodes and insert it in series with the dynamo wires. Certainly easier than trying to tuck it into the light housing. The only downside is that if the LED doesn't have suitable heatsinking, then the extra current that is delivered to the LED may lead to overheating and an early death.

I'd be interested in hearing from anyone else who has tried their hand at this and what sort of results they had.


Steve in Peoria

rhm

Yeah, okay. Since @agmetal expressed an interest in using veteran lighting components, here's one such experiment of mine.

This is my Fothergill bike, which is a frame built in Liverpool probably right before, or perhaps during, or immediately after WW2. I have it built up mostly with 1930's components.



The headlight on there now is a Sturmey Archer product, I think, from the early 50's.


When I got it I assumed I was getting a rusted out shell, but it turned out the original switch was still in working condition, though the rest of the wiring and the battery holder etc. were all corroded away or lost. I used the switch, quite unnecessarily, thinking it would be cool to have lights that I could switch on and off.


The bulb mounts in a removable cylinder that you can pull out the back; this part was lost. So here's what I have in there now: a coil of aluminum that acts as heat sink and mount; the LED is stuck to that, with its collimator.




And here's the best photo I have of the tail light. I don't have a photo of the LED inside it, but (if I recall correctly ) it's a smaller red LED mounted as I described before, glued to a threaded base.

rhm

The lighting system described in my last post is, well, pretty weak. It's better than incandescent bulbs, and certainly fine for making me visible, especially since the lights illuminate the spokes and rim as they rotate; but it does not illuminate the road ahead the way a modern LED headlight does. I have other bikes with better headlights, so this bike isn't my first choice for riding at night.

I like the gumdrop shape of the Sturmey Archer headlight. That's why I put that light on there. Before this one I had an even more clunky headlight, which was this Lucas housing:



This one was wired up with a bridge rectifier, but no tail light. The light was much more satisfactory, which I attribute to it having a more powerful LED, but I am not sure I know what I'm talking about.

I have a similar lighting setup on the Falcon that's my main commuter, and I find it pretty satisfactory. I will try to get some photos of that.

steelbikeguy

that's not bad at all! Nice to see that you've got the LED mounted to a "star", i.e. a metal core printed circuit board. This is a good way to get the heat out of the LED and move it to a heatsink. The molded plastic optics put the light onto the ground in the pattern that you desire, and certainly does a better job than the reflector would have done. The coiled aluminum moves the heat out to the reflector and to a lesser degree, to the body of the light.

There may be opportunities for improving the performance by optimizing the selection of the optics. Without knowing what your familiarity with the current offerings is, I'll just say that there are a handful of companies making these, usually specific to the model of LED. I've selected optics with the goal of approximating the beam width of bike lights that I've liked. I've ended up with optics that have a 8 degree beam.

Ideally, I'd like to come up with something that can be "dropped" into a light to replace the incandescent bulb. There might be two versions of this...
The first would be something the size of a light bulb that just has two LEDs mounted on it, with them aimed to the sides so as to put their light mostly(?) into the reflector. This would produce a beam pattern that is largely like it would produce with an incandescent bulb, and would visually not differ much from the original light.

The second might be analogous to what you've done, but with the smallest possible optics. It might not produce the best beam, but would probably still be an improvement over the original. The LEDs are pretty small now.. about 3mm square. The optics can be reduced quite a bit too, The down side is that with a single LED, the voltage drop will be 3V, instead of the usual 6V. This means that power delivered to the LED would be 1.5W when operated with a "standard" dynamo, instead of the usual 3W. It would also prevent the use of a conventional tail light that is wired in parallel with the headlight.

There used to be a LED from Luxeon that was the equivalent of two LEDs wired in series, and was great for retrofitting a LED into an old light. It had the option of side emitting optics, which could send light to the sides and into a reflector. I used one of these with an old reflector from a Union headlight, which ended up being a big improvement over a conventional incandescent Lumotec light. This was about 18 years ago, when white LEDs were new technology.

My only vintage light is a Jos "block" dynamo....



It has a small insert that the bulb threads into. There is no access to the front side of the reflector, so any LED bulb assembly would have to be inserted from the rear, and would have to have electrical contacts that mate with the light's existing contact points.

As noted, I'm still trying to find time to dig into this retrofit project. I'm also messing around with some possibly improved optics & LEDs for my main dynamo light....


It's not an attractive light... but is nicer than the original hack with the Luxeon LED and Union reflector....




Steve in Peoria

fietsbob

halogen bulbs burn brighter than tungsten filament, but you cant screw them in from the front,

because you leave skin oils,, and hotter bulb will blow with contaminated glass

and so flange base types , those bulbs feed from the back, I made up a battery powered head and tail light
(load draws what it needs from battery ) used radio shack sourced bulbs..


newer bike,
Initially ran a Schmidt e6, halogen.. hub dynamo; Schmidt .
wattage of load has to match wattage of dynamo output 3w ,
either 2.4 & 0.6 head and tail , or 3w head alone, no tail light load, its battery powered..

Tourist in MSN

That is why I use a piece of cloth or paper towel or something like that when I hold the bulb to put it into the socket on my truck. Have not burned out a headlight in several years.

fietsbob

Contact cleaner that evaporates, without residue, cleaned them for me

agmetal

I ended up getting some LED bulbs that have 5 emitters - 4 facing sideways, and one facing straight ahead. I got one in a 3000K "warm white" color, and it does a pretty good job of working with my setup, although there is noticeable flicker at lower speeds. I originally had it set up in an early 1950s light like the one @rhm showed above, but I happened across a 1930s light (actually the same model pictured on the GH8 spec sheet). It's definitely better than the #40 incandescent I had in there originally, but still not quite enough to see where I'm going on an unlit path with other riders and lights on houses and that sort of thing.

1950s (left) vs 1930s (right) lights, with LED bulbs installed:





Bike with 1950s light installed, picture taken with 1940s camera (Vokar 1)



1950s light with #40 incandescent bulb

Tourist in MSN

I am going to have to stop referring to my B&M D-Lumotec Oval headlamp as vintage.

agmetal

I go with 25+ years for "vintage" and 50+ for "antique"

steelbikeguy

oohh! That looks pretty good! Any idea who makes it or where it came from?

Maybe there's interest in an external electronic circuit that could rectify the AC power, convert it down to the 3V (or up to whatever voltage it needs?), and provide a standlight function?

Neat lights too! Was that a standard style for that era? They look suited to the roadster style bike... a bit heavy, but rugged.

Steve in Peoria