To the head of the piston rod is fixed a cap e e, which works between the guides f f, which are bolted to the cylinder cover, and thus take the strain off the piston rod in the oblique positions of the cylinder, and as the cylinder can be nearly counterbalanced on its axes in all positions, the strain upon the piston rod is never considerable.

Example 518

This arrangement is, we believe, the invention of Mr. Witty of Hull, who obtained a patent for it June 5th 1813.

Partly from the erroneous notion that is extensively entertained, that there is a loss of power in the employment of the crank to transmit the power given out by the piston, and partly from the advantages which would in certain purposes result from a circular motion of the piston upon which the steam impinges. A rotatory engine has long been regarded as a desideratum by numerous theoretical and practical mechanics, and many plans have been devised and some brought into partial operation for that purpose: from amongst these, we select a few of the most remarkable.

Example 519

Ericsson's Disc Engine. The accompanyingfigure represents a rotatory engine invented byCaptain Ericsson, which, although difficult to describe,so as to convey a clear idea of the way in which it operates, is alike remarkable tor the fewness of its parts and the simplicity of its actions. It has no valves, the action of the piston upon the driving shaft is at all times direct, and the engine can be started or reversed at any position of the piston. a a is a spherical chamber formed in two parts, which are joined together by flanges, and bolted to an end plate or cover b, which is cast in one with the bed plate; c is the engine shaft, which passes through the cover b, and has an obtuse cone d firmly fixed upon its end. e e are two sectors or fans, fixed on to the cone on opposite radii, and fitted with metallic packing/in their curved side: the cone d likewise has metallic packing i round its circumference. The sectors e e pass through slits r in a disc or circular plate g, the lower side of which is forced into close contact with the lower side of the cone, by means of a brass bearing I, which presses against its axis h.

The disc is retained securely in its position by a spherical nob on the end of the engine shaft, which works in a corresponding cup or socket in the centre of the disc; and the revolution of the shaft causes the disc to revolve with it by the pressure of the sectors on the sides of the slits, the lower side of the disc remaining throughout the revolution in close contact with the lower side of the cone. The slits in the disc gradually widen upwards to accommodate the continually varying angle which the sectors form with the disc during their revolution together, and to prevent the escape of steam past their edges they are lined with a metallic packing r; the disc is strengthened by thin flat arms s s, and has a metallic packing k round its periphery; the upper end of its axis works in a conical bearing m, governed by a set screw. The engine shaft works in conical bearings at n n governed by set screws o o.

Example 520

Fig. 2. is an end section which will serve to show more clearly the manner in which the engine operates.

The steam passes through the neck t into the spherical chamber, through an opening v cut through its side: this opening is of a triangular shape, and made as wide at the top as the circular plane is there distant from the base of the cone, and gradually tapering oft* downwards; w is the opening through which the steam escapes into the atmosphere, or into the condenser (as the case may be), through the neck y The dotted line x shows where the cone and the circular plane come in contact.

Steam being admitted into the spherical chamber by the neck t and opening v, and being there prevented from passing the line x by the pressure of the disc against the cone at that place, it presses against the upper leaf e, which, together with the cone and disc, is thereby carried round in the direction of the arrow. When the leaf has passed the upper part of the opening to, the steam that has been acting upon it escapes into the condenser, or into the atmosphere; but at the same time the opposite leaf has passed the top of the steam opening w, which iscarried round in a similar manner, and thus the motion is continued.

Example 521Example 522


If it be requisite that the engine should be capable of working with a reverse motion, this may be effected by reversing the inlet and outlet passages of the steam, by means of a four way cock, or a common slide valve.

Corder & Locke's Breast-wheel Steam Engine. - This machine is extremely simple in its construction, having neither piston nor valves, nor, in fact, any rubbing parts save the axle in its stuffing-boxes and bearings. According to the statement of Mr. Josiah Parkes, C. E., who was appointed to examine and report upon the performances of the engine, it is fully equal in effect to cylinder condensing engines consuming the same quantity of fuel. Mr. Parkes further states, that if applied as an auxiliary to a condensing cylinder engine, by causing the eduction steam from the latter to pass through the rotatory engine before it arrives at the condenser, that an additional power equal to one third of the power of the cylinder engine is obtained without any additional cost in fuel, or increase of the air pump or condenser.

This engine consists principally of a wheel, revolving in an air-tight case, in open communication with a condenser, and provided with air pumps, for keeping up an exhaustion within the case.