Fig. 3367.
If the indicators are attached to the side of the cylinder, the simplest form of pantagraph shown in [Fig. 3367] may be used. The working end a receives motion from the cross head, and the front piece b is attached to the floor. The cord pin d is fixed in line between the pivot and the working end, and the pulleys e, attached to the block c, guide the cords to the indicators.
The indicator rigging that gives the best results at high speeds is a plain reducing lever like that first described, provided at the lower end with a slot that receives a stud, screwed into the cross head. The length of the lever should be one and one-half times the engine stroke, as given on the preceding page.
Whatever plan is followed, it is desirable to avoid the use of long stretches of cord. If the motion must be carried a long distance, strips of wood may often be arranged in their place and operated with direct connections. Braided linen cord, a little in excess of one-sixteenth of an inch in diameter, is a suitable material for indicator work.
To take a diagram, a blank card is stretched smoothly upon the paper drum, the ends being held by the spring clips. The driving cord is attached and so adjusted that the motion of the drum is central.
For convenience two diagrams, one from each end of the cylinder, may be made on the same card, as shown in [Fig. 3368].
Fig. 3368.