I really don't want to derail Zorro's thread. However, SRAM Dual Drives have been around for at least 25+ years. The prior company Sachs, made a 7 speed version by the mid '90s and with SRAM there have been 8 and 9 speed cassette versions. My Cannondale MTB framed "Comfort" bike came equipped with a 1X9X3 Dual Drive in 2003. I converted it to a 3X9X3 system about 6-7 years ago.



This winter I've been working on upgrades to my Dahon folding travel bike (yes, it fits in a suitcase and flys for free on Southwest!). I stumbled upon a 20" (406mm) Dual Drive wheel on ebay and I couldn't resist. I ended up finding a matching rim Biologic Joule II dynamo hub with the same rim for a matching wheelset. It is a 2X9X3 system. The set up is not quite perfected yet, so the final is yet to be seen and will not be as pictured below. I'm planning on a test ride in the church fellowship hall soon and will post a thread in the Folding Bike Forum.