Is there any way to retrofit the dual sprocket setup seen on Brompton bikes to a standard Sturmey-Archer 3-speed? Does it require a new driver, or is there some sort of double sprocket assembly that attaches to the standard 3-spline one?
Also, how does the Brompton derailleur attach to the frame? Is it a standard hanger? If not, is there any reason a standard derailleur wouldn't work to shift between the two sprockets, if the limit screws were set right?
As you might imagine, I'm trying to turn a 3-speed into a 6-speed, just to see if I can. Any help from the various Sturmey-Archer gurus on here would be appreciated
Thanks in advance