THE NORIA OR BUCKET WHEEL.
This is a simple current wheel with pot buckets, rigid or swinging, arranged on the rim of the wheel, to carry up and discharge the water nearly at the top of the wheel, and through the long ages that it has been in use for irrigation, village water supply, and even for private establishments, has assumed a variety of forms in detail of construction ranging from the bamboo wheels of the Chinese to the light iron wheels of modern construction.
We illustrate the most simple of these forms in Figs. 26 and 27, in which the first is a series of boxes or chambers in the rim of the wheel with side openings in the forward part of the box as the wheel revolves, and a lip extending from the inner edge of the opening to direct the outflow into the trough.
Fig. 26.
Another form, Fig. 27, is arranged with swing buckets or pots, pivoted just above their centers, and with the catch trough so fixed as to tip the buckets at the highest point, thus giving this wheel the greatest possible advantage as to height of discharge for a given diameter.
Fig. 27.
The power value of these wheels for raising water is a matter of computation as nearly reliable as for other devices for the same purpose, when the velocity of the current is known at the point of contact with the blades.
The horse power of the wheel may be computed as for the current wheel, Fig. 23, and, as the horse power is equal to 33,000 pounds raised one foot high per minute, we may assume a construction of wheel that will allow of discharging at 8 feet above the stream; then 33,000 / 8 = 4,125 pounds of water discharged at 8 feet elevation per horse power per minute. As the net power of the wheel in the last example, for Fig. 23, was 0.468 of a horse power, then 4,125 × 0.468 = 1,930 pounds of water raised 8 ft. per minute by the size of bucket and velocity of current in that case. From this a deduction of 20 per cent. should be made for loss by spill and imperfect construction, so that 1,500 pounds or 176 gallons per minute would be the probable output—over 253,000 gallons per day; or, for irrigating purposes, equal to a rainfall of over 1¼ inches in depth on 50 acres in one week.
The proportion of capacity of the lifting buckets for such a wheel becomes of as great importance as its efficiency.
If the buckets are too large, the wheel will stall, and if too small, the wheel will not give its full duty.
For obtaining the approximate capacity of the lifting buckets, assuming the example as above computed, a 10 foot wheel with the velocity at periphery of 2½ feet per second is 150 feet per minute, or five revolutions per minute, nearly. Then 1,930 lb. per m. / 5 revolutions = 386 pounds water capacity for all of the buckets on the wheel.
If such a wheel is constructed with 16 blades and 16 buckets, one between each blade, then 386 / 16 = 24 pounds for each bucket, or 38 / 100 of a cubic foot.
The spill from this capacity of bucket being sufficient to compensate for the friction of the shaft journals.
The lifting buckets of the noria class, Figs. 26 and 27, can be made of positive dimensions to suit the computations as above; but those of the tympanum class, Fig. 25, should be made of dimensions to conform with the required capacity at the moment of leaving the water, as the water at this point flows into the arm.
(To be continued.)
To remove paint and varnishes, which resist the action of strong lye, Dr. Stockmeier recommends a mixture of water of ammonia, two parts, and turpentine, one part; this applied to the surface to be cleaned will, after a few minutes' action, enable the paint to be removed by use of cotton waste or similar material.— (Bayr. Gen. Ztg.), Rundschau.