NOVEL PLOUGH

New Zealand Herald, Volume LXXV, Issue 23233, 30 December 1938, Page 11

NOVEL PLOUGH

UNDERGROUND CABLES USE BY POST OFFICE RAPID WORK POSSIBLE Engineers of the New Zealand Post Office have successfully adapted the principle of the mole drainage 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 .'IOO pairs of wires in the largest diameters used in the Dominion. To bury the cables along miles of country roads would formerly have involved long and tedious trenching, with considerable disturbance of the soil. Howpver, the mole drainage plough, as adapted for Post Office use, makes for a quick job and leaves very 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 18in. and 21in. in five hours, by using zhe mole plough drawn by a tractoj\ It is estimated that the same work under the old trenchdigging method would have required the employment of 50 or 60 men. The job was clone mechanically by a staff of eight Method of Working The mole plough differs from the familiar agricultural implement because its blade works under the surface, a vertical steel bar attached to a heavy beam carrying, at the pre-determined depth for the excavation, a steel male and a cutter. The cable to be buried runs down behind the cutter and mole in a bent tube, and as the tractor moves forward, a cable drum mounted on a Specially-designed carrier unwinds its contents until the whole length is buried.

Grass margins alongside the highway are the most suitable places for using this system, as the existence of wilier 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 the mole plough will operate in a wide variety of soils, from heavy clay to light sand. Operations in Hawke's Bay

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 the equipment buried alongside the main road five drums of cable of a total length of 1500 yards. Hardly any trace was left of the work after the tractor had been driven back over the route of the buried cable. This ingenious device is being made in New Zealand to Post Office specifications.