. Farm implements, and the principles of their construction and use; an elementary and familiar treatise on mechanics, and on natural philosophy generally, as applied to the ordinary practices of agriculture ... d, so that this cord too may wind uponthe larger wheel. These twowheels (fastened together so>* as to form one), as they aremade to revolve on their axis,will now constitute, in a man-ner, a succession of levers, act-ing through an indefinite dis-tance according to the lengthof the cords. The levers heresuccessively acting are of thefirst kind, and the axis ofthe wheel is the fulcru
. Farm implements, and the principles of their construction and use; an elementary and familiar treatise on mechanics, and on natural philosophy generally, as applied to the ordinary practices of agriculture ... d, so that this cord too may wind uponthe larger wheel. These twowheels (fastened together so>* as to form one), as they aremade to revolve on their axis,will now constitute, in a man-ner, a succession of levers, act-ing through an indefinite dis-tance according to the lengthof the cords. The levers heresuccessively acting are of thefirst kind, and the axis ofthe wheel is the fulcrum. This arrangement consti-tutes in substance the wheel and axle ; and its power,like that of the simple lever, depends on the compara-tive velocity of the weight and the moving force. If,for example, the larger wheel is four times the circum-ference of the smaller, a force of one hundred appliedto the outer cord will raise a weight of four hundredpounds. The annexed figure exhibits at one view the pow-er exerted throughthe wheel and axle,where a small weightof 6 pounds will windup (or balance) oth-er weights separate-ly, weighing 8, 12,or 24 pounds, as thedifference increasesbetween the size of Fig. Wheel and axle, showing the heavier weight for WHEEL AND AXLE. 77 the wheel and of the axle, according to the rule of vir-tual velocities already explained. The thickness of the rope has not been taken intoconsideration. This is very small when compared withthe diameter of the outer wheel, but often considerablewhen compared with that of the inner. To be strictlyaccurate, therefore, the force must be considered as act-ing at the centre of the rope ; hence the diameter ofthe rope must be added to the diameter of the wheel. There are various forms of the wheel and axle. Inthe common windlass, motion is given to the axle bymeans of a winch, which is a lever like the handle ofa grindstone. The windlass used in digging wellshas usually four projecting levers or arms. The wheelused
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Keywords: ., bookcentury1800, bookdecade1850, bookpublishernewyo, bookyear1854
