1833 - Roentgen's Compound Steam Engine Tug

Gerhard Moritz Roentgen, 38 years old, a former naval officer and an engineer, who co-founded the Nederlandsche Stoomboot Maatschappij (NSM) in 1823, has invented a new compound steam engine and has decided to apply it to a sea-going vessel, a paddle wheel steam tug named Hercules, that he designed four years ago.

Roentgen discovered steam machinery and iron industry through a long study voyage in England on behalf of the Dutch government in 1818-20. As early as 1822, he co-founded a shipping line which built the first Dutch steamboat, De Nederlander (1823). The NSM, initially a shipping line succeeding to the ephemeral first body, founded its own shipbuilding company named Fijenoord in 1827. The company appealed much interest from German merchants through striking demonstrations of cargo transport on the Rhine and from industry, especially from newly established John Cockerill, a Roentgen's acquaintance, as a partner and as a supplier of machinery.

Definitively a visionary, Roentgen thought that the key of steam navigation was high pressure so as to save weight, space and fuel. As for warships, he also envisioned key features as armour, iron hull, steam and big guns of the Paixhans' type as early as 1825. He therefore proposed to set a steam engine in a sailing frigate, which was tried on the Rijn in 1826-27 but ultimately failed for unknown reasons - may the hull scantling be too light for the heavy machinery? The same fate plagued the Atlas, launched in 1826, a ship that was meant to being the first steam ocean liner to the Dutch Indies. It is said that the hull was not rigid enough for the machinery weight and twisted.

A two-stage steam engine is certainly not a new idea. It was invented and patented by fertile Inventor John Hornblower, 28 then, in 1781. He was prevented from using it, as his next invention of a rotary engine, by the ruthless and vindicative businessmen Boulton & Watts who achieved to keep their grip on steam power. It was reinvented in 1804 by Woolf, 38 years old then, who had developed and patented high pressure flue boilers in 1803, which enabled and called the possibility of two stages of expansion. Since then, it has been applied to a number of so-called Cornish engines pumping water out of coal mines.

It must be said that a Woolf engine had been set in 1824 in the 150-ton steamboat Henry Eckford, meant to transport passengers between New York and Albany. The machinery was made by the same Allaire Iron Works that already supplied the machinery of Savannah (1819) The two boilers feed the two-cylinder engine at the record figure of six atmospheres. The high-pressure 12-inch cylinder and the low-pressure 24-inch one display a 4-foot stroke. The boat is renowned for her speed of eight or nine knots that she maintains all along the trip that lasts half a day.

Hercules was launched in 1827 in Boom, near Antwerp, but remained in waiting for her machinery. Lately Roentgen imagined re-using the material from two failed projects, the twin high-pressure cylinders meant to a steam barge, Agrippina, which haven't found her usage, and the large low-pressure cylinder made for the Atlas, to compose a compound two-stage engine by setting a steam receiver between the two engines.

The boilers produce steam at a pressure of four atmospheres - a high pressure for our days, less risky than the one set in the Henry Eckford. The two hp cylinders display a 21-inch diameter and a 5-inch stroke, while the lp one displays a 54-inch diameter. Together they produce 200hp.

Commissioned in 1829 with the only hp engine, Hercules has finally been successfully equipped with the whole set. He has proven his strength by tugging the Agrippina and finally up to six barges.

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1819 - A Steamship Crosses the Atlantic ocean

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IN RETROSPECT FROM TODAY

Note A - on Hercules' fate

Hercules will serve as a tug on the Rhine then on the ocean as late as 1870. Forty years of duty prove it will have been a sound ship fitted with a robust machinery.

Note B - on the usage of double expansion on ships

The naval architects will remain for long reluctant about high pressure boilers. There were already boiler explosions with the typical low pressures of five to ten psi above the atmosphere, especially two accidents in 1824 which were attributed to poor metallurgy.. Enormous advantage of compactness and of efficiency nevertheless pushed the builders of steamboats for the Mississipi river to go to high pression, up to six atmospheres from the 1820s. Many boiler explosions have occurred with heavy casualties since the beginning, and carry on during the next decades. The Henry Eckford herself blows up in 1841.

Charles Dickens, in American Notes, 1842

The advent of compound engines on sea-going vessels will be postponed up to 1858, with the launch of steamship Bremen, the first liner of the brand new Norddeutscher Lloyd line, built by Caird & Company at Greenock.