188

MODERN STEAM PRACTICE.

comparison with the numerous brasses of the parallel motion, isvery trifling. The air pump is worked in a similar manner, whilethe plug rod is actuated with a separate wrought-iron beam, placedabove the main crosshead, and worked therefrom by means of asmall crosshead, fitted to the top of the piston rod with a parallelmotion—an unnecessary refinement, as when the plug rod is guidedat the top and bottom a plain link attachment is all that is needed.

Fig. 120.—Single-acting Side-lever Pumping Engine.

The other end of this beam vibrates on a gudgeon, with pillowblocks resting on the end wall of the engine-house. The springbeams of wood are placed on each side of the foundation, thesesprings being necessary to check the shock should the engine missa stroke or come in or out too rapidly—the ends of the side levers,striking against the spring beams, greatly reduce the blow, whichwould otherwise be feit very severely on the machinery.

There is another example of the side-lever pumping engine, Fig.120, which although not possessing the advantage of being securely