| Pipe Diameter | Velocity in Feet per Second | |||||||||||
| 4.6 | 4.8 | 5.0 | 5.2 | 5.4 | 5.6 | 5.8 | 6.0 | 7.0 | 8.0 | 9.0 | 10.0 | |
| 78.1 | 82.0 | 89.5 | 98.9 | 105.0 | 113.2 | 120.8 | 130.0 | 162.8 | 216.0 | 270. | 323. | |
| 3" | 13.6 | 14.2 | 14.8 | 15.3 | 15.9 | 16.5 | 17.1 | 17.7 | 20.6 | 23.5 | 26.5 | 29.5 |
| 52.3 | 57.0 | 61.5 | 68.0 | 72.5 | 78.2 | 83.1 | 89.5 | 121. | 155. | 198. | 242. | |
| 4" | 24.1 | 25.1 | 26.2 | 27.2 | 28.3 | 29.3 | 30.4 | 31.5 | 36.6 | 41.9 | 47.2 | 52.4 |
| 39.2 | 42.3 | 46.0 | 49.8 | 53.5 | 58.0 | 62.0 | 67.0 | 89. | 118. | 148. | 182. | |
| 5" | 37.6 | 39.2 | 40.9 | 42.5 | 44.1 | 45.8 | 47.5 | 49.1 | 57.1 | 65.4 | 73.7 | 82.0 |
| 30.6 | 33.1 | 35.6 | 39.0 | 41.6 | 44.6 | 48.0 | 51.6 | 69.0 | 89.0 | 114. | 140. | |
| 6" | 54.1 | 56.5 | 58.9 | 61.2 | 63.6 | 65.9 | 68.3 | 70.7 | 82.4 | 94.3 | 106 | 118 |
| 25.1 | 27.3 | 29.5 | 32.0 | 34.5 | 37.1 | 40.0 | 43.0 | 58.0 | 75.0 | 95.0 | 116. | |
| 7" | 73.7 | 76.9 | 80.2 | 83.3 | 86.6 | 89.8 | 93.0 | 96.2 | 112 | 128 | 145 | 161 |
| 20.0 | 22.5 | 24.9 | 27.0 | 28.8 | 30.6 | 32.8 | 35.5 | 47.5 | 61.2 | 78.6 | 95.1 | |
| 8" | 96.3 | 101 | 105 | 109 | 113 | 117 | 121 | 125 | 146 | 168 | 189 | 210 |
| 17.1 | 19.2 | 21.0 | 22.9 | 24.6 | 26.2 | 28.0 | 30.1 | 40.1 | 52.1 | 66.6 | 82.0 | |
| 9" | 122 | 127 | 132 | 138 | 143 | 148 | 154 | 159 | 185 | 212 | 238 | 265 |
| 14.8 | 16.7 | 17.9 | 19.9 | 21.0 | 22.7 | 24.3 | 25.9 | 34.8 | 45.9 | 58.0 | 70.1 | |
| 10" | 150 | 157 | 163 | 170 | 177 | 183 | 190 | 196 | 229 | 261 | 295 | 327 |
| 13.0 | 14.7 | 15.9 | 17.1 | 18.2 | 20.1 | 21.3 | 22.6 | 30.7 | 40.0 | 50.8 | 62.0 | |
| 11" | 182 | 190 | 198 | 206 | 214 | 222 | 229 | 237 | 277 | 316 | 356 | 396 |
| 11.6 | 13.0 | 14.0 | 15.1 | 16.1 | 17.8 | 19.1 | 20.2 | 27.1 | 35.9 | 45.4 | 55.9 | |
| 12" | 217 | 226 | 235 | 245 | 254 | 264 | 273 | 283 | 330 | 377 | 425 | 472 |
EXAMPLE
Assume the surveyed head as 240 feet, the water quantity as 207 cubic feet per minute and a pipe line 12 inches in diameter 900 feet long. To ascertain the friction loss, refer to column of pipe diameter and follow across the column for 12 inches diameter to the quantity, 207 cubic feet per minute. The heavy-faced figures above 207 indicate that the loss per 1000 feet of pipe length is 11 feet. Therefore, since the pipe in the example is 900 feet long, the loss will be 11.' × 900/1000 or 9.9 feet, and the effective head will be 240' - 9.9' = 230.1'
Steel tubing for supply pipes, from 3 to 12 inches in diameter is listed at from 20 cents to $1.50 a foot, according to the diameter and thickness of the material. Discounts on these prices will vary from 25 to 50 per cent. The farmer can cut down the cost of this pipe by conveying his supply water from its natural source to a pond, by means of an open race, or a wooden flume. An ingenious mechanic can even construct his own pipe out of wood, though figuring labor and materials, it is doubtful if anything would be saved over a riveted steel pipe, purchased at the regular price. This pipe, leading from the pond, or forebay, to the water wheel, should be kept as short as possible; at the same time, the fall should not be too sharp. An angle of 30° will be found very satisfactory, although pipe is frequently laid at angles up to 50°.
Other Types of Impulse Wheels
In recent years more efficient forms of the old-fashioned overshoot, pitch-back breast, and undershoot wheels have been developed, by substituting steel or other metal for wood, and altering the shape of the buckets to make better use of the power of falling water.
In some forms of overshoot wheels, an efficiency of over 90 per cent is claimed by manufacturers; and this type offers the additional advantage of utilizing small quantities of water, as well as being efficient under varying quantities of water. They utilize the falling weight of water, although by giving the water momentum at the point of delivery, by means of the proper fall, impulse too is utilized in some measure. The modern steel overshoot wheel receives water in its buckets from a spout set a few degrees back of dead center; and its buckets are so shaped that the water is retained a full half-revolution of the wheel. The old-style overshoot wheel was inefficient principally because the buckets began emptying themselves at the end of a quarter-revolution. Another advantage claimed for these wheels over the old style is that, being made of thin metal, their buckets attain the temperature of the water itself, thus reducing the danger of freezing to a minimum. They are manufactured in sizes from 6 feet in diameter to upwards of fifty feet; and with buckets of from 6 inches to 10 feet in width. In practice it is usual to deliver water to the buckets by means of a trough or pipe, through a suitable spout and gate, at a point two feet above the crown of the wheel. For this reason, the diameter of the wheel corresponds very closely to the head in feet.
The Reaction Turbine