IMPROVED METHOD OF REVERSING LOCOMOTIVE ENGINES. Sir,-When reflecting on the state of perfection which mechanics have arrived at, I often wonder that a more simple plan has never been devised for reversing focomotive engines than the present imperfect one, of using four eccentrics with forked rods, (two of which are always working to no effect). In one of your recent volumes, there was a method by Mr. Charles Pearce, for working the valves of locomotive engines with two fixed eccentrics, with a double set of forks, which is, so far, a great improvement on the common plan. I now beg to lay before your readers a method of reversing the action of locomotive engines with two eccentrics, the rods of which are without forks or coupling-rods of any kind, and are connected immediately from the crank-shaft to the valve-rod by a mere joint, (see fig. 1, Description of Engravings). In reversing an engine on my plan, the engine-driver has only the handle of the steam-cock to attend to, the same handle serving the double purpose of reversing the action of the engine, and letting on or shutting off the steam from the cylinders, (see figs. 3 and 4). I effect this by substituting a fourway cock, (placed in the smoke-box of the engine,) for the ordinary steam-cock. The four-way cock is employed in the following manner, that is to say, one of the passages serves for the blast-pipe, one for admitting steam from the boiler, one for giving the engine a forward motion, and the fourth for giving the engine the reverse motion, (see fig. 2). It will be seen that the steam from the boiler is admitted both above and below the valvecup (or slide); but, to prevent the slide from rising when the pressure of the steam is on its under surface, I have introduced a small roller, running in two supports on the top of the slide, the roller working against a smooth projecting piece of iron or rail, cast to the top of the valve-box, (see fig. 6.) Description of the Engravings. Fig. 1 represents an outline of a locomotive engine, with my method of reversing attached to it. A, the boiler; B, one of the cylinders; C, the valvebox; D, the slide; e, the piston-rod; F, the connecting-rod; G, the crank; H, the eccentric, with its rod attached to the valve by the joint I; J, the four-way (or steam) cock; K, the handle of the same, with its rod L, passing along the interior of the boiler, and firmly fixed in the centre of the plug, at m; N, the steam-pipe from the receiver, O, to the four-way cock; P, the exhausting or blast-pipe; Q, the pipe to admit the steam to the top of the slides, to give the engine a forward motion. The pipe for admitting the steam under the slides is not shown in this figure. Fig. 2 shows the interior of the smokebox, and the arrangement of the steampipes. A, the four-way cock, with the plug in the position for the steam to pass down the pipe B B, under the slides, and move the engine backwards, whilst the waste steam will pass through the valveboxes, along the pipes C C, to the blastpipe D D, into the chimney. Now, if we suppose the four-way cock-plug to be moved by the engine-driver a quarter of a revolution, the now steam-pipe will become the exhaust-pipe, and the exhaustpipe the steam-pipe; and, consequently, the motion of the engine will be instantly reversed, with the least possible amount of trouble. Figs. 3 and 4 represent enlarged sections of the four-way cock, as fixed to the engine, with the regulating lever attached to it, and shown in the following positions: in fig. 4, the lever is in the perpendicular position, with the steam shut off from the cylinders; but when it is in the position of fig. 3, the steam is directed down the pipe A, over the slides, and propels the engine in a forward direction; and when it assumes the position as shown by the dotted lines, the steam is directed down the pipe B, under the slides, and propels the engine backwards. Thus moving the handle of the four-way cock out of the vertical position, either to the right or left, we have a backward or forward motion, (as the case may require,) thereby obtaining the most complete control over the machine. Figs. 5 and 6 show the method by which the valve-cup is kept in immediate contact with its seat, when the steam pressure is on its under surface. A, the cup; B, the roller, turning in two small brass steps, C C, the steps sliding freely upwards and downwards in the supports, DD; F F are two slightly inclined iron wedges, which slide under the two steps that support the roller; G, a strong steel spring, fixed to the valve-cup by a pin through its centre, and pressing with its two ends against the wedges FF; so that, in the event of the valve becoming slack by use, the spring G will force the wedges under the brasses that support the roller, and bring it into close contact with the projecting rail H, fig. 6, and thus prevent the escape of steam. The four-way cock, when applied to the cylinder of a steam-engine instead of the slide-valve, possesses the advantage of reversing the motion of the engine by applying the steam to the eduction-pipe, and vice versa. Though the sliding- I remain, Sir, yours, &c., Preston, December 5, 1842. P.S.-I find I have omitted to mention, that the plug of the four-way cock is so constructed, that when the engine is going down an inclined plane, and the steam shut off, the exhaust-pipe may have a free communication with the atmosphere. Also, by a slight alteration in the eccentric, the valves may be made to have the lead both ways. LIGHTNING CONDUCTORS.-WIRE-ROPE RIGGING. Sir,-Had I the honour of a few years' personal acquaintance with Mr. Roberts, I have not the slightest doubt but that I should have implicitly believed any statement he might make, particularly if it bore the semblance of probability. Just so it is between myself and other parties with whom I have conversed on this subject. I cannot learn that Mr. Roberts ever applied wire- rope conductors to ships of the navy, or that his name is even known to the Lords Commissioners of the Admiralty. I am equally unsuccessful in my inquiries regarding ships in the merchant service, either in London or the outports, though having no particular reason for pursuing such an enquiry, it is quite possible that the mere accidental and limited information one person falls in with, may be far short of, and totally disagree with, the result of a more extended research. There is no person in existence less inclined than myself to withhold from Cæsar his due, or to heap honours on one individual at the expense of another, and I regret that Mr. Roberts should have thought so. It appears to me that it is only necessary for Mr. Roberts to inform the public of the ships he has fitted with wire-rope conductors, or of its serviceable application by him in any other way, and he will at once place himself in the honourable position of a useful projector, and obtain all the merit due for such services, and whatever may have been said by others will become as snow before the sun." 66 In making allusion to lightning conductors, when describing the Great Britain steam ship, I had no idea of the extent to which it had been carried, or of the interest it has occasioned in the public mind. A pamphlet, put forth by Mr. Smith, has lately been left at my office, by which I find that thirty-six ships of war, mounting in the aggregate 1411 guns, besides smaller craft, have been fitted with iron-wire standing rigging and lightning conductors in her Majesty's navy by Mr. Smith, and that fourteen other additional naval ships have been fitted with wire-rope lightning conductors, besides twelve steam ships and vessels for various companies in the English merchant service during the last seven years, as also some for the Russian and other governments. I am also informed that orders are now given for fitting thirty sail of the line with lightning conductors on the most efficacious and certain principle; there fore the subject appears to be considered of vast importance and deserving the most powerful investigation: I will therefore hazard a few additional remarks, more with a view to elicit useful and practical facts from others than from any idea that such can possibly result from myself. The devastating effects of storms and tempests, supposed by many to be of electrical origin, which have within the last few weeks sent so many valuable seamen to their last account, besides the destruction of a vast amount of property, make the inquiry into the most certain means of preventing the injurious effects of lightning at the present moment doubly interesting, particularly as the stern face of winter is so near us. I observe a lecture has lately been delivered by Lieut. Sabeen, R. N., at Plymouth, on the subject, embracing all the prominent considerations of lightningconductors, drawing a comparison between the plan projected by Mr. Snow Harris and that practised by Mr. Smith, and arriving at a conclusion decidedly in favour of the latter. In order that your readers may be able to judge for themselves I will, as briefly as possible, point out the object to be attained, and the means proposed and adopted by Mr. Harris and Mr. Smith for its accomplishment. The subject of aërial or atmospheric electricity has been so fully speculated and theorized on, that I presume it is generally supposed to consist of three different conditions; 1st, that the electric fluid surrounds and pervades every sub stance in nature with which we are acquainted in a quiescent or latent state, without affording the least sign of its existence; 2nd, that any body or substance may contain and be surrounded by more than is naturally due to it; and 3rdly, that such substance may contain less than its natural quantity by a portion having been removed. The first state has been called "latent," the second positive," and the third "negative." The positive and negative electrical states appear to be produced from any cause of disturbance sufficient to destroy the molecular attraction of matter when two or more elements are in operation, and any change, such as chemical action, is taking place. Electricity is evolved by liquids passing into a solid state, as also by the liquefaction of solids, and the production and condensation of vapours from liquids holding either acids or salts in solution. Hence the sea produces amazing quantities, which is probably the cause of a clear atmosphere being gene. rally positively charged-of contrary currents of wind, accompanied by humidityand of any other change that may take place in atmospherical matter. The earth, ocean, atmosphere and clouds, may therefore become charged by their natural operations on each other, one part or district positively, and the other ne gatively; and although it is said that the earth and sea are often in the positive condition, I am of opinion, from repeated observations of lightning, that the positive state generally exists in the clouds when the earth and atmosphere are in contrary states, though probably the electricity of the earth and sea is frequently in a passive state, whilst the most violent commotion of electrical discharges is going on be tween the clouds. But the matter under enquiry being when the sea and clouds are in opposite states, I will confine my observations to that consideration, only observing, that these are general sugges tions, details being foreign to my purpose. Suppose several square miles of clouds to be aggregated in a highly excited condition, and to be drifted by currents of wind towards a fleet of ships, and that the ocean in the immediate vicinity of the vessels is in the opposite electrical state, should the approach of the clouds be only a little more than is equal to the striking distance of the redundant elec tricity, it can easily be imagined that the tall masts of a vessel interposing between the clouds and water would form a medium of communication, although the distance might be such that the aerial resistance would prevent a discharge without some such intervening or conducting power. The direction of a concentrated mass of electric fluid when seen in the air is, I believe, almost always in straight lines, viz., taking the shortest path to the point where its presence is required to restore equilibrium; nor is the apparent zig-zag lightning an exception, because, although angular paths are formed, the cause of such appearances would be the vicinity of detached masses of clouds having their attractive and repellent forces in different directions as seen by the eye. I will therefore proceed to enquire what is the best means of constructing the conductors for ships which shall possess the greatest facility for the transmission of the electric fluid from the top of the mast to the water, in the most direct manner, and which, at the same time, shall not produce any obstruction or inconvenience to the seamen ? Mr. Harris's proposition is to let vertical slips of copper, about 2 inches wide, into the surface of the mast, to be fastened by nails, making the surface of the mast flush and even. These slips of copper to extend from the top of the upper mast down through the deck and hold to the kelson, and where, if I understand Lieutenant Sabeen's description, it ceases; having, in fact, brought the lightning into the hold of the ship, it has to find its own way out by the bolt of the frame work in the best manner it can. Lieut. Sabeen raises an objection to letting in the slips of copper, inasmuch as its contact on the inside and edges leaves only the outside surface free for the conducting operation. I do not consider this a very forcible objection. It is not possible, from the very nature of the work, that a carpenter can let in, and fix a copper plate with such extreme and perfect contact, as not to leave sufficient space for the passage of a subtle fluid, which, in such a case, is not supposed to require any; and, indeed, if it were so, the objection is nearly as applicable to the wire rope, as to the slips of copper; for the minute spaces formed by the tangential contact of the wires, would be almost as impermeable to the passage of electricity, as the partial contact of the slips of copper in the grains of the wood; therefore, I consider the objection is quite gratuitous when applied to the masts; but would, nevertheless, be particularly applicable to the bolts by which the electricity has to find its way out of the hold to the water. Bolts used in framing the ship, I apprehend, are in all cases driven in, and completely fill the holes: there can be no yielding. either in wood or metal, in this case, and therefore the contact may be presumed to be perfect; but I do not consider that even this has been the primary cause of the disruption of the frame-timbers spoken of as having occurred to Mr. Harris's plan, but should rather be inclined to ascribe it to the absence of a perfect continuity of the slips of copper forming the conducing material, and the bolts intended to transmit it to the water. A much stronger objection may be stated to take place at the junction of the pieces of metal for want of perfect contact. Dr. Priestley found that a considerable weight was necessary to bring the links of a chain in such a state of contact as to prevent decomposition of part of the metal, in conducting electrical discharges by it; besides which, other experiments have proved that bringing metals to touch does not produce perfect electrical contact, but that considerable pressure is necessary. The entire height of the masts of a first-rate war-ship being from 150 to 200 feet, and the slips of copper being, say 4 feet, there would be from forty to fifty partial interruptions by the "butt joints" in addition to those at the caps, cross-trees, and decks in a lateral direction. It has also been discovered in very carefully conducted experiments, that metals are shortened by powerful discharges of electricity being sent through them, which would sensibly increase the evil, though if long lapped joints were introduced, it would be obviated. The uppe masts and guns of a ship having to be so frequently removed and replaced in uncertain weather by the seamen, when neither time nor talent is sufficient to ensure perfect contact, and under circumstances too, when, of all others it is most required, appears to me a strong argument against the use of rigid plates or strips of metal, for such an important purpose; but the greatest absurdity of all is, that of bringing the most instantaneously destructive element into the hold of the ship, and making no other than a wildering" process for its escape. Not be much less reprehensible would have been the conduct of the builder of St. Martin's church (the accident to which, arising from carelessness, will be remembered by all your readers,) had he brought the conductor from the top of the tower into the sacramental plate chest, and from thence to the earth let it follow its own capricious fancy. The question of suitability having been considered, I will now speak of the cost. From the close observation of unquestionable authority, it appears that the various operations of letting in and fixing the copper slips, making all the necessary bends and junctions at the heads of the masts, decks, and hold, occupy a period of three weeks; and that the cost, in the few instances in which it has been applied, has been from 400l. to 500l. Three weeks so occupied, under the ordinarily judicious regulations of our naval service, would probably be of as little consequence as the above sum taken from our Treasury, provided the work were worth it; but such does not appear to be the case. Both, however, must be weighty objections to the proprietors of small trading craft; to which we must add, the injury to masts and spars by letting in and puncturing, by holding the water and thereby occasioning decay; as also the impossibility almost of transferring the materials from one ship to another; or, in the case of masts and spars being carried away or left unprotected, the labour of fixing which probably amounts to four-fifths of the entire cost. It only now remains for me to speak of the plan so successfully practised by Mr. Smith, and which, from its extreme simplicity, the facility with which it is applied, the certainty of its usefulness, and small cost, renders but few words necessary. I know of no instance amongst the numerous beneficial measures adopted by the present enlightened Government of this country, in which a more judicious and sound discretion has been evinced than in the adoption of Smith's Lightning Conductor. It contains all that is necessary and nothing further. A copper wire rope is tinned over and fastened on the cap of the topmast and is led down by the side of the masts to the cross trees, where it is fastened to a slip copper hook, and thence conveyed down the after shroud and shackled to a copper plate let into the ship's side, until it reaches the lower edge of the upper tier of copper sheathing, where it ceases. By this simple use and arrangement of a copper wire rope every necessary condition is complied with, and the ease and facility with which a flexible rope may be made continuous by knots, splices, and other means must be obvious to every one under every circumstance to which a ship is exposed. The consequence of such simplicity is, that it can be applied in a very short time, two days, I am informed, being sufficient to protect a first class ship of war, and the expense of which does not exceed 601. In the event of its being desired to transfer a set from one ship to another, the materials are in no way injured or rendered unfit; and in making alterations, the usual knowledge possessed by seamen will be equal to the task; and at all times, the materials forming these conductors, when removed, will be worth two-thirds the first cost. These important considerations of cheapness and facility with which it can be applied, bring it within the reach of all owners of vessels, who will doubtless eventually appreciate the value and avail themselves of the benefit. Mr. Smith's Pamphlet contains many most favourable certificates from naval officers, masters of merchant vessels, and others of nautical experience; and I have also seen certificates which have not been published, the whole of which form an additional link in the chain of evidence of its superiority over all other methods in usc 66 Not being fully acquainted with the copper works" of a ship, I do not see why the wire rope used at the topmast anould be of less diameter than the lower set; as far as the transit of lightning is concerned it would appear that a rope of uninterrupted and uniform diameter would be preferable; and if it were altogether increased from three-eighths to half inch, or five-eighths in diameter, it would be still better adapted for the conduction of large quantities of electricity, In the hope that these remarks may be sufficiently interesting to appear in your columns. I remain, Sir, yours respectfully, 98, Chancery Lane, Dec. 12, 1842. 1 1 |