SCREW PROPELLER

Wairarapa Times-Age, 31 December 1940, Page 9

SCREW PROPELLER

INTERESTING HISTORY SUGGESTED by falling SEED-POD. LANCASHIRE ENGINEER'S DISCOVERY. A seed-pod falling from a sycamore tree is said to have suggested to the of a Lancashire engineer the principle of the screw propeller. That he was intrigued by the rotary motion acquired by the pod in its descent through the air, and that it was the year 1681, is all we are told; there appears to be no record of his having attempted to do anything about it. writes Albert George in “P.L.A.” (Port of London Authority). Among the earliest recorded attempts to get something done is that of James Watt, who, in 1770, suggested a “spiral oar” for canal navigation. It was to Dr. Smalls, a college professor who had been.experimenting in that direction, that Watt made the suggestion, and his rough sketch depicting the idea still exists; but the learned professor retorted so discouragingly that Watt subsided.

EARLY PATENT. A patent in respect of a method of ship propulsion by “a wheel with inclined fans or wings, similar to the fly of a smoke-pack or the vertical sails of a windmill,” was granted to Joseph Bramah in 1785. Fixed on a spindle at the stern the wheel “may be wholly under water, when it would, by being turned round either way, cause the ship to be moved backward or forward.” Bramah thus seems to have had a pretty clear conception of the modern propeller but he was before his time, and he failed to arouse public interest.

Nine years later a patent for a similar scheme was granted to a Mr Lyttelton, but he, too, faded out. Then in 1802 a Mr John Shorter, of Doncaster, demonstrated a method of screw propulsion of becalmed sailing vessels, with man-power as the driving force.

Next comes Mr Robert L. Stevens, of Hoboken, New Jersey, who in 1804 carried out successful experiments on the other side of the Atlantic with both the single and the twin screw ideas.

Later in the records are such prominent engineering names as Trevithick, Millington, Lowe, Whytock. Perkins, and Samuel Brown, all of whom experimented to some extent with the screw method of propulsion. The type of screw favoured by the lastmentioned consisted of two blades fixed to a shaft either,in the bow of the ship or at the stern. It was demonstrated on the Thames in 1825, in a vessel 60ft. long, when it developed a speed of about seven miles an hour. The power was supplied by a gasvacuum engine, which also was the invention of Mr Brown.

Another screw aspirant was a London merchant named Charles Cummerow, who took out a patent in 1828. But steamship companies continued to turn a deaf ear, and went on fitting new ships with paddle-wheels in the orthodox manner, while the Admiralty maintained traditional indifference.

IDEA STOLEN. Next we hear a story from France of the type so frequently told in connection with inventions. Frederic Sauvage, a military engineer of Boulogne, on leaving the French army in or about the year 1826, devoted himself to marine engineering. For 10 years he experimented with an idea for a screw propeller, and at last, satisfied with its practicability, he patented it. His research work had so impoverished him, however, that he had got into debt; and for a paltry sum he was imprisoned. During his period in jail, during which his provisional patent expired, two rogues stole his idea and sold it to a shipbuilding firm. The first ship to be fitted with Sauvage’s screw was the Napoleon, a French Government vessel; and in 1839, released from prison, poor Sauvage had the mortification of seeing that ship at Le Havre functioning by means of the screw constructed from his plans. He sued the shipbuilders, but was unsuccessful; and he died at Le Havre shortly afterwards, a broken man.

In the meantime an English farmer had been constructing ship models and trying various methods of propelling them, using a clock spring for power. He was Mr Francis Pettit Smith, and a public demonstration was arranged at the Welsh Harp at Hendon in 1834. with a model having a wooden screw driven by clockwork. In May, 1836, he took out a patent. His next move was to form a company; but no engineer would risk professional ridicule by constructing the necessary machinery. Eventually, however, Sir John and Mr George Rennie not only undertook to construct the machinery, but subscribed a thousand pounds each to the company.

Smith laid no claim to the invention of a screw propeller, but only in its design and in the position in which he placed it—namely, in the “deadwood” between the sternpost and the keel of the ship. In one respect the design was achieved partly by accident, for during one of his trials damage sustained by contact with wreckage rendered the screw more effective. A small steamer was constructed and fitted with a screw in accordance with the Smith formula. Her first trial was made in November, 1836, on the Grand Junctioin Canal at Paddington. Later she was put on the Thames and accomplished a run from Blackwall to Margate in eight and a-half hours. This performance was deemed so satisfactory by the now constituted Smith Screw Propeller Company that orders were given for-the building of a screwdriven seagoing craft of 230 tons, 125 ft. long, and with a 22ft. beam. In due course this vessel, built on the Thames and christened Archimedes. was tried in company with two Dover-Calais mail packets with most satisfactory .results. DIRECTORS IMPRESSED. At this time (1839) the building at Bristol of the steamer Great Britain for the Great Western Steamship Company had just begun, and the directors were invited by the Smith Piopeller Company to take a trip in the Archimedes, and they were so impressed by the ship’s performance, especially in some rough weather which they happened to encounter, that orders were given to suspend work on the!

i machinery of the Great Britain pending a report from the company's engineer. the eminent Mr Isambard Kingdom Brunel. The report was drawn up. and Brunel, in face of a certain amount of opposition, induced the directors to change their plans and substitute a Smith propeller for the intended paddle wheels. Thus fell to the Great Britain the honour of being the first screw-fitted Atlantic steamer. In addition to Francis P. Smith and the unfortunate Frenchman Sauvage, there was yet a third man who was working on the same .idea during the same period. He was Captain Ericsson, of the Swedish navy, who patented a screw propeller in July. 1836, only two months later than Smith.

DEMONSTRATION ON THAMES. Ericsson demonstrated his device on the Thames with a boat called the Francis B. Ogden. She was fitted with two propellers, each sft. 3in. in diameter, and developed a speed of 10 miles an hour. She made several trial excursions, and was on one occasion used as a tug; but, although she did all her promoter claimed for her, and although the tests were witnessed by officials of the British Admiralty, Ericsson received no support whatever in this country. But among those who witnessed the trials of the Francis B. Ogden was Commodore Stockton, of the United States navy, and he was sufficiently impressed to order from Captain Ericsson two small boats fitted ( with his type of propeller. These were i built and taken to America in 1839. The British Admiralty were still, sceptical but eventually agreed to the I construction of a screw-driven ship, i the Rattler, of 900 tons and 200 horse- ( power, and on August 24, 1844 a trial ( was arranged against H.M.S. Prome-; theus, a paddle steamer of similar ton-, nage and power. < ( As was expected, the Rattler (the; new ship) beat the Prometheus, her screw driving her at 9.89 knots against the paddler’s 8.89. The Admiralty next arranged for the Rattler to try her strength against the Alecto. The two ships were tied together stern to stern by hawsers. For some time they tugged against each other with force rp equal that neither vessel moved the other. Then the Rattler began to get the better of the contest, and eventually dragged her struggling adversary away at a speed of nearly three miles an hour.

Thus the screw propeller came into use in three different parts of the world practically simultaneously—the Smith propeller in this country, the Sauvage on the Continent, and the Ericsson in the United States. Of the three promoters, the first-named received most of the honour. He was knighted in 1871, his portrait was placed in the National Maritime Museum at Greenwich, and a model of his ship Archimedes is in the Science Museum at South Kensington. Of Sauvage we read that his actual first screw is (or was) in the Paris Museum of Technology, and of Ericsson there is honourable mention in the annals of the United States navy and of the jiavy of his native Sweden.