in the 50s I bought a single piece of steel; machined to replace the stock Sturmey Archer cog , it was machined with 3 cog sizes in it.
snap ring as before held it on the hub Sturmey Archer still was the hub , but another British company 'Cyclo' Made the 1 pc cog cluster.
I fitted a derailleur to make the 3 cog cear change, with 1 lever & another lever for the 3 internal gears..
Now there are both S-A and Sram (who bought Sachs that made them ) have regular derailleur cassettes
on the driver assembly of 3 speed Hubs.. And..
Sturmey Archer-Sun Race makes a 3 speed hub with a 2 cog set on the driver, for Brompton .. now..
in the recent past, before the Sram buyout, Brompton got their 3 by 2 speed rear hub from Sachs, Germany.
And right Now, you can buy a S-A S3X hub & thread on a freewheel or a White industries 2 cog freewheel..
Last edited by fietsbob; 04-01-16 at 09:47 AM.