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



Turbine Thrust and Adjustment Blocks. — The turbine thrust and rotor ad- 

 justment blocks are arranged as follows: — 



In the case of the high-pressure ahead, the collars form part of the forward 

 end of the rotor shaft. 



In the case of the mid-pressure turbine and the low-pressure ahead turbines, 

 the)' are arranged between the two turbines on each of these shaft lines, the thrust 

 shaft being a separate forging having flanges at each end, which are bolted to the 

 shaft ends of the rotors. 



Each thrust shaft has ten collars 31 finches external diameter and 20 inches di- 

 ameter at bottom of collars, and about i ^ inches thick. 



The thrust shoes are secured in cast steel housings and are faced with white 

 metal, the total surface of the bottom shoes being approximately 2,100 square inches 

 in area, whilst the top shoes have an available surf ace of about 1,900 square inches. 



The adjustment of the rotors is made in accordance with Parsons' usual prac- 

 tice. To assist in the adjustment of the rotors, a special device is fitted which en- 

 ables the engineers to freely move the heavy rotors and the lines of shafting. 



A cast-steel bracket is secured to foundations under one of the shaft couplings 

 in each of the tunnels. At both ends of the bracket a square extension projects from 

 screw-cut threaded spindles, the nuts of which carry ball-bearing mounted steel 

 rollers which can be screwed hard against the flange couplings. By using this, and 

 at the same time having the turning gear in operation, the rotors can be moved 

 easily (Fig. 9, Plate 99). 



Impulse-Reaction Blading. — The standard Parsons' blade sections are used 

 throughout, the material being a common brass mixture ; the groove widths vary- 

 ing from J/2 inch to ij^ inches, the width of the blade section being dependent on 

 the length of the blade. 



The usual method of fitting separate packing sections between each blade is 

 adopted. 



About the center of the forward edge of each groove in casing and rotor, a 

 semicircular projection is left, and each blade and packing section is correspond- 

 ingly notched out so as to fit over the projection (Fig. 10, Plate 99). 



By this method each blade and packing section is held mechanically. The bind- 

 ing strips are of round brass wire, which is fitted in a hole drilled through the 

 blades, and the wire is then silver soldered to each blade. In the long blades there 

 are three rows of binding wires. The ends of all the blades are thin tipped, in 

 accordance with Parsons' usual practice. 



Impulse-Wheel Buckets. — The composition buckets of the impulse wheels are 

 fitted similarly to those of the reaction blading, that is, the buckets and the pack- 

 ing sections are separate. The method of holding them in the rotor grooves is, 

 however, slightly different. 



The rectangular grooves of the rotor have semicircular projections on each side, 



