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 . ollower rotation isthe same as that in Fig. 80. The intersections Rv R2, R3, etc., beingfound, the distances RtLv R2L2, R3L3, which the follower gets aheadof the radii, are set off exactly as in Fig. 80. In this case, however,the points Lv L2, and L3 are the centers of the rotated follower roll;and from these centers are struck the arcs representing the followerroll in its several rotated positions. 4. Tangen
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 . ollower rotation isthe same as that in Fig. 80. The intersections Rv R2, R3, etc., beingfound, the distances RtLv R2L2, R3L3, which the follower gets aheadof the radii, are set off exactly as in Fig. 80. In this case, however,the points Lv L2, and L3 are the centers of the rotated follower roll;and from these centers are struck the arcs representing the followerroll in its several rotated positions. 4. Tangent Line. A smooth tangent line is now drawn to theseveral positions of the rotated follower, thus giving the outline of 92 MACHINE DRAWING the cam. In this case the outline of the cam giving the period of restlies between the radii CN6 and CL6. In order that the full periodof rest may be accomplished, it is necessary that the portion of thecam between these two radii be a true arc, struck from center attention should be given this point. 5. Testing. The cam should be tested by the tracing-clothmethod, as before. 6. Pressure Line. The pressure lines are drawn as in Fig. 81. Fig. 82. Diagram of Cam with Roll Follower off Center by joining the center of the follower roll in its rotated positions tothe point of contact between the cam and the roll. Arrows, as before, indicate the direction of the pressure. Thesepressure lines may be rotated until they are collected along the lineof travel, indicating the change in direction of the pressure betweenthe cam and the roll as the roll passes over its path. A convenient MACHINE DRAWING 93 method of laying off these pressure lines is to join the center of thecam C with the center of each roll; measure the angle which the lineof pressure makes with this radius; and then transfer the angle to theproper point on the line of travel. This method is clearly indicatedin the figure. As before, it will be seen that the line of pressure lie
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