1204
THEORY AND PRACTICE OF ENGINEERING.
Book 11
arrive at the points which mark the stroke of the piston, in order that the distance from thecentre of the axle D to the centre of the bolt M'may be equal to the course Mm or ki ofthe bolts M h.
Fig.1S82.
The calculation of the dimensions and effect of this machine is based upon the followingdata, that the fall C D in fig. 1877. is 10 feet, the height FL of the pipe for raising thewater to the cistern M is 50 feet, the stroke of the piston 30 inches, and its velocity 1 footin a second of time; the resistance caused by the weight and friction of the machine mustbe taken into account, or be considered as raising the water 60, instead of 50 feet. Thegreat piston is 10 inches in diameter, the lesser inches, the discharge pipe 4.^ inches indiameter : the product of this machine will he about 793 cubic feet per hour.
Machines made use of by the engineer for pumping out foundations require arrange-ments to be provided, which are perfectly independent of raising the water, and the firstobject when selecting a contrivance for such a purpose is to discover where the usefuleffect is the greatest, with regard to the force expended by the moving power ; sometimes,however, it happens, that machines for pumping, apparently defective, may be used veryadvantageously ; men were employed with pails and scoops, at the bridge of Orleans, in thefirst experiment made by Perronet, and it was found that each man raised with a pail *0034cube metres of water per minute, at 1-79 metre of height, and in a second experiment*0069 cube metres of water at 0 97 metres of height in the same time, which in the firstresult amounts to 3-652, or the second 4-016, and mean 3-834 cube metres of waterraised per hour one metre high : the workmen laboured 12 hours, so that the usefuleffect produced during the 24 was 46 cube metres of water raised 1 metre, the pailcontained -0018 cube metres, but as the workman filled it one-fifth was lost before it wasdischarged out of the foundations; we must only estimate 55*111 cube metres of waterpoured out of the pail 3062 times. The weight of the pail is equal to 004 metres cubeof water, and this raised 3062 times furnishes a quantity of action of 12,248 cube metresof water, which added to the other gives 67,359 cube metres : a man using a wheel canraise about 200 cube metres of water 1 metre in height in a day’s work.
In the Chapelet at Rochfort, mentioned by Belidor , moved by 4 horses, 44-4 cubemetres of water were raised 7*8 metres high per hour, which makes the useful effect ofeach horse 86-6 metres of water raised a metre in an hour; and supposing the horse towork 8 hours, the daily useful effect would be 693 cube metres of water raised a metre :but if we suppose that the machine consumed two-fifths of the moving force, the quantityof daily action of each horse would be 1156 cube metres raised a metre.
Water Wheels moved by the stream have very variable effects: according to Smeaton two-thirds of the force is generally consumed by the resistance of the wheel, and only thereforeone-third is transmitted to the shaft : the Archimedean screw only gives for the useful effecta little more than half the force it consumes, and the French engineers assert that the rouea tympan is one of the most advantageous powers that can be made use of for pumping.
Spiral pumps, as improved by Bernouilli, were introduced with considerable effect atMoscow , where one raised a hogshead of water in a minute to the height of 74 feet, andthrough a pipe 760 feet in length : among the variety of forms given to them, it has notbeen yet sufficiently proved which is the best; some engineers giving the preference to thecylindrical plane, others to the conical : at Florence the machine most used had its spiralcylindrical; its diameter was 10 feet, and that of the pipe 6 inches. Eytelwein recotn-