This model was made solely for teaching students how a four-stroke internal combustion engine works. Unlike most other sectioned engine models, it was not designed to look like a real engine; it draws more on the conventions of engineering drawing than of engineering model-making. Its depth is considerably smaller than that of a real engine of the same length, and the cylinder is almost two-dimensional.

The model is representative of an important practice in engineering education, the elucidation of mechanism by revealing parts of machines. This practice rose to prominence in Germany in the nineteenth century with the work of Professors Ferdinand Redtenbacher and Franz Reuleaux, who analysed machines as chains of mechanism and applied mathematics to their study in the new discipline of kinematics. The model has additional didactic features that allow timing control via valves to be demonstrated and the concepts of inner and outer dead centre positions of the piston and clearance and stroke volumes of the cylinder to be taught. While all these ideas can be elucidated today with video animations, the physical model is still a useful tool.

Author: Debbie Rudder, Curator of Power Technologies, July 2008

References
http://www.msim.org.uk/media/161957/g.%20cussons%20and%20co.pdf

http://www.cussons.co.uk/

http://kmoddl.library.cornell.edu/

The model was manufactured by The Technical Works of Cussons Ltd of Manchester. The company began to manufacture a wide range of teaching models near the end of the nineteenth century. The company now manufactures equipment for teaching, research and production testing purposes in a wide range of engineering activities under the name of Cussons Technology Ltd, Manchester.

The model was used for teaching mechanical engineering students at the University of Sydney.

Didactic model, horizontal gas engine, wood/steel, made by Cussons Ltd, Manchester, UK, 1890-1920. This hand-operated sectioned model shows the essential features of a four-stroke gas engine. On the out-stroke of the piston, gas and air are drawn into the cylinder through the two poppet valves actuated from levers situated under the cylinder. The gas main connection and the air intake are indicated on the model. On the return stroke the gas-air mixture is compressed, its temperature rises and it is ignited by the firing tube which is heated by a Bunsen burner. On the second in-stroke of the piston the products of combustion are exhausted through the exhaust poppet valve. The engine is prevented from overheating by the water space surrounding the cylinder; the cooling water inlet and outlet are marked.

The piston pin connects the piston with the connecting rod which, in turn, is connected to the crank pin and then the crankshaft. The 'big end' of the connecting rod is sectioned to show the big end bearing and the bolted means of attachment. An arrow shows the direction of rotation of the crankshaft. The piston moves between two positions: the inner dead centre position is indicated by the shaded line separating the clearance space from the remainder of the cylinder volume; and the outer dead centre position occurs when the right hand end of the piston protrudes beyond the end of the cylinder. The model indicates that the ratio of 'clearance volume' to 'stroke volume' is about 50%, which was typical of gas engines built in the late nineteenth century. Running along the back of the model, and driven from the crankshaft at half engine speed, is a camshaft that actuates the inlet and exhaust valves.

Different parts of the model are painted grey, blue, orange and black. Part names and arrows are added in white paint. Sectioned parts have white hatching added in accordance with conventional engineering drawing practice.

Reference
Noel Svensson, 'Object documentation report, object number B1741' (unpublished).

Made: 1890 - 1920

In addition to part names and arrows, the model bears the maker's name: 'Cussons Ltd, The Technical Works, Manchester, England'.

It is also marked 'No 510'. This is probably a University of Sydney stock number.

B1741

1890 - 1920

640 mm

250 mm