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82-715: HMS Thames was a Mersey-class cruiser launched in 1885 for the Royal Navy. Thomas Benjamin Frederick Davis was a wealthy businessman, yachtsman and philanthropist. In 1920 Davis bought the Thames from the British Admiralty and sent her to South Africa. He donated the ship to the South African government and stipulated that it had to be used for the full-time training of boys for careers at sea. It

164-429: A length between perpendiculars of 300 feet (91.4 m), a beam of 46 feet (14.0 m) and a draught of 20 feet 2 inches (6.1 m). They displaced 4,050 long tons (4,110 t). The ships were powered by a pair of two-cylinder horizontal, direct-acting, compound-expansion steam engines , each driving one shaft, which were designed to produce a total of 6,000 indicated horsepower (4,500 kW) and

246-651: A vertical beam or overhead beam , and sometimes simply referred as a "beam", was another early adaptation of the beam engine, but its use was confined almost entirely to the United States. After its introduction, the walking beam quickly became the most popular engine type in American waters for inland waterway and coastal service, eventually making its way into American transoceanic steamships as well. The type proved to have remarkable longevity, with walking beam engines still being occasionally manufactured as late as

328-454: A Watt engine. Following Fulton's success, steamboat technology developed rapidly on both sides of the Atlantic . Steamboats initially had a short range and were not particularly seaworthy due to their weight, low power, and tendency to break down, but they were employed successfully along rivers and canals, and for short journeys along the coast. The first successful transatlantic crossing by

410-417: A beam (i.e. walking beam, side-lever or grasshopper) engine. The later definition only uses the term for engines that apply power directly to the crankshaft via the piston rod and/or connecting rod. Unless otherwise noted, this article uses the later definition. Unlike the side-lever or beam engine, a direct-acting engine could be readily adapted to power either paddlewheels or a propeller. As well as offering

492-550: A brief refit and Thames was renamed Training Ship (TS) General Botha , after Louis Botha , the first Prime Minister of the Union of South Africa . Before departing for Plymouth for extra crewmen on 6 January 1921, the ship was visited by Sir Reginald Blanckenberg , High Commissioner for South Africa , and his wife. She set sail from Plymouth on 18 January and ran into a heavy storm in the English Channel that smashed in

574-464: A centrally located crankshaft. Back-acting engines were another type of engine popular in both warships and commercial vessels in the mid-19th century, but like many other engine types in this era of rapidly changing technology, they were eventually abandoned for other solutions. There is only one known surviving back-acting engine—that of the TV Emery Rice (formerly USS  Ranger ), now

656-492: A common, T-shaped crosshead. The vertical arm of the crosshead extended down between the two cylinders and was attached at the bottom to both the crankshaft connecting rod and to a guide block that slid between the vertical sides of the cylinders, enabling the assembly to maintain the correct path as it moved. The Siamese engine was invented by British engineer Joseph Maudslay (son of Henry ), but although he invented it after his oscillating engine (see below), it failed to achieve

738-553: A compound engine gave a significant increase in fuel efficiency, so allowing steamships to out-compete sail on the route from the UK to China, even before the opening of the Suez Canal in 1869. A triple-expansion engine is a compound engine that expands the steam in three stages, e.g. an engine with three cylinders at three different pressures. A quadruple-expansion engine expands the steam in four stages. However, as explained above,

820-468: A compound walking beam type, compound being the cylinder technology, and walking beam being the connection method. Over time, as most engines became direct-acting but cylinder technologies grew more complex, engines began to be classified solely according to cylinder technology. More commonly encountered marine steam engine types are listed in the following sections. Note that not all these terms are exclusive to marine applications. The side-lever engine

902-430: A different design operating at only 90 psi (620 kPa). This was insufficient to fully realise the economic benefits of triple expansion. Aberdeen was fitted with two double ended Scotch type steel boilers, running at 125 psi (860 kPa). These boilers had patent corrugated furnaces that overcame the competing problems of heat transfer and sufficient strength to deal with the boiler pressure. This provided

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984-481: A lower armoured deck that was 2 inches (51 mm) on the flat and 3 inches (76 mm) on the slope. It sloped down at the bow to reinforce the ram . The armoured sides of the conning tower were 9 inches (229 mm) thick. Thames was the sixth ship of her name to serve in the Royal Navy. She was laid down on 14 April 1884 by Pembroke Dockyard in No. 4 slipway . The ship was launched on 3 December 1885 by

1066-474: A lower profile, direct-acting engines had the advantage of being smaller and weighing considerably less than beam or side-lever engines. The Royal Navy found that on average a direct-acting engine (early definition) weighed 40% less and required an engine room only two thirds the size of that for a side-lever of equivalent power. One disadvantage of such engines is that they were more prone to wear and tear and thus required more maintenance. An oscillating engine

1148-525: A maximum speed of 18 knots (33 km/h; 21 mph) using steam provided by a dozen cylindrical boilers with forced draught . The Mersey class carried enough coal to give them a range of 8,750 nautical miles (16,200 km; 10,070 mi) at a speed of 10 knots (19 km/h; 12 mph). The ships' complement was 300 to 350 officers and ratings . Their main armament consisted of two breech-loading (BL) 8-inch (203 mm) guns , one each fore and aft on pivot mounts . Their secondary armament

1230-729: A ship's economy or its speed. Broadly speaking, a compound engine can refer to a steam engine with any number of different-pressure cylinders—however, the term usually refers to engines that expand steam through only two stages, i.e., those that operate cylinders at only two different pressures (or "double-expansion" engines). Note that a compound engine (including multiple-expansion engines, see below) can have more than one set of variable-pressure cylinders. For example, an engine might have two cylinders operating at pressure x and two operating at pressure y, or one cylinder operating at pressure x and three operating at pressure y. What makes it compound (or double-expansion) as opposed to multiple-expansion

1312-407: A side-rod, extended down each side of the cylinder to connect to the end of the side-lever on the same side. The far ends of the two side-levers were connected to one another by a horizontal crosstail, from which extended a single, common connecting rod which operated the crankshaft as the levers rocked up and down around the central pin. The main disadvantage of the side-lever engine was that it

1394-511: A small, low-profile engine like the trunk engine to power the U.S. Federal government's monitors , a type of warship developed during the American Civil War that had very little space for a conventional powerplant. The trunk engine itself was, however, unsuitable for this purpose, because the preponderance of weight was on the side of the engine that contained the cylinder and trunk—a problem that designers could not compensate for on

1476-415: A smaller, lighter, more efficient design. In a steeple engine, the vertical oscillation of the piston is not converted to a horizontal rocking motion as in a beam engine, but is instead used to move an assembly, composed of a crosshead and two rods, through a vertical guide at the top of the engine, which in turn rotates the crankshaft connecting rod below. In early examples of the type, the crosshead assembly

1558-400: A steamship occurred in 1819 when Savannah sailed from Savannah, Georgia to Liverpool, England . The first steamship to make regular transatlantic crossings was the sidewheel steamer Great Western in 1838. As the 19th century progressed, marine steam engines and steamship technology developed alongside each other. Paddle propulsion gradually gave way to the screw propeller , and

1640-466: A two-year programme and the ship was formally christened as South African Training Ship (SATS) General Botha on 1 April by the wife of the Prime Minister , Jan Smuts . On 15 December, King George V agreed to become the ship's patron and sponsored an annual gold medal for the best cadet aboard. On 2 May 1925, Edward , Prince of Wales , inspected the boys and the ship. About a month later, she

1722-462: Is also an alternative name for the steeple engine (below). Many sources thus prefer to refer to it by its informal name of "square" engine to avoid confusion. Additionally, the marine crosshead or square engine described in this section should not be confused with the term " square engine " as applied to internal combustion engines , which in the latter case refers to an engine whose bore is equal to its stroke . The walking beam, technically known as

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1804-401: Is that the engine could be easily started from any crank position. Like the conventional side-lever engine however, grasshopper engines were disadvantaged by their weight and size. They were mainly used in small watercraft such as riverboats and tugs . The crosshead engine, also known as a square , sawmill or A-frame engine, was a type of paddlewheel engine used in the United States. It

1886-438: Is that there are only two pressures , x and y. The first compound engine believed to have been installed in a ship was that fitted to Henry Eckford by the American engineer James P. Allaire in 1824. However, many sources attribute the "invention" of the marine compound engine to Glasgow 's John Elder in the 1850s. Elder made improvements to the compound engine that made it safe and economical for ocean-crossing voyages for

1968-519: The Duke of Edinburgh as her patron. The South African Naval Museum in Simon's Town has an exhibit dedicated to the ship. Cave dive sites: Marine steam engine#Compound engine A marine steam engine is a steam engine that is used to power a ship or boat . This article deals mainly with marine steam engines of the reciprocating type, which were in use from the inception of the steamboat in

2050-417: The beam engine . The typical side-lever engine had a pair of heavy horizontal iron beams, known as side-levers, each secured in the centre by a pin near the base of the engine, allowing the levers to pivot through a limited arc. The engine cylinder stood vertically between this pair of levers at one end, with the piston rod attached to a horizontal crosshead above, from each end of which a vertical rod, known as

2132-524: The 1830s and the type was perfected in the early 1840s by the Scottish shipbuilder David Napier . The steeple engine was gradually superseded by the various types of direct-acting engine. The Siamese engine, also referred to as the "double cylinder" or "twin cylinder" engine, was another early alternative to the beam or side-lever engine. This type of engine had two identical, vertical engine cylinders arranged side-by-side, whose piston rods were attached to

2214-543: The 18th century greatly improved steam engine efficiency and allowed more compact engine arrangements. Successful adaptation of the steam engine to marine applications in England would have to wait until almost a century after Newcomen, when Scottish engineer William Symington built the world's "first practical steamboat ", the Charlotte Dundas , in 1802. Rivaling inventors James Rumsey and John Fitch were

2296-504: The 1940s. In marine applications, the beam itself was generally reinforced with iron struts that gave it a characteristic diamond shape, although the supports on which the beam rested were often built of wood. The adjective "walking" is believed to have originated from a corruption of the technical term "working beam". Walking beam engines were a type of paddlewheel engine and were rarely used for powering propellers. They were used primarily for ships and boats working in rivers, lakes and along

2378-507: The Hon. Mrs. Algernon Littleton and completed in July 1889 at a cost of £ 204,952. The ship went straight into reserve at Devonport after completion. On 21 March 1902 she was temporarily commissioned by Captain H. L. Fleet, with crewmen from the battleship HMS  Empress of India , to serve as a port guard ship at Queenstown , while the latter ship was undergoing alterations. In 1903,

2460-576: The RN returned her to the Board of Control, the ship was deemed uneconomical to repair and she was scuttled by gunfire from one of the local coast defence battery on 13 May 1947 in False Bay at coordinates 34°13′48″S 18°37′48″E  /  34.23000°S 18.63000°E  / -34.23000; 18.63000 . There exists an alumni association for those who served aboard General Botha , which has

2542-514: The United States and in Ericsson's native country of Sweden, and as they had few advantages over more conventional engines, were soon supplanted by other types. The back-acting engine, also known as the return connecting rod engine , was another engine designed to have a very low profile. The back-acting engine was in effect a modified steeple engine, laid horizontally across the keel of a ship rather than standing vertically above it. Instead of

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2624-412: The assembly maintained the correct path as it moved. The engine's alternative name—"A-frame"—presumably derived from the shape of the frames that supported these guides. Some crosshead engines had more than one cylinder, in which case the piston rods were usually all connected to the same crosshead. Because the cylinder was above the crankshaft in this type of engine, it had a high center of gravity, and

2706-513: The cadets in Buckingham Palace on 29 June shortly before the race during which they beat the cadets from Conway , but lost to Worcester . By the late 1930s, General Botha ' s guns and boilers had been removed and the former engine and boiler rooms converted into a gymnasium . The trust's Board of Control offered the ship to the RN with 30 days notice on 7 September 1939, the day after South Africa declared war on Germany, but

2788-488: The centerpiece of a display at the American Merchant Marine Museum . As steamships grew steadily in size and tonnage through the course of the 19th century, the need for low profile, low centre-of-gravity engines correspondingly declined. Freed increasingly from these design constraints, engineers were able to revert to simpler, more efficient and more easily maintained designs. The result was

2870-457: The close of the 19th century. Because they became so common, vertical engines are not usually referred to as such, but are instead referred to based upon their cylinder technology, i.e. as compound, triple-expansion, quadruple-expansion etc. The term "vertical" for this type of engine is imprecise, since technically any type of steam engine is "vertical" if the cylinder is vertically oriented. An engine someone describes as "vertical" might not be of

2952-640: The coastline, but were a less popular choice for seagoing vessels because the great height of the engine made the vessel less stable in heavy seas. They were also of limited use militarily, because the engine was exposed to enemy fire and could thus be easily disabled. Their popularity in the United States was due primarily to the fact that the walking beam engine was well suited for the shallow- draft boats that operated in America's shallow coastal and inland waterways. Walking beam engines remained popular with American shipping lines and excursion operations right into

3034-435: The conservatism of American domestic shipbuilders and shipping line owners, who doggedly clung to outdated technologies like the walking beam and its associated paddlewheel long after they had been abandoned in other parts of the world. The steeple engine, sometimes referred to as a "crosshead" engine, was an early attempt to break away from the beam concept common to both the walking beam and side-lever types, and come up with

3116-424: The crankshaft rotated—hence the term, oscillating . Steam was supplied and exhausted through the trunnions. The oscillating motion of the cylinder was usually used to line up ports in the trunnions to direct the steam feed and exhaust to the cylinder at the correct times. However, separate valves were often provided, controlled by the oscillating motion. This let the timing be varied to enable expansive working (as in

3198-416: The early 19th century to their last years of large-scale manufacture during World War II . Reciprocating steam engines were progressively replaced in marine applications during the 20th century by steam turbines and marine diesel engines . The first commercially successful steam engine was developed by Thomas Newcomen in 1712. The steam engine improvements brought forth by James Watt in the later half of

3280-410: The early 20th century. Although the walking beam engine was technically obsolete in the later 19th century, it remained popular with excursion steamer passengers who expected to see the "walking beam" in motion. There were also technical reasons for retaining the walking beam engine in America, as it was easier to build, requiring less precision in its construction. Wood could be used for the main frame of

3362-412: The engine in the paddle ship PD Krippen ). This provides simplicity but still retains the advantages of compactness. The first patented oscillating engine was built by Joseph Maudslay in 1827, but the type is considered to have been perfected by John Penn . Oscillating engines remained a popular type of marine engine for much of the 19th century. The trunk engine, another type of direct-acting engine,

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3444-526: The engine, at a much lower cost than typical practice of using iron castings for more modern engine designs. Fuel was also much cheaper in America than in Europe, so the lower efficiency of the walking beam engine was less of a consideration. The Philadelphia shipbuilder Charles H. Cramp blamed America's general lack of competitiveness with the British shipbuilding industry in the mid-to-late 19th century upon

3526-553: The establishment was changed to The South African Nautical College General Botha and the new Captain-Superintendent was Captain G V Legassick RNR. For the next 10 years General Botha prospered. A new engineering course was introduced as well. Then in 1958 the government decided to place the establishment under the control of the South African Navy. Captain Legassick was replaced with Commander SC Biermann, on whom rested

3608-404: The first Royal Navy steam vessel in 1820 until 1840, 70 steam vessels entered service, the majority with side-lever engines, using boilers set to 4psi maximum pressure. The low steam pressures dictated the large cylinder sizes for the side-lever engines, though the effective pressure on the piston was the difference between the boiler pressure and the vacuum in the condenser. The side-lever engine

3690-550: The first time. To fully realise their benefits, marine compound engines required boiler pressures higher than the limit imposed by the United Kingdom 's Board of Trade , who would only allow 25 pounds per square inch (170 kPa). The shipowner and engineer Alfred Holt was able to persuade the authorisation of higher boiler pressures, launching SS  Agamemnon in 1865, with boilers running at 60 psi (410 kPa). The combination of higher boiler pressures and

3772-672: The first to build steamboats in the United States. Rumsey exhibited his steamboat design in 1787 on the Potomac River; however, Fitch won the rivalry in 1790 after his successful test resulted in a passenger service on the Delaware River. In 1807, the American Robert Fulton built the world's first commercially successful steamboat, simply known as the North River Steamboat , and powered by

3854-560: The following year. General Botha continued to train cadets for the first several years of World War II , but the RN took over the ship in 1942 for use as an accommodation ship under her original name. She was scuttled by gunfire in 1947 and is now a diveable wreck. The Mersey -class cruisers were improved versions of the Leander class with more armour and no sailing rig on a smaller displacement . Like their predecessors, they were intended to protect British shipping. The cruisers had

3936-424: The growing dominance of the so-called "vertical" engine (more correctly known as the vertical inverted direct acting engine). In this type of engine, the cylinders are located directly above the crankshaft, with the piston rod/connecting rod assemblies forming a more or less straight line between the two. The configuration is similar to that of a modern internal combustion engine (one notable difference being that

4018-716: The gunboat type exists in the Western Australian Museum in Fremantle . After sinking in 1872, it was raised in 1985 from the SS ; Xantho and can now be turned over by hand. The engine's mode of operation, illustrating its compact nature, could be viewed on the Xantho project's website. The vibrating lever, or half-trunk engine, was a development of the conventional trunk engine conceived by Swedish - American engineer John Ericsson . Ericsson needed

4100-499: The higher boiler pressures that became prevalent in the latter half of the 19th century due to the difficulty of maintaining a steam seal around the trunk, and builders abandoned them for other solutions. Trunk engines were normally large, but a small, mass-produced, high-revolution, high-pressure version was produced for the Crimean War. In being quite effective, the type persisted in later gunboats. An original trunk engine of

4182-517: The inadequately boarded-up sponsons and forced the ship to turn about for Plymouth for repairs where General Botha arrived two days later. The ship departed on 8 February and arrived in Cape Town on 26 March where she was greeted by the Minister of Defence , Colonel Hendrik Mentz and other notables. Davis donated it to a trust on 9 May, with the stipulation that it be used exclusively for

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4264-444: The introduction of iron and later steel hulls to replace the traditional wooden hull allowed ships to grow ever larger, necessitating steam power plants that were increasingly complex and powerful. A wide variety of reciprocating marine steam engines were developed over the course of the 19th century. The two main methods of classifying such engines are by connection mechanism and cylinder technology . Most early marine engines had

4346-500: The literature of the early period then, an engine can generally be assumed to be simple-expansion unless otherwise stated. Compound engines were a method of improving efficiency. Until the development of compound engines, steam engines used the steam only once before it was recycled back to the boiler. A compound engine first recycles the steam into one or more larger, lower-pressure secondary cylinders, to use more of its heat energy. Compound engines could be configured to increase either

4428-459: The location of the lever pivot and connecting rod are more or less reversed, with the pivot located at one end of the lever instead of the centre, while the connecting rod is attached to the lever between the cylinder at one end and the pivot at the other. Chief advantages of the grasshopper engine were cheapness of construction and robustness, with the type said to require less maintenance than any other type of marine steam engine. Another advantage

4510-492: The nautical training of British and South African boys, so that they could subsequently serve in ships of the British Empire . The Admiralty agreed to cover the cost to convert General Botha into a training ship at Simon's Town Naval Dockyard and to tow her there from Cape Town in early September. It also agreed to grant the ship a mooring in Simon's Town. The first class of 75 boys reported aboard on 15 March 1922 on

4592-468: The next twenty years, during which 1,276 cadets received their training. The presence of German submarines in the southern oceans in 1942 caused the naval authorities to become concerned for the safety of the cadets living on board the TS General Botha . They were therefore moved up to Red Hill, but still went down to the ship for their daily training. At the end of the year the TS General Botha

4674-673: The number of expansion stages defines the engine, not the number of cylinders, e.g. the RMS Titanic had four-cylinder, triple-expansion engines. The first successful commercial use was an engine built at Govan in Scotland by Alexander C. Kirk for the SS  Aberdeen in 1881. An earlier experiment with an almost identical engine in SS Propontis in 1874 had had problems with the boilers. The initial installation, running at 150 psi (1,000 kPa) had to be replaced with

4756-410: The offer was declined. Nevertheless, they decided to build accommodations for the cadets ashore if the RN did decide to take them up on their offer. The RN did so in July 1942 and the boys and staff went ashore on the 28th and the ship resumed her former name shortly afterwards. She served as an accommodation ship and was used as a prison ship for at least part of her time in RN service. By the time that

4838-595: The same cylinder technology (simple expansion, see below) but a number of different methods of supplying power to the crankshaft (i.e. connection mechanism) were in use. Thus, early marine engines are classified mostly according to their connection mechanism. Some common connection mechanisms were side-lever, steeple, walking beam and direct-acting (see following sections). However, steam engines can also be classified according to cylinder technology (simple-expansion, compound, annular etc.). One can therefore find examples of engines classified under both methods. An engine can be

4920-455: The same widespread acceptance, as it was only marginally smaller and lighter than the side-lever engines it was designed to replace. It was however used on a number of mid-century warships, including the first warship fitted with a screw propeller, HMS  Rattler . There are two definitions of a direct-acting engine encountered in 19th-century literature. The earlier definition applies the term "direct-acting" to any type of engine other than

5002-541: The ship was converted to a submarine tender and served at Sheerness from 1907 to 1917 and then briefly at Portsmouth and Campbeltown , Scotland , before being paid off in 1919 at Chatham Dockyard . She was sold for £8,000 in November 1920 to the Jersey -born South African entrepreneur T. B. Davis as a memory to his son who died during World War I. Later that month, the ship steamed to West India Dock, Tilbury , for

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5084-475: The side-to-side motion of the connecting rod, which links a gudgeon pin at the piston head to an outside crankshaft. The walls of the trunk were either bolted to the piston or cast as one piece with it, and moved back and forth with it. The working portion of the cylinder is annular or ring-shaped, with the trunk passing through the centre of the cylinder itself. Early examples of trunk engines had vertical cylinders. However, ship builders quickly realized that

5166-406: The small monitor warships. Ericsson resolved this problem by placing two horizontal cylinders back-to-back in the middle of the engine, working two "vibrating levers", one on each side, which by means of shafts and additional levers rotated a centrally located crankshaft. Vibrating lever engines were later used in some other warships and merchant vessels, but their use was confined to ships built in

5248-436: The steam engine is double acting, see below, whereas almost all internal combustion engines generate power only in the downward stroke). Vertical engines are sometimes referred to as "hammer", "forge hammer" or "steam hammer" engines, due to their roughly similar appearance to another common 19th-century steam technology, the steam hammer . Vertical engines came to supersede almost every other type of marine steam engine toward

5330-404: The technical solution that ensured that virtually all newly built ocean-going steamships were fitted with triple expansion engines within a few years of Aberdeen coming into service. Multiple-expansion engine manufacture continued well into the 20th century. All 2,700 Liberty ships built by the United States during World War II were powered by triple-expansion engines, because the capacity of

5412-411: The triangular crosshead assembly found in a typical steeple engine however, the back-acting engine generally used a set of two or more elongated, parallel piston rods terminating in a crosshead to perform the same function. The term "back-acting" or "return connecting rod" derives from the fact that the connecting rod "returns" or comes back from the side of the engine opposite the engine cylinder to rotate

5494-543: The type was compact enough to lay horizontally across the keel . In this configuration, it was very useful to navies, as it had a profile low enough to fit entirely below a ship's waterline , as safe as possible from enemy fire. The type was generally produced for military service by John Penn. Trunk engines were common on mid-19th century warships. They also powered commercial vessels, where—though valued for their compact size and low centre of gravity—they were expensive to operate. Trunk engines, however, did not work well with

5576-705: The unenviable job of combining the courses for the Merchant Marine and the Navy, while remaining the commanding officer of the Naval Gymnasium in Saldanha. This difficult relationship between the two services continued until 1966, when the new South African Merchant Navy Academy was established at Granger Bay. 34°09′49″S 18°51′42″E  /  34.1635°S 18.8616°E  / -34.1635; 18.8616 HMS Thames (1885) HMS Thames

5658-420: The vertical inverted direct-acting type, unless they use the term "vertical" without qualification. A simple-expansion engine is a steam engine that expands the steam through only one stage, which is to say, all its cylinders are operated at the same pressure. Since this was by far the most common type of engine in the early period of marine engine development, the term "simple expansion" is rarely encountered. In

5740-652: Was a Mersey -class protected cruiser built for the Royal Navy (RN) in the 1880s. The ship was placed in reserve upon her completion in 1888 and was converted into a submarine depot ship in 1903. She was sold out of the navy in 1920 and was purchased by a South African businessman to serve as a training ship for naval cadets under the name SATS General Botha . The ship arrived in South Africa in 1921 and began training her first class of cadets in Simon's Town

5822-491: Was a paddlewheel engine and was not suitable for driving screw propellers . The last ship built for transatlantic service that had a side-lever engine was the Cunard Line 's paddle steamer RMS  Scotia , considered an anachronism when it entered service in 1862. The grasshopper or 'half-lever' engine was a variant of the side-lever engine. The grasshopper engine differs from the conventional side-lever in that

5904-406: Was a type of direct-acting engine that was designed to achieve further reductions in engine size and weight. Oscillating engines had the piston rods connected directly to the crankshaft, dispensing with the need for connecting rods. To achieve this, the engine cylinders were not immobile as in most engines, but secured in the middle by trunnions that let the cylinders themselves pivot back and forth as

5986-493: Was commandeered by the navy and berthed in the dockyard for the rest of the war. After the war it was found that the TS General Botha was beyond economical repair. On 13 May 1947 she was towed into False Bay to a position nine nautical miles ESE of the Roman Rock lighthouse and sunk by gunfire from Scala battery. At the end of April 1948 the cadets were moved to the former SAAF crash boat station at Gordons Bay. The name of

6068-541: Was docked to have her engines and funnel removed and her interior remodelled to create new messdecks , galleys and recreation spaces, returning to her moorings in August. In March 1935, Davis offered to sponsor a rowing competition between the cadets of General Botha and the British training ships, HMS Worcester , and HMS Conway in Britain and paid for their expenses to and from South Africa. King George V received

6150-464: Was large and heavy. For inland waterway and coastal service, lighter and more efficient designs soon replaced it. It remained the dominant engine type for oceangoing service through much of the first half of the 19th century however, due to its relatively low centre of gravity , which gave ships more stability in heavy seas. It was also a common early engine type for warships, since its relatively low height made it less susceptible to battle damage. From

6232-404: Was originally developed as a means of reducing an engine's height while retaining a long stroke . (A long stroke was considered important at this time because it reduced the strain on components.) A trunk engine locates the connecting rod within a large-diameter hollow piston. This "trunk" carries almost no load. The interior of the trunk is open to outside air, and is wide enough to accommodate

6314-619: Was rectangular in shape, but over time it was refined into an elongated triangle. The triangular assembly above the engine cylinder gives the engine its characteristic "steeple" shape, hence the name. Steeple engines were tall like walking beam engines, but much narrower laterally, saving both space and weight. Because of their height and high centre of gravity, they were, like walking beams, considered less appropriate for oceangoing service, but they remained highly popular for several decades, especially in Europe, for inland waterway and coastal vessels. Steeple engines began to appear in steamships in

6396-457: Was renamed TS (training ship) General Botha in honour of the South African prime minister. She was moored in Simon's Bay, outside the naval dockyard. On 15 March 1922 the first intake of seventy five boys joined ship in Simon's Bay. General Botha's wife was supposed to conduct the official christening, but she was feeling poorly, with the result that Isie Smuts had to officiate on 1 April 1922. The TS General Botha remained in Simon's Bay for

6478-403: Was ten BL 6-inch (152 mm) guns , five on each broadside in sponsons . Protection against torpedo boats was provided by three quick-firing (QF) 6-pounder Hotchkiss guns and three QF 3-pounder Hotchkiss guns. The ship was also armed with a pair of submerged 14-inch (356 mm) torpedo tubes and carried a pair of 14-inch torpedo carriages. The Mersey -class ships were protected by

6560-474: Was the first type of steam engine widely adopted for marine use in Europe . In the early years of steam navigation (from c1815), the side-lever was the most common type of marine engine for inland waterway and coastal service in Europe, and it remained for many years the preferred engine for oceangoing service on both sides of the Atlantic . The side-lever was an adaptation of the earliest form of steam engine,

6642-406: Was the most common type of engine in the early years of American steam navigation. The crosshead engine is described as having a vertical cylinder above the crankshaft, with the piston rod secured to a horizontal crosshead, from each end of which, on opposite sides of the cylinder, extended a connecting rod that rotated its own separate crankshaft. The crosshead moved within vertical guides so that

6724-433: Was therefore deemed unsuitable for oceangoing service. This largely confined it to vessels built for inland waterways. As marine engines grew steadily larger and heavier through the 19th century, the high center of gravity of square crosshead engines became increasingly impractical, and by the 1840s, ship builders abandoned them in favor of the walking beam engine. The name of this engine can cause confusion, as "crosshead"

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