. The railroad and engineering journal . espects the same ; thecommon center of all the circles in it being 0, fig. 351, is pro-jected to O in fig. 350. Hence it will be easy to construct theellipses representing these circles in the oblique projection, andconsequently to determine the points f,/, k, etc., in the curva-ture of the teeth ; observing that, as their center lines convergeto Cin the front face, they all tend to O in the lemoter surface,which is, however, for the most part concealed by the former. U would be superfluous to enter into any details regarding the construction of the obl
. The railroad and engineering journal . espects the same ; thecommon center of all the circles in it being 0, fig. 351, is pro-jected to O in fig. 350. Hence it will be easy to construct theellipses representing these circles in the oblique projection, andconsequently to determine the points f,/, k, etc., in the curva-ture of the teeth ; observing that, as their center lines convergeto Cin the front face, they all tend to O in the lemoter surface,which is, however, for the most part concealed by the former. U would be superfluous to enter into any details regarding the construction of the oblique view of the rim, hub and arms,which are drawn upon precisely similar principles to those whichhave already been so fully explained. INTERNAL GEARS. Fig. 352 represents a gear wheel, A, in which the pinion Bis within the circumlerence of the pitch circle. Such gears wereformerly quite extensively used, but of late years they havecome to be considered as clumsy contrivances, and are rarelyused except in special mechanisms.* Fig. 353-. The method of laying off cycloid teeth for such gears is asfollows : • Let A A, fig. 353. and B B be arcs of the pitch circles of awheel with 36 teeth of i in. pitch, and of an internal gearedpinion with 16 teeth, and P the pitch-point ; C a. tooth belong-ing to the wheel, and D one on the pinion. The flank P a olthe tooth C works on the face P b oi the tooth D. The outlineof the flank P a is an epicycloid described by the rolling of agenerating circle, P, on the pitch circle A A of the wheel ; andthe outline of the face P b 6{ the tooth of the wheel is also anepicycloid, described by the rolling of P on the pitch circle B Bof the pinion. The face P a of the wheel tooth C works withthe flank P b of the pinion tooth P>. The outline of / a is ahypocycloid, described by a generating circle, P, rolling insideof the pitch circle A A of the wheel ; and the flank P b is de-scribed by the rolling of P inside of the pitch circle B B ofthe pinion. A
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectrailroa, bookyear1887
