Search sheldonbrown.com and sheldonbrown.org
Would you like to ride a fixed gear, but do you need a choice of gears to cope with your local terrain? It would be great if you could find somebody selling a Sturmey-Archer ASC three-speed fixed gear hub, but the chances of that are very slim indeed.
What about converting an existing multi-speed hub into a fixed gear? Is this possible? A reader named Randy Gordon-Gilmore sent me a photocopy of a set of plans that he apparently got from Sturmey-Archer for converting a readily-available AW three-speed into a two-speed fixed gear, giving a direct drive and a 25% reduction gear. All he was able to provide was the drawings reproduced below, no instructions.
Note: I have not tried this modification (yet). I have written a rudimentary explanation below. If this is not clear to you, you don't know enough about Sturmey-Archer hubs to undertake this advanced project. Please don't ask me for more information on this, I don't have any!
For more info on Sturmey-Archer hubs in general, see my Sturmey-Archer page, Jane Thomas's site with the Sturmey-Archer AW shop manual online and my ASC Tech Page. (I cannot find a current link to Jane Thomas's site but the relevant material seems to be available at the Sturmey-Archer Heritage - Product Archive. - HJF 4/2010)
On the other hand, if you try this yourself, I'd be interested in hearing how it works out for you.
I would expect that there will be a bit of internal backlash, which you'll have to live with unless you feel ambitious enough to make a clutch with wider arms that won't rattle back and forth between the pinion pins.
It is possible that by fabricating non-stepped pinion pins you could reduce the lash a bit. Pins with a large head, like that of a nail migh eliminate it in the direct-drive gear.
Note that these parts are made of very hard, tough steel. A standard steel milling cutter may not be adequate for the task.
A groove must be machined in the center ridge of the ball cup to receive the bar shown in figure 3.
Figure 2 shows the planet cage, with a similar groove machinined into it.
Figure 3 shows the bar which must be fabricated. This bar will lock the planet cage to the left hand ball cup.
I would imagine that if this modification were done to a 4- or 5- speed hub, you'd get three speeds: direct and the two lows. This is basically how the ASC works, though not with a standard clutch.
|Articles by Sheldon Brown and others|