After posting about the damage to the sun pinion and the planet pinions previously, I ordered a new axle (including sun pinion) and planet pinions from SJS, who were thankfully much quicker to dispatch the items than expected.
The old axle and planets are at the top of the image, and the damage to the teeth can be seen clearly. The new axle and planets are below, looking particularly clean.
I will avoid writing about the internals of the X-RD3 hub extensively, partly because they are similar to the AW hub I have written about previously, partly because it is difficult to take pictures whilst your hands are covered in bike grease/filth, but mainly because when I was about to take apart my first hub, I did some reading and got the impression that it is a complicated job. When I actually took that first hub apart I realised that it is in fact quite simple, the best way to learn about these things is to simply have a go. The worst that can happen is that you won’t be able to fix it and have to take it to a bike shop and get them to do it, which is far from the end of the world.
After re-assembling the hub using the exploded diagram provided in Sturmey Archer’s excellent literature (although to be fair, it is pretty easy to figure out what goes where by trial and error), I noticed that the failure had also damaged my drive-side bearing cup, and slightly rounded the rear fork ends on the bike too. I decided to set the cone slightly loose so the bike could be ridden whilst I awaited my second order to SJS, a cone nut and some non-turn washers.
The damage to the bearing surface may look minor, but it had a noticeable impact on ride quality. The cone and non-turn washers are now fitted, and the rear hub is in better condition than it was when I got it, shifting easily and freewheeling well too.
Internal hub gears are much easier to work with than most people believe. The best advice I can give is to simply have a go.