G'day Hugh - some informative stuff there! My study of some of the pictures of Voss's aircraft as well as the report into the crash site indicate that a LeRhone 110hp Type J engine was fitted at the time of the crash - this engine is identified on the following links:
Le Rhone Rotary Engine - France
Le Rhone 110 hp
Pictures of Voss' tripe from the front back up that this type of engine, with its induciton pipes, rods etc fitted to the rear, was fitted to Voss' triplane.
I suspect that the engine with the induction pipes / rods to the front of the engine is either a different version of the 110hp engine or may be the 80hp version?
BC