WIMSHURST'S PATENT SCREW-PROPELLING MACHINERY. (Patent dated November 12, 1850. Specification enrolled May 12, 1851.) MR. WIMSHURST, the shipbuilder, who was the first person to apply the screw to sailing vessels as an auxiliary propelling power, namely, in the Novelly, built about ten years ago, and who has ever since continued to exert himself with a most praiseworthy perseverance to bring into general mercantile use this combination of the powers of wind and steam, has now patented a number of improvements in relation thereto, which may be considered as exhibiting the matured results of his long practical experience in this branch of naval combination, and of the great ingenuity and skill he has brought to bear upon it. The first object with Mr. Wimshurst has been to improve the method of applying steam power to the working of the screw. He would still, as in the Novelty, apply the power directly to the screw-shaft, without the intervention of gearing or any other kind of multiplying power; but he would prefer, it seems, before every other description of engine, one on the rotary principle, constructed in the manner represented in figs. 1 to 8 inclusive of the accompanying engravings. Fig 1 is an end elevation of Mr. Wimshurst's proposed engine; fig. 2, a transverse section; fig. 3, a longitudinal section; and figs. 4, 5, 6, 7, and 8, separate views of different parts detached from the others. Specification. In its general structure this engine so far resembles others of its class, that the power is obtained by means of a drum revolving eccentrically within an external cylinder, and the pressure of steam against a series of pistons successively protruded from the circumference of the drum as it revolves; but it differs from others in the following among other important particulars : First. The external cylinder is bored, not of a perfectly circular form as usual, but of unequal diameters at certain points, by which a nearer correspondence to the eccentric path described by the pistons carried by the inner drum is obtained. Second. The pistons have their chief bearing points on anti-friction rollers (within the recesses of the drum) whereby the frictional resistance to their movements is reduced to a minimum, or as nearly so as may be. And third, the steam is admitted (during the forward and ordinary course of the engine) from below into the external cylinder, and by its upward pressure on the pistons serves in a great measure to relieve the bearings and external cylinder from the weight ght and friction of the moving parts of the engine. In the figures, A represents the bed or foundation plate of the engine. B the external cylinder which has the peculiar form above-mentioned given to it by boring it from three centres in manner following:-Assuming the diameter of the cylinder to be 60 inches, it is in the first instance bored out of a true circle from a as the centre in the diagram, fig. 1"; the centre or axial line of the boring tool is then shifted in a vertical line from a towards b, about one-eighth of an inch, or about a fifty-third part of the cylinder's diameter; which being done, it is again shifted in a horizontal direction towards d, about three-eighths of an inch, or about 160th part of the diameter, which will bring the axial line of the cutter bar to the point f. The tool is then placed at such a distance from the last centre that it shall just touch the circumferential point g, about 2 inches above d, and while it is in this position, a cut is made through the cylinder from end to end, whereby a lune-shaped piece is cut away as indicated by the dotted lines. To make the lower side of the cylinder of a corresponding shape, a similar series of operations is gone through; that is to say, the cutter bar is first shifted from the centre a towards c, one-eighth of an inch, and next horizontally towards d, about three-eighths of an inch, when a third cut is made through the cylinder from end to end as before (beginning at the point h, about two inches from the under side of d). The slight ridges left by boring from different centres are to be then worked off, and the internal surface of the cylinder to be rendered quite smooth. The result of the peculiar form thus given to the interior of the external cylinder is that, although the inner drum is revolving eccentrically to the outer cylinder, yet the pistons, which are of one continuous length, passing through the inner drum, are kept nearly in constant contact with the inner surface of the external cylinder, and with as little movement of the necessary packings as may be. C is the inner drum, which may be cast wholly solid or partially hollow (as shown in fig. 4), and is divided by six slots or recesses, for as many pistons to work in, into six segments, c, ch, ch, ch, ch, c1. CC1 are bosses which are affixed to the ends of the drum (revolving with it) for the double purpose of strengthening the drum and affording a ready means of packing it at the ends. DD are two shafts that are keyed on one line with the two bosses, and carried by suitable standards FF, or they may be supported by bearings affixed to the ends EE of the outer cylinder; these two shafts form the main shaft of the engine, which may be coupled to any other machinery. The details of the mode of packing the drum at the end are shown in fig. 3, and in figs. 7 and 8. A metallic hoop H (figs. 7 and 8) is slipped loosely over each of the bosses CC; connected with the hoop there is a metallic ring y2; ysys are segmental pieces of metal, between which and the ring y2 and the bosses there are inserted packings (of cork or any suitable yielding material). y4y4 are pinching screws, by which the pressure given to the cork or other yielding packing is regulated; for regulating the pressure of the ring y against the cylinder cover, there are pinching screws passed through the hoop H. The segments, packing rings, and hoops are secured to the boss by screw bolts y'y', so that they all revolve along with the inner drum. When the drum revolves, the inner edge of the metallic ring packings runs against the inner edge of the cylinder cover (rendering that part steam tight), but to prevent them or the bearings from being injured by the heat, the whole are inclosed in cases SS, which may be filled with water or other liquid, and made also steam-tight round the shafts DD by means of packings, such as represented in the plan fig. 4. TT are the packings, which are formed of cork or some other like yielding material. TT are gaskins, and T2T2 metallic blocks by which the packings are pressed against the shaft by means of the pinching screws T3Ts. UU are the pistons, which are of a rectangular form, and connected together in pairs by means of bars V V, which are passed through the pistons, and secured at the ends by cotters; for which screws or nuts might be substituted. Each pair of pistons works to and fro through the drum in the recesses made for them, and they bear at the sides against antifriction rollers XX, placed at different distances, but near to the extremities of these recesses (when the pistons are fully protruded from the drum.) To keep these anti-friction rollers true in every change of position, they have at their ends small pinion guides mm (see fig. 5), which gear into fixed racks n n within the recesses in the body of the drum. The pistons are rendered steam-tight by means of packings, which are inserted at 3535 in pistons, running parallel to the recesses, and pressed by springs against the sides of the grooves by which means the steam is prevented from passing through into the eduction side. W W are caps or head-pieces, which are affixed on the outer ends of the pistons, and made on their rubbing surfaces of a convex form; and z z are metallic packings, which are inserted into these caps at the extreme points where they come in contact with the exterior cylinder. To keep these packings pressed out against the inner face of the external cylinder, they are acted on by spiral or other suitable springs inserted in recesses made in the pistons and caps. The springs are each covered by a plate, between which and the metallic packing a gaskin is inserted, if required, or any other suitable packing. a1 a are the induction or steam ports (supposing the engine to be revolving in the direction indicated by the arrows), and be be the eduction steam ports; c is a reversing slide, which is worked when necessary by means of the hand-wheel O, and the pinion O2 and rack O3, the last of which is affixed to the spindle of the reversing slide; d is the exhaust port. The steam ports and passages a1 a and b be open into the cylinder at different parts of its circumference, which enables the steam to be worked more or less expansively at pleasure, without the necessity of having a separate expansion valve for the purpose. If it is desired to work the steam expansively, then the reversing slide valve is so placed over the ports that it admits the steam only into the lower one (a1), in which case the quantity of steam admitted behind the piston during one-sixth of a revolution, after passing the port, has to expand in the compartment contained between that and the next succeeding piston, till, after having traversed over about one-half the entire circumference of the cylinder, it ultimately escapes through the exhaust port, the compartment having progressively increased in capacity during nearly the whole time, whereby the full expansive force of the steam is brought into action upon the piston, and transmitted to the main or driving shaft of the engine. If the steam employed in giving motion to the engine is not to be so much expanded, then the reversing slide is pushed further up, so as to open both the ports a1 and a for the supply of steam; and when this is the case, the steam entering by the port a1, after acting through one fourth of a revolution, is further augmented by steam through the port a3, so as again to fill the compartment with steam at the same pressure as that in the steam pipes. After producing its usual effect, or impelling the pistons and shaft, the steam escapes by the passages bi2, and so on continuously. Sometimes, instead of opening the parts a and b to their full extent for supplying the steam to the engine, I only partially open them, so that the pressure of steam admitted behind the piston in the first instance may be less than that contained in the boiler; when such is the case, a separate set of passages (either cast along with the cylinder, or pipes may be substituted for these passages), and valves are employed for admitting the full pressure of steam behind the pistons, after they have advanced a portion of their course under the influence of the lowpressure steam. The reversing of the engine is effected by simply moving down the slide c, so that it may admit the steam to the ports 662, and put the ports a1 a2 in communication with the exhaust port d. In large engines, it will be further necessary to shut off the steam by the throttle valve previous to moving the reversing slide valve. Gis the condenser, which I have placed over the engine, considering that the nearer the condenser is to the level of the water-line of the vessel (when the engine is used for marine propelling), the less will be the back pressure upon the air-pump piston. The condenser is enclosed in an outer casing G2, the intervening space being kept constantly filled with the injection water, which is allowed to flow through it into the condenser, whereby the temperature of the condenser is kept at a comparatively low state. His a double-acting air pump, the plunger of which is directly connected to the piston of an auxiliary " donkey engine" J, which in most cases I prefer to having the air pump worked by the rotary engine itself, as that would be revolving at too high a velocity for conveniently connecting the air pump directly to it. When, however, the rotary engine is of great power, and the cylinder of considerable length, then an auxiliary shaft may be employed to give strength, or prevent any risk of fracture from torsion; the auxiliary shaft in such case would be placed parallel to the main shaft, and be connected to it by wheel gearing placed at both ends of the cylinder. By adopting an arrangement of this sort, the auxiliary shaft may be made to revolve with much less velocity than the main shaft, and, under such circumstances, might be employed for working the air pump. K is a steam cylinder, the piston rod of which forms the slide-valve spindle of the cylinder J; the slide valve of the cylinder K is worked by tappets affixed to the piston rod of the air pump. Although this engine is presented to us as more especially applicable to marine propulsion, yet the reader will understand that Mr. Wimshurst by no means confines himself to this, or, indeed, any particular application of it. The first trial made of it has, in fact, been made on land, and the first proofs which Mr. Winshurst has been able to produce of its capabilities have been derived from its application as a stationary prime mover. We refer to an engine which has been constructed on this plan by the Butterley Iron Company, and is now in constant use there. Of the dimensions and performances of this engine, the following is an authentic account: "The diameter of cylinder is 60 inches, length of piston 40 inches, width 12 inches; effective area of piston 450 square inches, equal to 5-feet stroke; pressure of steam in the steam-box 20 lbs., pressure on the piston 13 lbs. The engine was tested by a break applied to a 6-feet friction wheel keyed on the shaft, with a groove in the edge to receive a band 5 inches wide; lever applied 5 feet on a 4-inch fulcrum; weight on the end of lever 672 lbs.; speed of engine 65 revolutions per minute. If, therefore, we multiply 672 by 15-9580 lbs. on the circumference, which is 18 feet 9 inches x 65 per minute=1228 feet x 9580 lbs. =356 horses power (at 33-000 lbs.) as indicated by the break. But if we take the pressure on the piston and its velocity, we shall find it much less; that is to say 450 area of piston, 13 lbs. pressure-5850 lbs., 65 revolutions; rate of piston 1040 feet per minute= 184 horses power. The difference is to be thus accounted for: The friction wheel worked in oil, and in all engines some allowance must be made for friction, but in this instance the indicator was applied to the piston, and at the minimum pressure of Ilb. of steam the engine made near thirty revolutions per minute. After realizing these satisfactory results, it was determined to test this engine at the Great Britain coal-pit, belonging to the Butterley Company. All we had to do, was to bury two railway sleepers in the ground, and to place our engine on them, securing it with six screw-bolts. At this trial we had no balance of any kind, no break or gearwork; but a single rope brought direct to 10 feet, drew up the weight of rope, 26 cwt., basket 13 cwt., chain 3 cwt., and 18 cwt. of coal, together 60 cwt., 175 yards in 32 seconds=1015 per minute=205 horses power. At this time the pressure in the steam-box was 28 lbs. x 450 area of piston=12400, rate of piston 57 revolutions, or 912 feet per minute=331 horses power (at 33.000 per horses power). This would indicate greater power than the weight raised by 126 horses power, which is no doubt to be imputed to friction on the pulleys, &c. The whole of this was done under the greatest command without the break; when the steam was shut off, the engine stopped almost instantaneously, and when the weight was lowered, and the steam shut off, the whole weight would dance or spring up with the rope." (To be continued in our next.) DEFICIENCY OF THE EXISTING ARRANGEMENTS FOR THE EXTINCTION OF FIRES. The frequent occurrence of destructive conflagrations in the metropolis, the acknowledged efficacy of Sir Samuel Bentham's arrangements for the prompt extinguishment of fire (see ante p. 166, current vol.), together with its applicability in a partial manner in all situations where any of the water companies have mains, indicate that it would be well worth the while of many private persons to adopt his invention immediately, without waiting for a general introduction of the measure, as recommended by the General Board of Health. Sir Samuel grounded his proposal to the Admiralty of 13th February, 1797, on a consideration of "The immense losses that have been sustained in con sequence of the devastations of repeated fires in His Majesty's Dockyards," and recommended in general terms the fireextinguishing works, which, early in the present century, were carried into execution at Portsmouth according to his plans; they provided a great supply of fresh water, and also for the raising seawater for the extinguishment of fire, as already shown. An ample supply of water for this purpose is already furnished throughout London by the several water companies; their mains, with fire-plugs upon them, are laid along all of our principal streets; the adaptation of those plugs to the reception of hose is all that is wanting to carry into effect the proposal to Sir Robert Peel, which appeared in No. 1464 of the Mechanics' Magazine.* In the present state of the water-supply question, it cannot be supposed that any of the water companies would be at the expense of altering their fire-plugs, but they would probably give permission to private persons to adapt at their own cost the fire-plugs on the mains to the reception of fire-hose. This might be done by a joint subscription amongst neighbours for the protection of private dwellings; and in the case of many manufacturers, the small cost of a screw-plug and suitable hose would be but a trifling premium paid for the security thus afforded against extensive conflagration; now that Hamburgh is in proof that the introduction of Sir Samuel's plan is to the interest of insurance companies, they might possibly diminish the rate of insurance on property whenever it might be protected by efficient apparatus for throwing water direct from the mains. Sir Samuel's views extended from the first far beyond the boundaries of a dockyard; in his first proposal of 1797, it was specified that the water mains "might be extended without the limits of the dockyard to the gun - wharf, victualling premises, barracks, and other public establishments;" he observed that such an undertaking on the part of Government would afford an example to the public, and concluded his proposal thus, "The reasons for affording the security above-mentioned to the naval establishments near Portsmouth seem to apply equally to all other establishments elsewhere in proportion to their importance. Where the establishment is less extensive the expense would be proportionably less. In the instance of Plymouth Dockyard, the water is already sufficiently elevated to be laid in according to the mode here proposed without the necessity of raising it by machinery." To what public establishments other than the Royal Dockyards has his plan to this moment been adopted? Ships have been on fire in Portsmouth Yard, and the flames have there been speedily extinguished by Sir Samuel's apparatus; where no such works exist, the other day at Havre (France), two costly ships Erratum in that Number, page 167, last line but one, for "immoveable" read" moveable." were burnt on the stocks. We have had a House of Commons consumed, a Royal Exchange, important buildings in the Tower of London, &c., all long after the efficacy of the Portsmouth Works had been experienced: may it not then be presumed that had the example been followed in regard to public establishments generally, many of those that have been destroyed by fire would be remaining to us at the present day? There is a steam-engine for raising water near Trafalgar - square; why should it not force water in case of fire for the protection of the public buildings in the vicinity? Why should not fire hose be immediately fitted on the mains that supply water around the Royal Exchange, the Bank of England, the Mansion-house, that beautiful structure, St. Stephen's, Walbrook, the Guildhall, &c., &c.? The mode of altering fire-plugs might not be so well contrived if left to different private persons as if some general plan were followed; but is it wise by waiting for perfection to forego a minor good attainable at small expense? The chief inferiority of separate to combined arrangements would arise from the want in the former case of a wellorganised and numerous set of persons always at hand to work fire extinguishing hose. This was a difficulty at Portsmouth; the police of the yard was not to be interfered with; but Sir Samuel placed all the fire-extinguishing works under the responsibility of the mastermillwright, who was entirely under his (Sir Samuel's) control. By the fifth article of his instructions, officially given, 1805, he made the master-millwright responsible for the good repair of the steam engine, and for its being "kept in full working order." The water companies may be depended on in this respect; but another article of the instructions, the eighth, would be to be attended to in private establishments by some person appointed by the master; it is an important article, namely, "that all the apparatus prepared for extinguishing fire be kept in good repair, and in constant readiness to work, night as well as day." Farther, the master- millwright was to cause all the engine-keepers and labourers "To be properly instructed in the management of the penstocks, also of the pipes and cocks for supplying |