WHEELER'S IMPROVED ROLLER FOR WINDOW BLINDS. this matter-conduct alike admirable for its vigour and promptitude, is-under the existing circumstances of the country, of a nature to give very general satisfaction. By nothing can such disasters as have lately befallen our arms in the East be so effectually repaired, or their recurrence more certainly prevented, than by the fitting out of a few such leviathans of war, as that which we have now described as being in progress. With half a dozen ships of this force at command6,000 men might within three weeks from the first receipt of the news from Affghanistan, have been landed at Alexandria-marched in six days through Egypt (with leave of its Viceroy,) to Cosseir, on the Red Sea-and transported thence in nine days more to Kurruckee on the south coast of Scinde. With such a force there is hardly a corner of the world which British thunder could not reach in early time enough to uphold, against all opposition, British influence 281 when linked in honourable alliance with the interests of human civilization and happiness (may we never know any other!) It is, moreover, a simple mechanical fact, which admits of no denial, that Great Britain can show forth a power in this way (thanks to her mechanics! thanks to her workshops! thanks to her practical science!) which no other country in the world can at all approach, far less rival. Every year, for the last half dozen, has witnessed some paper decree for the formation of a French steam navy, with engines of 300, 400 and 500 horse power, but where are they? It is notorious, that all France has never yet been able to produce an engine, good for anything, of more than 200 horses power. Were such an order, as has been just given by our Admiralty for a pair of 325 horses power each, to be furnished in nine months, to be given by the French government to French manufacturers, it could not be executed (if at all) in as many years. WHEELER'S IMPROVED ROLLER FOR WINDOW-BLINDS. B בי B The novelty in this roller consists in its being constructed of such materials, and in such manner, that it may be of any length required, without being heavier than one of the common width, and without its being liable to bend or droop in the centre. It is particularly applicable, therefore, to very large windows, such as those of shops, churches, halls, &c. The prefixed drawing is a representation of one of no less than 20 feet in length, which has been fitted by the inventor (Mr. Charles Wheeler, of Speenhamland, Newbury) to the shopwindow of an extensive draper. The construction will be readily understood from the following description. A is the brestsummer. BB two strong brackets secured to the brestsummer. Cis a-inch iron pipe, enclosed in a cylinder, D, and resting by its extremities in the brackets, B B, the parts outside of the brackets being screwed for the reception of two strong nuts. D, the outer cylinder, may be made of wood, or tin, or any other suitable light material; and between it and the fron pipe vertical stays are placed at intervals, (as represented in the engraving,) for the sake of greater support and security. At one end are two pulleys, by which the blind is raised and lowered, by means of lines passing from them under the cornice, down to a windlass in the inside of the shop. By screwing tight the nuts on the ends of the iron pipe, C, that pipe can always be kept in a perfectly horizontal position; and as long as it remains so, the wooden, or tin cylinder which incloses it, and on which the blind is wound, will remain equally So. When the blind is entirely up, the whole apparatus is concealed from view by a face-board (not shown in the drawing) which may be made of any suitable ornamental form. HINTS ON VALVES-MESSRS. MAUDSLAYS AND FIELD'S PRACTICE. The quantity of lap or cover proper to be put upon valves, is a question determinable altogether by the quantity of expansion required, and varies in different engines of the same power. But the upper and under faces of the valve are, in Messrs. Maudslays' (side lever) engines, in no case of the same breadth the cause for this inequality is that if the valve be at half stroke, that is, with both ports closed, and if the engine be moved round, the travel of the valve from half stroke to the extremity of the stroke downwards will be found to be not the same as the travel of the valve from half stroke to the extremity of the stroke upwards. In other words, the space described by the valve whilst the piston descends, and the space described by the valve whilst the piston ascends, are not equal; whereby it becomes necessary to make the superior and inferior faces of the valves of different depths, to compensate for this inequality. The accuracy of the preceding statement every engineer has it in his power to verify, either by a model, or by a drawing of the valve and piston in their several relative positions. The cause of the irregularity may be traced to the oblique action of the connecting and eccentric rods. If the piston be placed at half stroke, that is, midway between the top and the bottom of the cylinder, the crank will not be level. This is manifest from the ordinary method of ascertaining the length of the connecting rod, which is to level the beams, and take the vertical distance from the extremity of the beams to the centre of the crank shaft. When the beams are level the engine is at half stroke, but if we wish to attach the connecting rod to the crank pin-its length being ascertained as above-it will be necessary to bring the crank down a little, to compensate for the depression of the head of the connecting rod due to the deviation from the vertical line. If, then, the crank be not level at half stroke, the descent of the piston from half stroke, and its ascent to half stroke again will accomplish more than half a revolution of the paddle wheels; and the ascent of the piston from half stroke, and its descent to half stroke again, will accomplish less than half a revolution of the paddle wheels. The ratio of the disparity will vary with the length of the connecting rod, the circumstance of there being overhang or no overhang of the beam, the length of the beam, and other circumstances; but in all ordinary engines, the difference between the upper segment of the circle of the crank's revolution and the under segment of that circle will interfere with the valve's motion, and the proportionment of the valve faces ought to have reference to the extent of that interference. It is Messrs. Maudslays' practice in some of their very recent engines, to make the stroke of the valve considerably more than twice the depth of the port. All the valve levers are equal, and the stroke of the valves is in all cases equal to the throw of the eccentric. It is also their invariable practice, in all engines of considerable magnitude, to construct the valve casing with a faucet joint, to permit the expansion of the casing when heated with steam, without distorting the cylinder. In some large engines which have been without this provision, we have known the cylinder ports to be rent asunder by the expansion of the casing; and however frequently and however well the rust joints of the casing might have been made, they invariably became very soon leaky, from the effect of unequal expansion. The cylinder when hot will expand as much as the valve casing; and if the two were always equally heated, no detriment could ensue from the absence of an expansion joint. But as the throttle valve is never perfectly tight, and as the slide valve generally is so, the steam before the engines are started enters the casing and induces its expansion; whilst being excluded by the slide valve from the cylinder, the cylinder is not heated, and therefore does not expand. Injury of some sort or other, if the engine be large, is sure to be the result of these conflicting forces. In the double cylinder engines of Messrs. Maudslays, cylindrical slide valves are employed, and have been found to operate extremely well. The packing of these valves is metallic. The packing of the pistons made MERITON'S SLIDE-VALVES. A by the same firm are invariably metallic, and generally consist of a single ring turned eccentric, cut in one place, and the cut part fitted with a tongue piece to prevent the steam from passing through the cut. piece the same breadth as the ring is fitted over the back of the cut, ground tight, and then riveted to one part of the ring. The elasticity of the ring is in most cases found sufficient to keep the ring in intimate contact with the interior of the cylinder, and the force with which this contact is maintained, may be either augmented or diminished by a bridle. - - Civil Engineer and Architect's Journal. WALKER'S HYDRAULIC ENGINE. Sir, I am sorry that the use of the term cylinder, in the description of "Walker's Hydraulic Engine," in No. 971, should have misled your correspondent, "A Builder;" but if he had referred to my previous communication on this subject, I think this could not have happened, and therefore I hope he is single in this misconception: in his case, seeing for himself has put all right. With reference to the omission charged upon me, respecting the very ingenious valve which Mr. Walker has adapted to his machine, my apology is twofold. Firstly, I was desirous of calling the attention of your readers, simply to the general principle of the machine, without any reference to constructive details; because, as the thing is still (in this point of view) in its infancy, every day brings forth some improvement in the minutiae of the mechanism. And, secondly, the improvement in question did not exist at the time my paper was written. The shipping interest is, as "A Builder" observes, deeply interested in this invention. Wherever water has to be raised under circumstances which produce a liability in ordinary pumps to choke, or to wear rapidly, Mr. Walker's machine can be employed with pre-eminent advantage. In water containing large quantities of sand or gravel, this is the only elevator that can be used for a continuance. Mr. Walker has already been applied to for a machine to raise some sandy water which has disabled the best pumps that could be procured, in an hour; and the failure of every pump that has hitherto been tried (Shalder's wonderful" included) has compelled the suspension of the work. There is no doubt that Mr. Walker's machine will speedily surmount this difficulty, and enable the work (which is of the first importance to the maritime world) to be completed without any further delay. 283 MERITON'S SLIDE-VALVES. Sir, My attention has been drawn to a letter which appeared in your Magazine of the 19th of March, written by Mr. T. Meriton, of MillWall, and accompanied with five views of an improved slide-valve. The advantage of this valve is stated to consist in giving steam quicker than the common D valve; and this we may perhaps allow, providing it can be first shown that it will answer at all. The slides, he says, would only require to travel th part of the distance of the D valve (still sticking to the same valve) but I would remind Mr. Meriton that there are other sorts of valves beside the D valves, which would also require onlyth of their travel, such as double beat, or equilibrium valves. We are further told, (and to this point I would direct the special attention of your readers) that it does " away with a deal of work, such as the D valve, jacket packing, blocks, &c." Now, in the first place, it must appear evident to any person who looks candidly into the matter, that, to keep a ring steady, such as Mr. M. intends to make use of for a slide, there must be at least three valvespindles at the top, and three at the bottom, so that we should have not less than seven steam-tight stuffing-boxes immediately connected with the cylinder! Every engineer knows that the D valve, together with the cylinder, would only require two. again, there is the labour and expense of casting a cylinder with four small passages round it; indeed, I feel rather doubtful whether it would be possible to do it. So much for the dispensing with "a deal of work!" Then But what surprises me most is the blunder which Mr. M. has made in his intended application of a metallic ring for a slide. This ring, from Mr. M.'s explanation, I understand to be one of cast iron, or brass, turned true, inside and out, with one side thinner than the other, so that when it is cut in two at the thinnest side, it has a tendency to fly open, and press with its rim against the sides of the cylinder. It appears to be on the same principle exactly as the piston-rings now pretty generally adopted by engineers. Now it is evident that if a ring of this description be applied to the ports in Mr. M.'s cylinder (and your readers will oblige me if they will just turn to that gentleman's sketches) the steam will act continually against its rim, and force the two thin ends close together; which must consequently make the ring less in diameter than the bore of the cylinder, and admit the steam, whether it be required or not. I am, Sir, Yours, &c., D. ON PARACHUTES.-BY THE LATE BARON MASSERES. (From the MS. collections of the late Dr. Olinthus Gregory.) 1. If a cylinder of lead, or wood, or any other substance heavier than air, falls perpendicularly downwards through the air with its base, or flat side, foremost, or so that its axis shall always be perpendicular to the horizon, and the number of inches in the axis or height of the cylinder be denoted by the letter a, and p be the number which bears the same proportion to 1 as the specific gravity of the cylinder bears to the specific gravity of air, the greatest velocity which the cylinder can acquire by falling in this manner through the air will be such as will carry it through 384 pa inches in a second of time. This I have seen demonstrated. ( = 384 x 2580) = = 2. As an example of this, let the height of the cylinder be 3 inches, and its specific gravity the same as that of water, or 860 times the specific gravity of air. Then we shall have a 3, and pa (= 860 × 3) 2580, and 384 pa 990, 720, and consequently ✓990,720) =995 inches. Therefore the greatest velocity that can be acquired by such a cylinder in falling in this manner through the air is that of 995 inches, or about 83 feet, in a second of time. 384 pa If such a cylinder were 10 feet broad, or the diameter of its base was 10 feet, or 120 inches, the number of cubic inches contained in it would be (3 × 120 × 11 - 8 × 14400 × 14 - 48200 11 14 a pound avoirdupois. Therefore 33,943 cubic inches of water will weigh (33,943 × 0.0361 =) 1225 pounds. Therefore a cylinder, or parachute, of the same specific gravity as water, and of 10 feet diameter in the base, and 3 inches in height, or thickness, would weigh 1225 pounds. Box wood is heavier than water in the proportion of 103 to 100. Therefore a cylinder, or parachute, made of box wood whose height, or thickness, was three inches, and the diameter of its base 10 feet, or 120 inches, would weigh 1262 pounds. (1 1225 x 103 100 manner And as the difference of this specific gravity from that of water is so small, the utmost velocity which such a cylinder, or parachute, could acquire by falling in the above described through the air would be but little more than that of the former parachute, or than that of 83 feet in a second of time. Now let us suppose the height of this parachute of box wood to be reduced from 3 inches to an inch, or 4th of what it was before. Then it will follow that 384 pa will be less than it was before in the proportion of 1 to 2 6, or or of 1 to 2:44, and consequently will be Now let the diameter of the parachute be enlarged from 10 feet to 40 feet, and its height at the same time diminished from an inch to the 32nd part of an inch. Then it is evident that its solid contents, and consequently its weight, will continue the same, because its base will be increased in the same proportion of 16 to 1 in which its height is diminished. It will, therefore, still weigh 210 pounds. But the utmost velocity which it can acquire by falling through the air, in the manner above described, SPECIFCATIONS OF RECENT ENGLISH PATENTS. will be less than before in the proportion of 1 to 4, and therefore will be that of ( 34 time. If, therefore, a parachute can be formed of the diameter of 40 feet and of a very small thickness, so that its weight, together with that of a man hanging from it, shall be only 210 pounds, the utmost velocity such a parachute, and the man hanging from it, can acquire by falling through the air in the manner above-described, is that of 84 feet in a second of time, or about 5 miles in an hour. ABSTRACTS OF SPECIFICATIONS OF ENGLISH PATENTS RECENTLY ENROLled. LOUIS LACHENAL, OF TICHFIELD-STREET, SOHO, MECHANIC, AND ANTOINE VIEYRES, OF No. 40, PALL-MALL, WATCH-MAKER, for improvements in machinery for cutting cork. Enrolment Office, March 4, 1842. Two separate and distinct machines are employed for this purpose, driven by a steamengine or other suitable power. The first machine cuts the slabs of cork by means of revolving cutters into perfect parallelograms; the machine being so far self-adjusting as to adapt itself to the thickness of the slab whatever that may happen to be. The upper and under bark, or surface of the cork being removed, the parallelograms are fed down a square tube to the other or rounding machine. On reaching the bottom of the tube, the square pieces of cork enter into recesses formed round the periphery of a revolving wheel which regulates their admission to the holders; these holders seize the parallelograms of cork between them, and in revolving, present them to fixed knives, by which they are cut into the shape requisite for use. In order to preserve the fine edge necessary for cutting cork, revolving rubbers, the axles of which are mounted on springs, are kept in contact with the cutting edges of the knives or cutters. These rubbers are composed of copper or other suitable material, into the face of which, fine diamond powder has been driven, by hammering. The inventors of this machinery have bestowed a great deal of ingenuity and pains upon it, but on the whole, we see no reason to believe that they have succeeded much better than others in overcoming the economical difficulties which seem inseparable from all attempts at cork-cutting by machinery. 285 The cunning of the hand will still, we suspect, maintain its ancient mastery in this, as it has done in various other arts, to which machinery has been able to lend no assistance, for this simple reason, that the hand is itself a machine, surpassed by few in capacity and power. The method by which the present patentees propose to keep their cutters in constant working order is not new, the same having been before proposed by an American patentee (see Mech. Mag. vol. xxxvi. p. 127) for though the American cork-cutter makes no mention of the diamond powder-as never dreaming probably that it would answer to grind down diamonds to make corks-he claims "the use of emery or any other substance which will give an edge.' JOHN JUCKES OF LEWISHAM, KENT, for improvements in furnaces or fire-places.— Enrolment Office, March 4, 1842. An endless chain of moveable furnace bars passes round two wheels, one at the front of the furnace and the other at the back; and this chain is made to revolve at the rate of about three feet an hour, by means of sundry rollers, cog-wheels, pinions, levers, ratchets, clicks, rails, &c., the fresh supplies of fuel being dropped upon the bars from a hopper over the mouth of the furnace, and carried slowly forward into the burning mass, as the chain revolves. The action of the apparatus is precisely similar to that of the well-known dredging machine. The patentee says, "I wish it to be understood, that what I claim is the mode of constructing furnaces or fire-places by combining fire-bars into a chain, by which the parts may be changed in their position from time to time, and progressively go into and out of action as above explained." We do not think the patentee runs much risk of his claim being invaded. His apparatus is simply the most complicated and cumbrous of all which have yet been invented, whether for the better protection of fire-bars, or better consumption of fuel; and is of a great deal less promise in point of efficiency, than many others that might be named. Brunton's well known revolving grate, for example, the patent for which has long since expired, and which all the world therefore are now free to use, and may in many cases use with great advantage. MICHAEL COUPLAND, OF POND YARD, SOUTHWARK, MILL WRIGHT AND ENGINEER, for improvements in furnaces. Enrolment Office, March 4, 1842. Half of the fire-bars are made capable of being lowered and raised by means of an auxiliary apparatus of wheels, screws, &c. alternating with other bars, which lift upwards only, so that fresh supplies of fuel |