266

MODERN STEAM PRACTICE.

line is attained with the ordinary parallel motion, having fore andback links, parallel bars, radius rods, and cross gudgeons for theback links. The cast-iron crossheads are turned all over, and aresecured to the piston rods with jibs and cotters; on each side acast-iron ring and thin brass collar is laid on the gudgeon, whichis secured with a key at each end; the outside bearings are forthe main links, while the large eye of the parallel bar is placedbetween the main links and the brass washers.

The main links (Fig. 174) are plain wrought-iron straps, fitted withbrasses at the top and bottom, having a distance column betweenthem, bearing on wrought-iron plates fitted between the flanges ofthe brasses at the bottom of the top pair and at the top of the bottompair; these brasses are held in position with two jibs and one key, ascrew bolt being formed on the bottom jib, fitted with two nuts, oneon each side of the eye formed on the end of the key, an elongatedhole being made in the eye. The straps in some cases are turnedall over on the outside, and oil cups formed on their tops; when got

Fig. 175.—Bull’s Eye and Cross Shafts for Parallel Motion.a, Cross shaft for cold-water pump rod. b, Bull’s eye for cold-water pump rod. c } Cross shaft.

up in first-class style they add greatly to the beauty of the engine.The back links are two plain round rods; the one for the steamcylinder has eyes forged on the ends, fitted with brasses held by asingle key, and the one for the air-cylinder end has an eye at themiddle for taking a bent cross bar, to which the cold-water pumprod is secured. The bottom bar has an elongated eye at the middlefor the rod to pass through, the cross bar for the back link of the