In the governor shown in Figure 16 83) two levers (a, a) are piv oted to the arms of the containing case at one of their ends (as at b), while the movable ends are connected by links (B, B) to ears or flanges on the sleeve of the loose eccentric C, so that their outward movement in obedience to centrifugal force (as indicated by clotted lines) advances the eccentric in the direction of revolution. Springs (F, I-) oppose the centrifugal tendency, the tension being adjusted by a screw at c.
two special features in the frame of the "straight-line" engine are (i) its support on three self-adjusting points to free it from torsion, and (2) diverging straight arms in the frame, connect ing the cylinder and the main bearings, as shown in Figure 4 (pl. 92). All boundary-lines are straight, ending in curves; all cross-sections of stationary parts rectangular, with rounded corners; and all moving arms and levers double convex, wide and thin, with the longest axis in the direction of the greatest strain. The frame is cast in one piece with the cylinder, steam-chest, cylinder-jacket, and brackets for rock-shaft and other parts. The valve controls the steam-distribution very much like a common D-valve, but has a variable travel controlled by the gov ernor. As will be seen in Figure 6, the valve is a thin rectangular plate having through it five openings, working within an opening formed by the valve-seat and a pressure-plate and two distance-pieces. By recesses in the pressure-plate and the small openings through the valve there are opened double ports for the steam-admission and exhaust. A vertical section through cylinder and valve is shown in Figure 7. The piston-rod is made fast in the cross-head and the cross-head pin (or wrist-pin) is made fast to the connecting-rod, turning in two bearings in the cross-head. The eccentric is cast a swinging plate, which is pivoted to the boss of the fly-wheel. It is shifted by the governor, and change of its position changes its eccentricity or throw, the travel of the valve, and the point of cut-off. The crank-shaft and wheels, shown in vertical section in Figure 3, are very original. The crank-pin is oiled while the engine is in motion by means of an eccentric chamber on the outside of one of the balance wheels and of holes drilled through the crank-pin. The waste oil from the inner end of one of the main bearings also finds its way to the crank pin. The waste oil thrown from the cranks is caught in a recess in the inner surface of each wheel-rim. The main journal-boxes are split eccen tric sleeves lined with Babbitt metal. The governor, shown in Figure 5, is a single ball linked to the eccentric and a spring, and so located and weighted as to counterbalance the eccentric. Increase of engine-speed
moves the eccentric nearer the shaft, thus shortening both its throw and the valve-travel.
The (fig. 1), which claims to be the first and most perfect type of the high-speed steam-engine, is distinguished for originality of design and for its special adaptation to high-speed running, for attaining which every detail of construction and every movement arc made satisfac torily subservient. The central feature of the valve-motion is a link actu ated by a single eccentric by which separate and independent movements are given to the steam-admission and exhaust-valves. The eccentric is part of the main shaft and has its centre coincident with the crank itself, so that both arrive at their dead points simultaneously.
The valves are all flat frictionless slides, working under plates which protect them from steam-pressure and permit at once four lines of open ing, each the whole length of the port. Two valves for steam admission and two for exhaust are provided, each with the shortest practicable steam way and least waste room. A highly sensitive and unique governor controls the point of cut-off by moving the block in the link. The movement of the exhaust-valves is constant. Mr. Allen invented the valve-gear, and in 1863 Mr. Porter designed the governor, and also the bed, from which all similar beds have been modelled.
Ideal ideal" single-cylinder double-acting engine (pl. 92, fig. 8) is characterized by the valve (a hollow double piston, having steam on each end and on all sides) being driven by direct connection from a "shaft-governor" bolted to the fly-wheel and provided with a dash-pot; by the crank playing in a case containing a considerable quan tity of oil, in which the crank discs clip, and which is so thrown by the crank-motion that it lubricates slides, cross-head pin, piston-rod, and all other parts requiring lubrication; by "pop-out cups," which burst if a dangerous quantity of water gets in the cylinder; by the cylindrical guides bored at the same time as the cylinder; by a very heavy frame and bed plate; and by an "overhung" cylinder of the Porter type (known in England as the " Tangye "). The governor gives an open port at the beginning of stroke, and cuts off from zero to three-fourths stroke. There are no oil-cups on this engine, the system of lubrication providing for con tinuous circulation of oil through all bearings. About once a week the oil is drawn out of the case, filtered, and used over again.