. The science of railways . tch of the quadrant (220) and scratch a lineon the valve stem (49) close to the packinggland. Then I would place the lever in the for-ward notch of the quadrant and move the eccen-tric around by hand until the line on the valvestem appeared; then I would tighten the screwsthat fasten the eccentric to the axle. If the back-ward motion eccentric (i? Fig. 13) had slipped, Iwould proceed in the opposite manner. *This applies to indirect valve motion, as shown in Figs. 13,14 and 15. With direct valve motion, as shown in Fig. 123, thereasoning would be the reverse. OF THE
. The science of railways . tch of the quadrant (220) and scratch a lineon the valve stem (49) close to the packinggland. Then I would place the lever in the for-ward notch of the quadrant and move the eccen-tric around by hand until the line on the valvestem appeared; then I would tighten the screwsthat fasten the eccentric to the axle. If the back-ward motion eccentric (i? Fig. 13) had slipped, Iwould proceed in the opposite manner. *This applies to indirect valve motion, as shown in Figs. 13,14 and 15. With direct valve motion, as shown in Fig. 123, thereasoning would be the reverse. OF THE LOCOMOTIVE ENGINEER. 73 What is the position of the eccentric when thecrank pin is on the forward center^ With thestandard type of rocker arm (P), which gives in-direct valve motion, the forward motion, (go-ahead) eccentric always follows, and the back-upeccentric always leads the crank pin at rightangles, less the amount of lap and lead, when theengine is moving forward, see Skeleton Fig. 15. //y/;//f£cr y^LV£ Mor/orr o. In the event of a valve (47), valve yoke (48),or stem (49), becoming broken inside of a steamchest (44), how can the breakage be located^ Totest one side, place the piston at half-stroke andadmit a little steam to the cylinders, then movethe reverse lever (217), from full forward to fullbackward gear. If the steam escapes alternatelyfrom both cylinder cocks (68) it may be concludedthat the defect is in the opposite steam chest. Having located the defect, how would you putthe engine in safe running order? By taking offthe steam chest cover (43), and blocking or fasten-ing the valve (47) centrally as shown in Fig. 16, G vol 13 74 DUTIES AND RESP0NSTB1 fJTIES or by plugging the ports (56) with soft woodboards if the valve was broken. The defectiveside should then be disconnected and the cross-head (96) securely blocked. If the valve seat (52) is broken, what should bedone? Take off the steam chest cover, coverboth steam ports (56) as shown in Fig. 16 anddiscon
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