Raleigh Twenty dynamo light upgrade

The Raleigh Twenty I bought (which will now be known as Grimace) came with a Sturmey Archer AG dynohub, this is basically a 3 Speed AW with a dynamo built in. The lighting setup that I got it with was original and still working, not bad for something 35 years old. The lights were somewhat dim but just adequate, the biggest issue was that they lacked a standlight; modern dynamo lights have capacitors in them which build up a charge and keep them lit for a few minutes after you have stopped pedalling. Standlights have become pretty common on most decent dynamo lights nowadays, and I decided the time (and price) was right to upgrade. I did a bit of research on the Sturmey Archer AG hub and it turns out that they only put out 2w at 6V instead of the standard 3w at 6v. However LED lights tend to be more dependent on current for brightness than incandescents which are more dependent on voltage. I managed to find one post on a forum which reported reasonably good brightness using an old Sturmey Archer dynohub with modern LED's so I decided to just go for it and see for myself.

Sturmey Archer AG dynohub

The aim of this bike is to be able to jump on it at a moments notice and be able to go straight away with no fuss. Dynamo lighting was part of this equation, I have 4 bikes now and constantly swapping over lights, swapping flat batteries etc was becoming tedious. I was also wanting to have a light source that wouldn't blind oncoming users, as far as I know almost all battery powered lights have a symmetrical parabolic reflector which gives a spherical beam with a hot spot in the middle. Most decent dynamo lights have assymetric reflectors with a vertical cutoff which is more like a car's low-beam.

The B+M Lyt Senso has three positions for On-Senso-Off.

Since in Australia, cycling is more of a sport rather than transport, finding dynamo lighting is pretty difficult at anywhere but specialist touring/commuting shops. It's more a novelty than the norm. The opposite is Europe and Asia, where the standard fare is a bike with mudguards and dynamo lights. I hopped on teh intehnets and ordered the Busch & Muller Lyt Senso front light and the D Toplight plus rear light. The Busch & Muller terminology is somewhat confusing, each model comes in several variations, from a basic light with no switch and no standlight to the top of the range with an automatic light sensor switch with standlight. Because I was using a dynohub I had to go for a switched version so I chose the senso version for the front light, typical dynamo hub lighting wires the Dynamo>front light>rear light in serial which means you control both lights with the switch on the front light.

A slightly improvised mounting

A week and a bit after I ordered a parcel showed up at work with my lights, I was suprised at how small the front light was, it's about 60mm in diameter and included a stainless steel fork crown mount and a built in reflector. The rear light is intended for mounting on a rack, it can adapt to mount the standard 50mm or 80mm mounts. Installation was pretty easy as the orignal wiring had the same mini spade fittings. Only the front light came with a wiring which I ended up using for the rear light anyway.

I like the look of the original taillight so I just left it.

First impression was that the front light was a lot brighter than the original incandescent, the beam lays a nice even trapezoidal shape of light on the road. The side of the front lamp has side cutouts which gives you good side visibility. The front light gets to full brightness at about 15km/h, it's not super bright compared to my Ay Ups but plenty bright to see the road, in fact it's probably a more useful beam because it lights the road uniformly rather than with a hot spot and lots of spill like with the Ay Ups. The standlights work really well, although the only odd thing is that the rear light seems to stay lit for a few minutes whereas the front light stays lit for bloody ages, mind you it does get dimmer and dimmer. I've only had it for a few days so far but it's great being able to just get on the thing and go. That's all for now.

It's alive!


  1. If that original rear reflector/lamp has a screw-in bulb socket, you can add a 1/2W screw-in LED bulb for truly amazing rear illumination. It will flicker slightly in time with the AC output of the dyno hub.

  2. Good job with this. I've been searching all over for a viable modern option for my Raleigh Stowaway. In fact it's almost exactly the same as yours but in green.

    Looking at the size of the bulb lens on the B&M rear light it seems to me that I may be able to squeeze it into the original rear light enclosure on the bike and not worry about the modern look of the B&M clashing the vintage feel of my beloved Stowaway.

  3. I thought that as well, the size of the modern rear dynamo lights is pretty small, the supercapacitors for the standlights aren't particularly large either.

  4. Whoops! You should probably disregard the comment I left on your Superbe post...