Updated: 18 Oct 2007
Water Engines: Page 7 |
Updated: 18 Oct 2007
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"In many respects I believe water motors furnish as nearly perfect power as it is possible to attain. A motor, for instance, properly connected and supplied by the even pressure from a reservoir is probably the most reliable and steady power known, not excepting the most improved and costly steam engines. The convenience and little attendance necessary in operating make them especially desirable for many purposes. Where only small power is required, or even where considerable power for only occasional use is desired, they are particularly well adapted, and can be driven at small expense. Even for greater power they possess advantages over steam engines which, to a considerable extent, compensate for the large water rates that ought to be paid for their supply. These advantages are in the first cost of a motor, as compared with a steam engine, the saving in attendance and fuel, the convenience and cleanliness, and in some cases a saving in insurance by reason of their being no fire risks attendant upon its use. At just what point steam becomes preferable, however, is a question depending considerably upon water rates, but to some extent on other circumstances, leaving it largely a question of judgment. As with elevators, there are difficulties involved in their supply that unless carefully guarded make water motors anything but a desirable source of revenue. How often is the argument advanced: "Why, I only use water for a quarter of an inch jet!" Showing how little people who use motors or elevators or fountains realize the quantity of water they consume. This class of consumers may be placed on one footing, to wit, a class who, in spite of the fact that they are supplied with water for much less than any other, feel that they are imposed upon, and cannot be made to think otherwise.
Though not as large as for elevator supply, water motors require liberal openings in the mains, and frequently the fault of having too small supply pipes is sought to be remedied by openings in the water mains much larger than needful. A table prepared by an engineer who had given the matter study, or by some motor manufacturer, showing the size of taps, or openings, for the proper supply of motors, with the various jets, under different pressures, would be of general use to water-works people. In order to use water to the best advantage, the full pressure in the main, so far as practicable, should be had at the jet, but in order to accomplish this it is not necessary to use as large taps as are ordinarily demanded, but to provide supply pipes of sufficient capacity to deliver the water to the point of discharge with the least possible friction. Lately this theory has been put in practice to some extent by us, and the result has shown that in this manner we are able to supply motors through smaller taps than beforehand with as satisfactory results.
It is a general practice throughout the country to make annual or monthly rates for water motors, and from my observation I believe I can safely venture the assertion that in three-quarters of the cases the rates charged will not equal 50 per cent. of the lowest meter rates in force in these places. Although the Kansas City Water-Works has not perhaps been generally accorded the reputation of being the most liberal "monopoly" in the country, still I have had occasion at times to make some such claims as an inducement to its generous support. But with all its liberality, I am free to say that we cannot begin to meet the rates for motors that parties claim to have paid almost everywhere else.
The St. Louis Water-Works, where the rates are substantially the same as in Kansas City, have been quoted as having the following motor rates, but whether correct or not my inquiries have failed to determine:
"On the supposition that motors are to be used ten hours per day for 300 days per year, motors are assessed for--
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1/4 inch jets | $120 per annum. |
3/8 " | 198 " " |
1/2 " | 300 " " |
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These rates based upon a charge of 50 cents per 1,000 gallons."
From Col. Flad's Report as Engineer of Public Works, May 1, 1876, p.70, it is found that with 42 pounds pressure a 1/2 inch orifice will discharge 2,160 gallons per hour, 21,600 gallons in 10 hours, or 6,480,000 gallons in 300 days, which at 20 cents per 1,000 gallons would amount to $1,296, for which they assess the rate $300. From all of which I would conclude that there must be a lack of harmony somewhere between the engineering and office departments.
I have made some estimates myself for water motors, basing rates upon the number of hours it was claimed the motors would be in use, and afterward supplied the same motors by meter measurement; in every case found that at least twice as much water was used as had been estimated. Although estimates were carefully made upon what was believed to be a reliable basis, these repeated similar results have led me to the conclusion that the only way to supply motors is to make it an object to the users of them to be economical. In other words, I believe the way to supply water motors is upon an estimate that they will run 24 hours per day and 365 days per year, or, more properly still, supply them only by meter measurement. At all events this is henceforth my policy; or, in other words, "on this rock I stand," believing it the only equitable way out of this difficulty.
That class of motors or water engines operated by water pressure in close cylinders upon pistons as with steam in a steam engine, I believe could be easily supplied by measurement of water without a meter. This could be accomplished by the use of "revolution counters" or indicators, as the amount of water required per revolution could be readily determined, and when once computed the cylinders would measure out the water as accurately as a meter. The only objection to this plan is the expense of counters, which is considerable; and as to indicators, it may have been observed that I have little faith in their reliability. With cheap revolution this class of motors would be free from many of the objections raised in regard to motors generally.
The practical conclusion that I would draw from a consideration of this subject is that the question of whether the supply of hydraulic elevators and motors is desirable in its effects upon the water supply is one that hinges so delicately upon their being carefully governed, connected, and restricted, that while on the one hand they may be made the source of large profit, and at the same time a public benefit, on the other hand, unless all the details of their supply be carefully guarded by the wisest rules and greatest watchfulness, their capacities for waste are so great and the rates charged necessarily so low, that they may become the greatest source of loss with which we have to contend."
LINKS
Here however, is what appears to be a contemporary positive-displacement water engine http://www.InternalHydro.com (External link)
This device has no less than 48 cylinders, and runs from a 65 psi supply. It is claimed to produce 30kW when coupled to an electrical generator.
See also homepower.com
This is not a positive-displacement motor but a small Pelton turbine.
Hydraulic motors are still very much in use, though almost invariably driven by oil rather than water. They are used in construction machinery; a typical application is driving caterpillar tracks. See
http://www.allstar.fiu.edu/aero/Hydr19.htm (External link)
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