Cycling UK Forum

Hey all,

I just converted a Dyno-Four to five speeds (or rather upgraded my 5 speed alloy hub with a generator) and thought I'd let you know about the details. First, I'd like to thank Brucey for supplying the parts and detailed advice. Please excuse language deficits for english is not my mother tongue.

You may already know that the FG (Four speed Generator hub) is essentially an FW (Four speed Wide ratio) hub with an added generator and the FW is essentially a 5-speed with a simplified shift control. The differences between the FW and the 5-speed hubs is well documented around the web while the specialities of the FG are rarely mentioned. You can take a look at the explosion diagrams of those hubs, but as SA changed its naming scheme in the 50's or 60's, it'll take some time to spot the differences.

There are several approaches to a 5-speed Dynohub. If you own an FG with good innards, the easiest way is to put a 5-speed axle assembly into it (part 38 of the 5 speed explosion diagram) and of course add the left shifter, cable and toggle chain/bellcrank (depending on the version of the 5 speed hub). Or you could convert your axle assembly (this is period-correct tuning ), I read that people do this with a nail and an abused shimano bellcrank.

If you have an FG and a 5 speed, the latter probably is newer and its innards are in better shape. Then it is sensible to use only the specific parts of the FG with most of the innards of the 5 speed. You need these FG parts:

-Hub shell GL624(A) (obviously) (the A version has 36 spoke holes and seems to be pretty much nonexistent, most are 40 hole)

-Complete generator assembly and housing (obviously): GL611 (magnet cover plate), GL610 (patent number disk), GL603AZ (armature complete), GL343A (magnet), GL626 (magnet spacing ring), GL613 (terminal Nut, 2x), GL612A (magnet fixing screw, 4x, SA specific screw head), GL316 (nut for magnet fixing screw, 4x), GL333 (lock washer, 4x)

-Left hand ball cup K404, ball cup fixing screws K425 (4x): Different to any other ball cup. A square plate which has a ball cup on the left side and a circular sawtooth-like pattern for the specific ratchet mechanism on the right side. This part is prone to rust and wear especially at the ball cup as you have to remove the complete generator assembly to be able to service the left hand bearing correctly and probably not so much excess oil from the gearing found its way to this bearing. Contrary to other hubs, excess oil can run out of the left side of the hub without passing the bearing as the connection between the hub shell and the ball cup plate is not leakproof. The ball cup plate is only held by the four fixing screws while on other hubs the ball cup is either screwed or pressed directly into the hub shell. It probably is advisable to seal the connection with a nonelastic, not-too-hard-to-dismount, non-oil soluble sealant. There some matching sealants from loctite but please be careful, not every loctite is good here.

-Ball cage with 1/4" (ca. 6.4mm) balls K67Z (identical to the 5 speed one, but you'd have to remove the pressed-in outer dust cap to get it out). You can use loose balls instead, use the number of balls that fit into the bearing minus one ball (fix them temporarily in their place with grease ). If your ball cup shows wear, you probably should do so as the ball cage may not fit perfectly anymore. Very slightly larger or smaller balls may be advisable as they will run on a new path.

-Cone K427AZ, packing washer LB159, spacing washer K605, notched cone adjuster K428: These make shure you can adjust the LH bearing without removing the generator assembly.

-Planet cage K403, pinion pin K426 (3x), low gear pawl K413 (3x), low gear pawl spring K414 (3x), 3/16" (ca. 4.8mm) ball (3x): The planet cage had to be shortened by the size of the low gear pawls to fit beneath the generator. Thus, the ratcheting mechanism is different, the pawls are pins inside the planet cage beams in parallel to the axle which are forced against the back of the LH ball cup plate by springs. This change made different, shouldered pinion pins necessary. Nonetheless, the planet pinions are the same as on an FW or a 5-speed.

-Right hand ball ring (K60A): Another one from a 5 speed should fit but the huge diameter small pitch thread may be prone to tolerance issues.

To assemble the hub, it is advisable to read the S5 service instructions, especially for the correct adjustment of the RH bearing and the correct timing of the planet pinions. As sturmey-archerheritage.com is slightly broken at the moment, here are the direct links:
http://www.sturmey-archerheritage.com/images/photos/pic-979.jpg
http://www.sturmey-archerheritage.com/images/photos/pic-979.1.jpg
http://www.sturmey-archerheritage.com/images/photos/pic-979.2.jpg
http://www.sturmey-archerheritage.com/images/photos/pic-979.3.jpg


Some additional advice:

-If I'm not mistaken, the coil is insulated by shellac. This material does not withstand the elements very well. If the hub is oiled in excess regularly, some of the excess oil will work as a sealant (the SA recommendation of 2-3 drops every 2-3 weeks should be treated as an absolute minimum in regular all-weather use). Additional sealing with e.g. waxoyl is probably sensible (melt it in with a hairdryer). Especially when sealing the LH ball cup to the hub shell to get more lubricant into the ball cup during use (see above).

-The four hexagon headed ball cup fixing screws are hard to find 3/16" x 26 tpi threaded ones, be careful with them. The heads measure 8.15mm (a 2BA wrench size). Most 8mm spanners and spanner sockets will fit, the best would be a slim full hex socket with the end ground flush.

-The Dynofour is slightly wider than a 5 speed hub (and thus omits a spacer on the LH side in most cases), the very shortest axle available for the 5 speed probably won't work with the generator. Additionally, on some frames there may be clearance issues with the LH chainstay if the chainstays turn in apruptly.

-Lubricant: Sturmey-Archer recommended SAE 20 oil, 2-3 drops every 2-3 weeks. The excess will lubricate and preserve all non-gearing parts. Some of it will run onto the chain which pleases people who run their chain on SAE 20 oil. However, there are better lubricants available. Brucey uses a thixotropic (ketchup-like) semi-fluid grease he composed on his own (?) which contains synthetic oils, anti-corrosion additives, EP additives, and solid lubricants (he'll probably sell some if you're interested). I use a turning lathe slideway oil which contains similar additives and is made for lubricating not only the slideways but also the gears and spindles of a lathe. On the other hand, there are worse lubricants, too, like e.g. any oil a bike shop can sell you. Don't use any of those general purpose oils.

-The usual warning: In any event, do NOT seperate magnet and armature! The AlNiCo magnet will lose most of its magnetism instantly.


I'll add some photos soon. Sadly, I don't have many of them as I didn't want to touch a camera with oily fingers, so I can't show many steps of the procedure.

I hope I didn't forget something but if so, I'll add it.

Best regards

Hi There, I realise this is from some years back. I am looking to source some Sturmey Archer low gear pawl springs K414 (3x) (or modern replacement) and came across this post. Any help would be greatly appreciated.

these parts have been NLA for a long time now. Fortunately it isn't that important that these springs are in really super condition in order for the hub to work OK. They are meant to be as feeble as they usually appear to be; how bad are yours?

I daresay you could wind your own replacement springs without too much difficulty if you had to, but it is easiest if you get another hub for spare parts.

One thing I would not advise is a different design of spring, not without a good deal of consideration; these springs see an enormous fatigue load because they are repeatedly flexed fully whenever the hub is used in gears 3,4, (or 5) because this clutch is overrun. This is what gives the FG its very distinctive tick-tick-tick sound, much louder than in an FW or AW hub.

if the hub is run dry, the plunger pawls and their bores will wear; the repeated sliding movement is OK when there is lube present but not otherwise.

BTW I have often wondered whether a small washer(that is a better fit in the bore diameter) between the spring and the plunger might improve the damping of the plunger motion if the parts are slightly worn; air/lubricant is forced past the sides of the plunger, and once the parts are worn there is less damping action in this motion, and a suitable washer may restore it.

cheers