Chap. XVII.

MACHINES FOR RAISING WATER.

1195

Fig. 1855. represents a wheel somewhat similar to the preceding, but the faces A B andC D are straight, being rounded at the summit and base alone : the rollers F are attachedto balance beams of a proper length : in this case the pumps are reversed, the pistonsforcing upwards, but if a different arrangement be desired, the wheel may be made to workas in fig. 1858; and this manner is preferable, as the balance beam may then be of anyrequired length without regard to its weight. After the position of the posts C and D isfixed, in such a manner that the horse is not inconvenienced when turning, the length tobe given to E F is known, and the other arm must be two-thirds of this : the height of theposts is so arranged that when the roller I arrives at the summit of a tooth K, the balancebeam G II may he horizontal. When the roller E is at the bottom N of the opposite tooth,the angle M E F formed by the vertical M L and the line L F, which joins the centres ofmotion of the roller and balance-beam E F will be greater than a right angle ; whereforethe direction I, F of the power, which sustains the weight I, on an inclined plane, not beinghorizontal, it is very nearly to the weight as the height of the plane is to its base: themore the base of the inclined planes formed by the teeth exceeds their length, the lessresistance will there be to the rollers; but as the bases cannot be increased without ex-tending the circumference on which they are placed, and so removing the weight furtherfrom the centre of the wheel, which may be regarded as the fulcrum of the lever to which themotive power is applied, the power will evidently gain nothing. The base should be twicethe height; the roller 8 inches in diameter, rising 12 inches, and the play of the piston 8inches. The length of the base of the teeth is 4 feet 4 inches comprising the bottom inwhich the roller rests; this multiplied by 5, gives 21 feet 8 inches for the circumferenceof the wheel at the middle of its thickness, or 3 feet 10 inches for the external radius. Thewheel is constructed as in ordinary mill-work. The inclined planes are attached togetherby a band of iron 4 inches wide, on which the roller works. Fig. 1856. shows themanner in which the roller is attached to the balance-beam. The rule for finding theproportion the motive power bears to the weight is thus expressed: the power is to theweight raised by the teeth, as the product of the radius of the wheel multiplied by theheight of the inclined plane, is to the product of the length of the lever multiplied by thebase of the same plane. Supposing the lever A I) to he 14 feet long, and the force of ahorse to be 180 lbs., we shall have x 1 : 14 x2 :: 180 lbs., or 1 : 8 :: 180 lbs., showing thatthe power is one-eighth of the weight, which will consequently be 1440 lbs. Now, since ina state of equilibrium, this weight should be to that of the column of water in the reciprocalproportion of the arms of the lever, or as 2 to 3, the motive power will only be one-twelfthpart of the weight of the column which each piston forces, equal to the weight of 2160 lbs.To find the diameter of the piston, multiply the weight of the column of water each canforce by 1728, as a constant number: multiply the height the water is to be raised ininches by 55, another constant number : divide the first of these products by the second,and extract the square root of the quotient, which will be the diameter required. Since ahorse can easily make 120 turns in an hour, and at each turn the pistons force ten timeswith a stroke of 8 inches, they will raise 1200 columns of water 6 inches in diameter8 inches high, in one hour. The cost of this machine is moderate, and it may be madeto draw water from a verydeep well, by using suction-pumps at 25 feet apart.

Bascule used by Perronetat the bridge of Orleans, wasworked by twenty men, tenbeing placed at each end;

150 motions were given to iteach quarter of an hour, andat each, 4 cubic feet of waterwere raised 3 feet high, or 2400cubic feet per hour.

The Chapelets employed atthe same bridge were placedvertically, and from 12 to 18 feetin length, and about 6 inchesin diameter: four men workedthe winches, and were relievedevery two hours; they made20 to 30 turns in a minute,according to the height towhich the water was to beraised; 500 cubic feet of water, or 62$ muids, were raised per hour, and at each turn4J feet of the chain were wound round.

Fig. 1859. BASCULE USED AT ORLEANS BhIDGE.