For many hundreds of years motive power, mainly for mills and forges, was provided by water and wind and of course human and animal effort. In other words by simple transformation of one form of motion into another. A quantum jump occurred in the early eighteenth century, when Newcomen built the first machine to transform heat energy into rotary motion. This first usable heat engine, using steam, was put to pumping water from the tin mines of Cornwall, around 1726.
It was terribly inefficent. Steam was injected under the piston to raise it and then rapidly cooled by inje ting water. A partial vacuum was thus created and the piston forced down by athmospheric pressure on the top. The steam helped by the weight of the pump, pushed it up again and the process repeated. A small boy originally turned the taps to let the steam in and out, but according to legend, he soon replaced himself with an automatic valve and wandered of to play.
Some fifty years later, James Watt had the idea of doing away with this successive heating and cooling, which was obviously inefficient, by making steam the driving force, which, once expanded, was condensed and reheated. This produced a big jump in efficency: the engine could turn faster, more than twenty strokes per minute rather than just five to ten, and with much more power per stroke. It was still too heavy to be mobile and it was left to Trevethick, a somewhat erratic but brillant inventor, to develop a light high pressure machine which could move itself around. Incidentally, the French inventor Cugnot should not be forgotten. He built a machine as early as 1770 which did move itself successfully. Unfortunately, by running into a wall he also invented the first mechanised road accident. His machine can still be seen in Paris
Two development branches for mobile steam power were thus opened in the early 19th century: one led to the railway locomotive; the other to the lighter steam road vehicle . The former essentially won, and steam remained runner-up as far as road vehicles were concerned, although it did become quite popular for trucks for nearly thirty years during the last century. Of course, it remained popular for ships for many years and is still the energy source for turbines of nuclear power plants and ships. A steam powered aircraft even flew in the early thirties.
Electricity as a source of motive power developed almost in parallel with steam during the 19th century but at a slower rate since much basic research was required before engineers could exploit it. A primitive electric motor rotated in 1828 and a generator, essentially its inverse, some years later. By the 1850's electricity was providing usable amounts of motive power and not long afterwards, fixed generators and mobile motors were integrated in tramways. Battery development, necessary for complete mobility has been slow. Even today, to compete with conventional vehicles, electric motors must be combined with a heat engine to charge the battery and provide supplementary power. Of course, the former has had over a hundred years to define the rules.
The gas engine, invented by Lenoir in 1860, ushered in the principle of combustion inside the engine itself rather than in a seperate boiler. However, since the gas was ignited at only athmospheric pressure, its efficency was rather low. Nevertheless by dispensing with the boiler and its enormous quantites of water and coal and using instead town gas made from coke, piped in from the mains, it saved a lot of space in factories, as well as being clean and completely silent. It was not however, mobile, being too heavy and anyway attached to its energy source.
With the formulation of the four stroke cycle (compression, combustion, expansion and exhaust), and the exploitation of the high specific energy and portability of crude oil derivatives, the first internal combustion engines attached to hastily adapted carriages started puttering around towards 1884. Benz is generally considered to be the key figure. However, as usually happens at key turning points, many others were also successful. From then on it was a question of finding better ways of vaporizing fuel, mixing it with air, getting it into the engine at the right time, and finally igniting it. For many years afterwards, with tyres as a welcome change of subject, carburettors and sparks ( fat or thin; present or absent) were the stuff of motorist conversations as well as the cause of long and grubby hours spent by the roadside.
