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Sturmey-Archer 4 Speed Hub Gear Stripdown

Introduction

The Sturmey-Archer FW four speed gear was invented during the second world war and brought to the market in 1946. Sturmey-Archer's publicity material stated that:

"It will be of particular interest to those cyclists who consider that the high gear in the AW wide-ratio three speed is too high, and the low gear not low enough."

This is true- just. The FW has only a very marginally wider range than the AW, a few gear inches. But it does have smaller jumps between gears and a lower gearing overall. The reason is that the FW is actually a five speed gear that does not use it's top gear for reasons of simplicity of operation. They could not think of a good way to use two cables to operate the higher gear until some years later. Instead, a single trigger was designed to pull the gears in sequence from one end making use of a clever balance of spring force.

In fact, the FW is essentially an AW with an "underdrive". This takes the form of a second sun gear that can be switched in and planets with two different diameters, joined together, to mesh with the new sun. These are called compound planets. Now, if the second sun is engaged when the gear is in the low gear position, what we get is a 'super-low' or underdrive. That is the first gear of the FW. Conversely, if the second sun could be engaged in high gear, we would get a 'super-high' or overdrive. This latter ratio is what all FW's are capable of but never had, sadly.

One great thing about the Sturmey-Archer FW and AW is that they are so well-designed for maintenance. Nothing on them is difficult to remove or fiddly. The job is really one of just taking everything off, cleaning it and putting it back together again like a sort of puzzle. Personally, it is a task that I really enjoy. And if you meet a part that is not in such great condition, you can usually substitute it with a similar part from another hub. Even in a neglected condition, Sturmeys usually run without trouble, but all hub gears love to be overhauled. They run beautifully smoothly and silkily afterwards.

From a practical point of view, taking the FW apart is no more complicated than taking apart an AW. It is essentially the same process until you reach the axle. An AW has a single sun fastened to the axle- there's no more to do. The FW on the other hand has several moving parts assembled on it's axle and a long, thin spring inside. There's often no need to take the axle assembly to pieces. Generally it can be cleaned and oiled and will be fine. However, the photostrip does show dismantling and it is not at all difficult. But you must pay attention to the order that you take off the parts and lay them all out methodically.

Dismantling the FW hub

You can do it on the kitchen table, but it is very much easier if you have a vice handy to fasten the axle pointing vertically upwards. Also, if you can get hold of a Sturmey-Archer cone spanner, the process of bearing adjustment is simple. And this should really be perfect.

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Last Updated on Sunday, 07 November 2010 22:39