has been found to be best adapted for receiving the impulse of the steam jet. There are no stationary or guide blades, the angular position of the nozzles giving direction to the jet. Fig. 143 shows the form of wheel FIGURE 144, and the nozzles. The nozzles are placed at an angle of 20° to the plane of motion of the buckets, and the course of the steam is shown by the illustration. The heat energy in the steam is practically devoted to the production of velocity in the expanding of divergent nozzle, and the velocity thus attained by the issuing jet of steam is about 4,000 ft. per second. To attain the maximum of efficiency the buckets attached to the periphery of the wheel against which this jet impinges should have a speed of about 1,900 ft. per second, but, owing to the difficulty of producing a material for the wheel strong enough to withstand the strains induced by such a high speed, it has been found necessary to limit the peripheral speed to 1,200 or 1,300 ft. per second. Fig. 144 shows a De Laval steam turbine motor of 300 H. P., which is the largest size built up to the present time, its use having been confined chiefly to light work. The turbine illustrated in Fig. 144 is shown directly. connected to a 200 K. W. two-phase alternator. The steam and exhaust connections are plainly shown, as also the nozzle valves projecting from the turbine casing. The speed of the turbine wheel and shaft is entirely too high for most practical purposes, and it is reduced by a pair of very perfectly cut spiral gears, usually made 10 to 1. These gear wheels are made of solid cast steel, or of cast iron with steel rims pressed on. The teeth in two rows are set at an angle of 90° to each other. This arrangement insures smooth running. and at the same time checks any tendency of the shaft towards end thrust, thus dispensing with a thrust bearing. The working parts of the machine are clearly illus trated in Fig. 145, and a fairly good conception of the assembling of the various members, and especially the reducing gears, may be had by reference to Fig. 146, which shows a 110 H. P. turbine and rotary pump with the upper half of the gear case and field frame removed for purposes of inspection. The slender shaft is seen projecting from the center of the turbine case, and upon this shaft are shown the small pinions meshing into the large spiral gears upon the two pump shafts. Referring to Fig. 145, A is the turbine shaft, B is the turbine wheel, and C is the pinion. As the turbine wheel is by far the most important element, it will be taken up first. It is made of forged nickel steel, and it is claimed by the builders, the De Laval Steam Turbine Co. of Trenton, New Jersey, that it will withstand more than double the normal speed before showing any signs of distress. A clear idea of the construction of the wheel and buckets may be had by reference to Fig. 143. The number of buckets varies according to the capacity of the machine. There are about 350 buckets on 300 H. P. wheel. The buckets are drop forged and made with a bulb shank fitted in slots milled in the rim of the wheel. Fig. 147 is a sectional plan of a 30 H. P. turbine connected to a single dynamo, and Fig. 148 is a sectional elevation of the same. The steam, after passing the governor valve C, Fig. 148, enters the steam chamber D, Fig. 147, from whence it is distributed to the various nozzles. The number of these nozzles depends upon the size of the machine, ranging from one to fifteen. They are generally fitted with shut-off valves (see Fig. 144) by which one or more nozzles can be cut out when the load is light. This renders it possible to use steam at boiler pressure, no matter how small the volume required for the load. This is a matter of great importance, especially where the load varies con |