Some Steam Engine Prehistory

| September/October 1973

Case Model

Mr. Ball's Case Model at Blaker's Reunion in 1948. Courtesy of Ernest Hoffer, 444 Starr Ave., Toledo, Ohio 43600

Ernest Hoffer

178 Emerson Place, Brooklyn, New York 11205.

After reading the May-June issue of I.M.A. I especially enjoyed the article, 'My First Engine' by George Eves. Hopefully Mr. Eves can be persuaded to give us some more of his experiences.

Many history books and encyclopedias have taken to copying earlier material without checking out all the facts and have thus been guilty of perpetrating errors. For example, how many history books state that Robert Fulton 'invented' the steamboat? Similarly Watt is commonly known as the inventor of the steam engine when his credit should actually be an improver of an already existing machine, for the Newcomen steam engine was at work for over 60 years before Watt put his hand to it.

Numerous attempts were made during the late 1600's to harness the force of steam but almost all proved impractical. Ironically, the man who came closest to 'discovering' the principle of the steam engine did not apparently realize what he had and didn't follow up his experiments. This was Denys Papin who was one of the large number of amateur scientists of the 17th century who together did so much of the work which laid the foundations of 'hard science', which was to follow.

As one of his experiments, Papin fitted a piston in a small vertical cylinder and attached a cord to the piston which ran up over pulleys and was attached to some weights. Water was placed into the cylinder and a fire (probably an alcohol or similar type lamp) placed under it. When the water boiled the resulting steam allowed the weights to pull the piston up in the cylinder. The source of heat was removed and when the cylinder had cooled the steam condensed and formed a vacuum. Atmospheric pressure then forced the piston down which, by means of the cords, pulled the weights up. Here was the Newomen type engine in principle but Papin saw it as nothing more than a toy and of no practical use. To add to the irony, Papin used a type of device which had been developed by Von Guericke about 1672 in the course of his experiments on atmosphere pressure. The difference between the two was that Von Guericke used an an pump to create his vacuum while papin used the condensation of steam. Papin did not invent the piston and cylinder concept, for not only Von Guericke, but the ancient Romans knew of piston type water pumps. Plunger type pumps were also known at the time of Christ, but without packing glands, which made them of little use. It was not until Sir Samuel Morland invented the packed Plunger pump in the late 1600's that this type became practical. There are some writers who do not even credit Papin with pioneering the use of steam under a piston to develop a vacuum and as early as 1678 experiments were being made to create a vacuum in closed vessels by exploding gun powder. By 1698 Thomas Savery had developed his pumping ' engine', which involved creating a vacuum by means of steam condensation and the stage was now set for the reciprocating steam engine. Savery's device consisted of two closed copper chambers connected at the top to a steam supply from a boiler and at the bottom to the water suction and discharge lines. The attendant started the apparatus by opening a cock, or valve, in the steam line and filling one of the chambers with steam. The steam supply was shut off and cold water from another line was allowed to run over the outside thus condensing the steam inside. As a vacuum formed, atmospheric pressure forced the water to be pumped up the suction pipe into the chamber. When the steam cock was once again opened, steam (which at one point was reported to be as high as 120-150 psi pressure) was admitted into the top of the chamber forcing the water out. Check valves in the suction and discharge lines directed the flow thru the proper lines and with two chambers in use, one was filling while the other was discharging. All valve operations were performed by hand. The practical suction lift of this device was about 25' or so and as Savery had developed his pump for use in mines deeper than this, he planned to install both pump and boiler in the mine itself. Available steam pressure limited the discharge head, however, and this device still left much to be desired, especially insofar as economy of operation. The same theory interestingly enough was used for 'Pulsometer' type sinking pumps for mine work which remained in service until fairly recently especially in Europe. One of Papins other developments without which steam boilers would be rather dangerous, was the safety valve. This was of the simple lever and weight type and here again we find that although a person (in this case Papin) is credited with discovering an idea, he actually took an existing concept and made it practical. Very primitive types of safety valves consisting merely of tapered plugs driven into a hole had been used for hundreds of years on stills and retorts. Papin's, however, was first of all capable of fairly fine pressure adjustments and, secondly, was self resetting when the steam pressure dropped below the blow off point. And on this basis he gets and deserves credit.

Papin developed this device for use on the pressure cooker he invented in 1680. Here again, one writer, Thomas Ewbaun, on page 393 of 'Descriptive and Historical Account of Hydraulic and other Machines for Raising Water', published in 1856, quotes several Biblical sources which he interprets as referring to a type of pressure cooker, thus indicating that the item in question was known previously.