This is a new arrangement, patented by Mr. Joseph Maudslay, in 1841. We understand that several engines have been constructed on this plan by the firm of Maudslay, Sons, and Field. Its distinguishing feature is the annular form of the working cylinders. Fig. 1 (p. 695) is a sectional elevation, and Fig. 2 a plan. At a is the exterior steam cylinder; b a smaller cylinder, fixed in the centre of the steam cylinder; c c the piston, of an annular form, and working in the space between the two cylinders; dd the piston-rods; e the cross-head; ff rods uniting the cross-head with the guide block g, which moves in the cylinder b. From a pin in the guide block, the connecting rod h is connected with the crank. The air-pump and other parts may be attached to the engine in various convenient ways.
The peculiarity of this engine consists in there being two steam cylinders, each of half the area necessary for the intended power, combined so as to form one engine, and placed so far apart, as to leave a space between them for the connecting rod, and the lower end of a T-shaped cross-head, to which the connecting rod is attached, to work in; the piston-rods being attached to the horizontal extremities of the T cross-head, and moving up and down simultaneously with it and with each other, whereby the combined action of both pistons is applied to one crank of the paddle shaft. In the accompanying drawings Fig. 1 exhibits a longitudinal elevation of one of the engines, consisting of two steam cylinders Fig.l worked by one slide valve, as shown at k in the plan Fig. 2. Fig. 3 exhibits a transverse section of a portion of the vessel, with one of the engines in elevation. At a a, Fig. 1, are the two connected working cylinders; bb their piston-rods, the upper ends of which rods are affixed by keys to the cross-head ccc; at the lower end of the cross-head there is a slider d, working between ribs ee, fixed on the outer surfaces of the cylinders; to this slider d one end of a connecting rodfis attached, the other end of that rod being attached to the crank g of the propelling shaft.
From this arrangement it will be perceived, that by the simultaneous ascent and descent of the two pistons in their working cylinders a a, the rods b b will cause the cross-head c c to move perpendicularly up and down between its guide bars e e, and in so doing to raise and depress the slider d with the connecting rodf, which rod will by that means be made to give a rotatory motion to the crank g, and thereby cause the paddle-wheel shaft to revolve. The air-pump, and the feed and bilge - pumps are worked by the lever m, which is connected to the slider d by the rods n.
The mode of adapting the steam valve to the combined cylinders is shown in Fig. 2. The steam is admitted to, and withdrawn from, these cylinders by one slide valve k common to both, through a pipe, in the ordinary way; the steam passing through the curved passages or tubes 11 into both cylinders. There is also a narrow passage of communication always open, by which the steam, is allowed to pass from one cylinder to the other, for the purpose of keeping the pressure equal at all times in both cylinders.
The advantages stated to be realized by this arrangement are: 1. Simplification of construction; 2. More direct action on the crank; 3. Saving of space and weight of material; and 4. Obtaining the greatest length of stroke and connecting rod in a given height, without any lateral pressure on the pistons or piston-rods.