Stobie pole

A Stobie pole is a power line pole made of two steel joists held apart by a slab of concrete in the middle. It was invented by Adelaide Electricity Supply Company design engineer, James Cyril Stobie (1895-1953). He used the materials easily at hand due to the shortage of timber caused by the arid and treeless nature of much of South Australia. His invention of two spare pieces of railway track bolted together with cement in the middle was patented in 1924.

The first poles were erected in South Terrace, Adelaide in 1924, and were then used extensively in building the electricity transmission and distribution infrastructure throughout the state. The poles carry voltages from 415 to 275,000 volts and come in various sizes from 9 to 35 metres in length. The expected service life of a Stobie pole is predicted to be in excess of 80 years. It is now commonly regarded as a South Australian icon. ETSA Utilities manufactures Stobie poles at a plant in Angle Park, South Australia.

Its modern construction is a composite of two steel beams connected intermittently by bolts to manage compressive buckling, with the gap between the beams filled with concrete. The bolts transfer the shear, with an equal number of bolts above and below ground. The poles are tapered from ground level to the top and the toe. This construction utilises the tensile properties of the steel, giving the poles excellent properties in bending. The poles are fireproof, rotproof, and termiteproof.

Some have described them as 'hideous', with attempts to beautify their appearance through Stobie pole gardens and Stobie pole art projects. Renowned artist Clifton Pugh painted Adam and Eve in the Garden of Eden on a Stobie pole in 1984, but was asked to "cover up" the genitals on his painting.


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