I have more than an average interest in The Schlumpf Mountain drive. I intend to put one in a long tail cargo bike. I thoroughly look into products before purchasing. I followed the Rohloff hub through online sources for over 12 years before purchasing my Co-Motion Pangea Rohloff. The same has been with the Schlumpf mountain drive. Kinetics bicycle shop has a gear calculator that is some type of executable file for windows and it is the only gear calculator that I have found with the Schlumpf in it. Type in (K_gear.exe) to locate it with your browser. If you look for info on the Schlumpf they do say that they have Tandem versions of their setup. This being said it is more complicated than that. You will need a bicycle shop that is familiar with what you want. Utah Trikes sells allot of Schlumpf drives. After you or a knowledgeable shop has figured out fitment and compatibility. Not being the common setup it will probably be a special order. There are Two ways to mount a Schlumpf into a standard BB. The most common way is with the use of a hand mill. You cut a taper into the bottom bracket. They also have them with a torque arm. The setup has a light seal so they use a light molly grease that needs refreshing every few thousand miles. you can also use lighter lubrication that they sell or heavy gear oil to reduce friction but you will need to add it more frequently and wipe seeping oil off with a rag. I believe the unit has a grease port for this. By the way: you do no how to shift it don't you. Remember the Wizard of OZ. Dorthey click your heels.