Specifications
Joseph Peress' Tritonia Diving Suit was the starting point for the design of the JIM suit, manufactured from cast magnesium alloy and first successfully tested in September 1930 by Jim Jarret. Following a dive on the wreck of the RMS Lusitania in 1935, Peress attempted to sell the Tritonia to the Royal Navy and initial sea trials were carried out, but the offer was rejected when it was decided by the Admiralty that Royal Navy divers had no reason to dive to the depths it was capable of. The suit was later retired, and eventually found its way to a junk shop where it would be discovered by Mike Humphrey and Mike Borrow in the mid-1960s. UMEL would later class Peress' suit as the "A.D.S Type I", a designation system that would be continued by the company for later models.
The first UMEL JIM suits, classified as A.D.S II, were constructed from cast magnesium for its high strength-to-weight ratio and weighed approximately 1,100 pounds (498.95 kg) in air including the diver. They were 6 ft 6 inches (1.98 m) in height, 3 ft 5 in (1.04 m) in width, 3 ft 1 in (94 cm) in side width and had a maximum operating depth of 1,500 feet (457 m). Corrosion problems were countered through surface preparation and coating. The suit had a negative buoyancy of 15 to 50 pounds (6.8 to 23 kg). Ballast was attached to the suit's front and could be jettisoned from within, allowing the operator to ascend to the surface at approximately 100 feet (30 m) per minute. The suit also incorporated a communication link and a jettisonable umbilical connection. The original JIM suit had eight annular oil-supported universal joints, one in each shoulder and lower arm, and one at each hip and knee. The JIM operator received air through an oral/nasal mask that attached to a lung-powered scrubber that had a life-support duration of approximately 72 hours, although actual survival for this time would have been unlikely due to thermal transfer through the magnesium body. As technology improved and operational knowledge grew, Oceaneering upgraded their fleet of JIMs. The magnesium construction was replaced with glass-reinforced plastic (GRP) and the single joints with segmented ones, each allowing seven degrees of motion, and when added together giving the operator a very great range of motion. In addition, the four-port domed top of the suit was replaced by a transparent acrylic one that was taken from Wasp, this allowed the operator a much-improved field of vision. Trials were also carried out by the Ministry of Defence on a flying Jim suit powered from the surface through an umbilical cable. This resulted in a hybrid suit with the ability of working on the sea bed as well as mid water.
In addition to upgrades to the JIM design, other variations of the original suit were constructed. The first, named the SAM Suit (Designated A.D.S III), was a completely aluminium model. A smaller and lighter suit, it was more anthropomorphic than the original JIMs and was depth-rated to 1,000 ft (300 m). Attempts were made to limit corrosion by the use of a chromic anodizing coating applied to the arm and leg joints, which gave them an unusual green color. The SAM suit stood at 6 ft 3 in (1 m 90 cm) in height, and had a life-support duration of 20 hours. Only three SAM suits would be produced by UMEL before the design was shelved. The second, named the JAM suit (Designated A.D.S IV), was constructed of glass-reinforced plastic (GRP) and was depth-rated for around 2,000 ft (600 m). Two were constructed for Oceaneering, as well as an experimental US Navy version, modified with a torso made of carbon fibre reinforced plastic that would prove unsuccessful. The prototype failed at approximately 1,000 ft (300 m) when tested to destruction.
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