The Yorkshire Engine Company Half Janus is a 0-6-0 wheel arrangement, diesel electric locomotive which weighs 31 longs tons with a maximum speed of 23 mph. The Half Janus was built by the Yorkshire Engine Company in Sheffield between 1956 and 1965.
Each locomotive was built, out of the factory, with one Rolls Royce C6SFL 220 hp (300 kW) engine which was paired with one Generator to power the traction motor mounted to the wheel set at the back of the locomotive (Under the Cab).
The locomotive was called nicknamed the Half Janus because of its twin the Yorkshire Engine Company Janus because the Half Janus is Half the power and body of the Janus. The Janus locomotive has two bonnets and the Half Janus has one. The Yorkshire engine company Janus got its name from the Two-faced god, Janus. The Half Janus Earning its name, from only having one bonnet / face, therefore being called the Half Janus.
Half Janus Wikipedia
There are two 'working' examples of 'Half Janus' at the Appleby Frodingham Railway Preservation Society based at the Scunthorpe Steelworks in North Lincolnshire and a third at the South Devon Railway.
One example is 'Arnold Machine' which was brought into preservation at the society from Eccles Slag Co LTD. The locomotive served at Scunthorpe Steelworks, Normanby Park Works ran by United Steel Company at the time. 'Arnold Machine' was built with the works number '2661' in 1958. The locomotive is currently being Overhauled at the society sheds.
'Arnold Machine' has a twin sister which is also at the Appleby Frodingham Railway Preservation Society which is Loco '1382'. Its is currently preserved in its Colsterworth Mines, United Steel Company Maroon livery. Loco '1382' spent most of its working life at the Colsterworth Mines. When this closed it moved to the Scunthorpe Steelworks Normanby Park Works site until the Normanby Park Works was closed in the 90's. The locomotive was then preserved at Rocks by Rail. She moved to the Appleby Frodingham Railway Preservation Society in May 2015 and is currently being Overhauled at the society sheds.