1188

THEORY AND PRACTICE OF ENGINEERING

Book II.

power is applied, has a fly-wheel B to produce uniformity of motion : on the axle isa pinion C, engaging a wheel I), whose axle is a crank GLMKI NO II, to which aresuspended the piston rods E, F. The crank A is 12 inches long; M X is 6, and wheel D isC inches in radius, and the pinion C 2, and the fly-wheel B 3 feet. Supposing the waterto be raised 28 feet by the powerof a man, equal to 25 pounds ap-plied to the winch A, it is requiredto find the diameter of the pistonsin order that the weight of the columnof water may be proportioned to thepower applied.

This machine may be considered asconsisting of a single pump barrel,whose piston raises the water in anuninterrupted stream, and the arm ofthe lever which corresponds to theweight as expressed by two-thirds ofthe arm LM or NO of the which.

Now as there are four arms of onecommon lever united between thepower and the weight, namely the armL M reduced to 4 inches, the radiusof the wheel D to 6, that of the pinionC to 2, and the arm of the winch A to 12 ; the power will be to the weight as 4 x 2 is to6 x 12, or as 1 to 9, which may be stated thus, 1 : 9 :: 25 : 225 pounds, the weight of thecolumn of water which the power has to raise, and the volume will be obtained by stating,as 70 pounds of water arc to 728 cubic inches, so are 225 pounds to 5554 cubic inches, whichmust be divided by 28 feet, or 336 inches, the height of the column of water ; we shall thenhave about 16^ inches for the superficies of the circle of the base, or a diameter of *1 T 6 5 inches.

To calculate the Effect of this Machine .—The arm of the crank MN being 6 inches, thestroke of the piston will be 12; thus in each revolution of the crank, the two pistons willtogether discharge a column of water 2 feet high, 4-^ inches in diameter, weighing 15.^pounds. The pinion C being one-third the radius of the wheel D, the power must makethree turns of the winch A to one of the crank MN; and as this power can make 1000turns in an hour, the crank MN will make 333, which multiplied by 15J gives 5161 pounds,or 184 inches of water per hour.

Fig. 1839. shows a very simple method forworking two pumps by means of a balancebeam, A B, loaded with a weight at eachextremity; it works on gudgeons at C. Twofoot-boards are attached to the beam at1,1; on these a man is placed who gives itmotion: the whole is supported by fourposts. At 10 inches from each side of thegudgeons the iron piston rods M,N areattached, which draw the water in thepump barrels 0,1\ and force it up thepipe LII to a height proportionate tothe diameter of the piston ?nd the actionof the mover. It will be found usefulto place an iron roller carried by steelsprings, F,G, on each side, to assist theaction of the balance beam : M. Morel,the inventor of this and several othermachines, having remarked that whereseveral men are required to ring largebells, a single person could put them inaction by working a treadle, applied thesame cella to working two pumps.

Pumps with three barrels are sometimes used where the object is to keep up a con-tinued current of water by the action of three pistons, one of which is at the bottom of itsworking barrel, while the second is in the middle, and the third at the top of each respectiveliarrel. Mr. Smeaton made use of three pumps at the London Bridge water-works:when the pumps are small, the barrels are made of brass, and sometimes iron: opposite tothe aperture of each barrel there is a short pipe, covered at the end by a door, throughwhich a workman can get access to repair the valves, which are of iron, and which shutdown upon hinges like a door, being covered with leather on the lower side.

Fig. 1839.

B

Fig. 1838.