For this week’s episode of The Secret Life of Machines, hosts Tim Hunkin and Rex Garrod complete the second half of their examination of automobile technology by focusing exclusively on the internal combustion engine.
The science content stands out early on, when the pair use a modified fireworks mortar to look at the difference in explosive power between a teaspoon of gunpowder and a teaspoon of gasoline – a short experiment that also comes with the first “Don’t try this at home” of the series. After demonstrating (quite definitively) which of the two materials has the greater potential, Hunkin moves on to discuss the early history of the engine.
The two key players, a Belgian engineer named Étienne Lenoir and a German engineer named Nikolaus Otto, gradually devised a mechanical process using a captive piston to draw liquid fuel into a combustion chamber, compress it, detonate it, and expel the exhaust gasses. Hunkin provides a simple yet effective animation of this process and, as he phrases it, these steps – suck/squash/bang/blow – comprise the four strokes that still characterize engines today.
The remainder of the episode examines the other component parts of the engine, some of which – like the carburetor – feature less prominently with modern cars. Be on the lookout in this portion of the program for Hunkin to demonstrate, in a very messy manner, the volume of oil required to keep a motor in running order. Hunkin and Garrod close out with a nod to the increasing reliability of cars in general, and address a number of environmental concerns that were just coming to the fore when this episode first aired.