2 Sturmey Archer Questions
 

I now have the second part of my Dynohub kit here-- the lamps. I managed to get my hands on a used, complete set of SA lamps with wiring.

1. Does anyone have a source of replacement bulbs for the SA 6 volt headlamp and tail light? The originals look ok, but I have no backups. I've heard of people even using something called a #40 Radio dial bulb, but don't really know what this is (I don't work on old radios).

2. Does anyone have a wiring diagram for the dynohub lamp system?

for the bulbs, you can try harris. also try oldroads.com. our local co-op carries them for sure, but they don't ship.

just be sure to use 2.4W, 6V in the headlamp and 0.6W, 6V in the taillamp. combined wattage of greater than 3W may cause damage to the dyno, and combined wattage of less than 3W can cause the bulbs to burn out fast.

no wiring diagram for the system, which means the little switch circuit in the headlamp.

I saw this tonight, what is the wisdom on using the following:

"I tried using a standard Type 40 lamp (bulb) which is 6.3V 0.25A (1.5W) (screw base) and it produced about 300% more light than the 6V 0.4A (2.4W) (screw base) bulb. This increased light is still barely enough to see what is in front of the bike when traveling down a dark country road, but so far, the Type 40 bulb is the brightest one I have tried. They are readily available at antique radio specialty stores and are commonly sold in boxes of 10 each. "

Using an undermatched bulb like that results in the dynamo producing overvoltage. It'll burn out the bulb pretty quickly. It'll also be dimmer at low speeds.

Both of you make good points-- I've located and ordered a pair of front and a pair of rear bulbs as back ups.

Headlamp looked to be Union-type "Marwi brand" 2.4 w, 6 v,
tail lamp Union-type (Union brand?) 0.6w, 6 v

I'll look into that Type 40 bulb in the future, but for now I guess I'll stick with the stock types.

I actually ended up ordering from Niagra Cycle Works, so add Amazon.com as a source for the bulbs too, if anyone else is interested.

I'm still working on cleaning up the parts. I'll have to get some wire-end hooks for the wires, I think.

Let us know where you find wire hooks like the OEM. I ended up using speaker wire and regular crimp on terminals from Radio Crap:rolleyes: when I did the wiring on my Twenty.

Aaron:)

Total specified output of the old SA Dynohubs was 1.8 watts, not 3 watts, so it is not surprising that the 2.4 w bulbs work poorly. The original bulb specifications were 6v 0.2a (1.2w) for the headlight and 6v 0.1a (0.6w) for the taillight.

Reflectalite sells a 5v 0.3a halogen bulb (GH107) that they recommend for Dynohub headlights. They are in the UK but I have ordered from them and gotten good service to the USA. As far as I know there is no replacement available for the original wedge base SA taillight bulbs.

If I wanted to use an original SA Dynohub and lights nowadays I would seriously consider converting the lights to LEDs. Here is one example of such a conversion: http://minisystem.blogspot.com/

What source specifies those output numbers? I usually see 6 v 3 w come up, but not 1.8 watts. Perhaps that #40 bulb is the better pick if the numbers you state are right.

I know that the rear dyno hubs are lower output. I read somewhere that they were 2.4watts versus the 3 watt of the front hubs. One of these days I will mount my B&M Retro on the Superbe and see if it gets any brighter than it does on the Twenty with the AG hub. Only way to really tell would be to hook up an ammeter and start spinning away.

Aaron:)

i'm guessing those original wire hooks are impossible to find, outside of a NOS headlamp kit. i used standard crimp terminals as well, they seemed to fit perfectly snug.

I did a little research:

According to the 1951 Service Manual on the Sturmey Archer Heritage web site:

"The output is 6 volts, .34 amps (2 watts) when the cycle reaches a speed of 12 miles per hour"

The 1952 Trade Parts List book lists .3 amp (1.8 watt) and .25 amp (1.5 watt) headlight bulbs to be used with front and rear Dynohubs respectively, in combination with a .04 amp (.24 watt) taillight bulb.

Although I believe the total hub output remained more or less the same, the bulb specifications were later changed. When I bought Dynohub bulbs in the 1970's and 80's the headlight was .2 amps (1.2 watts) and the taillights were .1 amps (.6 watts).

This page from the 1971 Sturmey Archer catalog lists a .2 amp headlight bulb "for large wheel models i.e. 24" and over", a .25 amp headlight bulb "for small wheel models" and a .1 amp taillight bulb.

Interesting-- I've tried to find a cost effective modern bulb that is as close as I can get to the specs you've provided, in addition to the standard Union style bulbs.

What I've found and ordered are some relatively common small bulbs used in repairing old radios:

#40 bulb is a threaded bulb and has specs at 6.3v .15 a
#46 bulb is a threaded bulb and has specs at 6.3v .25 a

I was hoping to use the standard Union spec tail lamps with these.

I also have the stock bulbs. They look OK, but I haven't tested them yet. I think I'll run some tests and compare them.


My hope in this is to discover a cost effective incandescent replacement for the stock bulbs, which I have not found available in the USA. The #40 and #46 bulbs are something like 60 cents apiece. Any thoughts on those cheap bulbs and how you think they'll run?

I'm not sure of the wattage of each, I think the conversion would be:

watts divided by volts equals amps

??

Hmmm sounds like they are all under 2 watt output...explains the glow worm effect with the OEM lights.:twitchy: and why I could not get the AG to light up a B&M 4D Lite plus tail light AND a 2.4watt B&M Retro headlight.:rolleyes: If the ~2 watt is the total output I definitely need to rethink my lighting on my Twenty. FWIW the Retro will get pretty well lit up at 12-15mph and the single LED Spanninga tail light comes on too, but seems dim.

Aaron:)

Here is the brochure where I found the info on the wattage (I think). It is from 1952, so it appears that they are rated at 2 watts total output.

If I get a chance this weekend I am going to take the Lumotec IQ Fly off my city bike and stick it on one of the Raleighs and see what kind of lighting I get. Now if B&M would just do an LED conversion of the Retro. And hurry up and get the Aluminum coloured Cyo to the US distributors...

Thanks cyqlist for doing the research:thumb::beer:

Aaron:)

I found this online, but I can't remember where. I can PM you the original, if you would like.
Page 6 has some information on wiring headlamps and tailights.

I think we're working on the same path--I recently purchased a Dynohub and a old teardrop headlamp. To my surprise, the headlight works. It doesn't put out much light, though. I've been prowling the Electronics forum some lately, and there are some recommendations to wire a bridge rectifier to the Dynohub output and use LEDs for better light. While I can read a wiring diagram, solder components together, and build simple circuits, I am not an Electrical Engineer and am not qualified to judge any of the designs on their merits.

From my understanding even with a bridge rectifier you are going to get the strobe affect, it is just reduced. From what I gather reading the various ads and brochures the SA Dynohubs were designed to provide full output somewhere over 15mph.

At the ABCE the head honcho had a couple of LED bulbs in his old lamps that were a direct swap, but when he rode they looked more like a blinky than a usable light. I don't want to take one of my new lights apart, but suspect there may be more to a new LED than just the bridge rectifier. But it is a step in the right direction.

Aaron:)

Right.

I did those experiments 30 or so years ago, using various bulbs that I could get at Radio Shack, and comparing them to the original Dynohub bulb. I would install the bulb in my light, hook up a volt meter and ride the bike on rollers in my basement and record the voltage readings and my impressions of brightness at various speeds. I don't remember all the results, but the bulb I ended up using for many years was the #50, rated at 7.5 volts, .22 amps. I did not have a taillight connected to the circuit when using that bulb.

FWIW, I would no longer consider any system using an original SA Dynohub and incandescent bulbs adequate for safe night riding - at least in part because my older eyes don't see in the dark as well as they used to. I switched over to using modern 3 watt hub generators with halogen bulbs about 10 years ago, and now with LED lights. But I do think adequate lighting could now be gotten from the original Dynohubs using LEDs.

Someone mentioned earlier possibly damaging the hub by running at a higher wattage than rated. Is that true? I've never heard of that before (though I've heard running overrated bulbs makes the bulbs burn too dimly).

With standard tail light and head lamps as:

Using a stock Union spec generator bulb set would be 2.4 watts + 0.6 watts= total 3 watts of bulb
Using a #40 light (specs above) would be 6.3 x .15= .945 watts + 0.6 watts= total of 1.545 watts of bulb

Using a #46 light (specs above) would be 6.3 x .25= 1.575 watts + 0.6 watts= 2.175 watts

I figure using the #40 combo will result in an overburn in the #40. It's not the end of the world since they're so cheap (though that could depend on bulb life).

But what about the others being over in terms of the 1.8 watt spec?

My question is will the use of the Union spec bulbs or the #46 combo damage the hub as asserted earlier?

i think i was the one who mentioned that up above, although i don't have concrete proof that damage would occur. however, my logic is that the armature windings could burn out if too high a demand was put on the dynamo (higher demand = lower resistance between the output leads). for example, what would happen if you just shorted the output leads altogether? if the armature wiring were thin enough, it would heat up and melt. i've never dismantled the magnet from the armature, so i've never seen what the wiring looks like.

on the practical side, i doubt any damage would be done by an amperage difference of 2-fold, but if someone unknowingly put a bulb in there that was rated at many times the specified amperage (don't know if such a bulb even exist?), it could in theory burn out the windings.

I see-- I suppose that could be possible, though I imagine it would have to get pretty hot.

If we take the 1.8 watts and divide by the 6 volts to get amps, we get a .3a system in that hub. The cumulative amperage of the common tail lamp and the #46 would yield .35a, whereas with a #40 .25a (owing to the difference in the headlamps). The standard Union bulb set would be .6a (.5 for a the headlamp, .1 again for the tail lamp).

So taking those figures, it appears a standard Union spec generator lamp set has double the amperage of the hub's output, whereas using the cheaper small bulbs, it's a bit closer to the Dynohub. #46 in theory would be just a bit high, #40 somewhat low. The practical implications of this I'll have to test, but if we use the Dynohub specs kindly provided above (1.8 watt spec set), it strikes me that perhaps the common generator set bulbs that are tempting to use might be overrated for the Dynohub.

This is all assuming there's continued interest in using incandescent sets of lights. Most people don't want them anymore, though I appreciate their originality. I guess what I'm trying to do is to keep it as original as possible, while also getting the most light for my buck with incandescent bulbs. I guess halogen or LED would be preferable for most people wanting more useful light, though I'm trying to cobble something nice together using original parts and hopefully cheap, available incandescent bulbs. I don't ride this bike as a commuter or in bad weather. I also don't generally ride it in pitch black night (though I've run across the road with it to the store to get things a couple times). I generally am using the lights to be seen more easily (supplement reflectors) and also to "extend daylight" a bit toward dusk when I ride after work on the bike trail.

No. hub generators are "current limited" meaning they cannot produce significantly more than their rated current, even if they are shorted out. As compared to batteries which being "voltage limited" cannot produce much more than their rated voltage, but can produce dangerous high current if shorted. Hub generators can and do produce relatively high voltage when they are not connected to anything, or if they are connected to a relatively high resistance load such as a taillight with no headlight, which would be likely to damage the taillight.

The speed at which you will reach those rated wattages will vary a lot. You will never get 3 watts from a Dynohub.

It is pretty normal practice to run bulbs above their rated voltage. You get more light per watt that way, at the expense of bulb life. The #50 bulbs I used to use with my Dynohubs ran at their rated voltage (7.5 volts) at about 15 mph but I regularly ran them up to 10 or 11 volts at higher speeds and they still lasted pretty well, especially considering their low cost.

You're right about that 3 watts, I'll bet. Do you have any idea how the speeds would vary vs output? I'll be running at generally low speeds.

You could consider using an LED instead. I switched a similar chinese dynamo headlight over to LED and it went from maybe enough to be seen to enough to see decently by.

One of the brochures I was looking at on the Sturmey Archer Heritage site showed a graph, but now I can't find it.:o

Aaron:)

Does anyone have a diagram or pictures of the wiring of a dynohub to SA lamp set with the switch in the head lamp? The one I have is from the 1960s, but I can't find any images or diagrams to show me how it's wired.