GIANT TOWER EXCAVATORS

Press, Volume LXXXI, Issue 24599, 22 June 1945, Page 7

GIANT TOWER EXCAVATORS

ONE FOR LAKE FORSYTH CUT ORIGINALLY BUILT FOR MISSISSIPPI The giant excavator which is to be used in cutting a permanent outlet from Lake Forsyth to the sea is one'of four originally designed for the construction of levees on the Mississippi river and used in the construction of a huge hydro-electric station at Beauhamois, close to Montreal, in Canada, Two of the machines have been imported to New Zealand. The one earmarked for use at Lake Forsyth is being erected at Otaki, where flooding frequently occurs. Although the dimension of the work on which it will be tested is somewhat .small for the capacity of the excavators, the work will give valuable information in the. application of the machines to river improvement work in New Zealand, and will also assist in the training of operators. • Millions of yards of material were shifted by the machines in the construction of the Beauharnois power station. All the water of the St. Law-, rence river passes through this station, which at present has a generating capacity of 700,000 h.p., and on completion its output will be 1,800,000 h.p. The machines are a type of drag-line and are known as tower excavators. The whole machine is approximately 2SO tons in weight and consists principally of two towers—the head and the tail towers, which weight 370,0001b and 290,0001b respectively. The head tower is 130 feet high, and the working span of the whole output ranges up to 1000 feet, and it can therefore operate on a fairly wide river. Each tower has an output of 1,000,000 yards in six months. Briefly, the machines are operated as follows:—a track cable of IJin in diameter stretches from the top of the bead tower to the tail tower, and on this is a carrier supporting the bucket, which is dragged across the area to be excavated. The bucket, which has a capacity of 10 cubic yards, weighs five tons, and discharged its load on the banks, thus forming an embankment or levee. The head tower is mounted on a double rail track and the tail tower on crawler tracks, and as both the towers are self-propelled, they can follow up along a defined path as the excavation proceeds. The machine is powerful enough to deal with any snags or fouls encountered in the river. Electric Drive Each machine is operated electrically by a 600 h.p. motor, which drives a d.c. generator, which in turn supplies power for the individualmqtors on the hauling and trsck gear. The latter consist of three motors of 187 h.p. each. The tall tower is jfiowered with an 80 h.p. Internal combustion engine. The motors are worked on the ward Leonard system, which gives case and flexibility of control. , ■ , Independent Diesel generating plants to brovide electric power are being acquired, so that the exeavitors can be operated independency of the local electric power system, and so that they can also be operated in areas where electricity is not available—for example, in bush-clad valleys or rough back country. '