Boulton and Watt Engines Were Amiably at Work in London
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BOULTON ANDWATT ROTATIVE STEAM ENGINE 1785 Sydney, Australia April 17, 1986 An International Historic Mechanical Engineering Landmark The American Society of Mechanical Engineers This engine of 1785 srands known that: (1) given a ve- Newcomen’s Influence at the second beginning of tical, open-topped cylinder This was the first beam steam power; it is the moment with piston, atmospheric engine, a style that would carry when the chain connection be- pressure would drive the piston on for long over a century. The tween the piston and beam of down into a vacuum formed overhead beam of wood with the 73-year-old steam pump beneath it; (2) such a vacuum its arc ends was 24 ft (7.3 m) was replaced by two links that could be created by the con- long and centrally pivoted on formed a “parallel motion.” densation of steam under the stout engine-house Wall 22 ft The piston could now add an piston. Thomas Newcomen (6.7 m) above the floor. In upward push to the former (1663- 1729) of Devon, using reality the beam was a partial down-only pull permitted by these ideas and others, put pulley, for the chains to the the chain, giving an almost together the first practical reciprocating piston rods, continuous flow of power from steam engine and pump for steam at one end, pump at the the two-fold or double action draining distressed mines or other, were always tangent to on the piston that allowed the supplying water. This event of the ares of half-beam radius, engine to be rotative and so 1712 was immortalized by thus providing rod guidance in turn the shafts of manufactur- Thomas Barney’s engraving the vertical (or perpendicular, ing industry to achieve a long- dated 1719 relating to a coa1 as was said two centuries ago) sought goal. mine in Staffordshire near as the beam oscillated. It can The steam engine’s transi- Dudley Castle. Well-executed, be read that the open-topped tion from pumping duty to its the print includes a key to the cylinder had a diameter of 21 second and more versatile form parts of the “Steam Engine” in. (533 mm) with a length of came slowly. Tracing the story and “A Scale of Feet & 7 ft 10 in. (2338 mm). of the rotative engine means Inches” enabling the deter- The boiler-really an enor- returning to the early eigh- mination of principal dimen- mous tea kettle of 5.5-ft teenth century when it was sions. (1.67 m) diameter - was direct- ly below the open-topped cylinder and would furnish steam at atmospheric pressure to the space under the piston, the piston having been hauled to the top of its cylinder by the weight of the pump rod and its gear. Injection of cold water in- to the steam under the piston caused condensation with the formation of a vacuum into which atmospheric pressure, acting down, shoved the piston. This was the power stroke with which the pump rod at the other end of the beam was hauled up. If an incomplete (poor) vacuum of say 10 psia (68 kPa) is assumed, the force on the 21-in. (533 mm) piston would have been about 3400 lb (1542 kg), giving a pivot reac- tion on the wall of twice that. to be deliberately condensed whatever profits might be Someone’s note on the engrav- for the power stroke. This con- made, went bankrupt. Great ing remarks that 10 gallons of clusion led to his first patent in good fortune brought Watt the water were raised 51 yards 1769; it might be called the engineer into partnership with “perpendicular” when run- “Keep It Hot” patent, for cen- Matthew Boulton (1728-1809) ning at 12 strokes per minute. tral idea was to keep the the astute industrialist. It was This works out at about 5.5 cylinder hot, as close to 212° F 1776 before the propositions of horsepower (4.1 kW) for the as possible, to discourage the 1769 patent were reduced water end. A calculation for that senseless steam - to successful practice. the cylinder (assuming a 6.5 - ft consuming initial condensation Public achievement came [1981 mm] stroke) yields an in- caused by a cool system. This with a mine pumping engine dicated horsepower of about “coolness” stemmed from hav- having a 50-in. (1270 mm) 8.2 (6.1 kW). There are no real ing the piston top and the diameter cylinder and a blow- data on the thermal efficiency, cylinder wall in constant con- ing engine (for an iron works) but by any guess it was appall- tact with ambient air, and a with 38-in. (965 mm) cylinder. ing, one-half percent has been cylinder bottom shockingly Their most satisfactory perfor- suggested. In fact, these pump- cooled everytime the condens- mance was in part due to the ing engines that did a splen- ing water was injected. accurate steam cylinders finish- did job in saving the drowning Patent No. 913, January 9, ed on ironmaster Wilkinson’s coal mines could be afforded 1769, for “a new Method of newly contrived boring mill. only there, being run on the Lessening the Consumption of Fuel consumption of these coal that was so poor that it Steam and Fuel in Fire engines was third of that nor- couldn’t be sold. Mineral Engines” featured a three- mal for the time. Word got mines (non - coal regions) could point program of direct con- around, and enquiries from the hardly take advantage of the cern: (1) reduce condensation long-suffering metal mines of engine because of the cost of at the piston by closing the top Cornwall were followed by transporting coal. of the cylinder, letting the orders from there and other piston rod come through a places as well. gland, and use hot steam at at- Keep It Hot mospheric pressure instead of The Industrial Push James Watt (1736-1819) was cool ambient air to force the With the ever-increasing in- born 24 years after that first piston down; (2) arrange for a dustrial activity of the Newcomen engine went to steam jacket around the burgeoning eighteenth cen- work at Tipton. As instrument cylinder; (3) have a seperate tury, especially in England, maker at the College of vessel or “external condenser” rotational power beyond that Glasgow, he was brought into connected to the cylinder bot- derived from animals, water, or contact with the steam engine tom, and carry out the conden- wind was desperately needed. in 1763 by being asked to sation in this remote vessel, Animal power was bulky and repair a model Newcomen thus keeping the cold condens- troublesome what with feeding engine used in the “Natural ing water and condensate away and stabling; wind power was Philosophy” class. The problem from the cylinder. uncertain except in favored was that the model, having Some seven years would areas and hardly suited to the large boiler and small cylinder, elapse before the merits of the regularity of industry; and would make but a few strokes patent could be demonstrated, water power could only be ex- before stopping for want of for development costs posed a ploited further by going farther steam. He recognized that the problem. Watt had his living away from the cities to tap the cylinder cooled between to earn, doing so as civil remoter portions of already strokes, that several volumes of engineer and surveyor; his pa- well-populated streams. Mine steam were therefore condens- tent sponsor, an industrialist drainage and water supply to ing idly before one remained with two-thirds interest in municipalities and canal feeders (canals constituted the the crank, in Patent No. 1306, main transportation system, October 25, 1781, “circular the roads being wretched) were motion round an axis.” handled by Newcomen (at- Of the several schemes the mospheric) pumping engines, sun- and- planet gear (epicyclic) but here the heavy cost of fuel was chosen and would be used for the primitive engine set until 1802, even though the limits. More and more crank patent expired in 1794. millwork and machinery, With a large flywheel, this arrange- dependent upon shaft power, ment worked well-enough for was in the making but faltering some purposes in the manner for lack of adequate drives. of the crank. After all, the The need was met, in small engine was single-acting— part, by the awkward arrange- power on only the downstroke, ment of having an engine the piston being returned to pump water over a waterwheel the top of the cylinder by iner- from a reservoir to which the tia from the wheelwork. Dou- water returned to be again ble action, or power from the pumped over the wheel. upstroke too, a notion Watt That a rotative engine would had been toying with since have unlimited industrial ap- 1775, came into view again. plication was very clear to Watt addressed the problem Boulton who began to urge with his next patent, No. With the rack-and-sector Watt to take the matter in 1321, March 12, 1782, in hookup, a rigid rack replaced hand, as by letter in 1781, June which he presented a number the flexible chain as an exten- 21: “The people in London, of “new improvements”: the sion of the piston rod. When Manchester, and Birmingham expansive principle; double ac- kept in engagement with the are steam mill mad. I don’t tion to double the power and gear sector that replaced the mean to hurry you but we get a more regular motion; a arch head around which the should determine to take out a compound engine in which chain had wrapped, the rack patent for certain methods of steam used in a first cylinder held the piston rod to the same producing rotative motion would act expansively in a vertical as the chain would, from the fire engine.” second; a rack-and-sector with the advantage of being The basic problem at this relating piston rod to beam to able to transmit not only the stage was to convert the beam’s permit “push” as well as pull of the conventional single- oscillation into rotation, readily “pull” for double action; and acting piston, but also the done with a connecting rod to a steam wheel or rotative push from a double-acting a crank, an idea unfortunately engine.