544 



NIAGARA FALLS, ELECTRICAL POWER AT. 



lected, consisting of Dr. Sellers, Mr. Herschel, 

 Mr. Burbank, Mr. Bogurt, Mr. Porter, and Mr. 

 Forbes. The work was begun in 1890, and it 

 was prosecuted day and night with from 800 to 

 1,500 men, until the great tunnel was completed 

 late in 1893. The tunnel, over 7,000 feet long, 

 and at an average depth of 200 feet below the 

 surface, corresponds to the "tail race" of an 

 ordinary mill. Its importance is due to the fact 

 that the disposal of the utilized water is as great 

 a factor in hydraulics as the harnessing of the 

 power. The tunnel is horseshoe shaped, 21 feet 

 high and 18 feet 10 inches wide at its widest 

 part. It has a downward slope of 4 to 7 feet in 

 the thousand, and a chip thrown into the water 

 at the wheel pit will pass out of the portal in 

 three minutes and a half, showing the water 

 to have a velocity of 26^ feet a second, or a 

 little less than 20 miles an hour. The tunnel 

 was driven simultaneously from the portal and 

 from the bottom of 2 shafts. It was not until 

 the bottom of the shafts was reached that it was 

 discovered that it would be advisable to line the 

 tunnel with brick. This process involved the 

 expenditure of an immense sum of money. The 

 rock in many places was a soft shale, and when 

 exposed to the air crumbled like chalk. It was 

 decided to line the tunnel throughout. Thirteen 

 millions of first-quality brick were used, besides 

 which the lower end of the tunnel, for a distance 

 of 95 feet, is faced with steel plates. Thus pro- 

 tected, the tunnel is prepared to withstand the 

 wear of the water for generations to come. Al- 

 though nearly 200,000 tons of rock were re- 

 moved from the tunnel, it was all carried away 

 as fast as it was elevated to the top and dumped 

 along the river bank, where, by accumulation, it 

 turned several acres of marshy land into build- 

 ing property. 



Soon afteV the beginning of work on the tun- 

 nel work was also begun on a canal to bring 

 the waters of the river alongside the power 

 house. This canal is 180 feet wide at the mouth, 

 110 feet wide at the upper end, and 1,400 feet 

 long. On the side toward the power house it 

 is supplied with 14 gates, after the manner of 

 the ordinary mill race. Each gate, when opened, 

 allows the water to run through a short race- 

 way, whence it is carried by penstocks 7 feet 

 in diameter to the wheel pit below, where it 

 falls upon a turbine wheel of the Fourneyron, or 

 Boyden, type, designed to develop 5,000 horse 

 power under about 140 feet head and 250 revolu- 

 tions a minute. The turbines are cast of bronze 

 of the same quality as that used for the pro- 

 pellers of steamships. The water is then dis- 

 charged through directing passages upon the 

 movable blades of the wheel, of which there are 

 32, the directing passages being formed by 36 

 deflecting plates. The shaft is vertical, bring- 

 ing the wheels proper into a horizontal position, 

 1 at the top and 1 at the bottom of each case, 

 and gates controlled by the governor are made 

 to uncover more or less of the discharge, open- 

 ing according as more or less power is required. 

 It is expected that the governing mechanism 

 will control the speed under ordinary variations 

 of load within a variation of less than half of 

 1 per cent., and when a quarter of the entire 

 load is thrown off at once the variation of speed 

 is not expected to be more than 3 per cent. A 



very serious engineering problem was that of 

 supporting the weight of the long vertical shaft, 

 the attached portion of the dynamo, amounting 

 to about 150,000 pounds, and the column of 

 water in the penstock. This was solved by clos- 

 ing up the bottom of the casing, so that the 

 water can not act downward upon any of the 

 parts attached to the shaft, while in the upper 

 end of the casing are apertures through which 

 the water can act upon the under side of the 

 disk, carrying the movable blades of the upper 

 turbine and relieve the bearings of the weight 

 of the shaft. In this way the weight of the 

 water column is sustained by the stationary por- 

 tions, which can be braced and supported for 

 the purpose, and the pressure due to the head 

 made to act upward for supporting the weight 

 of the revolving shaft, which is thus nearly in 

 the condition of a shaft spinning upon the wa- 

 ter. The area involved is so proportioned that 

 when the wheels are lightly loaded the upward 

 pressure will be about 2,000 pounds in excess of 

 the weight of the shaft ; and when the wheels 

 are running at full speed, about the same amount 

 less than the weight of the shaft, on account of 

 the lesser pressure in the casing. The shaft 

 consists of a steel shell 30 inches in diameter, 

 with smaller solid portions in the journals, 

 which require to be of less frequency on ac- 

 count of the stiffness due to the large diameter 

 of the hollow shaft. The latter is of rolled-steel 

 tubing, without any visible vertical seam. No 

 fly wheel is required, sufficient momentum and 

 inertia being furnished by the heavy fields of 

 the dynamo which are carried upon the shaft. 

 For the accommodation of the turbines, an im- 

 mense wheel pit, 140 feet long, 18 feet wide, and 

 178 feet deep, has been excavated through solid 

 rock at the head of the great tunnel. This will 

 be extended to a length of 400 feet to provide 

 for additional turbines. 



The vertical shaft carries the power thus 

 generated back to the surface, where it can be 

 used directly by the ordinary methods of gear- 

 ing or by electrical dynamos. The Westing- 

 house dynamos, of 5,000 horse power each, are 

 thus described : To a circular foundation is 

 bolted a vertical cast-iron cylinder, provided 

 with a flange on which rests the stationary 

 armature. The inner part of the cylinder is 

 bored to the shape of an inverted cone, and 

 serves as a bearing for another conical piece of 

 cast iron, supporting the shaft bearings. The 

 armature core is made of thin, oxidized iron 

 plates, held together by 8 nickel-steel bolts. In 

 the outer edge of the plates are 187 rectangular 

 holes to receive the armature winding. The 

 outer rotating field magnet consists of a wrought- 

 steel ring to which are bolted the 12 inwardly 

 projecting massive cast-iron pole pieces. The 

 ring constituting the field magnet is supported 

 by a six-armed cast-steel spider keyed to the 

 vertical axis. The field magnets act also as a 

 fly wheel. The shaft rests on 2 bearings sup- 

 ported by 4 arms projecting from the inner 

 adjustable cast-iron cylinder. The bushings of 

 the bearings are made of bronze, provided with 

 zigzag grooves in which oil constantly circu- 

 lates. On the outer side of the bushing there 

 are also grooves into which cold water may be 

 pumped, if required. The armature conductors 



