|John Fuller Ryan, Wartime Woodburners, Gas producer vehicles in WW2. An Overview. Schiffer Military History 2009|
The Imbert gas producer unit consists of (from left to right) the boiler or firebox with air injectors near the base. In the middle is the radiator unit used to cool the gases from the firebox, below that a prefilter unit that baffles the gas through water. To the left of that is the large filter which contains oiled wood chips, oiled cork, or some other finely-divided material to remove ash, soot etc. Above the large filter is the fan used to accelerate gas for startup and an air intake to mix the produced gases with air.
A while back The Duke did a post entitled The Original Thule to which a comment was made, suggesting the large containers on the roof were actually methane bags- which made me wonder about gas producer vehicles, another alternate fuel arrangement. When I happened upon a book on the subject, I had to pick it up to learn more about these vehicles. After scanning, I see gas producers are an entirely different thing and quite likely commenter Steve is right (or could it be an early natural gas bladder arrangement?)
In any case the gas producer vehicles look like they were a viable if not convenient or efficient alternate fuel for a hard-pressed population requiring motorized transportation. Pick up a copy of the book for more info.