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In the Crewe engine the flywheel, it will be noticed, is provided with a balanceweight. The admission of the steam to and its release from the cylinder is effected by a four-way cock provided with a lever, which is actuated by a tappet rod attached to the crosshead, as seen on the back view of the engine.
The latter, as a rule, exert a uniform and decreasing, instead of an increasing, purchase on the rudder, in moving it from midgear to hard over. This important object is attained in the gear under notice chiefly through the arrangement of the quadrant and the spring buffers, which form an essential part of it, and of the tiller crosshead.
Webb, these parts having been broken up before the engine came into his possession. The piston rod is attached to a long cast-iron crosshead, from which two bent connecting rods extend downward, the one to a crank, and the other to a crank-pin inserted in the flywheel. The connecting-rods now on this engine were supplied by Mr.
To the crosshead is also coupled a lever having its fulcrum on a bracket attached to the boiler; this lever serving to work the feed pump. Unfortunately the original pump of the Crewe engine was smashed, but Mr. Webb has fitted one up to show the arrangement.
The crosshead and the chains, weighing more than 50 tons, descended with a fearful crash upon the press, and the tube itself fell down upon the packing beneath. Though the fall of the tube was not more than nine inches, it crushed solid castings, weighing tons, as if they had been nuts. The tube itself was slightly strained and deflected, though it still remained sufficiently serviceable.
Park, who was cook this week, had gone to the village for supplies, and so the captain and Tod were alone in the house, the others, with the exception of Morgan, who was at his home in the village with a sprained ankle, being at work some distance away on a crosshead over which the life-line was always fired in gun practice.
The motion of the connecting rod of a reciprocating steam engine is very clearly understood from the simple statement that one end travels in a circle and the other in a right line. From this statement it is also readily inferred that the path of any point between the centers of the crank and crosshead pins will be neither circular nor straight, but an elongated curve.
The dies are held in position by clamp pieces, e e, secured to the end of the chambers A A', by screws, and on each side of these clamp pieces are guides, with grooves, in which moves a bar with a crosshead, termed the guillotine, and which moves across the openings of the dies, and opening or closing them.
Adjusting the Guides. Put the connecting rod in place on its pins, and revolve the crank until the guides have taken up that position which allows the crosshead to move freely. Then mark off the holes for the guide holding-down screws, and drill and tap them. Packings. The glands and piston should be packed with asbestos string.
The spring buffers, which, as has been said, form an essential part of the quadrant, are fitted with steel rollers at the point of contact with the crosshead, thereby reducing the friction to a minimum. The springs, by their compression, absorb any shock coming on the rudder, and greatly reduce the vibration when struck by a sea. They are made adjustable, and can be either steel or rubber.
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