The 1936 BMW R12 Schneekrad Snow cycle with sidecar on ski was an experimental winter vehicle meant for the German Army. Only three models were made but were rejected for service due to complexity of operation (too hard to steer and uncomfortable). It was meant to carry the rider and one other soldier with a MG Mount plus ability to tow a weapons sled, troop sled, or provisions. BMW had a civilian streamliner version nicknamed the Elephant, but that too was far too complex to be taken seriously. Today, the Germans make a new tracked Snow bike for those well off enough to waste money on it. Germans used half-tracked motorcycle Kettenkrad instead plus captured Soviet aerosans (snow vehicles with pusher fans)!

Note: Amazingly, the French made a similar tracked motorcycle, but with two sets of tracks fore and aft. The BMW had one continuous flextrack system with rollers that pivoted with the forks up front. Very hard to turn though...