Description of a Stationary Steam Engine of 200 H.P

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396 EODMER’S’ ENGINES.

with the cranks, consequently are suitable for either a backward or forward motion of the engine without reversing their positions), and are connected to the spindles (60 and 61) which work through the hollow rod (62) of the slide valve (one only being shown in section) by the rods (63 and 64.) The lower extremity of the spindle (60) works in the bush (65), in which a groove is cut for the purpose of receivinga keywhich is fitted intothe spindles, so thatupon turning the bushes (65) by the screw wheels (66 and 67),whichare in connexion with thespoke wheel (68), the expansion slides are made to approach or recede from one another by means of the right and left screws which are cut upon the upper part of the spindles, thus regulating the amount of steam which is to be admitted into the cylinders. Thecylinders are supported by the four wrought iron columns (a, a, a, a), to whichalso are attached the guide bars (69 and 70.)

Description of a Stationary Steam Engine of 200 H. P. constructed upon I. G. Bodmer’s compensating principle, and furnished with his variable expansion gear. (See Plates 28 and 29.) Fig. 1 Plate 28, is a ground plan partly in section, and Fig. 2 a sectional elevation. Fig. 3 a transverse section throughthe cylinder and valve box, and Fig. 4 a sectional elevation of the feed pump. Fig. 5 Plate 29 is a ground plan of the engine. Fig. 6 a front elevation in which the front plate of the cistern is removed. Fig. 7 is a horizontal section through the cylinder and valve box showing the centre steam passages. Fig. 8 shows a section of the cylinder through the lower steam passage ; the same letters having reference to the figures on both the plates. This engine being calculated to work with steam at a pressure of 60 lbs. per square inchabove the atmosphere, the slide and expansion valves are cylindrical instead of flat, for the purpose of avoiding the friction and consequeut wear and tear caused by such a pressure of steam. Thesteam is admittedinto the cylindrical valve box (l), which is cast of one piece with the cylinder (2), through the pipe (3), from whence it passes through the cylindrical slide valve (4), and the expansion slides (5 and S), so as to establish an equilibrium. To the valve (4), the shoulders (7 and S) are cast, between which and the rings (9 and lO), which may be screwed upon the cylindrical valve, the elastic piston rings (11 and 12) are fitted. In the position in which the valves and expansion slides are now shown, the steam is admitted through the aperture (13) in the cylin-

drical valve, through a series of diagonal openings in the piston rings and through the port (14) and steam passage (15), into the cylinder (2), and causes the pistons (16 and 17) respectively, to move in the direction of the arrows, and by the time that the pistons have per- formed about@h of thestroke, the expansion slide (G) willhave covered over the aperture (13), when the stroke will be completed by the expansive action of the steam contained in the cylinder and passages. The expansion slides are so constructed, that they can be adjusted to work freely within the cylindrical slide valve when they are hot; they are prevented from turning round by a groove and feather, and respectively connected with the expansion slide rod (18) by one right and one left-handed screw thread. The expansion slide rod (18) works through a stuffing-box (19) at the top of the cylindrical valve box (l), and is connected inits prolongation by a groove and feather with the bush or boss of the contact wheel (20), which latteris acted upon by thecontact pulleys (21 and 22), which are controlled by the governor. When the governor causes the expansion rod (18) to turn in one direction, the expansion slides (5 and 6) will approach, and admit steaminto the cylinder..duringa greater action of the stroke, and when,by the same means, therod (18) isturned in the opposite dirertion, the expansion slides will recede from one another and cut the steam off at an earlier part of the stroke, whereby the velocity and power of the engine are regulated. It has beenabove explained, how the two pistonsare caused to advance towards the middle from the two ends of the cylinders; it is evident, that on the steam being afterwards admitted between them, through the port (23), they will be forced apart again, the pressure exerted upon each being the same, and so on alternately. The piston (16) being connected with the crank (24), by means of the solidpiston rod (%), crosshead (2G), and the connecting rod (27); andthe piston (17) withthe crank (26), by means of the hollow piston rod (29), the cross head (30), and the connecting rod (31), it will be perceived, that the whole strain, at whatever velocity theengine may work, is confined to the pistons,piston rods, con- nectingrods and cranks. The crossheads (26 and 30) haveslide blocks attached to them, which work between guides, fixed to the frame. The slide valve (4) is connected with the eccentric (33) by means of the hollow valve rod (34), and the expansion slide rod (18), which passes throughthe hollow valve rodwith the eccentric (35), by means of the bush (36), in which the valve rod revolves, and the eccentric rod (37) ; and the eccentrics (33 and 35) would be placed at right angles to each other, but for the lead. The governor shaft is worked by R screw pinion (38), and 11 ecrew

wheel (39), fixed on the crank shaft (32). The air pump rod (40) is fixed at its upperend into a projection (41) of the cross head (30), and in the middle into the cross head (42), into which are also fixed the cold water pump rod (44), and force pump rod (45). And as the crank-shaft of this 200 H. P. engine, which is of wrought iron and turns in sphericalbearings, is intended to perform 90 revolutions per minute,at which speed the valves ‘ofthe air pump (which is 27 inches in diameter) could hardly be expected to work easy, and to last for any length of time, the air pump is constructed as shown in section in Fig. 2. The piston (46), which is fixed to the pump rod(40), terminates in a truncated cone; and is provided on its upper surface with a conical cavity, the former corresponding with the conical cavity in the bottom of the air pump, and the latter with the truncated conical end of the valve piston (47). The air pump barrel is cast witha canal (48), round the top, from which, in its whole circumference, a passage opens into the barrel, and the widthof this passage is rendered completely uniform by being turned in the lathe. A rim (49) is adjusted into the top part of the barrel, between the flanges of which the lid (50), which is attached to the valve piston (47), fits, room being left between the valve piston (47) and the under part, and between the flange of the lid (50), and theupper part of the rim (49), fortwo tiers of Vulcanised India rubber. By thisarrangement the passage from thecanal (48) is closed, and the connexion between the barrel of the air pump and the atmosphere is entirely cut off. The air pump is connected with the air of the condenser, by the passage (51), md with the water by the passage (52) ; and supposing now the water which has been collecting in the air pump during the up stroke, to have beensent through the semicircularpassage (52) upon the upper surface of the piston (46), and perhaps to the same level into the condenser (53), it will be carried upwards by the next; up stroke, and the air contained in the air pump, above the water, will be com- pressed by the rising piston, as soon as the latter has risen above the passage (51), until, by its density becoming equal to that of the atmosphere and the weight of the piston (47), the latter is raised, when boththe air and water contained between the two pistons will be completely expelled, through the canal and passage(48) before the piston (46) has begun its return stroke, and since the air forms an elastic medium between the two pistons, the action of the pump is supposed to be attended with scarcely any concussion or noise, the less so, as the truncated ends of the conically shaped pistons will always be the first to come in contact with the water both at top and bottom. It is evident that, as no room whatever is left for any air to lodge in, after

the two pistonshave met, a perfect vacuum willbe established between them,and that the air from the condenserwill rushinto theair pump, as soon asthe piston (46) haspassed heyond the passage (51). The condenser (53) is connected with the eduction port (54) (see section Fig. 3) by the pipes (55 and 56), and the injection pipe (57) is provided with an elastic top (58), for the purpose of compressing the injection water, in whatever quantity it may enter into the condenser, so as to spread it in a disc or sheet. The bottom plate of this engine is fixed to the cistern, and rests on brickwork on three sides, apassage beingleft on the fourth and underneath the condenser, so as to afford easier access to the valves of the feed and cold waterpumps. The frame which is open on two sides, is fixed by bolts tothe bottomplate, thesteam and valve cylinders, cast as before mentioned of one piece, being fixed on the top of it.

Mr. Joshua Burrows Hyde exhibited a model of an adaptation of the AmericanExcavator forDredging, andthus described thema- chine :- Thismachine is upon the same principle as the Excavator, in- vented by Mr. William S. Otis of Massachusetts, U. S., and which was worked for some time on the Eastern Counties Railway, where it wns inspected by numbers who weresceptical, until they had nar- rowly examined it and had become convinced of its power. At thefirst view, the machine appears complicated ; but it is notso in reality. Still it is probable some of the arrangements may be sim- plified, as the machine has remained much as it was originally constructed for Messrs. Carmichael, Fairbanks, and Otis, eminent rail- roadcontractors in the United States, who were driven to thein- vention of some method of rendering themselves independent of their workmen, who by constantly striking, prevented the completion of the contracts undertaken by their employers. Thetrialsof the Excavator on the Eastern CountiesRailway (Fig. 1) were made under very disadvantageous circumstances ; the workmen were inexperienced, the formof the shovel was not adapted to the nature of the material to be excavated, and so few waggons were provided, that frequent stoppages occurred, from the inability to carry away the earth as fast as it could he dug up ; yet in spite of these drawbacks, the machine has delivered as much as 100 cubic yards per hour, and the cost of working it, including fuel, wages, wear and tear, and in- terest of capital, did not exceed fifty shillings per day.