The Kossack is a redesign of Blomker's Kossel-mini NEMA17 extruder using a 608 bearing instead of a 625, combined with biomushroom's NEMA17 40:9 planetary gearbox.
By their powers combined, I have a working Bowden-compatible extruder using a MK7 gear despite my rather lackadaisical stepper motor.
1 x 608 bearing
1 x 625 bearing
6 x M3 25mm cap-screw
7 x M3 15mm cap-screw
7 x M3 nut
1 x M5 hex-head screw
3 x 1gear.stl, 1 x every other STL
This is assembled more or less the same way as the "Raldrich planetary nema17". The Kossack completely replaces its top plate. Also see the exploded view.
As usual, the SCAD is on bld3r: http://www.bld3r.com/obj/5842251410309120