Converting the Sturmey-Archer FW 4-speed hub into a 5-speed

NB: It is important to note that these instructions were written in the mid 1980s. Many items that were then current or easily available may no longer be so. The article is based on Appendix B of The Sturmey-Archer Story by Tony Hadland, published in 1987 by John Pinkerton.

Converting an FW into an S5/2

By far the easiest way to convert an FW to five-speed operation is to obtain a complete axle assembly for the S5/2 (HSA 329, HSA 330 or HSA 331, depending on axle length). This comes ready assembled, complete with sun pinions, dog ring, axle key and associated springs. The FW is merely rebuilt around the S5/2 axle assembly.

This conversion offers a gear which is virtually identical to the current five-speed hub. In the past Sturmey-Archer disapproved of five-speed conversions but, at the time of writing, the company is prepared to issue a list of the necessary parts for rebuilding FWs around S5/2 axle assemblies. They also market a retro-fit list consisting of the complete S5/2 internals and accessories for fitting into an FW shell, or an AW shell made before April 1984.

Converting an FW into an S5 (original pattern)

It is also possible to convert four-speeds to the original S5 style of operation; this involves a push rod in the left end of the axle, rather than the toggle chain used in the S5/1 and S5/2. The following conversion instructions for the FW were written by Denis Watkins of Castle Bromwich, after the discontinuance of the S5 and before the introduction of the S5/1.

1. The FW is really a five-speed hub in which, to permit its control with only one lever, only four speeds are used.

2. The extra low gear of the standard FW is brought into play by pulling the two sun pinions K409 and K408 to the right such that the dogs on K408 engage with the axle dogs.

3. If, when the FW is in top, it were possible to put K409 and K408 into the same position as in 2. above an extra high gear would be obtained.

4. To obtain both extra high and extra low, movement of K409 and K408 must be controlled by an additional lever. This can be done as follows.

5. Compression spring K8l3B is not required and must be removed.

6. Axle key K526A must be replaced by axle key K526 (used in AW).

7. Coupling/indicator rod K807ZA must be replaced by the type used on the AW.

8. Replace axle key K402 by a further axle key K526 and file ends of latter flush with surface of pinion sleeve K406.

9. Remove indicator rod K804 (K804A) and replace by a suitable push rod with end threaded to suit axle key K526. This is the only real difficulty. It is possible to use the rod portion of K504AZ (indicator for AW with long axle). It might be better to cut the outer end off an AW indicator rod and have a bit of similar rod welded “end on” to provide a total length such that, when the rod is pushed in to move K408 into engagement with the axle dogs, the outer end of the rod is flush with the end of the axle.

10. The push and release of the rod is conveniently controlled via a bell crank. Shimano have a very nice bell crank arrangement on their three-speed hub. Unfortunately it is threaded for a standard 3/8” (9.5mm) axle and there may be insufficient metal to permit drilling and tapping to Sturmey axle size.

11. A very important point; in early versions of the FW, K408 was made with parallel dogs. This is OK for conversion. Later versions of the FW had these dogs chamfered on the one face to facilitate engagement. These are unsuitable for conversion (unless an old type K408 can be obtained) as, if attempted, it will be found ‘ratcheting’ occurs in extra high gear and no drive is possible.

With regard to 11. above, the later FWs can also be converted if the larger sun of an S5 (HSA 269) or of an S5/1 (HSA 317) can be obtained. Of course, Sturmey-Archer produced a bell crank and push rod for the S5 (HSJ 679 and HSA 297 or HSA 288) but these are no longer available. The design of the bell crank evolved through three versions; plastic, pressed steel and machined steel. The latter seems to have been the most reliable. Some riders replaced the push rod with a modified flat-headed nail for smoother and more reliable operation.

An alternative to the bell crank was devised by Jack Lauterwasser. The push rod is made from a section of 12 gauge spoke and protrudes from the axle end by about 20mm. Threaded onto the external end of the push rod is a brass bush (made from a solderless nipple), drilled to permit the control cable to pass through freely at 90 degrees to the rod. An oversized tear-drop shaped brass washer is fitted to the wheel axle, with the pointed end of the washer pointing 180 degrees away from the cable fulcrum clip. The pointed end of the washer is cut out to house a solderless nipple, fixed to the control cable.

When the control cable is tightened, its far end cannot move because it is anchored to the tear-drop washer. The cable therefore straightens itself and, because it passes through the end of the push rod, pushes the rod into the hub, thus shifting the suns. The system works very smoothly.

The cable anchorage cut out, being keyhole shaped, permits quick release of the cable, merely by depressing the push rod whilst unhooking the cable end. Because the cable end is fitted with a solderless nipple, the push rod remains attached to the cable – with the bell crank system it is fairly easy to lose the push rod. The biggest disadvantage with this system is the risk of accidental damage to the exposed end of the push rod.

The Lauterwasser left-hand cable device

A somewhat similar system was devised by Mr P. Pottier of London during the 1950s. He used a Sturmey-Archer toggle chain, the end of which was riveted to the pointed end of the tear-drop washer; the chain passed through a steel bush push-fitted onto the end of the push rod. The control cable was attached to the toggle chain in the usual way; hence, when the cable was tightened, the chain moved the push rod further into the gear.

Non-Standard Controls for the S5

Many riders using the S5 type converted four-speeds use a derailleur lever for the left changer. This gives good ‘feel’ to the change (which, unlike that of the S5/1 and 2, is not designed to cope with crash changes) and reduces the need for cable adjustment.

Some riders advocate use of a derailleur lever also for the right hand changer; a practice greatly disapproved of by Sturmey-Archer because of the ‘no gear’ slip position between high and normal gears.

The Californian cycle engineer, Ernest Rogers, devised a Duo-Trigger Shifter for five-speed hubs. This consists of two of the metal three-speed triggers (not the current bulbous plastic type) bolted one on top of the other, the clamp of the top trigger body having been first removed. The effect is somewhat similar to the triggering arrangement on a double-barrelled shotgun.

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