Man's imagination let to the often quoted saying, "Necessity is the Mother of Invention." In early days when men watched the unexplained phenomena of nature that dealt with forces of power, their imagination undoubtedly led to experiments applying energy to useful purposes. Historical records of such events has given us the story of the lives of many great pioneer inventors.
It would be as difficult for an engineer of today to solve problems if he had only the limited knowledge of the wheel, the lever, a vacuum, electricity and many other basic laws of physics and mechanics, as it was for the inventors of the fifteenth century to find solutions to visions they contemplated.
So it was in the time of the great artist, Leonardo da Vinci using his talent and imagination to draw sketches of a cylinder and the possibility of power being produced by a piston driven by some sort of propellant. Leonardo lived from 1452–1519, and aside from his great masterpieces in painting and sculpturing, he conceived ideas of many designs of machines using gears, link roller chains, ratchet and pullies. His drawings satisfied his imagination and he did not put these practical designs into use. During the next century there is little recorded of further achievements with engines, until 1629 when Giovanni Branca made a shovel wheel propelled by a blast of steam. Through a set of gears, he was able to run a stamp mill, a pump and a spit to turn meat.
Otto Von Guericke 1602–1686, made experiments of a vacuum through which the idea of the piston and valves were conceived. Then, during this same period a Dutchman by name of Christian Huygens propelled a piston using gun powder to actuate the driving force. The idea came from the principle of a cannon, however his endeavor to connect this force to a machine did not work.
About 1700 Frenchman Dionysius Papin used steam in a cylinder to force a piston forward and a vacuum to effect the return stroke. He was unable to construct a machine to make use of these forces. However, his efforts were another step toward practical designs. It was not until 1712 in England, during the early coal mining era, when mine pumps were being operated by horses (and the unit of work began to be known as horsepower) did Thomas Newcomer experiment with steam by improving on Papin's and Thomas Savery's ideas, produce an operative steam engine to replace for power on the mine pumps.
James Watt (1736–1819), a mathematical instrument maker of Glasgow and Dr. John Robinson had their steam engine which propelled a vehicle. Thus was the first steam engine to operate under pressure on the piston. The other earlier designs depended on an open and cylinder and a vacuum to cause the piston to complete a stroke. Watt's engine was the first mechanical engine to turn a flywheel.
One may wonder why we have gone into the development of the steam engine, when we are concerned with the internal combustion type of prime mover. It was not until the middle 1800s when such men as Ferdinand Redtenbacher, Gustow Zeuner, Robert Mayers and Clausins worked on the basic laws of heat energy and thermodynamics. After their discovery of the possibility of burning a fuel directly in the confined area of a cylinder and using the resulting energy to move a piston, was their applications made to the already developed mechanical engines that had been driven by steam pressure.
So, it was the discoveries of the application of heat to turn a wheel that gave the early inventors the idea of using an enclosed cylinder with a piston operating as a crude source of mechanical power. They also gained knowledge of many other features and later used the idea of the open horizontal frame, slide valves and side shaft that operated cams/for opening poppet valves, as well as igniters.