Chap. XVII.
1193
fourth. The three being never in the same situation, while one of the rollers mounts thetwo others descend, after which one descends and two mount, the pistons sucking andforcing accordingly six times during each revolution of the axle, whilst they would onlyplay three times during one revolution of a crank : thus ellipses have the advantage ofdoubling the velocity of the pistons, and of rendering the action of the power more uniform,because the angles formed by the axes of the ellipses are only 60°, or half those formed bythe simple crank.
The great wheel of this machine is 6 feet in radius from the centre to the teeth; theteeth, 101 in number, are 16 inches long, project 4 inches, are 3^ wide, 2^ thick at the top,and 2\ at the base; the axle is 18 inches in diameter : in order that the horse in turningmay pass under the axle L K of the lantern, the summit of the teeth of the wheel must beraised 5£ feet above the ground; the shaft; or lever must be 14 feet long from the centreof the turning shaft to the attachment of the swing-trees, and the horse should have a clearway of 18 feet radius: the spindles of the lantern are 20 in number, and inches indiameter; their centres form a circle 2 feet 10 inches in diameter, and that of the hoopinground them 3 feet 8 inches, which is of timber 5 inches thick: the axle of the lanternand ellipses is 16 inches in diameter; the ellipses are 6 inches apart and 7 thick; thechannel in their edge is 4 inches wide, and 1^ thick : thus they have two edges forming nopart of the length of the axis, which is to be measured to the bottom of the channel, inwhich is a band of iron to keep the timbers together ; the greater axis of the ellipsis shouldbe 5 feet, and the lesser 3 feet; thus half the difference is 12 inches, which is the quantity ofalternate elevation and depression of the rollers: the length of the balance beams from thecentre of the rollers to the suspension point of the piston rods should be 25 feet, and theirscantling 5 inches by 9 ; their centre of motion should be 9 feet 6 inches above the ground :the wooden rollers should he 1 foot in diameter, and 3 inches thick, with a ring of copperon the edges : the centre of motion of the balance beams should be 15 feet from that ofthe rollers, in order that the arm nearest the pistons, being ij of the other pistons, may rise8 inches, or | as much as the rollers. The pump-barrels are inches inside diameter, and
Fig. 1851.
Fig. 1850.
Fig. 1849.
Fig. 1847.
Fig. 1848.
Fig. 1852. 1853.
PISTONS.
12 inches high ; they have four faces, each 3£ inches wide, andare united at the base by a pipe pierced with holes ; to admitthe water between this pipe and the pump-barrel is a valve,fig. 1847.; in one of the faces of the pump-barrel is an orificeto which the branch is adapted ; this branch is only 1 inch indiameter, and comprises a valve similar to the preceding: thepistons, fig. 1852. 1853. are cast-iron cylinders, with a plate ofthe same metal attached to a double fork, to hold the pistonrod, which is a deal batten, 4 inches square. The pistonsare composed of two parts, one 8 inches high andinches in diameter, and the other 4 inches high, and 1 \ indiameter: at its extremity is a screw and nut serving totighten a number of roundles of leather : when the pistonsucks, the weight of the atmosphere forces the water toenter the barrel by opening the valve which is at thebottom ; the moment the piston forces, the valve closing,the water passes into the branch, opens the second valve,and rises in the discharging pipe. The branches of thepump-barrel being only 1 inch in diameter, while thepistons are the water is forced into a pipe, which isonly one-sixth the size of the piston; and thus the horseemploys a part of the force he exerts to overcome theobstacles which are opposed to the water’s progress.
To calculate the Product of this Machine -The horse per-
forms two turns in a minute, or 120 per hour, and at eachturn goes over 88 feet; thus the velocity is 10560 feetper hour: the wheel having 101 teeth, and the lantern
20 staves, it will make 5^ turns whilst the wheel makes 1; and as this latter performs120 revolutions per hour, it follows that the lantern will make 606 in the same time, and