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3 inch scale Allchin traction engine - stock code 3576

A largely completed 3 inch scale agricultural traction engine, built as a doubled up version of Hughes' "Royal Chester" design.

Steel boiler with brazed steel tubes, feed by injector and crank-driven pump. Single cylinder with slide valve actuated by Stephenson's valve gear, pole reverser on footplate, mechanical lubricator. Two road speeds. Winch mounted behind nearside rear wheel with fairleads on tender.

Never steamed before the builder's demise, the engine has had a twice working pressure hydraulic certificate issued for 100psi working, it will require a steam test when completed. It runs very well on air, with a crisp exhaust note and good even beats – there’s a clip of it running here.

Jobs to complete include fitting a pressure gauge and associated pipework, making a pair of drive pins and attending to half a dozen loose fasteners on the cylinder block flange – it is currently held down with some fairly grotty bolts, in the past I have made up studs and silver-soldered a nut on to simulate the original carrot bolts which were assembled in from inside the boiler.and nutted up outside.

I think this is a decently-built engine with plenty of potential – it makes a big 3 inch model, nearly six inches longer than the ubiquitous 6nhp Burrell and I would guess around half a hundredweight heavier. Complete with a two-wheeled driving truck running on pneumatic tyres.

Length 54 inches
Weight approx 3 cwt

scale 3 inch