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Opitec 112.778 Hot Air Motor Stirling engine


This is a simple small Stirling engine, sold as a kit with the most critical parts ready made but with some metalwork still required. An interesting design feature is that the displacement piston is made of steel wool, so it acts as a heat regenerator. This means that the engine can truly be classed as a Stirling cycle engine.

The displacement cylinder consists of a short glass test tube, heated at one end by a meths burner and air cooled at the other end by a finned block of aluminium. The cylinder is 17mm diameter x 17mm stroke. The displacement piston consists of steel wool, formed into shape to fit the glass cylinder and attached to a wire rod. The rod exits from the back of the cooling block and is connected to a crank pin on one of two flywheels.

The two flywheels are at either end of a shaft which passes through a substantial bearing block with brass bearings and oil holes. On the other end is the second flywheel, driven by the power piston. The single acting power cylinder is 12mm bore x 13mm stroke. The connecting rod small end is built into the piston so that there is no need for a crosshead. The pipe between the two cylinders is firmly clamped to a heatsink, so providing a further nominal regenerator.

The whole is mounted on a plywood base. The kit is supplied without a burner but I have provided a small glass meths burner, of a type commonly supplied with similar engines.

Make Opitec
Model 112.778 Hot Air Motor
Made 2019
Description Stirling engine
Cylinders 1
Cylinder Type Single acting
Bore mm 12
Stroke mm 13
Mechanical Condition Good
Cosmetic Condition Good
Purchased 11 Oct 2019
Purchase cost 46.79
Additional cost