d which is represented in Figure 273,
removed from the lines used in constructing it.

[Illustration: Fig. 274.]

The engravings from and including Figure 274 illustrate the lines
embracing cut-off cams of varying limits of cut-off, but all of like
travel and dimensions, which are the same as those given for the full
stroke cam in Figure 272.

In drawing cut-off cams, the stroke of the engine plays a part in
determining their conformation, and in the examples shown this is
assumed to be 4 feet. Figure 274 illustrates the manner of finding
essential points in drawing or marking out cut-off cams. With X as a
centre, and a radius of 2 feet, draw the circle E 1, showing the path of
the crank-pin in making a revolution. This circle has a diameter of 4
feet, equal to the stroke of the engine. Draw the horizontal line B,
passing through the centre of circle E 1. Within the limits of circle E
1, subdivide line B into eight equal parts, as at 1, 2, 3, 4, etc. Draw
the vertical lines, 1, 2, 3, 4, etc., until they each intersect the
circle E 1.

[Illustration: Fig. 275.]

With X as a centre, draw the circle E, having a diameter of 18 inches,
equal to the space in the yoke embracing the cam.

From the centre X draw the series of radial lines through the points of
intersection of the vertical lines 1, 2, 3, 4, etc., from the circle E
1, and terminating at X. We will now proceed to utilize the scale
afforded by Figure 274, in laying off the cut-off cam shown in Figure
276, of half stroke limit.

[Illustration: Fig. 276.]

With X as a centre, draw the circle E, Figure 275, having a diameter of
18 inches. Bisect this circle with the straight lines A and B, which
bear the same relation to their enclosing circle that the lines A, B,
do to the circle E in Figure 274.

[Illustration: Fig. 277.]

It will be observed, in Figure 274, that the vertical line A is (at the
top half) also No. 4, representing 4/8, or half of the stroke. With a
radius of 18 inches, and one point of the dividers placed at V, which is
at the intersection of the circle E with the horizontal line B in Figure
275, draw the arc P. With the same radius and with one compass point
rested at V', draw the arc P'; then two arcs, P and P', intersecting at
the point S.

With the same radius and one point of the compasses at S, draw the arc H
H. The arcs K 1 and K 2 are drawn from the centre X, with a radius of
10-1/2 for K 1 and 7-1/2 inches for K 2, and only serve