SMALL DEFECT THAT SLOWED DOWN THE QUEEN MARY

New Zealand Herald, Volume LXXIV, Issue 22741, 29 May 1937, Page 9 (Supplement)

SMALL DEFECT THAT SLOWED DOWN THE QUEEN MARY

THE triumph of the French liner Norraanclie, which has recently made the west-to-east Atlantic crossing at an average speed of 30.99 knots, bo breaking the Queen Mary's record, came at a time when one of the Queen Mary's experts was explaining what happened to slow down the British ship on her maiden voyage last year. It seems that when the Queen Mary failed to come up to expectation it was because some small steel blades in her machinery had gone wrong. The record was missed because a few bits of steel went wrong in turbines which altogether have more than a million of these steel blades. Turbines which drive the dynamos to light cities as well as the screws of transatlantic liners are an invention something more than half a century old, and the idea sprang from the brain of Sir Charles Parsons. Knew All About It A story told about Sir Charles in his later years is that one day in his club a naval captain who did not know him got into a discussion about steam power with the old engineer. After Sir Charles had gone the naval man said to a friend: "Who was that argumentative old gentleman? Ho seemed to think he knew more about my engines than ] do." Sir Charles was the least disputatious of men, but he did know more about naval engines than most, for he had been making the turbines for them since his tiny Turbinia astonished the world at the Diamond Jubilee -Review of 1597 by travelling at 81 i knots. The Admiralty gave him an order for a turbine-driven destroyer, and it attained a speed of over 37 knots, or 4JI miles an hour. The steam turbine had arrived. First Steam Turbine The root idea of the turbine is that of the water-wheel, with steam taking the place of falling water. Parsons had in mind a steam wheel with a row of tiny blades sticking out around it which might be set in motion by jots of steam. The first steam turbine, built in 1884, now stands in the British Science

Museum, near Puffing Billy and tho Rocket. The turbines of the Queen Mary have developed almost as far from the first model as the modern streamlined locomotive has moved forward from the lirst involutions of George Stephenson. In a simple form of modern watorwheel tho water discharged through a nozzle strikes the buckets in turn and makes the wheel revolve. In an improved form the water does not striko the buckets or .blades on the wheel directly, it first passes a ring of im-

movable blades called guides, which direct it on to the blades of a moving wheel. The Parsons turbine is modelled on the second of these ideas. Imagine a great fixed cylinder with a perfectly balanced shaft inside it called a drum, and having hundreds of thousands of little steel vanes or blades arranged round it in rings. • The steam enters the cylinder and strikes against the vanes, turning the

drum which revolves the liner's screw. The steam is constantly directed against these moving blades by curved vanes which are fixed to the inner side of the encasing cylinder. The steam strikes the first row of vanes on the revolving drum, and is then deflected by the fixed guide vanes, so as to be. thrown directly on to the next ring of moving vanes, and so on. The steam returns along spaces around the drum. More Than a Million Blades This description may be taken as a sketch of the turbine, which has been developed by many inventions to reach the complete design. For example, Sir Charles had to arrange his rings of fixed guides and moving blades in sets. The first set was comparatively small, the second set larger, the third larger still. In the first big liner, the Mauretania, fitted with his turbines, which "had in all more than a million blades, the sizes of the blades were successively enlarged. Those at the beginning, where the steam entered, were less than three inches long, but those at the end were 22 inches. Later tests have found the best form of the blades to save steam power. The guide blades must not touch the drum, or the drum blades scrape the inside of the casing. If the clearances are not small enough steam will be lost; and the whole of the inside of the turbine cylinder with its myriad blades must be as exact as the works of a watch. Trouble Ahead That is why, when it was found, at the very outset of the Queen Mary's maiden voyage, that a small piece of metal had been lodged under part of the steam system driving the turbine, the engineers prepared for trouble. At Cherbourg suspicion was confirmed. Pieces of blading in one turbine were found to be missing, and one

blade was fractured in the first row of blades in the first turbinb examined. In each turbine was some damage to the first row of blades. This tiny damage was sufficient to reduce the Queen Mary's speed, and, till it was put right, compelled her for three voyages to steam under reduced power and at lower speed.