Why would anyone ever want to try this? Is there some percieved benefit of propulsion coming from a prop?
There are still border patrol cars in Finland that get their motive power from a rear mounted prop - but the cars float, and have large retractable skis, to make them capable of traversing roads, lakes, snow, and ice, just as effectively. That seems to be the only place where a prop-propelled-car would actually make sense.
Could these cars not be meant to be an effective form of locomotion, but rather a "Sound Screen"? In some tank engagements, the British would fly aircraft over the enemy lines to drown out the sounds of the oncomming tanks. Could this be a mobile sound-screen maker, meant to set up close to the front lines and drone out the sounds of tanks, troops, etc?
But how would they get such vehicles up to the front line? The tanks could barely cross No Man's Land, so how were those aero-cars supposed to? Plus the aero-cars predate the Great War. I think you underestimate the degree to which inventors were prepared to experiment then - after all, they had little more than a decade of automotive experience to look back on; we have well over a century, so what looks absurd or impractical to us wasn't so obvious then. Those aero-cars are what they appear to be - strange expeiments in alternative methods of locomotion. The fact that so few were built shows the extent of their failure, and the misguidedness of the concept.
Perhaps I've missed something here.... what makes us think this was a military inovation? the vehicle appears quite civilian; street clothes, wooden body.....
The engine (and radiators) is a German military aircraft engine. Such engines were fitted to a number of later model Taubes from several manufacturers. Most other windwagons have had a military (or quasi military) purpose and the general idea has been to provide propulsion under conditions where wheels would not have traction (ice, snow, loose sand etc). There was a British experimental armoured car that had an areo engine (bigger) and propellor (smaller) mounted in a similar fashion intended for desert use. It appears that all it did was to move large quantities of sand backwards without moving the car forwards.
Centurion wrote: I rather associate them with the film 'The Great Race' with Jack Lemon as the evil inventor and peter Falke as his hapless assistant Max.