A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder; this pushing force is transformed, into rotational force for work. The term "steam engine" is applied only to reciprocating engines as just described, not to the steam turbine. Steam engines are external combustion engines, where the working fluid is separated from the combustion products; the ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term steam engine can refer to either complete steam plants such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine. Steam-driven devices were known as early as the aeliopile in the first century AD, with a few other uses recorded in the 16th and 17th century. Thomas Savery's dewatering pump used steam pressure operating directly on water.
The first commercially-successful engine that could transmit continuous power to a machine was developed in 1712 by Thomas Newcomen. James Watt made a critical improvement by removing spent steam to a separate vessel for condensation improving the amount of work obtained per unit of fuel consumed. By the 19th century, stationary steam engines powered the factories of the Industrial Revolution. Steam engines replaced sail for ships, steam locomotives operated on the railways. Reciprocating piston type steam engines were the dominant source of power until the early 20th century, when advances in the design of electric motors and internal combustion engines resulted in the replacement of reciprocating steam engines in commercial usage. Steam turbines replaced reciprocating engines in power generation, due to lower cost, higher operating speed, higher efficiency; the first recorded rudimentary steam-powered "engine" was the aeolipile described by Hero of Alexandria, a mathematician and engineer in Roman Egypt in the first century AD.
In the following centuries, the few steam-powered "engines" known were, like the aeolipile experimental devices used by inventors to demonstrate the properties of steam. A rudimentary steam turbine device was described by Taqi al-Din in Ottoman Egypt in 1551 and by Giovanni Branca in Italy in 1629. Jerónimo de Ayanz y Beaumont received patents in 1606 for 50 steam powered inventions, including a water pump for draining inundated mines. Denis Papin, a Huguenot refugee, did some useful work on the steam digester in 1679, first used a piston to raise weights in 1690; the first commercial steam-powered device was a water pump, developed in 1698 by Thomas Savery. It used condensing steam to create a vacuum which raised water from below and used steam pressure to raise it higher. Small engines were effective, they were prone to boiler explosions. Savery's engine was used in mines, pumping stations and supplying water to water wheels that powered textile machinery. Savery engine was of low cost. Bento de Moura Portugal introduced an improvement of Savery's construction "to render it capable of working itself", as described by John Smeaton in the Philosophical Transactions published in 1751.
It continued to be manufactured until the late 18th century. One engine was still known to be operating in 1820; the first commercially-successful engine that could transmit continuous power to a machine, was the atmospheric engine, invented by Thomas Newcomen around 1712. It improved on Savery's steam pump. Newcomen's engine was inefficient, used for pumping water, it worked by creating a partial vacuum by condensing steam under a piston within a cylinder. It was employed for draining mine workings at depths hitherto impossible, for providing reusable water for driving waterwheels at factories sited away from a suitable "head". Water that passed over the wheel was pumped up into a storage reservoir above the wheel. In 1720 Jacob Leupold described a two-cylinder high-pressure steam engine; the invention was published in his major work "Theatri Machinarum Hydraulicarum". The engine used two heavy pistons to provide motion to a water pump; each piston was returned to its original position by gravity.
The two pistons shared a common four way rotary valve connected directly to a steam boiler. The next major step occurred when James Watt developed an improved version of Newcomen's engine, with a separate condenser. Boulton and Watt's early engines used half as much coal as John Smeaton's improved version of Newcomen's. Newcomen's and Watt's early engines were "atmospheric", they were powered by air pressure pushing a piston into the partial vacuum generated by condensing steam, instead of the pressure of expanding steam. The engine cylinders had to be large because the only usable force acting on them was atmospheric pressure. Watt developed his engine further, modifying it to provide a rotary motion suitable for driving machinery; this enabled factories to be sited away from rivers, accelerated the pace of the Industrial Revolution. The meaning of high pressure, together with an actual value above ambient, depends on the era in which the term was used. For early use of the term Van Reimsdijk refers to steam being at a sufficiently high pressure that it could be exhausted to atmosphere without reliance on a vacuum to enable it to perform useful work.
Ewing states that Watt's condensing engines were known, at the time, as low pressure compared to high pressure, non-condensing engines of the same period. Watt's patent prevented others from making high pres
A steamship referred to as a steamer, is a type of steam powered vessel ocean-faring and seaworthy, propelled by one or more steam engines that move propellers or paddlewheels. The first steamships came into practical usage during the early 1800s. Steamships use the prefix designations of "PS" for paddle steamer or "SS" for screw steamer; as paddle steamers became less common, "SS" is assumed by many to stand for "steam ship". Ships powered by internal combustion engines use a prefix such as "MV" for motor vessel, so it is not correct to use "SS" for most modern vessels; as steamships were less dependent on wind patterns, new trade routes opened up. The steamship has been described as a "major driver of the first wave of trade globalization" and contributor to "an increase in international trade, unprecedented in human history." The steamship was preceded by smaller vessels designed for insular transportation, called steamboats. Once the technology of steam was mastered at this level, steam engines were mounted on larger, ocean-going vessels.
Becoming reliable, propelled by screw rather than paddlewheels, the technology changed the design of ships for faster, more economic propulsion. Paddlewheels as the main motive source became standard on these early vessels, it was an effective means of propulsion under ideal conditions but otherwise had serious drawbacks. The paddle-wheel performed best when it operated at a certain depth, however when the depth of the ship changed from added weight it further submerged the paddle wheel causing a substantial decrease in performance. Within a few decades of the development of the river and canal steamboat, the first steamships began to cross the Atlantic Ocean; the first sea-going steamboat was an ex-French lugger. The first iron steamship to go to sea was the 116-ton Aaron Manby, built in 1821 by Aaron Manby at the Horseley Ironworks, became the first iron-built vessel to put to sea when she crossed the English Channel in 1822, arriving in Paris on 22 June, she carried passengers and freight to Paris in 1822 at an average speed of 8 knots.
The American ship SS Savannah first crossed the Atlantic Ocean, although most of the voyage was made under sail. The first ship to make the transatlantic trip under steam power may have been the British-built Dutch-owned Curaçao, a wooden 438 ton vessel built in Dover and powered by two 50 hp engines, which crossed from Hellevoetsluis, near Rotterdam on 26 April 1827 to Paramaribo, Surinam on 24 May, spending 11 days under steam on the way out and more on the return. Another claimant is the Canadian ship SS Royal William in 1833; the first steamship purpose-built for scheduled trans-Atlantic crossings was the British side-wheel paddle steamer SS Great Western built by Isambard Kingdom Brunel in 1838, which inaugurated the era of the trans-Atlantic ocean liner. The SS Archimedes, built in Britain in 1839 by Francis Pettit Smith, was the world's first screw propeller-driven steamship for open water seagoing, it had considerable influence on ship development, encouraging the adoption of screw propulsion by the Royal Navy, in addition to her influence on commercial vessels.
The first screw-driven propeller steamship introduced in America was on a ship built by Thomas Clyde in 1844 and many more ships and routes followed. The key innovation that made ocean-going steamers viable was the change from the paddle-wheel to the screw-propeller as the mechanism of propulsion; these steamships became more popular, because the propeller's efficiency was consistent regardless of the depth at which it operated. Being smaller in size and mass and being submerged, it was far less prone to damage. James Watt of Scotland is given credit for applying the first screw propeller to an engine at his Birmingham works, an early steam engine, beginning the use of a hydrodynamic screw for propulsion; the development of screw propulsion relied on the following technological innovations. Steam engines had to be designed with the power delivered at the bottom of the machinery, to give direct drive to the propeller shaft. A paddle steamer's engines drive a shaft, positioned above the waterline, with the cylinders positioned below the shaft.
SS Great Britain used chain drive to transmit power from a paddler's engine to the propeller shaft - the result of a late design change to propeller propulsion. An effective stern tube and associated bearings were required; the stern tube contains the propeller shaft. It should provide an unrestricted delivery of power by the propeller shaft; the combination of hull and stern tube must avoid any flexing that will bend the shaft or cause uneven wear. The inboard end has a stuffing box; some early stern tubes were made of brass and operated as a water lubricated bearing along the entire length. In other instances a long bush of soft metal was fitted in the after end of the stern tube; the Great Eastern had this arrangement fail on her first transatlantic voyage, with large amounts of uneven wear. The problem was solved with a lignum vitae water-lubricated bearing, patented in 1858; this is in use today. Since the motive power of screw propulsion is delivered along the shaft, a thrust bearing is needed to transfer that load to the hull without excessive friction.
SS Great Britain had a 2 ft diameter gunmetal plate on the forward end of the shaft which bore against a steel plate attached to the engine beds. Water
An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of rotation of a shaft. Electric motors can be powered by direct current sources, such as from batteries, motor vehicles or rectifiers, or by alternating current sources, such as a power grid, inverters or electrical generators. An electric generator is mechanically identical to an electric motor, but operates in the reverse direction, converting mechanical energy into electrical energy. Electric motors may be classified by considerations such as power source type, internal construction and type of motion output. In addition to AC versus DC types, motors may be brushed or brushless, may be of various phase, may be either air-cooled or liquid-cooled. General-purpose motors with standard dimensions and characteristics provide convenient mechanical power for industrial use.
The largest electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors are found in industrial fans and pumps, machine tools, household appliances, power tools and disk drives. Small motors may be found in electric watches. In certain applications, such as in regenerative braking with traction motors, electric motors can be used in reverse as generators to recover energy that might otherwise be lost as heat and friction. Electric motors produce linear or rotary force and can be distinguished from devices such as magnetic solenoids and loudspeakers that convert electricity into motion but do not generate usable mechanical force, which are referred to as actuators and transducers; the first electric motors were simple electrostatic devices described in experiments by Scottish monk Andrew Gordon and American experimenter Benjamin Franklin in the 1740s. The theoretical principle behind them, Coulomb's law, was discovered but not published, by Henry Cavendish in 1771.
This law was discovered independently by Charles-Augustin de Coulomb in 1785, who published it so that it is now known with his name. The invention of the electrochemical battery by Alessandro Volta in 1799 made possible the production of persistent electric currents. After the discovery of the interaction between such a current and a magnetic field, namely the electromagnetic interaction by Hans Christian Ørsted in 1820 much progress was soon made, it only took a few weeks for André-Marie Ampère to develop the first formulation of the electromagnetic interaction and present the Ampère's force law, that described the production of mechanical force by the interaction of an electric current and a magnetic field. The first demonstration of the effect with a rotary motion was given by Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury; when a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire.
This motor is demonstrated in physics experiments, substituting brine for mercury. Barlow's wheel was an early refinement to this Faraday demonstration, although these and similar homopolar motors remained unsuited to practical application until late in the century. In 1827, Hungarian physicist Ányos Jedlik started experimenting with electromagnetic coils. After Jedlik solved the technical problems of continuous rotation with the invention of the commutator, he called his early devices "electromagnetic self-rotors". Although they were used only for teaching, in 1828 Jedlik demonstrated the first device to contain the three main components of practical DC motors: the stator and commutator; the device employed no permanent magnets, as the magnetic fields of both the stationary and revolving components were produced by the currents flowing through their windings. After many other more or less successful attempts with weak rotating and reciprocating apparatus Prussian Moritz von Jacobi created the first real rotating electric motor in May 1834.
It developed remarkable mechanical output power. His motor set a world record, which Jacobi improved four years in September 1838, his second motor was powerful enough to drive a boat with 14 people across a wide river. It was in 1839/40 that other developers managed to build motors with similar and higher performance; the first commutator DC electric motor capable of turning machinery was invented by British scientist William Sturgeon in 1832. Following Sturgeon's work, a commutator-type direct-current electric motor was built by American inventor Thomas Davenport, which he patented in 1837; the motors ran at up to 600 revolutions per minute, powered machine tools and a printing press. Due to the high cost of primary battery power, the motors were commercially unsuccessful and bankrupted Davenport. Several inventors followed Sturgeon in the development of DC motors, but all encountered the same battery cost issues; as no electricity distribution system was available at the time, no practical commercial market emerged for these motors.
In 1855, Jedlik built a device using similar principles to those used in his electromagnetic self-rotors, capable of useful work. He built a model electric vehicle that same year. A major turning point came in 1864; this featured symmetrically-grouped coils closed upon themselves and connected to the bars of a commutator, the brushes of which delivered non-fluctuating current. The first c
A pump is a device that moves fluids, or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift and gravity pumps. Pumps operate by some mechanism, consume energy to perform mechanical work moving the fluid. Pumps operate via many energy sources, including manual operation, engines, or wind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps. Mechanical pumps serve in a wide range of applications such as pumping water from wells, aquarium filtering, pond filtering and aeration, in the car industry for water-cooling and fuel injection, in the energy industry for pumping oil and natural gas or for operating cooling towers. In the medical industry, pumps are used for biochemical processes in developing and manufacturing medicine, as artificial replacements for body parts, in particular the artificial heart and penile prosthesis; when a casing contains only one revolving impeller, it is called a single-stage pump.
When a casing contains two or more revolving impellers, it is called a double- or multi-stage pump. In biology, many different types of chemical and biomechanical pumps have evolved. Mechanical pumps may be placed external to the fluid. Pumps can be classified by their method of displacement into positive displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valveless pumps. There are two basic types of pumps: centrifugal. Although axial-flow pumps are classified as a separate type, they have the same operating principles as centrifugal pumps. A positive displacement pump makes a fluid move by trapping a fixed amount and forcing that trapped volume into the discharge pipe; some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses; the volume is constant through each cycle of operation.
Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, theoretically can produce the same flow at a given speed no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. However, a slight increase in internal leakage as the pressure increases prevents a constant flow rate. A positive displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is damaged, or both. A relief or safety valve on the discharge side of the positive displacement pump is therefore necessary; the relief valve can be external. The pump manufacturer has the option to supply internal relief or safety valves; the internal valve is used only as a safety precaution. An external relief valve in the discharge line, with a return line back to the suction line or supply tank provides increased safety.
A positive displacement pump can be further classified according to the mechanism used to move the fluid: Rotary-type positive displacement: internal gear, shuttle block, flexible vane or sliding vane, circumferential piston, flexible impeller, helical twisted roots or liquid-ring pumps Reciprocating-type positive displacement: piston pumps, plunger pumps or diaphragm pumps Linear-type positive displacement: rope pumps and chain pumps These pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquid. Advantages: Rotary pumps are efficient because they can handle viscous fluids with higher flow rates as viscosity increases. Drawbacks: The nature of the pump requires close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which causes enlarged clearances that liquid can pass through, which reduces efficiency. Rotary positive displacement pumps fall into three main types: Gear pumps – a simple type of rotary pump where the liquid is pushed between two gears Screw pumps – the shape of the internals of this pump is two screws turning against each other to pump the liquid Rotary vane pumps – similar to scroll compressors, these have a cylindrical rotor encased in a shaped housing.
As the rotor orbits, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump. Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes, while valves restrict fluid motion to the desired direction. In order for suction to take place, the pump must first pull the plunger in an outward motion to decrease pressure in the chamber. Once the plunger pushes back, it will increase the pressure chamber and the inward pressure of the plunger will open the discharge valve and release the fluid into the delivery pipe at a high velocity. Pumps in this category range from simplex, with one cylinder, to in some cases quad cylinders, or more. Many reciprocating-type pumps are triplex cylinder, they can be either single-acting with suction during one direction of piston motion and discharge on the other, or double-acting with suction and discharge in both directions. The pumps can be powered manually, by air or steam
An impeller is a rotor used to increase the pressure and flow of a fluid. An impeller is a rotating component of a centrifugal pump which transfers energy from the motor that drives the pump to the fluid being pumped by accelerating the fluid outwards from the center of rotation; the velocity achieved by the impeller transfers into pressure when the outward movement of the fluid is confined by the pump casing. An impeller is a short cylinder with an open inlet to accept incoming fluid, vanes to push the fluid radially, a splined, keyed, or threaded bore to accept a drive shaft; the impeller made out of cast material in many cases may be called rotor, also. It is cheaper to cast the radial impeller right in the support it is fitted on, put in motion by the gearbox from an electric motor, combustion engine or by steam driven turbine; the rotor names both the spindle and the impeller when they are mounted by bolts. In a failing heart, mechanical circulatory devices utilize a continuous axial-flow impeller pump design.
Open shrouded impeller. The main part of a centrifugal compressor is the impeller. An open impeller has no cover, therefore it can work at higher speeds. A compressor with a covered impeller can have more stages than one; some impellers are similar without the large blades. Among other uses, they are used in water jets to power high speed boats. Since impellers have no large blades to turn, they can spin at much higher speeds than propellers; the water forced through the impeller is channelled by the housing, creating a water jet that propels the vessel forward. The housing is tapered into a nozzle to increase the speed of the water, which creates a Venturi effect in which low pressure behind the impeller pulls more water towards the blades, tending to increase the speed. To work efficiently, there must be a close fit between the housing; the housing is fitted with a replaceable wear ring which tends to wear as sand or other particles are thrown against the housing side by the impeller. Vessels using impellers are steered by changing the direction of the water jet.
Compare to propeller and jet aircraft engines. Impellers in agitated tanks are used to mix fluids or slurry in the tank; this can be used to combine materials in the form of solids and gas. Mixing the fluids in a tank is important if there are gradients in conditions such as temperature or concentration. There are two types of impellers, depending on the flow regime created: Axial flow impeller Radial flow impellerRadial flow impellers impose shear stress to the fluid, are used, for example, to mix immiscible liquids or in general when there is a deformable interface to break. Another application of radial flow impellers are the mixing of viscous fluids. Axial flow impellers impose bulk motion, are used on homogenization processes, in which increased fluid volumetric flow rate is important. Impellers can be further classified principally into three sub-types Propellers Paddles TurbinesAll these can be discussed after example. If one heats a pot of soup on the stove the pot will develop a temperature gradient.
Mild agitation will increase the rate of heating by dissipating the heat through the entire pot. See: Law of cooling. More significant, agitation disturbs the soup directly in contact with the hotter pot surface. Turbulent flow at the warming surface is important to good heat transfer; this is the same effect as the "wind chill" factor where moving air and turbulent action on surfaces resulting in enhanced heat transfer. In unusual circumstances, overly-severe agitation may decrease the rate of heating which defeats the purpose. Propellers are axial thrust-giving elements; these elements give a high degree of swirling in the vessel. The flow pattern generated in the fluid resembles a helix; some constructions of top loading washing machines use impellers to agitate the laundry during washing. Fire services in the United Kingdom and many countries of the Commonwealth use a stylized depiction of an impeller as a rank badge. Officers wear one or more on their epaulettes or the collar of their firefighting uniform as an equivalent to the "pips" worn by the army and police.
Impellers are an integral part of axial-flow pump, used in ventricular assist devices to augment or replace cardiac function. Air pumps, such as the roots blower, use meshing impellers to move air through a system. Applications include blast furnaces, ventilation systems, superchargers for internal combustion engines. Axial fan design Centrifugal fan
A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power in a watermill. A water wheel consists of a wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface. Water wheels were still in commercial use well into the 20th century but they are no longer in common use. Uses included milling flour in gristmills, grinding wood into pulp for papermaking, hammering wrought iron, ore crushing and pounding fiber for use in the manufacture of cloth; some water wheels are fed by water from a mill pond, formed when a flowing stream is dammed. A channel for the water flowing to or from a water wheel is called a mill race; the race bringing water from the mill pond to the water wheel is a headrace. In the mid to late 18th century John Smeaton's scientific investigation of the water wheel led to significant increases in efficiency supplying much needed power for the Industrial Revolution. Water wheels began being displaced by the smaller, less expensive and more efficient turbine, developed by Benoît Fourneyron, beginning with his first model in 1827.
Turbines are capable of handling high heads, or elevations, that exceed the capability of practical-sized waterwheels. The main difficulty of water wheels is their dependence on flowing water, which limits where they can be located. Modern hydroelectric dams can be viewed as the descendants of the water wheel, as they too take advantage of the movement of water downhill. Water wheels come in two basic designs: a horizontal wheel with a vertical axle; the latter can be subdivided according to where the water hits the wheel into backshot overshot, breastshot and stream-wheels. The term undershot can refer to any wheel where the water passes under the wheel but it implies that the water entry is low on the wheel. Most water wheels in the United Kingdom and the United States are vertical wheels rotating about a horizontal axle, but in the Scottish highlands and parts of Southern Europe mills had a horizontal wheel. Overshot and backshot water wheels are used where the available height difference is more than a couple of meters.
Breastshot wheels are more suited to large flows with a moderate head. Undershot and stream wheel use large flows at no head. There is an associated millpond, a reservoir for storing water and hence energy until it is needed. Larger heads store more potential energy for the same amount of water so the reservoirs for overshot and backshot wheels tend to be smaller than for breast shot wheels. Overshot and pitchback water wheels are suitable where there is a small stream with a height difference of more than 2 meters in association with a small reservoir. Breastshot and undershot wheels can be used on high volume flows with large reservoirs. A horizontal wheel with a vertical axle. Called a tub wheel, Norse mill or Greek mill, the horizontal wheel is a primitive and inefficient form of the modern turbine; however if it delivers the required power the efficiency is of secondary importance. It is mounted inside a mill building below the working floor. A jet of water is directed on to the paddles of the water wheel.
This is a simple system without gearing so that the vertical axle of the water wheel becomes the drive spindle of the mill. The earliest known reference to water wheels dates to about 400 BCE, the earliest horizontal axis wheels date to about 200 BCE, so vertical axis mills pre-date horizontal axis mills by about two centuries. A stream wheel is a vertically mounted water wheel, rotated by the water in a water course striking paddles or blades at the bottom of the wheel; this type of water wheel is the oldest type of horizontal axis wheel. They are known as free surface wheels because the water is not constrained by millraces or wheel pit. Stream wheels are cheaper and simpler to build, have less of an environmental impact, than other type of wheel, they do not constitute a major change of the river. Their disadvantages are their low efficiency, which means that they generate less power and can only be used where the flow rate is sufficient. A typical flat board undershot wheel uses about 20 percent of the energy in the flow of water striking the wheel as measured by English civil engineer John Smeaton in the 18th century.
More modern wheels have higher efficiencies. Stream wheels gain little or no advantage from head, a difference in water level. Stream wheels mounted on floating platforms are referred to as ship wheels and the mill as a ship mill; the earliest were constructed by the Byzantine general Belisarius during the siege of Rome in 537. They were sometimes mounted downstream from bridges where the flow restriction of the bridge piers increased the speed of the current, they were inefficient but major advances were made in the eighteenth century. An undershot wheel is a vertically mounted water wheel with a horizontal axle, rotated by the water from a low weir striking the wheel in the bottom quarter. Most of the energy gain comparatively little from the head, they are similar in design to stream wheels. The term undershot is sometimes used with related but different meanings: all wheels where the water passes under the wheel wheels where the water enters in the bottom quarter. Wheels where paddles are placed into the flow of a stream.
See stream above. This is the oldest type of vertical water wheel; the word breastshot is used in a variety o
A paddle steamer is a steamship or riverboat powered by a steam engine that drives paddle wheels to propel the craft through the water. In antiquity, paddle wheelers followed the development of poles and sails, where the first uses were wheelers driven by animals or humans. In the early 19th century, paddle wheels were the predominant way of propulsion for steam-powered boats. In the late 19th century, paddle propulsion was superseded by the screw propeller and other marine propulsion systems that have a higher efficiency in rough or open water. Paddle wheels continue to be used by small pedal-powered paddle boats and by some ships that operate tourist voyages; the latter are powered by diesel engines. The paddle wheel is a large steel framework wheel; the outer edge of the wheel is fitted with regularly-spaced paddle blades. The bottom quarter or so of the wheel travels underwater. An engine rotates the paddle wheel in the water to produce backward as required. More advanced paddle wheel designs feature feathering methods that keep each paddle blade closer to vertical while in the water to increase efficiency.
The upper part of a paddle wheel is enclosed in a paddlebox to minimise splashing. There are two types of paddle wheel steamer, a sternwheeler with a single wheel on the rear, a sidewheeler with one on each side. Both were used as riverboats in the United States; some still operate for example on the Mississippi River. Although the first sternwheelers were invented in Europe, they saw the most service in North America on the Mississippi River. Enterprise was built at Brownsville, Pennsylvania, in 1814 as an improvement over the less efficient side wheelers; the second sternwheeler built, Washington of 1816, had two decks and served as the prototype for all subsequent steamboats of the Mississippi, including those made famous in Mark Twain's book Life on the Mississippi. Sidewheelers are used as coastal craft. Though the side wheels and enclosing sponsons make them wider than sternwheelers, they may be more maneuverable, since they can sometimes move the paddles at different speeds, in opposite directions.
This extra maneuverability makes sidewheelers popular on the narrower, winding rivers of the Murray-Darling system in Australia, where a number still operate. European sidewheelers, such as PS Waverley, connect the wheels with solid drive shafts that limit maneuverability and give the craft a wide turning radius; some were built with paddle clutches that disengage one or both paddles so they can turn independently. However, wisdom gained from early experience with sidewheelers deemed that they be operated with clutches out, or as solid shaft vessels. Crews noticed that as ships approached the dock, passengers moved to the side of the ship ready to disembark; the shift in weight, added to independent movements of the paddles, could lead to imbalance and potential capsizing. Paddle tugs were operated with clutches in, as the lack of passengers aboard meant that independent paddle movement could be used safely and the added maneuverability exploited to the full. In a simple paddle wheel, where the paddles are fixed around the periphery, power is lost due to churning of the water as the paddles enter and leave the water surface.
Ideally, the paddles should remain vertical while under water. This ideal can be approximated by use of linkages connected to a fixed eccentric; the eccentric is fixed forward of the main wheel centre. It is coupled to each paddle via a lever; the geometry is designed such that the paddles are kept vertical for the short duration that they are in the water. The use of a paddle wheel in navigation appears for the first time in the mechanical treatise of the Roman engineer Vitruvius, where he describes multi-geared paddle wheels working as a ship odometer; the first mention of paddle wheels as a means of propulsion comes from the 4th–5th century military treatise De Rebus Bellicis, where the anonymous Roman author describes an ox-driven paddle-wheel warship: The Italian physician Guido da Vigevano, planning for a new crusade, made illustrations for a paddle boat, propelled by manually turned compound cranks. One of the drawings of the Anonymous Author of the Hussite Wars shows a boat with a pair of paddle-wheels at each end turned by men operating compound cranks.
The concept was improved by the Italian Roberto Valturio in 1463, who devised a boat with five sets, where the parallel cranks are all joined to a single power source by one connecting-rod, an idea adopted by his compatriot Francesco di Giorgio. In 1704, the French physicist Denis Papin constructed the first ship powered by his steam engine, mechanically linked to paddles; this made him the first to construct a steam-powered boat. He has poured the first steam cylinder of the world in the iron foundry Veckerhagen. In 1787 Patrick Miller of Dalswinton invented a double-hulled boat, propelled on the Firth of Forth by men working a capstan that drove paddles on each side. One of the firsts functioning steamships, Palmipède, the first paddle steamer, was built in France in 1774 by Marquis Claude de Jouffroy and his colleagues; the 13-metre steamer with rotating paddles sailed on the Doubs River in June and July 1776. In 1783 a new paddle steamer by de Jouffroy, Pyroscaphe steamed up the river Saône for fifteen minutes before the engine failed.
Bureaucracy and the French Revolution thwarted further progress by de Jouffroy. The next successful attempt at a paddle-driven steam ship was by the Scottish engineer William Symington, who suggested steam power to Patrick Mi