PROTOTYPE – FROM SAIL TO STEAM
Rodger describes the challenges faced and overcome in transferring the innovation of steam power to the challenging environment of the ocean-going ship.
Britain has always been regarded as a maritime nation. At the heart of this has been its ships and shipping heritage, adopting and adapting technologies to further its commercial trading activities, and not always as peaceful neighbours.
That heritage was largely built on sail – both merchant and military – but the Victorian era saw the beginnings of major technological advances, in both construction and propulsion. In the early years, and prior to the reign of Queen Victoria, the first use of iron and perhaps crude attempts to harness the power of steam had already appeared.
One of the main issues when it came to steam power at sea was of course cost – in the 1800s, sail still ruled supreme, and the wind was free! Another aspect that presented a challenge to steam at sea was the simple fact that you could not transfer a Newcomen-type engine, or a boiler that was supported by bricks/stones and timber, to a ship.
Yet as the use of steam progressed on land, it was mirrored at sea, especially from the 1820s onwards, although during that time it tended to be used primarily on canals, rivers, or in coastal waters. By the end of the century coal-fired merchant and military vessels, with rotary steam engines ruled the roost, and were only supplanted in the 20th century by turbines and of course oil firing and later still diesel power.
Early experiments
In the late 1700s, these were a long way off – propelling a vessel through water by steam power was for the experimenters. Amongst the first was Edinburgh-based mechanic William Symington. He had made successful experiments on Dalswinton Lake, near Dumfries, in the late 1780s and patented a steam engine design in 1787 – he was largely responsible for the use of steam on water.
By the turn of the century, Symington’s technology appeared in the form of the ‘Charlotte Dundas’ – a wooden-hulled vessel built at Grangemouth as a tug for use on the Forth-clyde Canal, and which successfully hauled loaded 70-ton barges at around 6 mph.
We have the American engineer Robert Fulton to thank for the next stage in the growth of steam power at sea. Fulton had been working with the French Navy and seen the Charlotte Dundas in operation in Scotland. Returning to America he contracted English locomotive manufacturer Boulton & Watt to build a 24hp engine. This was intended – along with the copper boiler from Cave & Son in London – to be installed in a vessel to be built in New York.
Fulton returned to America in 1807, and by August the new steampowered vessel was ready for trials, which were a great success. The
‘North River Steam Boat’ (unofficially the ‘Claremont’) – became the first steam-powered vessel to provide a commercial service as a ferry between New York and Albany. During its construction numerous changes were made to the original Boulton & Watt designs, with Fulton and his partners using their own ideas and most of the components and fabrications were the result of local engineering and foundry innovations.
Back in Britain, the first steamship to run in regular service was the Clyde-built ‘Comet’ in 1812, operating between Glasgow and Greenock. The Comet was built by John Wood and Co at Port Glasgow to the design of Henry Bell and equipped with a single-cylinder beam engine
– the cylinder was 12½ inches in diameter with a 16-inch stroke, a 6-foot diameter flywheel attached to one side.
Mechanically and operationally, the vessel was a success, but it did not pay its way financially. John Wood & Co built three more paddle steamers with similar mechanical layouts: The
‘Elizabeth’, ‘Clyde’ and ‘Glasgow’, and before long, other builders began to launch their own steam-powered river-going vessels.
Six years after the Comet began operations, in the USA the hybrid sail/ steam ship the ‘Savannah’ was launched. This was the first ship intended for a trans-atlantic service and was built as a three-masted packet ship with full sail, but was also equipped with a pair of paddle wheels, driven by a single 90hp steam engine.
Engine Designs
In the early years, the dominant steam engine designs were based around those from the Boulton & Watt stable, in the form of beam engines supplied with steam from a multi-tubular boiler. It was common practice in early designs to allow steam to be admitted to the cylinder for the full length of the stroke – but this was wasteful and inefficient. The solution was to cut off the supply of steam part way through the stroke, saving steam, fuel and money, and variable cut-off steam engines became the norm.
The first shipboard steam engines had still basically transferred the single-cylinder beam engine to the hull of a wooden ship. It was impractical to install a beam above the then vertical cylinder since it would be above deck level, and so most steam engines were ‘side-lever’ types. In this, the centre of the beam was either near or at the bottom of the cylinder, with connecting rods linking up to the piston and the paddle shaft – the lower the placement of the beam driving long connecting rods the better.
The side-lever engine was a design of three key elements: a single cylinder, air pump and condenser (jet and surface types), with appropriate parallel-link motion attached to the connecting rods, provided a marine steam engine that was in common use between the 1820s and 1840s. In fact, the Cunard company was still operating transatlantic mail paddle steamers with side-lever engines until 1862, when the steamer ‘Scotia’ was launched and fitted with an enormous pair of these engines. They were simple, rugged and they worked, but they were inefficient, and in ships such as the Scotia consumed more than 350 tons of coal a day at speeds barely above 14 knots.
Throughout the 1820s and 1830s, engine builders on the Mersey, Clyde and Thames rivers supplied side-lever engines to shipping lines and some Admiralty-sponsored projects, and the earliest of these was ‘HMS Lightning’, which when introduced in 1823 boasted a pair of side-lever engines from Maudslay, Sons & Field. On the Mersey, Caird & Co built a number of side-lever types for the Royal Mail fleet in the 1840s, along with Maudslay’s – which had the honour of being the first company to supply engines for ‘Enterprise’ on the first steam voyage to India.
The American builders also adopted the side-lever design for the
Atlantic trade, and amongst the first of these was the SS ‘Pacific’ of 1849. Some early river steamers in the USA included the ‘walking beam engine’, which used numerous wrought-iron trusses, and a large A-frame style constructions to connect to the piston rod and on to the paddle wheels.
One of the most intriguing designs appeared in 1827 and proposed connecting the piston rod directly to the paddle-shaft crank – a direct drive from the cylinder. This was the oscillating engine, and its first practical application was made by the Maudslays – in this case Joseph Maudslay. This style first appeared on a Thames pleasure boat and later a cross-channel packet, the ‘Dover Castle’. In the 1830s, improvements to the basic design were implemented, with cast-iron frames replaced by wrought iron, while D-type slide valves operated through eccentrics became the standard for this layout.
The Admiralty bought into the idea with enthusiasm, and many naval vessels were fitted with oscillating engines, mostly built by John Penn & Sons of Greenwich. Confirming the design’s status and popularity, John Scott Russell & Co was awarded the contract and supplied the oscillating engines for Brunel’s ship the ‘Great Eastern’ in 1858.
The oscillating engine proved popular for shallow draft, river and coastal ferries as well as pleasure craft – including lake steamers. Some classic examples of paddle steamers appeared on lakes in Switzerland,
Italy, Germany, and other European locations, and across the world as far away as Australia.
As paddle wheels for ocean-going vessels were displaced by screw propulsion, changes in the layout of the machinery space were made, and these included placing cylinders horizontally, with the propeller shaft driven through gearing.
This format was used by both naval and commercial ships in order to keep a low profile, but in the last quarter of the Victorian era, vertically mounted cylinders became common, and provided the possibility of a direct drive from the cylinder connecting rod to the propeller shaft.
This layout in the machinery space was rapidly adopted as standard practice, whether simple expansion or compound, a vertical engine, supplied with steam from a Scotch boiler, with increasing sophistication, higher pressures and superheaters. By 1900 a major change in the steam plant had also arrived in the shape of the water-tube boiler.
“They were
simple, rugged and worked, but they were inefficient, and in ships
such as the Scotia consumed more than 350 tons of coal a day...”
Compound Designs
Vertical engines soon became commonplace with screw propellers, and eccentric link motion as standard, and from simple, through double and triple-expansion compound cylinders.
These provided greater efficiency, added to by the arrival of higher pressure Scotch-type, and later water-tube boilers.
The earliest compound engines were described as inverted vertical types, with the high-pressure cylinders mounted in tandem and on top of the low-pressure. This was the arrangement installed in the P&O liner ‘Carnatic’ in 1863, which had all four of its cylinders arranged in a fore-and-aft position.
The low-pressure cylinders were 8 feet in diameter, the high pressure 3 foot 7 inches, with a common 3-foot stroke, and were supplied with steam at 26lb/sq in which was superheated by externally attached copper superheaters. On the outer end of this assembly were mounted the surface condensers, with cooling water circulated by a separate engine.
It was another decade before this type of power plant began to gain a major foothold, with a good example being the White Star liner ‘Britannic’, built by Harland & Wolff in 1874. The engines in this vessel were much larger tandem compounds, in which the high-pressure cylinders were 4 feet in diameter, the low pressure 6 foot 11 inches with a common stroke of 5 feet – the whole assembly was some 14 feet in height. These engines were built by Maudslay, Sons and Field.
Triple expansion
The final stage in the development of the marine steam engine in the transition from sail to steam was likely the introduction of tripleexpansion working. In the same year as the Britannic arrived, John Elder & Co of Govan had built the screw steamer ‘Propontis’, fitted with a triple-expansion engine design that would become the standard marine steam engine for another 50 years.
The ship was commissioned by Liverpool shipowner W H Dixon, and at John Elder’s yard, A C Kirk set about the design of this new engine which would provide maximum fuel economy. The inverted vertical design included a 1 foot 11-inch diameter high-pressure cylinder, a 3 feet 5-inch intermediate, and 5 feet 2 inches for the low-pressure, with a common stroke of 3ft 6 inches, fed with steam at 150lb/sq in from water-tube boilers.
The ‘Propontis’ was not, however, a great success – largely down to boiler problems, and it was not until the arrival of the SS ‘Aberdeen’ in 1881 on the Australia and China runs that the new triple-expansion design finally achieved sustained success.
By 1889, the White Star line had shown just how far the tripleexpansion engines had come with the arrival of the ‘Majestic’ and ‘Teutonic’ from Harland & Wolff’s in Belfast – these were the first ships in the White Star fleet in which sail power finally came to an end. It was the turning point in the move from sail to steam in commercial service and mirrored the transition in naval vessels too, with new ships fitted with tripleexpansion engines from 1885.
To provide the necessary power to drive these engines, the more efficient water-tube boilers had their pressures raised from 130lb/sq in in the first ships, to an almost standard 155lb by 1895. In the final years of the century, the world-renowned Vickers Shipyard at Barrow-in-furness turned out the heavy cruiser HMS ‘Powerful’, – the boiler pressure for this vessel’s triple-expansion engines had reached no less than 260lb/sq in.
This latest Royal Navy warship was some 14,000 tons in displacement, with a draught of 27ft and a beam of 71ft, but perhaps the most impressive statistic was the power. HMS Powerful could generate 25,000hp to drive its twin screws, through no less than 48 of the ‘Belleville’ design of water-tube boiler and its twin triple-expansion steam engines built by Vickers.
This was a fitting close to the changeover from sail to steam at sea perhaps, for both commercial and naval ocean-going vessels.
Raising Steam
Putting a coal-fired boiler on ship – be it a ferry or a transatlantic vessel – was never an easy prospect, and simply transferring existing land-based technology to the water was not ideal.
Several different designs appeared, some more successful than others. The early trials using ‘haystack’ boiler designs among others resulted in numerous explosions, due to faulty materials, design or construction.
As a result of this activity, a Government inquiry held in 1817 resulted in legislation that all ships must be registered, and boiler designs driven by rules requiring the use of wrought iron or copper for their construction. These regulations also stated that two safety valves must be fitted, and the boilers tested at three times their normal working pressure before being passed for installation.
From 1820, the ‘box boiler’ was effectively the standard design, with rectangular flues leading from the furnace, through the water tank on as long a path as possible to ensure the largest heating surface, and then up and out through the ship’s funnel. These boilers were big enough to allow a man to crawl inside, or even to stand up to enable maintenance or repairs.
The sides of the furnaces were flat, but the roof and floor were usually slightly curved, and the distance from the firebars to the floor needed to be deep enough to allow adequate air flow. Keeping the whole assembly together was achieved with numerous iron stays, and this form of boiler persisted from the 1820s to the 1850s.
Thus arrived the marine boiler with a typical working pressure of between 30 and 40lb/sq in and described by Sennett in his 1899 treatise The Marine Steam Engine as “low-pressure boilers”. They were a heavy fabrication, and although proving to be good steamers were soon replaced by the later, conventional cylindrical designs.
The next evolutionary step was the “high-pressure boiler” – according to Sennett these were either return or through-flue types – operating at between 150 and 180lb/sq in.
Multiple tubes
Boiler development made its next advance through the use of smoke tubes in similar form to the multitubular design adopted by Stephenson on the railways. The first recorded application in Britain was for HMS ‘Janus’, launched in 1844 – its use was promoted by Thomas Cochrane, tenth Earl of Dundonald, who was a noted advocate of steam at sea. In his approach, the boiler was fired from one end, leading to a combustion chamber at the opposite end, where the hot gases then passed through the water space via smoke tubes, then on to the smokebox at the front and through the uptake to the funnel.
Various changes and innovations were made over several years, fuelled
by the demand for higher working pressures taking hold following the wider use of surface condensers, and compound/double expansion from around 1860. The traditional flatsided box boilers were unsafe at higher pressures, and so the main design change was the adoption of cylindrical shapes for the boiler casing and flues, retaining the successful smoke tubes and combustion chambers.
During this time the most well-known marine steam boiler appeared – the ‘Scotch Boiler’ – which was adopted by many shipbuilders, and in its basic design was actually a descendant of the ‘Lancashire Boiler’ used in cotton mills. Where the Lancashire normally had twin tubes for firing, Scotch Boilers in marine use had two, three or four ‘fire tubes’ at the base of the boiler, with the gases returning to the front of the boiler through the combustion chamber and smoke tubes – commonly referred to as a ‘return-tube boiler’. This type of Scotch Boiler was adopted universally in the later Victorian era, and with hot gases passing through the water space twice, provided the same heating surface of a Lancashire Boiler, but in half the length.
Water-tube boilers had appeared even earlier than the ‘locomotive’ style cylindrical design, one of the first produced in 1804. In this two sets of inclined water tubes – closed at the lower end – connected to an upper, central drum, with a fire grate at the lower ends.
“Three-drum water-tube boilers were
fitted in some Royal
Navy late 20th century frigates, and were manufactured
up to the mid 1970s...”
Compact power
A similar layout was used on John Penn’s Thames paddle steamers, but following the development by the French inventor Belleville the design was adopted more widely for marine use. The ‘Belleville Boiler’ appeared in 1850, and by 1880 the general design consisted of a series of slightly inclined, large-diameter tubes running from front to back over the fire grate.
These boilers provided – in a compact space – a much greater water capacity, and so greater evaporative capacity than the Scotch Boilers – and became popular for large ocean-going vessels, burning coal and later oil as fuel. Their design was further developed through the Yarrow, Thornycroft and Palmers-reed types, to makers that remain household names to this day, including Babcock & Wilcox. Three-drum water-tube boilers were fitted in some Royal Navy late 20th century frigates, and were manufactured up to the mid 1970s.
The classic UK example is the Palmers-reed design from Palmers shipyard at Jarrow. This appeared after 1893, developed by engine works department manager J W Reed. Viewed end-on the boiler was shaped like an inverted V, with one steel tube/ drum at the top and two at each of the bottom corners, between which were sandwiched typically three fire tubes. Two banks of water tubes connected the lower and upper drums, the upper drum only part-filled with water to create space for steam generated by the inclined tubes.
Water-tube boilers operated at higher pressures and were much lighter than the older generations of boilers, especially when used in ships, and were ideal for the next generation of steam engines used at sea – the steam turbine. But that is a story for another day...