WOODHOUSE'S ROTARY STEAM ENGINE. Sir,-The accompanying are sketches of a rotary engine, the arrangement of the slides of which I made more than two years ago, and which is intended as an improvement upon Trotter's, patented many years since, (described in vol. 9, Repertory of Arts, 1805,) by avoiding the difficulties which that invention presented in the working parts upon its revival by Earl Dundonald. This The central axis contains two slides passing through it, and alternately closing the steam chamber, to accomplish which, the power is admitted by means of small moveable plugs, or spring valves, which traverse small openings, communicating each way with a small chamber or chambers, between the slides. produces a requisite pressure of each slide against the inner circumference of the cylinder or case, and is done without the least waste of the power applied. The slides afford a mutual support, and never separate, but alternately work within each other, as shown, fig. 2,being one arrangement of the plan. The whole of the foregoing arrangements I believe will be found original, and are calculated to produce good effects without needless friction; for so long as the power is exerted, whatever it may be, the slides will be influenced by its operation, and in proportion to its extent. The leverage power will more than compensate for its friction, which though more in proportion than the plan of my former engine, published, July, 1837, yet its parts being fewer and more compact, are so far preferable. The power though variable is never reduced to less than one-third. The ingress for the motive power, it will be seen by fig. 1, can be applied at either side of the machine. The slides are rendered air-tight by means of friction-plates at their sides and ends, and also within the axis, by wedgeshaped plates, as shown; friction-plates are also introduced at the sides, where the inner, (B) exceeds the diameter of the outer portion of the axis, (A). The situation of the axis shows the increase made to the leverage power, and the advantages likely to be gained in reduced bulk. I have also combined this plan with that of my former engine, acted upon by guides or racers; that is, by making the slides to work in the axis, by which means I avoid the use of the cogged wheels and pinion, and make the machine still more compact; but there will be a small addition to the friction. Fig. 1. is a section of the rotary engine, showing the plan of working the slides through the axis, and of making them to support each other during the whole movement; also one method of introducing the power into the slidechamber, which, if plugs are used, the openings pass the friction plates; but if spring-valves are used this is immaterial. The foregoing arrangement of passing the power into the slides, I proposed to Earl Dundonald in 1835, as an improvement to the working of his engine, by allowing a communication between the inner and outer circumference of the eccentric wheel, and taking off a portion of the friction which its stress upon the vacuum or outlet-side of the engine produced. A, the working axis, passes through the cheeks of the cylinder or case, and may be adapted to any rotative or reciprocatory movement. CC, openings to connect the power and discharge-pipes. D, lower friction-plate, to prevent the passing of the power to the discharging-pipe. The above, and the one acted upon with guides, are equally suitable as water or forcing-engines. Fig. 2. is a section of the slides with the side-plates off, showing an arrangement of the method of working them together; the small fubular opening from the plug-opening passes down the centre, midway in the thickness and solid part of each slide, and are here shown. The arrangement of the packingplates is such, that the pressure upon them will effectually hinder the escape of the power, as the power itself presses them agaist the case, in addition to the springs which I should use. As the subject of the rotary engines has at last obtained notice, it would probably not be unacceptable to your readers, if the arrangement of working Earl Dundonald's engine in the manner I proposed, be sent you, which, although certain difficulties attend that invention, might show one among the many novelties on that head. Sir, I believe all practical mechanics will allow that the common mode of connecting catgut or other bands used for driving machinery, by screwing on to the band a socket having a hook or eye formed in it, is objectionable, inasmuch as the screwed socket is frequently flying off, thereby causing considerable annoyance and loss of time, and to some bands (such as the patent elastic band made by the London Caoutchouc Company), it is entirely inapplicable; for the screw in the socket cuts the fibres so that it actually destroys the parts it is meant to hold by. The annexed sketches are intended to show a scheme of mine to obviate those difficulties. Fig. 1, a section and figs. 2 and 3 the external appearance. a a, in the section, a conical socket screwed internally as far down as shown at bb, cc the eye having a short cylindrical screw, as shown at dd, made to fit the screwed part of the socket aa, E is a conical brass screw having a fine thread cut on it, and F is the end of the band or catgut. Mode of Fastening.-Force the end of the band through the socket aa about an inch or two; screw into the end of the band the brass screw E, then draw it back into the position shown in the sketch, and screw the eye c c, into its place. I have put those fastenings to some very severe tests, among others I hung four half-hundred weights to the end of a piece of patent elastic band (which by the bye is admirably adapted to driving machinery) five-eighths of an inch diameter, and let them fall through a space of five feet, three times, when the band broke some two or three feet from the eye, without in any way injuring it or disturbing its hold of the band. As I imagine this will be useful to some of your readers you will oblige me by inserting it in your valuable publication. I am, Sir, respectfully, December 18, 1838. REMARKS ON MR. FIELD'S EXPERI MENTS ON THE POWER OF MEN- Sir,-Of all the very desperate attacks yet made upon the existence of my father's patent invention for raising or conveying water or other fluids-not one of them is worth notice compared with the attempt of Joshua Field, Esq., F.R.S. and V.P., Inst. of C. E.; (See Mech. Mag. p. 237), and if I cannot parry this attack, (the force of which, or the intention of making, I am convinced this gentleman is altogether unconscious of,) I would at once retire from the everlasting scheming and study required in adapting the invention to its almost infinite variety of applications. After the experience of two apprenticeships a time surely sufficient for to enable any flat to find out his folly still flattering myself that the Fountain Pumps are perfect, both in principle and practice, or at least so near perfection as to leave little chance of improvement to be told that a common crane, with its many incumbrances, will beat it in raising a weight (fluid or solid, makes no difference) beyond all chance of competition, is most disheartening. To prove, however, that we are not so far wrong, by the favour of Messrs. Boardman and Harmer, Wharfingers, Norwich, I have made some experiments recorded beneath. In the foregoing experiments, the height, weight and age of the men are given from their own statements, which I had no reason to question, as they appeared quite correct enough for such a rough trial. 1st and 2nd Experiments were in hoisting a butt of currants neat weight, marked as 15 cwt. 2 qrs. 24 lbs. ; for this short spell and light weight, the difference between the most powerful man and myself was scarcely discernible. 3rd Experiment-a scale and chains, weighing cwt., were taken, and 35 half cwts. A 13-inch crank was used in this and the former experiments, which was changed for a 15-inch crank in all the others. 4th Experiment; here the resistance which I fixed upon with the men's concurrence, as most suitable for their strength, proved, as I expected, too heavy for me for a minute's spell; greater speed and less power being more beneficial, as shown in the last experiments. 5th, 6th, 7th and 8th Experiments, by powerful compact-built wharf and watermen, who all entered into the spirit of the trials and did their best. 9th Experiment; by the most powerful men, same as trial the 1st and 3rd Experiments. 10th Experiments, with less resistance; still I believe I should have done more work; and for all the men, except the strongest, perhaps rather less resistance REMARKS ON MR. FIELD'S EXPERIMENTS ON THE POWER of men. would have shown a trifle heavier result. The nearest easy-made practical guess I could give of the friction of the crane was made by hanging a sufficient weight upon the crank-handle, just to bring it down from a little above to a trifle below the horizontal line; and then trying what proportion of this weight would be drawn up again through the same space by the hanging load: the medium between these weights, taking the average at several different elevations of the load, appeared to show about 10 per cent. friction for the movements of all the working parts-they being well oiled before making the trials. It may be as well to observe, the chains and hook to which the chain and weights were attached, on the average, appeared to about balance its own weight on each side the guide pulley. Comparison between the power expended by myself in working the crane, and the effect I have produced and can produce, again, with a well made and well proportioned Fountain Pump. Crane. Half Minute Trial.-Actual weight raised 1 foot high Add the friction of the working parts.... lbs. 8,946 894 9,840 Fountain Pump trial, with heavy lever, suitable for two men to work at for a continuance, for filling road watering 71 feet, is equal to raising 1 foot high Add 3 per cent. gudgeon friction.. Effect produced.... 293 15,691 470 16,161 For a minute's spell, I am of opinion that a crank motion, with the addition of a fly-wheel, besides overcoming in its simplest applications to pumpwork, at least 5 per cent. extra friction, will enable a man to produce full 15 per cent. more work than a lever, provided both are adjusted for their best effect. I should not therefore despair of making a Patent Fountain Pump, which suits such a 12 stone man as performed the 1st, 3rd and 9th Experiments, able to raise in one minute's time, either 224 Imperial gallons of fresh water to 10 feet high 66 300 68 7 or in proportion to any elevation or number of such operations. But as the length of the spell increases, the scale gradually turns in favour of the lever power, owing to the smaller size and less distance travelled by the mechanical bearings, and in its superior maintaining position for manual labour; and, judging from many Experiments made with Fountain Pumps, the lever fulcrums of which being fixed about 6 feet high, and the resistance properly proportionate to the men's strength, I have found that sturdy labouring men, of middling height, from 25 to 40 years of age, weighing 150 to 170 lbs. each, can, by making the most of their strength, average the fol lowing results, expressed in pounds' weight, raised I foot high; each minute for short and long spells : lbs. For 1 minute's spell 15,000 to 16,000 233 9,001 lbs. Crane.-Minute Trial. My most effective spell raised 1 foot high 14,336 Add the friction, 10 per cent... 1,434 Total expenditure of power.... 15,760 lbs. Fountain Pump.-Minute Trial. 34 strokes of 6 lbs. each to "10 "15 Any person, therefore, wanting to know the quantity of water he can have supplied by a man's power, has only to divide any of these sums by the height to which he wants the water raised. Let any man try whether he can run treble the distance in one minute, or double in 5 minutes of what he can average, through a very long spell, or up a flight of steps with convenient handrails, or a mining-ladder, which may be a less disputable criterion :-if he does not find that task tough enough, I am much deceived; therefore for any man of common dimensions, English or Foreign, to fully double this effect, according to Mr. Field, appeared to me to be clearly impossible—3,675 lbs. weight raised 16 feet high in 2 minutes by the Irishman, and in 2 minutes by the Englishman; the latter, too apparently, very soon after a bye-play exertion that would cause millions of strong men to "kick the bucket" before they could accomplish the same. From the length of the crank given, the diameter of the chain barrel and combination of cogs, I can find no error in the statement of the crane giving 105-fold purchase; consequently, the men's hands passed through 105-times 6 feet, which, for the Irishman, gives near 84 revolutions per minute with an 18-inch crank, and may possibly have been done with a one-hand load of half the resistance stated. I shall, therefore, conclude by giving a guess, that instead of the weight being raised 16 feet, it must have been that 16 feet of chain was wound upon the barrel, the end of this chain passing under a moveable pulley to which the load was attached, and up to the hook at the extremity of the crane's jib, which additional pulley would give double the purchase, and show only half the effects for all the trials. I am, Sir, Your obliged, W. SHALDER, jun. Bank-place, Norwich, Jan. 23rd, 1839. ON AN EXPERIMENT OF PERKINS, TO PROVE THE CALORIFIC REPULSION OF A WATER GLOBULE FROM AN IGNITED METALLIC SURFACE-BY DR, SCHAFHAEUTL. Sir, Mr. C. Tomlinson has had the kindness to direct my attention to one of his ingenious researches contained in No. 703 of your valuable Magazine, which I much regret not being earlier acquainted with. He likewise alludes to an experiment made by Mr. Perkins, of which I was perfectly ignorant, and which he seems to consider a convincing proof of the doctrine of calorific repulsion of certain heterogeneous bodies. The following is the experiment to which Mr. T. refers : "If a platinum capsule be drilled with an immense number of holes, as in a coffee or wine strainer, it will not, of course, retain water for a single minute; but if brought to a white heat by means of well-prepared incandescent charcoal, so that fire only, with. out flame, be produced, and water be dropped into it, a large globule may be collected, and it will exhibit all the phenomena, just as if a common platinum crucible had been employed." Now if I am allowed to give an opinion on the subject, Mr. Perkins's experiment tends to prove nothing more or less than the well known fact, that a drop of water evaporates very slowly in an ignited vessel. We have a certain phenomenon before us by which, through the medium of our senses, we are convinced of the fact, that a water globule in an ignited metallic vessel is extremely slow in evaporating. Now in searching for the cause of this slow evaporation, two different explanations have been given of it. One party ascribes the slowly increasing temperature of the drop of water to the repulsion developed by the ignited metal, I, on the other hand, consider it to arrive from the difficulty we experience in heating any liquid by applying caloric to its surface, and to the development of steam by touching the ignited metal. In both cases the ignited surface is the essential medium through which the effect is produced, viz., the slow evaporation of the drop of water, and where this ignited surface is wanting, no effect whatever can be produced. As an ignited metallic surface is therefore absolutely necessary, a hole in this surface cannot possess the essential means, and can have no influence whatever on the drop of water, and if the drop is of smallar diameter than the hole, and is moving in the axis of the hole, it will certainly fall through it. This will be the case whether the vessel be hot or cold, provided the current of air does not throw the drop out of the axis of the hole. If the drop of water be of larger diameter than the hole, then it must of course touch the ignited surface, and the development of steam and the spinning |