. Encyclopaedia : or, A dictionary of arts, sciences, and miscellaneous literature; constructed on a plan, by which the different sciences and arts are digested into the form of distinct treatises of systems ... . cumference to the whole circumference of theaxle. To exemplify this, let ABCD, fig. 83. repre-fent the nave of the wheel E, the inner circumferenceof which is 18 inches, and the axle fo fmall that itmay be confidered as a point. Let F and G be tworollers clofely fitted between them : if then the wheelbe turned round, the rollers will alfo be carried alongwith it round the point which
. Encyclopaedia : or, A dictionary of arts, sciences, and miscellaneous literature; constructed on a plan, by which the different sciences and arts are digested into the form of distinct treatises of systems ... . cumference to the whole circumference of theaxle. To exemplify this, let ABCD, fig. 83. repre-fent the nave of the wheel E, the inner circumferenceof which is 18 inches, and the axle fo fmall that itmay be confidered as a point. Let F and G be tworollers clofely fitted between them : if then the wheelbe turned round, the rollers will alfo be carried alongwith it round the point which we confider as an axle jfor there can neither be rolling nor friction againft amere point. But if the axle be of any fenfible fize,,for inftance one inch circumference, then muft eachroller move round by the motion of the nave againftit, and the refiftance of the angle on the oppofite in order to do this, it muft roll in a retrogradedirection upon the nave, and confequently the latter*muft go as far beyond a revolution as is equal to the-circumference of the axle upen it, before the rollercaix go once, round the axle, which in this cafe is by ©•fie. ? MECHANIC S. Plate CCLXXXVU. LTLTLTLTU B. /. / , • Sea. iv. MECHANICS. Wheel- one iSth part of the circumference. Should the cir-earriages, cumference of the axle be nine inches, and that of theinner part of the nave remain as before, the wheelmult perform one revolution and an half before therol*ler could be moved once round, and fo on in the fameproportion : but as the circumference of an axle muftalways be lefs than the inner part of a nave turningupon it with rollers between them, it never can amountto two revolutions of the wheel round the axle, how-ever nearly it may approach to it; for no fegment of acircle can ever be a ftraght line. It will now be apparent, that if feveral rollers beplaced all round between the nave and axle, which-ever way the wheel be turned there cannot be any realfriction, but merely a
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