Machine drawing; a practical guide to the standard methods of graphical representation of machines, including complete detail drawings of a duplex pump and of a direct-current generator . draw a tangent lineto these, the line of the cam will be method, however, from the drawing-boardcenterof cam standpoint, is clumsy and inaccurate, because ofFig. 77. Layout for Posi- the wearing of the pinhole and the error of trans- tions of Cam Follower „ , . „ . „ „ .. ierrmg the shape or the lollower to the tracingcloth. It is readily seen by reference to Figs. 77 and 78, that thesame result
Machine drawing; a practical guide to the standard methods of graphical representation of machines, including complete detail drawings of a duplex pump and of a direct-current generator . draw a tangent lineto these, the line of the cam will be method, however, from the drawing-boardcenterof cam standpoint, is clumsy and inaccurate, because ofFig. 77. Layout for Posi- the wearing of the pinhole and the error of trans- tions of Cam Follower „ , . „ . „ „ .. ierrmg the shape or the lollower to the tracingcloth. It is readily seen by reference to Figs. 77 and 78, that thesame result will be attained in a much easier and more accuratemanner if we artificially rotate the follower about the cam on thedrawing-board by means of a pair of compasses, laying off equalangles to complete one revo-lution of the cam and show-ing the follower in position ateach step. This is shown inFig. 81, and is the method usu-ally followed in cam does not mean that thetracing-cloth method should bediscarded, for it is useful instudying complicated cam move-ments; and also in testing thecam development when it is completed, to make sure that no errorhas been -#^ Fig. 78. Layout for Cam MACHINE DRAWING 85 PRACTICAL EXAMPLES IN LAYING OUT CAMS Statement of Problems. From the principles just stated, theuniform course of procedure in laying out a cam is as follows: 1. Draw the follower in several positions in its path. 2. Draw cam radii corresponding to these positions. 3. Rotate the follower about the cam. 4. Draw tangent line. 5. Test the cam. 6. Draw the line of pressure for each position. Plate Cams with Uniform Motion In Figs. V9 to 86 inclusive, it is required to move the follower Fwith uniform motion from position 0 to 6, while the cam rotatesthrough 450°; it is then to remain at rest during a cam movementcf 30°; then to return to its original position, moving uniformly fromposition 6 to 0, while the cam turns through the remainder of thecircle, or 1
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Keywords: ., bookcentury1900, bookdecade1910, bookpublis, booksubjectmachinery
