A Stobie pole is a power line pole made of two steel I-beams, joined by tie-bolts, and held apart by a slab of concrete. It was invented by Adelaide Electric Supply Company engineer James Cyril Stobie, who suggested the use of readily available materials due to the shortage of suitably long, strong, straight and termite-resistant timber in South Australia.
They have continued to be used in the state capital, Adelaide, and around South Australia ever since, and there are some in other places in Australia as well. Since the 1980s, many Stobie poles have been decorated with artworks or surrounded with plants to beautify them.
In July 1924 engineer James Cyril Stobie (1895–1953) [1] submitted the patent application for his pole design in both English and French. It was accepted in November 1925. Stobie described his invention as
...an improved pole adopted to be used for very many purposes, but particularly for carrying electric cables, telegraph wires... [it] consists of two flanged beams of iron or steel, preferably rolled steel joist of 'H' or of channel sections, placed one beside the other with their flanges inward and preferably at a very slight angle one with the other and held together by means of tie bolts, the space between them being filled with cement concrete. [2]
A second patent was granted to Stobie and Frederick William Herbert Weadon in 1946. With John Ragless Brookman they formed The Stobie Pole Syndicate [3] for the purpose of patenting the design and then selling the patent or manufacturing rights. The Hume Pipe Company became their first agents and, while there were numerous international enquiries, as of the mid-1990s South Australia remained the only place where they are widely used. [2]
The first poles were erected in South Terrace, Adelaide city centre, in 1924, and were then used extensively in building the electricity transmission and distribution infrastructure throughout the state. The Stobie pole was central to the speedy expansion of Adelaide Electricity Supply Company's supply. It was cheap and simple to produce, had a uniform appearance, saved an enormous amount of timber from being harvested, had a long life expectancy and, at the time, was seen as more environmentally sensitive. [2]
Stobie poles are also common in Broken Hill, as well as the Darwin CBD, and there are a few thousand installed across Tasmania.[ citation needed ] A few also exist in Canberra [4] and isolated settlements in the Goldfields-Esperance region of Western Australia such as Eucla and Rawlinna.[ citation needed ]
SA Power Networks review alternative pole designs available on the market from time to time and has yet to find one with the benefits offered by the Stobie pole, which include long life, low cost and ease of maintenance, and resilience in bushfire and flooding events. One disadvantage is greater susceptibility to lightning strikes. [5]
Each year SA Power Networks manufactures around 4,500 Stobie poles at a plant in Angle Park, South Australia. [5]
The poles carry supply voltages from 240 to 275,000 volts and come in various sizes from 9–26 m (30–85 ft) in length, though studies indicate heights to 36 m (118 ft) are feasible. [6] The 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. [5] [7]
Its modern construction is a composite of two steel I-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 uses the tensile properties of the steel, giving the poles excellent properties in bending. Stobie pole strength in the strong direction may be up to 4.5 times the weak direction strength. [8] Small holes through the concrete enable attachment of modular cross-arms, insulators and other hardware. The poles are fireproof, rotproof, and termiteproof. Stobie poles are widely regarded in Australia to be dangerous to vehicles, with collisions sometimes "almost cutting the vehicle in half". [9] [10] [11]
Stobie pole designs are calculated to ensure the installation uses a suitably sized pole. Factors such as physical mass (static load) of transformers, cross beams, voltage regulators, protection devices, conductors (including tension), etc. are considered, and the wind loading (dynamic load) of this equipment must also be calculated. In some cases the wind loading factors far exceed the static load values. [8]
Stobie poles were first used for art in the 1980s by pioneering artist Ann Newmarch, who lived and worked in Prospect. [12]
Artist Clifton Pugh painted Adam and Eve in the Garden of Eden on a Stobie pole in 1984, but was subsequently asked to "cover up" the genitals on his painting. [13]
Since then, various attempts have been made to beautify their appearance through Stobie pole gardens [14] [15] and Stobie pole art projects. [16] [17]
SA Power Networks has an application process for submitting designs for Stobie pole art, used by community groups, artists, and primary and high schools, which have painted murals or installed mosaics on Stobie poles located outside their premises. [5]
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. In a more general context, a coupling can also be a mechanical device that serves to connect the ends of adjacent parts or objects. Couplings do not normally allow disconnection of shafts during operation, however there are torque-limiting couplings which can slip or disconnect when some torque limit is exceeded. Selection, installation and maintenance of couplings can lead to reduced maintenance time and maintenance cost.
A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength ; for easy attachment/transfer of contact force with another object ; or for stabilizing and guiding the movements of a machine or its parts. Flanges are often attached using bolts in the pattern of a bolt circle.
Electric power distribution is the final stage in the delivery of electricity. Electricity is carried from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 33 kV with the use of transformers. Primary distribution lines carry this medium voltage power to distribution transformers located near the customer's premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level.
Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at lowest cost. Its distinguishing feature is that the earth is used as the return path for the current, to avoid the need for a second wire to act as a return path.
A transmission tower, also known as an electricity pylon or simply a pylon in British English and as a hydro tower in Canadian English, is a tall structure, usually a steel lattice tower, used to support an overhead power line.
A distribution transformer or service transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. The invention of a practical efficient transformer made AC power distribution feasible; a system using distribution transformers was demonstrated as early as 1882.
A utility pole is a column or post usually made out of wood used to support overhead power lines and various other public utilities, such as electrical cable, fiber optic cable, and related equipment such as transformers and street lights. It can be referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, depending on its application. A Stobie pole is a multi-purpose pole made of two steel joists held apart by a slab of concrete in the middle, generally found in South Australia.
A plate girder bridge is a bridge supported by two or more plate girders.
I-beam is a generic lay term for a variety of structural members with an I or H-shaped cross-section. Technical terms for similar items include H-beam, w-beam, universal beam (UB), rolled steel joist (RSJ), or double-T. I-beams are typically made of structural steel and serve a wide variety of construction uses.
Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.
A girder is a beam used in construction. It is the main horizontal support of a structure which supports smaller beams. Girders often have an I-beam cross section composed of two load-bearing flanges separated by a stabilizing web, but may also have a box shape, Z shape, or other forms. Girders are commonly used to build bridges.
Structural steel is a category of steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, sizes, chemical composition, mechanical properties such as strengths, storage practices, etc., are regulated by standards in most industrialized countries.
The Electricity Trust of South Australia (ETSA) was the South Australian Government-owned monopoly vertically integrated electricity provider from 1946 until its privatisation in 1999.
A girder bridge is a bridge that uses girders as the means of supporting its deck. The two most common types of modern steel girder bridges are plate and box.
Glenunga International High School (GIHS), formerly Glenunga High School (GHS), is a publicly-funded international school in Adelaide, South Australia. It is located approximately 4 km (2.5 mi) south-east of the Adelaide city centre in the suburb of Glenunga, between L'Estrange and Conyngham Streets, adjoining the major thoroughfare Glen Osmond Road. The school serves the surrounding suburbs of the cities of Unley, Burnside and the Adelaide Hills.
Mobile cell sites are infrastructures transportable on trucks, allowing fast and easy installation in restricted spaces. Their use is strategic for the rapid expansion of cellular networks putting into service point-to-point radio connections as well as supporting sudden increases in mobile traffic in the case of extraordinary events. Mobile cell sites are also used by law enforcement organizations to gather intelligence. Mobile cell sites require neither civil works nor foundations, just minimal requirements like commercial power and grounding. The mobile units have been designed to be a temporary solution, but if requested, they can be transformed into permanent stations.
Sir George Brookman KBE was a South Australian businessman who made a fortune from a gold discovery in Western Australia, and is remembered as a generous benefactor of the South Australian School of Mines and Industries and the University of Adelaide.
Ann Foster Newmarch, known as "Annie", was a South Australian painter, printmaker, sculptor and academic, with an international reputation, known for her community service to art, social activism and feminism. She co-founded the Progressive Art and the Women's Art Movement (WAM) in Adelaide, and is especially known for her iconic 1978 colour screenprint piece titled Women Hold Up Half the Sky!.
The South Australian blackout of 2016 was a widespread power outage in South Australia that occurred as a result of storm damage to electricity transmission infrastructure on 28 September 2016. The cascading failure of the electricity transmission network resulted in almost the entire state losing its electricity supply, affecting 850,000 SA customers. Kangaroo Island did not lose its supply, as the Kangaroo Island power station had been built to supply the island for the contingency of a failure in the power cable under the Backstairs Passage.
Anchor channels, invented by Anders Jordahl in 1913, are steel channels cast flush in reinforced concrete elements to allow the installation of channel bolts for the fastening of components.
Media related to Stobie poles at Wikimedia Commons