| On this page you will find a design overview prepared by Don Edwards, web master of this site and USS Atlanta historian, a detailed design history of the Atlanta class diesel generator prepared by Preston Cook who has donated much material for this web site, and a design history donated by Don Cavanaugh who works for Gibbs and Cox, the original designers of the USS Atlanta. |
Design Overview - by Don Edwards
These cruisers were designed in the late 1930's under the constraints of the London Naval Treaty of 1936 which tried to place an 8,000 ton limit on cruisers with the abandonment of 8" gun (heavy) cruisers. Initial design concepts called for a "mini all prupose " Brooklyn class cruiser with dual purposes 6" armament but was quickly changed as it became apparent that a sucessful design could not be achieved on that displacement and a dual purpose 6" mount would not be ready for some time. It actually was developed and appeared in the Worcester class "large" light cruiser completed after WW2.
The success of the new 5"/38 weighed heavily in the design discussions of the Atlanta class. The dual purpose 6"/47 gun would fire only about half as fast as a 5"/38, although its shell weighed roughly twice as much as the 5". The 5"/38 mount could fire 15, and with some well trained crews 20 rounds per minute while the 6" mount could fire 8 to 10 rounds per minute. Additionally, the value of very long range antiaircraft fire was open to speculation as the increased range of the 6"/47 was at the time outside the range of effective fire control. Hence the benefits of the dual purpose 6"/47 mount over a 5"/38 was not completely evident, and more importantly, could not be produced in time.
Their initial purpose, contrary to popular belief,was not only that of an anti-aircraft cruiser but that of a small, fast scout cruiser that could operate in conjunction with destroyers on the fringes of the battle line in addition to the defense of the battle line against destroyer and aircraft attack. While they were not designed to "slug it out" with heaver ships,they were well suited to close surface action in bad weather (poor visibility) and to night actions, where their fast firing 5"/38's and eight 21" torpedos could be used to advantage.
While these ships were conceived of as partly flotilla leaders they were armed with depth charges and sonar. Additionally, they were originally planned with 2 triple torpedo tubes which were to come from the Pensacola and Astoria class heavy cruisers. A change to quadruple tubes was made when tubes from the Sim's class of destroyers were removed for stability reasons and became available.
One of the design features that generated the most intrest in these ships is their use of true high pressure steam power plants. While some writings state that these ships were only capable of 32.5 knots at service weight, my father, who served aboard the Atlanta and was assigned to her prior to commissioning and hence on all trial runs, said that the ship did attain a speed in the high 30 knot range on trials. Since officially, the trial board stated that the Atlanta was good for about 85,000 SHP and 34 knots and she had acheived 33.67 knots on 78,985 SHP at 7,404 tons my fathers claim of a much higher speed seems probable given that the ultimate output was considered to be 90,000 SHP. I remember him mentioning that on a trial run at high speed the ship was put into a turn and water was washing over bothe the bow and stern as the ship executed the turn. They appeared to be very manuverable ships based on written stories as well as my fathers accounts of her in battle, especially against aircraft.
Note that in later production ships the speed did in fact fall as weight increased. For example the Oakland made only 31.4 knots on 81,813 SHP at a higher weight of 8,150 tons.
The machinery plant reintroduced the alternating engine room and firerom arrangement. This proved critical to the survivability of the ship to torpedo damage by providing protection against the total destruction of the powerplant.
While there was much discussion and debate concerning the design and use of an all 5 inch main battery, they were generally well thought of and were ultimately ordered on April 25, 1939 to be completed in 1942. The Atlanta and Juneau were ordered from Federal (Kearny, NJ) and completed in the Brooklyn Navy Yard.
They were well designed ships and could withstand a great deal of punishment. See Atlanta Battle Damage page.
Design of the USS Atlanta's generator, which provided emergency power for pumping and for powering the only operable 5"/38 mount(#8)is provided by Preston Cook along with an excellent photo.
Gibbs & Cox Design details of the Atlanta Class Cruisers
The following information has be provided by Don Cavanaugh who currently is employed by Gibbs & Cox, Inc. the designers of the Atlanta Class.
In the late 1930's, Gibbs & Cox, Inc. was tasked to design a new type of vessel for the US Navy. This class was developed to satisfy the need for a light displacement, high speed vessel whose mission was primarily combating large scale attack by aircraft, but which also possessed the ability to perform certain types of cruiser duty. The design consisted of many novel features, including the provision of an innerbottom extending to the second deck and following the contour of the outer shell. The side armor was of watertight reveted construction forming part of the watertight envelope of the hull. Armor protection was moderate, due to the weight limitation dictated by speed requirements, and consisted of side armor in way of the machinery spaces, bulkheads enclosing magazines, conning tower and steering engine room, with lighter protection on decks and on the boundaries off other vital areas. The propelling machinery was of improved design based on experience gained in the operation of destroyer machinery. Manufactured by Westinghouse Electric Corporation, each set of turbines consisted of one cruising, one high pressure and one double flow low pressure. The cruising turbine conected to the forward end of the high-pressure turbine rotor shaft through a single reduction gear. Reduction gears were locked train, double reduction type manufactured by DeLaval. The four boilers were designed by Babcock & Wilcox. Shaft horsepower was 75,000, maximum speed was 33 knots with a standard displacement of 6,000 tons, overall length of 541'9", and beam of 52'10". Armament consisted of sixteen 5-inch guns in twin mounts, three quadruple 1.1" antiaircraft machine guns, and two quadruple mount torpedo tubes.
There were 8 ships in this class.
Three follow-on ships (Juneau Class) were commissioned in 1946 and were distinguished from the Atlanta Class by a reduction of the superstructure height by one level, a reduction in the distance between the stacks, and a substantial increase in the antiaircraft batteries. This class had an array of various types of radar antennae installed on the fore and main masts.
*The Navy often reused names of lost ships.