The practical application of the slide valve and link motion to stationary, portable, locomotive, and marine engines : with new and simple methods for proportioning the parts by Auchincloss William Stuart 1842-1928

Author:Auchincloss, William Stuart, 1842-1928
Language: eng
Format: epub, pdf
Tags: Steam-engines
Publisher: New York : Van Nostrand
Published: 1897-03-25T05:00:00+00:00

The principal fact to be borne in mind is that, within & aitable limits, the greater this distance the more readily can the motion be equalized.

From the foregoing we perceive that Link No. 1 is appropriate to a motion requiring acceleration for any cut-off point beyond the neutral position A, and hairing its smaller t crank angles laid off between the link and centre of the

main shaft (as in Fig. 29). The four typical forms of such motions are here presented with a suitable arrangement of the parts, when the link is dropped in the full gear forward, for a positive motion of the crank. But if a negative motion be demanded, it is only necessary to transpose the entire motion so that the cylinder comes on the opposite side of the shaft, in other words to take the power off the opposite extremity of the shaft after first turning the engine end for end.

It was remarked (page 61) that the crank angles of a back-action engine are invariably the reverse of those common to one of direct action; hence, if we wish to preserve the identity of the motion in laying off a figure like 29 for such an engine, it will be necessary to locate the initial positions F and B of the eccentrics opposite to those proper for a direct action, and apply thereto either of the two schemes offered in the Diagram.

EXAMPLE.

The following dimensions have been taken from a most successful freight engine; their application will serve to familiarize the student with the principles of the foregoing method : 6 driving wheels, 57 inches diameter. Outside cylinders, 18 inches x 22 inches. Connecting rods 86 inches in length. Ports 15" in length; steam, If" wide ; exhaust, 3". Diameter of eccentric circle=5 inches. Maximum cut-off=0.8 of stroke. Mid gear lead= 1 5 g inch. Rocker from shaft=55 \ inches. Length of rocker arms=9 inches, c. to c. of eccentric pins=13 inches. Tumbling shaft arm= 18 inches. Hanger=13^ inches. Pins back of arc=3| inches.

^Required. —Radius of link, distance of point of suspension back of link arc, lap of valve, full gear lead, and location of the tumbling shaft.

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