CABLE LAYING

Evening Post, Volume CXXVI, Issue 156, 30 December 1938, Page 13

CABLE LAYING

NEW METHOD USED

MOLE PLOUGH PRINCIPLE

By the adoption of the principle of the mole plough the Post Office engineers are now able to lay subterranean cable more rapidly and efficiently than to erect poles and install overhead lines. The new method, which is

being put into practice in many parts of New Zealand, also eliminates the upkeep of poles and the replacement of broken insulators, which require frequent renewal. The underground cable, which is heavily sheathed with \ead, will in the course of time replace jnany of the overhead line systems.

Formerly the laying of the subterranean cables would have involved much tedious trenching. By adapting the mole plough principle, however, a quick job is done and one that is much neater. Nearly a mile of cable has been laid by this method at the Milsom Aerodrome, Palmerston North, at a depth of between 18 and 21 inches in five hours, by a staff of eight, whereas ii is estimated that under the old trench-digging method it would have been necessary to employ 50 or 60 men.

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 speciallydesigned carrier unwinds its contents til] the whole length is buried.

It has been found that the 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 mole plough. In one day it buried alongside the main road five drums of* cable of a total length of 1500 yards. Hardly any surface trace was left by 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.