File:Cornish Engine valve gear components.png

English: THE CORNISH PUMPING ENGINE. No. XIX. The Valve Gear.—

In continuing to illustrate details of the Cornish engine, we this week publish details of the valve gear of a 50in. engine. The details represented in Figs. 1,2,3, 4, 5,6,and 7,page 430,are all drawn in the position which they would occupy supposing all the valves to be closed. Fig. 12 is the side view of the gear arbor posts. The quadrants, Figs, 1 and 2, are usually fixed on the arbors outside the posts. Fig. 3 represents the position of the steam, equilibrium, and eduction eyes; Fig.4,the equilibrium release quadrant; Fig.5,the handles and horns; Fig. 6,the weight eyes; and Fig. 7,the locking quadrants. It will be seen that the valve rods which connect the gear eyes with the valve levers must be cranked to clear the gear arbors for the equilibrium and eduction eyes. Sometimes the weight eyes are connected to weighted treadles placed in the cockpit, and at other times simple weights are hung on the rods. Grose, in some of his engines, made the steam valve to serve as a governor valve as well, by employing a treadle weight for the steam arbor, with a screw adjustment which could be actuated from the engine floor, and which enabled the engine man to adjust the lift of the valve to the requirements of the engine. Fig. 11 represents a portion of the plug rod with the expansion tappet frame. A plan of the double plug eyes, shown in elevation in Fig. 11, is represented in Fig. 13. Fig. 8 is a plan of the single plug eyes for the other.

Fig. 10 is an elevation of the injection gear plug rod. A small set-off is provided on the eduction weight rod, to which the cheek, marked a in Fig. 10, is fitted, the cheek marked b being fitted to the injection valve, so that the injection valve is made to open simultaneously with the eduction valve. Fig.9 is an elevation of the air pump rod.