Steam-engine theory and practice by Ripper William 1853-

Author:Ripper, William, 1853-
Language: eng
Format: epub, pdf
Tags: Steam-engines
Publisher: London, Longmans
Published: 1905-03-25T05:00:00+00:00

GOVERNORS.

211

In Fig. 229, if the governor arm were made to slide in the cap at a, then the centrifugal force F would vary as the radius r, and the

FIG. 228.

FIG. 229.

lengths de, ce, and be respectively represent both the radius r and the centrifugal force F.

To compare these two cases, Figs. 228 and 229, by plotting the results and superposing them, let Fig. 230 be constructed, making the ordinates = F and the abscissae = r. We shall then have for Fig. 229 the line joining the intersections of F and r a straight line, namely, OS. But for Fig. 228 we notice that the values of F 3 F and r when plotted do not coincide with the straight line. Thus, for the r 2 position / of the ball (Fig. 228), fb = F = r ; but for position d of the ball, de, the radius, is less than cb, the centri- f fugal force; also gk, the radius, is i greater than ib, the centrifugal force.

Let or s (Fig. 230) = radius de (Fig. 228), and let r. A c (Fig. 230) = centrifugal force cb (Fig. 228), and so on for the other points. Then the line joining the respective intersections will be a curve of the form cfg.

The relation which the curve cfg bears to the straight line oS, drawn from the origin o is important. Thus, since the values of F for the curve cfg increase more rapidly than the values of r, the curve is steeper than the straight line oS, in which F varies as r.

The angle made by a tangent to the curve cfg at /, with a line (of) joining the point of contact / to the origin o, is a measure of the stability of the governor.

If the curve cfg coincide with the line oS, then the governor

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