629. Q.—­Will you describe the eccentric and eccentric rod?

[Illustration:  Fig. 51.  ECCENTRIC AND ROD.  Messrs. Penn.]

A.—­The eccentric and eccentric rod are shown in fig. 51.  The eccentric is put on the crank shaft in two halves, joined in the diameter of largest eccentricity by means of a single bolt passing through lugs on the central eye, and the back balance is made in a separate piece five eighths of an inch thick, and is attached by means of two bolts, which also help to bind the halves of the eccentric together.  The eccentric strap is half an inch thick, and 1-1/4 inch broad, and the flanges of the eccentric, within which the strap works, are each three eighths of an inch thick.  The eccentric rod is attached to the eccentric hoop by means of two bolts passing through lugs upon the rod, and tapped into a square boss upon the hoop; and pieces of iron, of a greater or less thickness, are interposed between the surfaces in setting the valve, to make the eccentric rod of the right length.  The eccentric rod is kept in gear by the push of a small horizontal rod, attached to a vertical blade spring, and it is thrown out of gear by means of the ordinary disengaging apparatus, which acts in opposition to the spring, as, in cases where the eccentric rod is not vertical, it acts in opposition to the gravity of the rod.

630. Q.—­Will you explain in detail the construction of the valve gearing, or such parts of it as are peculiar to the oscillating engine?

A.—­The eccentric rod is attached by a pin, 1 inch in diameter, to an open curved link or sector with a tail projecting upward and passing through an eye to guide the link in a vertical motion.  The link is formed of iron case-hardened, and is 2-3/4 inches deep at the middle, and 2-3/8 inches deep at the ends, and 1 inch broad.  The opening in the link, which extends nearly its entire length, is 1-5/16 inch broad; and into this opening a brass block 2 inches long is truly fitted, there being a hole through the block 3/4 inch diameter, for the reception of the pin of the valve shaft lever.  The valve shaft is 1-3/4 inch diameter at the end next the link or segment, and diminishes regularly to the other end, but its cross section assumes the form of an octagon in its passage round the cylinder, measuring mid-way 1-1/4 inch deep, by about 3/4 inch thick, and the greatest depth of the finger for moving the valve is about 1 inch.  The depth of the lever for moving the valve shaft is 2 inches at the broad, and 1-1/4 inch at the narrow end.  The internal breadth of the mortice in which the valve finger moves is 5/16 inch, and its external depth is 1-3/4 inch, which leaves three eighths of an inch as the thickness of metal round the hole; and the breadth, measuring in the direction of the hole, is 1-1/2 inch.  The valve rod is three fourths of an inch in diameter, and the mortice is connected to the valve rod by a socket 1 inch long, and 1-1/8 inch diameter, through