Check my previous reply
not the Flevotrike.
So if we're playing detectives.
Relatively small wheels, 20-24" at a guess at the back and a small wheel at the front.
Rear wheeles were canted inwards at the top.
Drive was to the right hand side with a derailleur cluster on the drive.
Left hand side appeared undriven.
Rear axles were not joined.
Stub axles were long (about a foot I would guess, maybe more).
So the frame was a shallow V at the back, split for the drive chain, the stub axles were therefore (presumably) supported in tubes at least a foot long.
Is this still describing the Kettweisel?
Aha.. more images
Almost certainly this is what I saw with the boom reeled in.