Brucey wrote: ↑28 Feb 2024, 3:17pm
he first production 5-star hubs all broke because some twit let them be put together and then sold with dodgy sun pinions, that simply had't been made properly. in truth, the hub design (which included such things as cantilevered planet pinions) wasn't that great anyway, but by the time the first batch left Nottingham, the die was already cast. The chances are that your hub was made later and has sun pinions that are OK but there is no way to check them easily. Since the consequences of failure are pretty dire (think of the 'chestburster' scene in the first Alien movie, yes failure can take out the hubshell too) it may be prudent to change the Sun pinions anyway.
Both the S52 and the 5-star use a pull chain on the left side. This arrangement in the S5/2 relies on two springs fighting one another in gears 1 and 5 which is somewhat sub-optimal. Folk do say this can work OK, but the S5/1 never had a pull-chain on the left, it had a pushrod instead. The original S5/1 pushrod control has been nla for years, but having successfully converted numerous similarly-sprung 4s hubs (mainly FG and FW models).to 5s, and ridden a very long way (over decades) on them to boot, I can safely tell you there is a much better way. Now I didn't come up with this idea, but I wish I had.
The better way involves using a simple pushrod on the left which is not difficult to make. The pushrod itself can be made from any convenient 3/16" steel rod (I have used a 6" nail before now) which can be bent into an 'L' shape, where the short side is about 20mm and the length of the long side is determined by the length of the axle. A standard SA chain and adjuster is fitted to the short side of the L. I used a short length of old spoke as a rivet, having drilled everything to 2mm diameter and filed a suitable feature onto the pushrod. The toggle key can be replaced with a reshaped and shortened pawl pivot pin, which is far stronger. In use, the 'pull' of the gear lever is turned into a 'push' into the hub by the simple expedient of routing the control via the back of the dropout. In many cases there is already a triangular cut-out in the dropout which can be used. All that is required is to ensure that the SA chain runs on a nice radius, which can usually be achieved using a swiss file.
If the spring in the hub is particularly feeble (which you might like because it reduces parasitic.drag in gears 2 and 4) then it may not be strong enough to pull the cable properly, in which case you can fit an additional external 'helper' tension spring whose only job is to pull the cable towards the hub. If you fit a 'helper' spring it can be hooked between the frame and the adjuster and in addition, it can remain connected even when the wheel is out.
Particularly if one is fitted to each side, this can help the gear cables not to come unshipped when the wheel is out, since they are always under tension from the helper springs. I have made perfectly satisfactory helper springs using old spokes. They can be coiled around a suitable mandrel (about 6mm is best) and a typical long spoke is long enough for about 12 turns and can still have ~40mm at each end for hooks to be made. It isn't a bad idea to run the gear cable down the middle of the helper spring; this makes everything neat and tidy as well as ensuring that the pull of the helper spring is correctly aligned.
The parasitic drag in gears 2/4 in all S5 type hubs as well as converted FW and FG hubs can be greatly reduced by modifying the larger sun pinion so that a carrier can be used beneath it. It is possible to make a suitable carrier from an AW clutch carrier. In use, the spring bears against the carrier instead of the sun and the sun is completely unloaded and free to rotate. In fact, the only load the carrier should ever see is the spring load, so even a very thin-walled carrier such as the modified AW part will work fine.
It is necessary to revise the springing inside either hub when fitting a left side pushrod; In the case of some S5 hubs it is simply a case of removing the spring hidden inside the gear 2/4 sun locking cup. However, if you have an axle where the left side toggle key works on the larger sun pinon directly then you will need to fit a weak spring inside the cup, to ensure that the smaller sun comes unlocked when making the 4-5 shift or the 2-1 shift. In the case of the 5 star, I think it is possible to fit something in the slot for a short compression spring to bear against and make the pushrod work, but there is perhaps less to be gained here; sure, the hub will be more reliable and you won't ever have to find a difficult toggle chain and you won't be at the mercy of your toggle key integrity in the same way, but you are not solving a fundamental problem like you are with the S5/2.