Live Steam 
Duplex Tandem Twin Cylinder "Mill" Model Steam Engine 
Fully Machined Kit in Brass, Bronze & Steel

The horizontal twin cylinder Tandem or Duplex "mill" engine is two single cylinder mill engines connected via a large flywheel on a steel plate and optionally inlet/outlet manifolds. As such it is still relatively simple and retains the basic mechanics of engines which powered mills and workshops and which needed the extra power provided by a twin cylinder engine.

NOTE: Pictures are of the finished, assembled and painted model, this listing is for the kit of parts, see picture.

This mill engine layout has two double acting cylinders, eccentric driven slide valves and the large brass flywheel offers smooth running and is capable of powering a range of accessories, in a variety of roles. The engine also includes twin split bronze pedestal bearings for each of the two crank shafts, two cast bases and a steel base plate.

The cranks for each cylinder are offset by 90° which means the engine will self-start in any position.

The engine will run in reverse by applying the steam (or air) input to the outlet ports. Our Reversing/Throttle Valve (optional extra) will control the direction and speed of the engine in either direction.

The kit consists of precision produced parts each carefully made and checked to ensure ease of assembly and reliability in service.

The cylinder assembly and piston are manufactured from brass and the piston shafts, connecting rods and valves from stainless steel so are not susceptible to corrosion. The piston shafts passes through adjustable glands and the steam inlet can be on the top or bottom of the chests.

Detail Specification:

- Type: Horizontal Slide
- Bore: 14mm
- Stroke: 18mm
- Flywheel Diameter: 70mm
- Valve type: Piston
- Height (excluding optional manifold): 75mm
- Length: 150mm
- Width: 130 mm
- Weight: 2.2Kg
- Connections: 1/4" x 40 tpi ME

The kit consists of a set of fully machined parts that can easily be assembled using simple tools such as a screw driver, small spanner, allen keys, pliers and metal file. The parts are mainly unfinished metal and will also require painting, polishing, filing, etc. to achieve the appearance shown in the pictures.

NOTE: By default a set of slot head screws is included in the kit. Socket and hex (as per the pictures) head screw sets are also available as options. Some screws as provided may need to the cut or filed to length to complete the model.

The pictures show the optional Manifold set which combines two inlet or outlet ports together into a single port.

When assembled the engine is fully working and can be run using steam or simply using compressed air e.g. from hand or foot pumps.

To power the engine with live steam, connect it to one of our Model Steam Boilers.