THE PROPELLING MACHINERY OF THE U. S. S. LEVIATHAN. 221 



There are loi rows of standard impulse-reaction blades in casing and rotor re- 

 spectively, arranged in four expansion stages, with blade heights varying from ^% 

 inches to 6^ inches. 



The Parsons type of contact dummy is fitted at the steam inlet belt, and the 

 fore-and-aft clearance between the casing and rotor is measured by the usual mi- 

 crometer. Two steam pipes, each 183/^ inches diameter, admit steam to the tur- 

 bine, and the exhaust nozzle is about 42 inches diameter. 



The by-pass valves are fitted between the first and second stages, which allow 

 for an overload of about 25 per cent above the designed power. 



The rotor shafts are shrunk into the hubs of each disc, and the thrust collars 

 for the rotor adjustment are arranged at the forward end of the rotor. 



High-Pressure Astern (Port Inboard) . — This casing is bolted rigidly to the 

 aft end of the high-pressure ahead. The body is made of cast iron in two half- 

 sections and bolted together at flanges on the horizontal center line. Cast-iron ped- 

 estals are bolted to facings at each end of the turbine body and support the rotor 

 bearings, supporting feet to the ship's foundations and the columns of the lifting 

 gear. 



The fixed foot which transmits the propeller thrust through these turbines to 

 the hull of the vessel is arranged between the two casings ; thus the high-pressure 

 ahead is free to move forward and the high-pressure astern moves aft, the foot at 

 forward end of the high-pressure ahead and aft foot of the high-pressure astern 

 being arranged to slide freely. 



An impulse wheel having three rows of rotor buckets, about 12 feet mean di- 

 ameter, receives the steam from the regulator valves, and this is followed by four 

 expansion stages of the regular impulse-reaction blading on a drum construction, 

 having a diameter of 9 feet 10 inches. There are 42 rows of impulse-reaction blades 

 in casing and rotor, with blade heights varying from i -[^^ inches to 5 inches. 



A radial fin type of dummy is fitted to the steam belt, and the overall length 

 of the rotor drum is approximately 8 feet 6 inches. 



Fig. 4, Plate 97, shows the general design of the rotor drum and impulse wheel. 

 The steam inlet pipe is about 14^^ inches diameter, and three sets of nozzles fitted in 

 cast-steel chambers are bolted into openings arranged on the top half casing, each 

 having an inlet branch of 8^ inches diameter, the exhaust nozzle opening being 

 about 29 inches diameter. 



Mid-Pressure Ahead and H. P. Astern (Starboard Inboard) . — The casing of 

 the mid-pressure turbine is built up in sections made of cast iron, and the two halves 

 are bolted together at flanges on the horizontal center line. Cast-iron pedestals are 

 bolted on to facings at each end of the turbine body and support the rotor bear- 

 ings, etc. 



The high-pressure astern turbine is bolted directly to the forward end of this 

 unit and is similar to the high-pressure astern of the port inboard side. 



The fixed foot which transmits the propeller' thrust through these turbines is 



