The pulleys over which they pass should incline from a vertical plane and point to the indicators wherever they may be located. If the indicators and the reducing lever can be placed so as to be in line with each other, the pulleys may be dispensed with and the cords carried directly from the segment to the instruments, a longer arc being provided for this purpose. The arm which holds the carrier pulleys on each indicator should be adjusted so as to point in the direction in which the cord is received.
In all arrangements of this kind the reduced motion is not mathematically exact, because the leverage is not constant at all points of the stroke.
Pantagraph motions have been devised for overcoming these defects. Two forms have been successfully used, which, if well made, well cared for, and properly handled, reproduce the motion on the reduced scale with perfect accuracy. They are shown in working position in [Figs. 3366] and [3367].
Fig. 3366.
[Fig. 3366] represents the manner of attaching the pantagraph motion, or lazy tongs, as it is sometimes called, when the indicators are applied to the side of the cylinder. It works in a horizontal plane, the pivot end being supported by a post b erected in front of the guides, and the working end receiving motion from an iron attached to the cross head.
By adjusting the post to the proper height and at a proper distance in front of the cross head, the cords may be carried from the cord pin c to the indicators, without the intervention of carrier pulleys.
