internally geared cranksets

In the late 90's, Swiss inventor Florian Schlumpf introduced three innovative concepts to the bicycle market: the Speed-Drive, Mountain-Drive, and Highspeed-Drive.

Each of these systems integrates the bottom bracket with the crankset and a planetary gear system to give cyclists gearing without conventional front derailleurs and multiple chainrings.

The eponymous Schlumpf drives have two modes: geared and non-geared. In non-geared mode, the planetary gears are bypassed and just transfer power from crank to chainring.

In geared mode, though, they introduce a layer of planetary gears between the crank and chainring that give you extra gears higher or lower than normal (depending on the system used.)

A Schlumpf drive instantly doubles your gears and increases your gear range provided the rest of your gearing stays the same.

We have been happily installing Schlumpf drives since there ever were Schlumpf drives and on all manner of cycle.

More recently, the Patterson Metropolis has been introduced to the mass market at a lower price level and with fewer options than the Schlumpf Speed-drive.