Ted Eldred

Edward Francis Eldred (16 December 1920 to August 2005) was a pioneer of scuba diving in Australia. He invented Porpoise scuba gear.

Early years Eldred was born in Melbourne in 1920. As a young man he lived by the sea near Sorrento on the Mornington Peninsula south of Melbourne. He started snorkelling as soon as mask, fins and snorkel were available, and wished that he could make or obtain some sort of free-swimming breathing set, until World War II intervened. After World War II in the late 1940s he designed a sport diving oxygen rebreather. Eldred said he had never dived with the Cousteau-Gagnan model of the Aqua Lung, but knew of its existence and its principle. The Aqua Lung was protected by patent and difficult to obtain in Australia. Siebe Gorman had the license to manufacture for Commonwealth countries and could not meet demands. When Eldred decided that rebreathers were not suitable for general sport use, he shifted his focus to developing the world's first single-hose open-circuit scuba set, both with tradename "Porpoise".

Closed-circuit oxygen rebreathers

Eldred's initial efforts were to make an oxygen rebreather safe for sporting use. Pure oxygen used in early rebreathers causes CNS poisoning below 6 msw. Eldred reasoned that the rebreather should be designed to stop flowing oxygen when the diver descended below that depth. At a demonstration by the Flinders pier, on Western Port Bay, south east of Melbourne, a diver passed out because he failed to purge the system of air. This failure to purge had resulted in a nitrogen build up. Eldred realised at this point that he needed to turn his efforts toward open circuit compressed air breathing apparatus. He was accompanied on this demonstration by Bob Wallace-Mitchell, who would become his distributor.

Open-circuit compressed air

The French-designed open circuit scuba, called the Aqua-Lung, was protected by US and international patents, so Eldred set about designing the Porpoise CA (a prototype), the world's first single hose regulator. Eldred referred to the French model as the Gagnan Aqua Lung, as designer Émile Gagnan was the Frenchman who actually designed the device for Jacques Cousteau. This new design was superior to the Aqua-Lung, and did not violate any of the existing patents. Eldred's regulator was never patented as his business was too small for the expense. The first production model was designated the CA-1. (C A for compressed air, 1 for single cylinder) He began using an oxygen welding reduction valve for his prototype. His chief design effort was developing the demand valve which people now call the second stage. It was sold as a complete single cylinder, single hose scuba early in 1952. The cylinder was inverted so the diver could reach the innovative regulator mounted reserve. Only about a dozen of these exist and are now in the hands of scuba collectors. Eldred also made the CA-2, which was a double cylinder model. Only two CA-2 Porpoises are still known to exist. About three quarters of the Porpoises made were surface supplied 'hookah' units. The 'hookah' was the device which started the demise of the standard dress helmet diving equipment. The Porpoise single hose scuba found its initial international praise in Arthur C. Clarke's 1955 book Coast of Coral. It was difficult for Wallace-Mitchell to market in those early days, as compressed air was not readily available. His first task was to locate a compressor with a sales point in each of the Australian capital cities. Once this was done, dealers could stock his scuba and refill the cylinders. In 1954 Eldred also created the Porpoise Universal, which had a high supply rate of over 300 liters per minute. The Universal used the same demand valve and was modular in design. The reduction valve was a balanced diaphragm type, which was modified to become a piston type. It became his flagship model. Eldred also made a cheaper model, called the Sportsman. The Sportsman was a very compact regulator with innovative features now found on regulators of today. It was made of plastic and had an unbalanced first stage. Market needs made this model necessary, but Eldred did not like it.

The Royal Australian Navy (RAN) supported Eldred's efforts and adopted the Porpoise Universal for military use.