Marine engines and boilers
By John Riley 1998 (c) NSW Heritage Office
(Models of engines and boilers by John Riley. Photography, unless otherwise indicated,David Nutley)
The development of engine powered vessels is credited as early as 1783. However, the first practical steam vessel was constructed in Britain in 1802. In Australia, the first steamer to operate on the coast was the ps Sophia Jane, while the first to be built in Australia was the paddle steamer Surprise that same year. These events both occurred in 1831. Other paddle steamers soon followed, and included, the William The Forth (1831), Tamar (1833), Maitland (1837), Rose, Shamrock and Thistle (1841), Seahorse and Juno (1842), Phoenix (1846) and Illalong (1854).
The paddle steamer Juno made the first voyage across the Tasman Sea to New Zealand as early as 1847 3. It was not until 1851 however, that the first screw steamer began work in Australian waters. This was the steamer, ss Keera.
Information on nineteenth century marine engines and boilers located in New South Wales comes from a variety of sources. Shipwrecks provide the greatest source of information. The study of surviving engine remains adds significant detail to the minimal amount of information contained in contemporary ship registers. These registers include the Lloyds Register of British Shipping, London and the Register of British Ships (in Australian Ports). The listings are somewhat vague about engine (cylinder) numbers, size and arrangement. Over time they provide more detailed descriptions, although information on marine boilers is almost totally lacking until the later part of the nineteenth century.
Definitions also changed over the years. The notation, "one engine", might have referred initially to one cylinder, but later to an engine with two or more cylinders. "Two engines" generally referred to an engine with two cylinders of the same size, ie "simple engines". Later, "two engines-compound" referred to a compounding engine that had two cylinders, both of different sizes. Triple Expansion Engines were described as "three" (ie three cylinders), with the diameter of the cylinders and the piston stroke recorded.
The terms "low pressure" and "high pressure" also had a different meaning through the nineteenth century as boiler pressures developed with new technological improvements. Pressures increased from 15 p.s.i. (pounds per square inch) at the beginning of the nineteenth century to 200 p.s.i. at the century's end.
While not a focus of this study, engines attributed to river steamers have been included. Of the seven engine types identified in the NSW's shipwreck resource, the Portable Engine is confined to inland river vessels.
The initial screw steamers used engines developed to run the earlier paddle steamers. Nine types have been identified culminating in the Triple Expansion Engine. Two vessels wrecked in New South Wales had engine types not represented elsewhere. These included a very small Quadruple Expansion Engine and one Steam Turbine engine. The other Turbine Engines identified belonged to scuttled Naval vessels. Motor vessels have not been included in this study.
ps Yarra Yarra (1851-1877)
Side Lever Engines were a development of the early land based steam engines developed in 1791. Power was transmitted from a vertically placed cylinder to the paddle wheel shaft via rods and levers. These distinctive side levers gave the engine its name. The levers were mounted low to keep the engines center of gravity down. They initially ran under low pressure steam of about 15 p.s.i. but later versions could accommodate 200 h.p. They are the earliest type of marine engines detected on New South Wales wreck sites. They were a slow reving engine suitable only for paddle wheel use. They were jet condensing engines which ran using steam generated from seawater.
Side lever engine
Oscillating (geared) Engine
ss Royal Shepherd (1853-1890)
This was the most popular type used to power paddle wheel steamers. They were later adapted using a system of gears to power screw steamers. Screw vessels required a greater number of revolutions to make the propeller function. Oscillating Engines used to power paddle steamers have been located at the Prince of Wales (1862) and Agnes Irving (1879) wreck sites. The Oscillating Engine was popular because it was easy to start and stop. It also took up little inboard room. A compact engine because it dispersed with the connecting rod. The piston rod attached directly to the crankshaft. During operation, the cylinders rocked to take up the motion, hence its other name, the "vibrating engine".
An excellent example has been found on the screw steamer Royal Shepherd (1890), wrecked near Sydney and probably the most important engine detected in NSW. They were also of the jet condensing type requiring a steam pressure of between 15 to 20 p.s.i. The large gear wheel evident on the Royal Shepherd had wooden teeth - a weak link that was repairable in the field.
Trunk Engines arranged diagonally opposed
ps Mimosa (1854-1863)
This engine type was a neat use of trunk engines to fit a small paddle steamer hull. They were jet condensing, using seawater and initially required a boiler pressure of between 15 to 20 p.s.i. Trunk Engines lost favour when high-pressure boilers become available. Particular problems were noted in sealing the trunks with a higher pressure steam source. The engine visible at the ps Mimosa (1863) site is a rare example of the type used to power paddle steamers.
Trunk engines can be found on the screw steamers, ss City of Sydney (1862) and ss Lord Ashley (1877).
Diagonally opposed trunk engine
P.S. Ballina (1865-1879)
This engine was a good compromise to earlier paddle wheelers, providing a long stroke while the engine fitted into a shallow hull. The engines could generate approximately 80 horsepower with a steam pressure of between 10 to 15 p.s.i. Of the jet condenser type using seawater, both cylinders (engines) were of the same size.
Grasshopper (side lever) Engine
ps Commodore (1878-1931)
This was a Side Lever Engine of different layout to that noted at the ps Yarra Yarra site. It had a Fulcrom at front, cylinder at rear and crank in middle. The engine had a similar motion to the Grasshopper insect, from which it derived its name. The engine was perfected for paddle tugs and was used into the mid twentieth century. Each engine could turn its paddle wheel in opposite directions or be tied together by a large circular clutch. This gave paddle tugs more maneuverability than current screw tugs explaining why they operated for such a long period. Grasshopper Engines were a magnificently complicated engine and took up a substantial amount of engine room space. A platform was required above the cylinders for the engineer to operate the engine.
The example can be found at the ps Commodore (1931) off Newcastle. They were a surface condensing type using fresh water and required a steam pressure between 80 and 100 p.s.i.
Simple Inverted Engine
ss Lady Darling (1864-1880)
Two cylinders (engines) same size 100 h.p. 25 p.s.i.
"Simple" Inverted Engines were the first modern steam engine. They had two cylinders (engines) of the same size mounted vertically (inverted from old arrangements). They took up little room and were of the jet condensing type using sea water. The first efficient propeller steam engine, they could run at high revolutions without gearing or vibration problems. The Simple Engine is known as the engine of the 1860's, but was soon replaced by the development of the Compound Engine. These were initially of similar size but generated more power with greater economy.
Simple Engines were developed from the steam hammer, a device used to forge steel and iron, and were sometimes called Steam Hammer Engines. They are a rare engine type on New South Wales wreck sites. To date, examples have only been found with the ss Lady Darling (1880) and ss Woniora (1882) wreck sites.
Simple inverted engine
Engine from Lady Darling
ss Duckenfied (1875-1889)
Compound Engines had two cylinders (engines), one of high and the other of low pressure. The high-pressure cylinder was proportionally smaller to the low pressure one. They were the first engine designed to use high pressure steam economically. With a steam pressure of 70 p.s.i., they could generate 60 horse power. Compound Engines are the most common engines found on steamship wrecks in New South Wales, far outnumbering all other types. There are many examples from the huge example on the ss Catterthun (1895), to the small one fitted to the ss Wandra (1915). They took up little room but required a steam pressure between 80 and 120 p.s.i. This could only be provided from Scotch Boilers. Compound Engines were first introduced in the late 1860's, but were still being fitted to vessel's in the early twentieth century. They are of the surface condensing type using fresh water.
Photograph of diver and engine by Mark Spencer
Triple Expansion Engine
ss Satara (1901-1910)
Triple Expansion Engines were the final development of the inverted compounding engine used in New South Wales. No intact examples have been found on New South Wales' shipwrecks upright and fully visible. The example on the ss Satara (1910) was rated at 383 h.p. and is the largest example found to date in New South Wales. They required a steam pressure of 200 p.s.i. and required more than one Scotch Boiler to operate.
These engines were expensive to build, as were the higher-pressure boilers used to power them. The engine was longer than previous types, having three cylinders (engines) and therefore took up more hull space. Shipbuilders persisted to fit the simpler Compound Engines, particularly for vessels designed for shorter voyages.
Triple Expansion Engines were introduced in the 1880's and used until the present day. They were fitted with a Surface Condenser using fresh water. The popular Compound Engine remained more favoured with 164 compounds known to have been lost aboard vessels wrecked or dumped in New South Wales compared to 67 Triple Expansion examples.
Examples in New South Wales include those at the ss Myola (1919), ss Tuggerah (1919) and ss Annie M. Miller (1929) wreck sites.
Triple expansion engine
Three main types of marine boilers are represented on shipwreck sites in New South Wales. These include the Square (Box) Boiler, the Cylindrical Boiler and the Scotch Boiler. A rarer type known as the Egg Boiler is present at only one wreck site, the Alexander Berry (1901), while many wrecks include examples of auxillary Donkey Boilers. Water Tube Boilers were fitted to the many naval vessels purposely scuttled, and to one non-naval site sunk off Newcastle.
ss Royal Shepherd (1853-1890)
The first Square Boilers had flues not fire tubes. Of the located Square Boiler examples, all are of the fire tube type. All are replacement boilers, probably copied from the original installed during the vessel's construction, to the original design. Only the boiler located at Seal Rocks Beach from the paddle steamer Trio (wrecked 1870) is the fitted original.
Most early steamers were fitted with Box Boilers. They were expensive to build because they required heavy internal staying across all three planes to maintain rigidity. These early boilers used seawater and required periodic de-scaling to remove internal build up of deposits and corrosion. They produced a low boiler pressure of up to 25 p.s.i., sufficient to power early paddle steamers. The boilers only had a working life of around five 5 years. The majority of Box Boilers found on New South Wales wreck sites are therefore replacement boilers, probably built to the original boiler design.
The example on the ss Royal Shepherd had three furnaces. Improved Box boilers were still built after the 1870's and fitted to new vessels such as the ps Maitland. This was after improved boiler designs such as the Cylindrical and Scotch Boilers were in common use.
1870- early 1900's
Donkey Boilers were fitted to sailing vessels and steamships equipped with low pressure boilers, and to most later types. The early boilers could not provide sufficient steam pressure to operate newly developing steam operated equipment such as winches, windlasses and pumps. This machinery, often retrofitted to existing vessels, required an operating pressure of about 80 p.s.i. Donkey Boilers were an economy measure, especially when fitted to vessels with high-pressure boilers, to power the auxiliary machinery when the main boiler was not in steam, for example, when the vessel was in port during loading and unloading.
Donkey Boilers were introduced in the 1870's to provide steam to power winches, windlasses and pumps, previously hand powered. This auxiliary steam driven equipment needed at least 75 pounds per square inch to operate. This was generally much higher than the vessel's main boilers could supply in the early period. Donkey boilers were retrofitted to early sailing vessels and steamers and, in this case, were generally mounted on deck. When fitted into later vessels, they were generally positioned in or near the engine room. Donkey Boilers can be seen on Agnes Irving (1879), Bonnie Dundee (1879), Lady Darling (1880), Yarra Yarra (1877) and Catterthun (1895) wreck sites.
ss Lady Darling (1864-1880)
It appears that all Cylindrical Boilers present on NSW's wreck sites were new boilers built locally to replace earlier fitted Square Boilers. These Cylindrical Boilers may be described as the later Scotch Type, but they had very low boiler pressures of about 30 p.s.i. with wet uptakes. They were also longer than their height (diameter). They differ from the true Scotch Boiler which has a length shorter than its height (diameter), a dry uptake and could produce a far greater steam pressure up to 200 p.s.i. These pressures were required to operate the improved compound marine engines.
The Cylindrical Boiler was a development mid way between the Square (Box) Boiler and the later Scotch Boiler. They were low-pressure boilers generating approximately 25 p.s.i. and, due to their circular construction, only required stays across the 'flat' ends. The uptake to the funnel was generally mounted within the top of the boiler, to allow more heat to be extracted from the smoke before it was lost.
The observed example at the Lady Darling (1880) wreck site is sixteen feet in diameter, a very large example of the type. It would not have been the original boiler, but have been modeled on the earlier design. Cylindrical Boilers still used sea water but were easier to clean and maintain because of the fewer number of internal stays.
c.1870's - Present
Scotch Boilers were a natural development of the Cylindrical Boiler. They were more robust and could generate a working steam pressure of up to 200 pounds per square inch. The design incorporated greater ability to roll iron plates leading to greater strength, thicker plating and fewer riveted joins. Scotch boilers could accommodate greater steam pressures and were developed from the 1870's and have been fitted into vessels until well into the twentieth century. They were originally made of iron, then incorporated steel sections, until they were entirely constructed of steel. Scotch Boilers used fresh water in a closed circuit system. The steam originating from the boiler fed into the engine, through a surface condenser and the water was re-circulated to the boiler. The boilers, like the earlier Cylindrical types, only required stays across the two flat faces.
Many examples can be found on New South Wales wreck sites ranging in size from ten to sixteen feet in diameter. They are usually the most high profile element of a steam shipwreck.
Photograph of boiler by Mark Spence
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In text references:
1 Richards, Mike, 1996, Pig and Whistle Run. Grafton. p.9.
2 Richards, Mike, 1996, Pig and Whistle Run. Grafton. p.5-16.
3 Parsons, Ronald, 1979, Steamers in the South. Melbourne. p.8.
Page last updated: 31 August 2012