Originally Posted by
elbows
The bike in question is a '73 Raleigh Superbe, complete with cottered cranks and 26 TPI bottom bracket threads. So changing cranks is an adventure in itself. I'm not sure how small a chainring I could get on the existing cranks. Plus it has one of the cool old Raleigh chainrings (like
this one), and it would be a shame to have to swap that out.
The Sturmey 5-speed looks promising, though. It's available with a 114mm OLD, so no spreading would be needed at all, and the range isn't bad. Plus direct drive is 3rd gear, which will work a lot better on a large-wheeled bike.
I know the SA 8-speed had some quality-control issues at one point. Does anyone know if the 5-speed had similar problems?
Addressing your three questions in reverse order!
My impression of the SA-8 is problematic not because of quality-control issues, but the difficulty of getting it adjusted just right. If the cable is off by a tiny bit, the gears skip occasionally (which is really annoying). It doesn't help that the most common use for this hub is folding bikes, and the process of folding can change the adjustment-- so this compounds the problem. SA has reportedly fixed this problem with the new, improved version of the hub (which is good news) which they won't sell until they sell the older ones (which strikes me as bad policy).
I believe the SA-5 is an old design --fifty years old, or so-- that has been improved over the years. It is essentially an expanded version of the AW hub, on the market since the 30's, which in turn was an improvement on even older ones. I have no first-hand experience with it, but I have not heard of any problems with adjustment, quality control, or other issues.
Finally, you're absolutely right, it will be difficult to find a cottered crank with a chain ring small enough to use the SA-8 hub with a 26" wheel. You can get a
decent one with a 36T chain ring (I have one, and it's fine), but that's not small enough for your purposes. Finding a cotterless spindle that will fit your existing BB won't be THAT difficult; but a cotterless crank, with a tiny chain ring, would look terrible on a Superbe.
My vote: SA-5 hub. Or spread the frame and use a Nexus-8.