Sturmey-Archer FG Dyno-Four – Raleigh Superbe 1955 Restoration

Sturmey Archer FG

In this week is a Sturmey Archer FG Dyno-Four hub, part of a customer’s 1955 Raleigh Superbe restoration project. During the 1950’s, the Superbe was the deluxe version of Raleigh’s top of the range lineup. The equivalent price of such a bike in today’s money? Around £650. A modern version of the Superbe is available but in terms of quality of materials and build quality, it’s not in the same league. The originals are superbly put together, over-engineered machines that use high quality materials.

The customer is aiming to do a sympathetic restoration, keeping the paintwork and patina intact and getting it mechanically sound. Originally from Twickenham, the current owner obtained it from a garage clear-out in Middlesex. As a local vintage bike club member, he intends to ride it at local events in Surrey. During the restoration process, the rear hub was found to be seized so a strip down was started. As things started to look worse the further it progressed, he decided to reach out to me for assistance.

The Sturmey Archer FG Dyno-Four (“F” for Four speeds and “G” for Generator) was Sturmey Archer’s model that incorporated the same four gear ratios of the FW with their patented frictionless “dyno-hub”. The dyno-hub, a generator used in both front and rear hubs produces 6 volt alternating current (AC), technically making it an alternator rather than a dynamo. First introduced in 1947, the Dyno-Four had a fairly modest production run of thirteen years. Internally, there was much less space to accommodate the gears due to the space taken up by the generator. Because of this, the designers had to come up with new ways to pack the four ratios within the restricted space.

Sturmey Archer Dyno-hub

As mentioned, this one came into the shop mostly dismantled with parts bagged up and cabled tied together. The customer reported that some were missing, indicating it had been apart before. Whether this was to fix an issue many years ago, we can only guess. Both wire terminals had also been broken off flush which unfortunately makes this part scrap.

Pitted Sturmey Archer Cones

Once finished with the stripping down it was soon evident that the hub had been used for an extended period with no lubrication. There was no corrosion as such, the normal cause of these to become unserviceable, but all bearings and bearing surfaces (cones, ball ring, driver and ball cup) were pitted and unusable. My stock was raided to locate the parts, both missing and replacements, ready to start the rebuild process. Most are new-old-stock but items like the armature had to be taken from a donor hub. The customer wanted to keep this bike original as possible and after a chat on the phone to talk through the fairly long shopping list of parts required to get this particular hub back into working condition, the go-ahead was given.

New-old-stock spares

With all the serviceable parts cleaned and new parts selected, the fun part of putting it all back together begins. There’s no more surprises at this point as everything has been checked and should just work. Brand new grade 100 bearing are used throughout with red waterproof grease for the bearings and labyrinth seals. This age of hub used oil lubrication but the grease helps to keep the oil in, water and dirt out as well as extend the service internals.

With both sun gears fitted, the axle is flipped 180 and the planet cage and the three planet gears installed. Next is the ring gear with its pawls fitted (new springs in this case). The clutch, axle key, thrust washer and spring are next and finally the ball ring and driver. The right-hand cone is backed-out to the correct preset position and then locked off with the washer and locknut. Hub play is taken up by adjusting the non-driveside cone only, there is no adjustment on the drive side.

With the new-old-stock left-hand ball-cup installed into the shell, the internal assembly can be screwed back in. The replacement magnet and armature is then installed making sure all spacing washers are in place. The only step remaining is to adjust the bearing play and test the Dyno-Hub is producing power.

Please check my hub-gear workshop page if you have a similar hub that need attention.