Philip G Graham
Not many of this category imported into Australia post WWII, but enough to create some interest.
Particularly Orenstein & Koppel, so well known up until the WWI put paid to most things German [see John Browning's excellent O&K steam loco article in the "Light Railways" Issue 246], and then in fits and starts for non-steam mostly in surrounding territories.
However in the 1950s, and on, virtually nothing until two diminutive O&K Model Type MB7N show up in 2007 in New South Wales for a track laying contract. Details of the loco's resurfacing recently are covered now and later elsewhere in LRRSA records, but some comments on the locomotives themselves will not go astray.
The MB7N was a common type in Germany that serviced the typical smaller factory or yard that had to move a few dozen wagons each day from a mainline interchange into a close nearby factory location. About 200 or so units including the older MV6 and the modernized MB170N were built - in the range of about 120kW and 20 tonnes. With the changing nature of less-than and of wagon-load traffic, there as with elsewhere in the world, lots became available on the second-hand market and there is a reasonable dispersal around Europe, particularly with track maintenance companies, privatized there as here. In the southern hemisphere not so much, hence a degree of surprise at these on our doorstep so to speak.
Mechanically, with still common Deutz engine and Voith transmission there is still a reasonable amount of spares available even here. The actual transmission arrangement for the MB7N and family is a unique O&K design: where the axle is combined in an overall one piece inside frame assembly incorporating the sprung suspension and final drive which is supported above by the Megi rubber/metal 'sandwich' (think Metalastik) and mechanically interconnected with the adjoining axle unit, guiding and tracking rather like a bogie. The under frame side members do not have any axle box openings, only small inspection/adjustment access holes. The whole thing is reminiscent of the articulated wheel arrangements that O&K had used in their 0-8-0 and 0-10-0 plantation locos.
All of which makes for a little variety in an otherwise fairly limited Australian industrial locomotive scene.