Hey Lusche do you know what Kettenkrad stands for and do you have any pictures?
Kette = "chain", but it's also the common word for the tracks of a tracked vehicle
Krad is a (nowadays rare) clipping of the word "Kraftrad" = motorcycle
Thus Kettenkrad is a tracked motorcycle.
A picture search for "kettenkrad" on google brings up a lot of pictures, also the Wikipedia entry of Kettenkrad has one (along with some valuable information)
Kettenkrad in action:
http://www.youtube.com/watch?v=PsWl1l632N4 (just ignore the crappy music)