[GerritJ9]

The diesel engine was an opposed-piston two-stroke engine, with scavenge ports at one end of the cylinder, exhaust ports at the other end and the combustion space in the centre, when both pistons are at their respective TDC. Those familiar with marine diesel engines need only hear the name "Doxford" to understand . The term "boxer" engine is totally incorrect for this design.
I don't have any further details of the Junkers engine design, but I suspect that it had two crankshafts- one at the top of the engine, one at the bottom, connected by a gear train.