MODERN ENGINEERING.

Waimate Daily Advertiser, Volume XXIV, 25 June 1928, Page 5

MODERN ENGINEERING.

MARVELLOUS MACHINES. MIGHTY “CREEPER” CRANES. Cranes that can lift and carry 122 tons have been specially built for one job; then they will be scrapped. Modern engineering feats call for the most elaborate apparatus, says an English writer. Aa works of engineering have grown greater so have the tools employed in them. On a big job today as much as a quarter of the total cost may be for colossal machines and temporary structures, which are little more than scrap when the work in hand is finished. The two “creeper" cranes built for the erection of Sydney Bridge at a cost of nearly £lOO,OOO are examples. This bridge, a great steel arch to span Sydney Harbour, rises in the middle to a height of 450 ft—nearly three times the height of Nelson's Column! And the mighty creeper ’ cranes are designed to crawl out along the top of this arch, up a slope of about one in four, on carriages 120 ft wide, until they reach the centre. The main jib of eaeh crane can lift a weight of 122 tons at a rate of 124 ft per minute. Slow, but when one thinks that 122 tons is the weight of a healthy locomotive. and that this, dangling at the end of a 600 ft cable, is no plaything, he is con tent to play for safety. The slowest movement of all is when the whole crane creeps up the arch, heaving its 620 tons of steel and machinery along at an impre.-sive one foot per minute. Besides the big main jib. each crane carries a smaller 25-ton jigger, a 5-ton walking crane, and two derricks. And there is no part of this wonderful machine that is not made “fool-proof.” If the driver is taken ill while the crane is climbing or hoisting, it stopn automatically. Although the Sydney cranes are the largest ever built for use on one job only, they are not the biggest in the world. In the main basin of H.M. Dockyard, Rosyth, is a 250-ton crane that was used on the repair of H.M.S. Lion and other ships after the Battle of Jutland. And the foremost place of all must be given to a. steam floating crane that will lift 350 tons and is built on a giant pontoon with twin screw engines. But, needless to say, these two have not been built merely for a couple of years, work, like their Sydney brothel's. Another of the mighty tools used in connection with the Sydney Bridge is the newtesting machine, built at Middlesbrough at a cost of £20,000. This is the largest testing machine in the world. It can apply a load of 1250 tons—this is equivalent to the weight of 100 London buses. The next largest testing machine in England—at Birmingham University—only has a quarter of this capacity. It can crush or snap great burlt-up steel girders 50ft long arid 40 square inches in cross section. It has jaws of forged steel that weigh many tons each, and the crushing and recording of the load applied is done by eight 12in. turned steel cylinders, 76ft long, that weighs 2j tons apiece. Among its other diversions it can test a 6in. thick steel hawser to destruction, the wires snapping with a noise like pistol shots, till suddenly they all go with a flash and recoil like that of a 6in. gun. And all the time the machine measures the load applied to within a hundredweight and the stretch of the cable to witbin a thousapdth of an inch! For its satellites the “tester” has a 30ton walking crane overhead to feed the cables or girders into it for testing. Some of these test pieces weigh as much as 4 tons and cost £l5O each to make. Great girders they are, 50ft long and several feet wide, like any of those that carry the London railways over the Thames. And in half-an-hour the tester has crippled them. But the results are invaluable to the designers of a bridge of this size. The pumps, cost £50,000. Another little item for the estimating department on this “outsize” job!

A great deal of “last word” machinery is now being installed at British collieries. The biggest dynamo is one of a million volts, used on the Continent to convert coal into electrical pow’er at the pithead. But already some of 132,000 volts have been built for this purpose in England. Another marvel is the biggest plough in the world, recently sent to Cuba from England. This monster can plough a, width of 10ft at a time to a depth of 2ft. It weighs 20 tons, and is driven by at 220 h.p. engine. As it travels at about the same rate as a horse plough, its economy in u.se is prodigious.

Excavators have made giant strides of late. The most up-to-date is a machine like a huge tank that runs on two caterpillar wheels. Between these is a revolving drum fitted with semi-circular steel blades that scoop out a trench 10ft deep and 6ft wide as easily as if they were mowing grass.

The world, in fact, is approaching the time when the tools used in big engineei - ing works will be larger and more costly than were most, jobs themselves twenty years ago.