http://sheldonbrown.com/awfixed.html
CB2,
You've seen the above link before, but for the purposes of this post I thought I'd insert it again. It is a less than thorough description of how to convert a common Sturmey Archer AW 3 speed internally geared hub as found most often on old English 3 spd bikes. These are not hard to find. So, the conversion is from a freewheel to a "fixie" type of hub. The conversion ends up with two gears which would in effect be something like the old Bendix 2 speed hub with hi and low. For most of us that would be enough to make a world of difference on our motored bikes, allowing for a higher top end speed at lower engine rpms... quieter and less wear. Low for starting out and hill climbing, and high for cruising.
I do wish someone would make this conversion with detailed photos and clear how to commentary. It would mean a lot for those of us on a budget to have a way to do this ourselves. I see in the description the word "machined" and for most of us that is a turn off since we have hand tools. But maybe hand tools are enough. Maybe a file or a little rotary tool (Dremel is one) along with effort and patience can do the "machining" necessary. Maybe this conversion is not so daunting as one might imagine. I don't know and I would like to know.
CB2,
You are obviously a capable guy with a lot of know-how and intuitive understanding of mechanics. Some of us who read this thread, see what you have done, try to follow the discussion with others who are knowledgeable are left scratching our heads, trying to understand. I'm one of those kids in the back of the class trying to understand, but not quite making it. I do know that my checkbook will not allow me to send off for the hub you used. That's out. But I do have some old S.A. hubs I've salvaged. The only one at hand is a coaster brake model, which I understand is not what we're looking for. The old AW model is freewheeling and was supposedly fairly robust and well made. Also parts are readily available. So, once I can dig through my "stuff" I'll be looking for an AW. It seems like a good choice to experiment with since it is the most common. I'll look for two of them and will be happy to send one to you. Would you try to make the conversion and document with pictures and words what you're doing? And if you see how things can be done with a hand tool instead of a lathe, can you keep us poor boys in mind?
A couple of questions. First, what exactly is a "fixie" hub? Why is that what we need for using the hub as an external transmission? (I'm guessing that flipped over it would not drive the wheel, but would "freewheel", is that right?)
Once the internal modifications are made would we do what you have done by flipping the hub over so the sprockets are on the left hand (engine driveline side)? Would we mount the sprockets in the same way you did?
I know it is asking a lot for you to back up and do this conversion, but if you would I suspect there would be many of us digging around for an old AW hub to convert. The high dollar SX3 is a fine thing with it's three speeds and it would be a thrill to find one in my mailbox. But the freebie AW hub with two speeds is also a fine thing if we can make it happen. Think about it, eh? I'd like to do one, but don't have the confidence to do it without a mentor, photos and such.
SB