CABLE LAYING

Waikato Times, Volume 123, Issue 20692, 30 December 1938, Page 7

CABLE LAYING

POST OFFICE METHODS USE OF THE MOLE PLOUGH MILE WORKED IN FIVE HOURS New Zealand's Post Office engineers have successfully adapted the principle of the mole drainaign plough to the laying of cables underground. In the course of time many of the aerial line systems will give place to the underground cable, heavily sheathed with lead, and containing as many as 300 pairs of wires in the largest diameters used in the Dominion. To bury these cables along miles of country roads would have formerly involved long and tedious trenching, with considerable disturbance of the soil. But the mole drainage plough, as adapted for Post Office use, makes for a quick job and little sign of It on the surface. At the Milsom Aerodrome, Palmerston North, nearly a mile of cable was laid at a depth of between 18 and 21 inches in five hours, by uMng the mole plough drawn by a caterpillar tractor. It is estimated that the same work under the old trench-digging method would have required the employment of fifty or sixty men, though the job was done mechanically by a staff of eight. Operation Described The mole plough differs from the familiar agricultural implement because its blade works beneath the surface, a vertical steel bar attached to a heavy beam carrying, at the predetermined depth for the excavation, a steel mole and a cutter. The cable to be buried runs down behind the cutter and mole in a bent tube, and as the caterpillar tractor moves forward. a cable drum mounted on a specially-designed carrier unwinds its contents until the whole length is buried. The grass margins alongside the highway are the most suitable places for using this system, as the existence of water and other reticulations in populous areas creates a problem which must be overcome by careful trenching with the pick and shovel. It has been found that tbe mole plough will operate in a wide variety of soils from heavy clay to light sand. If there are unexpected obstructions, the machinery is safeguarded against damage by including in the haulage chain a link of wire, which will snap before a dangerous strain is imposed on the plough. A big cable carrying 150 pairs of wires is being laid between Hastings and Napier by the mole plough. in one day it buried alongside the main road five drums of cable of a total length of 1500 yards. Hardly any trace was left of this operation after the tractor had been driven back over the route of the buried cable. This ingenious and highly economical device is being made in New Zealand to Post office specifications.