Lapas attēli
PDF
ePub

REPORT OF EXPERIMENTS ON THE

VIII. To observe accurately the sort of bursting produced by a gradual increase of pressure within cylinders of iron and copper,

It has been contended by some, that ruptures produced by a gradual increase of pressure within steam-boilers do not bear the character of explosions, but that a mere rending takes place, giving escape to the contents. This has been assumed to be espe cially the case with copper boilers. To make the observation required by the above ques tion, cylinders of iron and copper were prepared, of sufficient size to make a small thickness of material answer for rending by & pressure which was easily attainable. Two experiments made, one with an iron and another with a copper cylinder, afforded so direct an answer to the query, that it was not deemed necessary to carry the experiments further, especially as they were tedious, and not without danger. A further experiment of the same tenor resulted from a trial of Perkins's assertion in regard to the effect of making an opening in a vessel containing water, and heated to a high temperature.

[ocr errors]

The boilers used were cylindrical, 8 inches in diameter, and 10 and 12 inches respec tively in length, of iron '02 inch thick, and of copper 03 inch thick, having iron heads 05 inch thick, to which the couvex surface was fixed by iron rivets, placed nearly touch ing each other. A single opening in the middle of one of the heads of each boiler was. provided to introduce the water, and was furnished with a screw, into which to insert a tube and piston, connected with a small spring weighing-machine, which is represented at a in the wood-cut below. Upon the cylinder of this machine a ring was placed, which was moveable along the cylin der by a slight pressure: this ring was forced. towards the end of the cylinder nearest to the boiler-head, as the spring was bent and remaining in its place when the spring relaxed, served to register the maximum pressure to which the piston had been exposed previously to observing it.

The iron boiler was placed in a heavy cylinder of wrought-iron, which served as a furnace, the axis of the boiler being nearly horizontal, and that of the furnace cylinder

[blocks in formation]

vertical. The boiler, having been half filled with water, was placed upon a fire of charcoal, and when the water boiled the register. machine for the pressure was screwed in.

The place selected for the experiments was in a deserted quarry on the banks of the Pennypack, near Holmesburgh. The high bank served as a protection, by the aid of which the experiments were viewed with little danger. A wire and cord were attached to the head of the boiler, to draw it from the fire when the latter required to be replenished A leak in the riveting of the iron boiler allowed so much steam to escape, that the boiler did not give way on the first trial. As soon as the escape of steam was observed to cease, the boiler was removed from the fire and again half filled with water. The fire,, was urged, and the boiler settled lower into it, and by once replenishing the fuel, without removing the boiler, an explosion was produced. Part of the Committee were engaged in observing the progress of the experiment at this moment. The fire was near the middle line of the boiler, burning not strongly near that line, but very rapidly below the boiler; the steam issued freely through the leak be-føre alluded to, and the whistling sound which it produced, and which had increased gradually in strength as the experiment progressed, seemed constant. The length of. time during which the steam had escaped. showed the water to be low, and induced the supposition that a second time the object would fail, when an explosion occurred. The explosion tore off one of the heads, be, of the cylinder, projecting the other parts of the boiler in an opposite direction, carrying with them, for a portion of the distance, the iron cylinder forming the furnace, and scattering the fuel in every direction. The report attending the explosion resembled that from a small mortar (eprouvette) fully charged, the steam mixed with the smoke was not considerable in quantity, and few marks of water were to be seen. The boiler-head was thrown 15 feet, the boiler and spring-register about 6 feet, and the furnace, weighing about 45lbs., was overturned and carried 4 feet. The pressure indicated by the register was 114 atmospheres.

In examining the boiler it appeared that

[graphic][subsumed]

203 REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.

the head b, which was thrown off, had first struck against the iron furnace, which had deflected it outwards; this is shown by the indentation, be, in the figure. This head was forced off all around in the line of rivets which attached the head to the boiler, the metal remaining between the rivets being less than the space occupied by them. The convex surface and the other head were thrown likewise against the furnace, and the head indented at de, overturning the furnace and carrying it 4 feet, as already stated. The boiler finally struck against the side of the bank of earth. The piston of the weighing-machine was somewhat bent in the experiment.

The circumstances of this experiment show that the steam rose quite gradually on account of leaks in the boiler, increasing, probably, more rapidly as the quantity of water diminished, the intensity of the fire meanwhile increasing. That at a certain period the tension within had attained about 11 atmospheres, when the boiler exploded violently.

The accompanying figure will serve to give an accurate idea of the appearance of this boiler after its rupture.

The cylinder of copper, before referred to, was next put in the place of the iron boiler, and the fire again kindled; the general arrangements being as before described. This boiler being longer than the former, would

not descend so far into the furnace, and an attempt to raise the steam sufficiently high to burst it failed: there was a considerable leak in the junction of the curved surface with one of the ends. When the water was nearly exhausted, the fire having passed its period of greatest heat, the cylinder was removed and water again introduced, filling about three-fourths of its capacity. A new furnace was constructed of stones, allowing the boiler to rest more closely upon the fuel, and affording a screen from the wind, which was blowing quite strongly. The part of the boiler in which the leak had been observed was turned downwards, but a similar escape was found for the steam in the part now uppermost. The tension of the steam appeared to incre ise very slowly, and the fire passed its best ar tion without effect; it was renewed, and as the water became lower the tension of the steam increased considerably. As before, nothing remarkable occurred previous to the instant of explosion, and the members of the Committee employed in the experiments were engaged in observing the boiler at the instant it exploded. A dense cloud of smoke and flame, capped by steam, rose from the. pit; the stones and combustibles were widely scattered, and the boiler was thrown, in a single mass, about 15 feet from the furnace. The noise attending this explosion was like that from the firing of an 8-inch mortar.

The boiler was rent as shown in the accompanying figure, giving way in an irregular

[graphic][merged small][merged small]

Mechanics' Magazine,

MUSEUM, REGISTER, JOURNAL, AND GAZETTE,

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors]

226

CURTIS'S SAFETY RAILWAY-CARRIAGE.

CURTIS'S SAFETY RAILWAY-CARRIAGE.

Sir, Thanking you for your notice of my safety-break (published in No. 670), I have now to request the additional favour of your introduction to the public of the safety-carriages invented and constructed by me for the London and Greenwich Railway Company. A train of six of these are now upon the line; and the whole establishment of the carriages of the Company are in the course of being altered to the same plan. The alteration, it will be seen, consists principally in the carriage, which is inverted or suspended. The frame lies within four inches of the rail when loaded, which is sufficient to clear all the projections at the crossings; while in the event of the axle of the wheels breaking, the frame drops upon the rail and becomes a sledge, the friction of which, even when empty, will be sufficient to pull up the engine. In the event, again, of the wheel running off the rail, the frame, which projects eight inches beyond the wheel, falls upon it, and the same result follows, namely, that the friction stops the train; joggles are fixed to the front and side Tails of the frame which act as flanges, and thus hold the frame on the rail. Another valuable feature of this arrangement is, that at each end of the line, or at each stopping-place, supplemental side-rails will be fixed, which will be moveable; so that in the event of the train not stopping with the necessary precision-whether from the rails being wet, er from the engine running away with the train, or from any other cause--the carriages will run upon the side-rails, being supported by the frame and not upon the wheels. I have tried this with a single carriage, and have found it an admirable and perfect means of bringing it to a stand. The position of this siderail is shown by the dotted line z in fig. 1. Another feature of some importance connected with this train is the mode of Connecting the carriages; there is but one buffer, and that to the leading carriage, a draught-spring being affixed to the engine, and both connected together by an inflexible rod. By this arrangement all tremor and vibration is avoided; there is neither collision nor jar in starting, stopping, or moderating the velo. city; there is, besides, decidedly less noise than in the old carriages; and,

moreover, the carriages being connected by inflexible bars throughout, this supplies the means of carrying ten more passengers upon the same carriages, viz. outside, between each carriage. I find, from the reduced height, that the train loads and unloads in less than half the time required upon the old system. It is further important to observe, that all the old carriages and bodies, of whatever construction, may be altered to the new mode at a very rifling cost.

Fig. 1 is an elevation of the carriages now upon the line. a, the body; b, suspended carriage; c, steps; de, outside seats; f, door; the interior is fitted up in the usual omnibus style.

Fig. 2. Section of an improved carriage upon the same system, consisting of five bodies. a, a coach-body; bc, chariot-bodies, the flooring being at once upon the frame ten inches from the ground; de, either outside seats, or raised bodies above the wheel; the floor of the same height as in the present carriages. For a long journey, such as from London to York or Birmingham, I should recommend the bodies, de, to be converted into holds for luggage, placing thus the heaviest load immediately over the wheels; and thus the roof may be either converted into a deck for outside passengers, or a roof may be added, and it will become an omnibus-body or secondclass coach. In this arrangement it will be perceived that the springs are placed over the axle, a method to be recommended in all cases where practicable.

I may observe, that the engines start with the load without the least difficulty, notwithstanding the whole weight is put in motion at the same moment. I mention this merely to meet any objection which may suggest itself on that head. Fig. 3 is an elevation of fig. 2. I remain, Sir, Your obedient servant, W. J. CURTIS.

11, Grange-road, Bermondsey, June 15, 1836.

APPLICATION OF STEAM TO AGRICULTURE.

Sir,-Some incorrect statements having appeared in several provincial papers, relative to a recent exhibition near Bolton-le-Moors, of the application of steam to bog cultivation, as invented by Mr.

"APPLICATION OF STEAM TO AGRICULTURE.

Heathcoat, I should feel obliged by the insertion of the accompanying remarks, on the part of myself and those gentlemen who accompanied me to witness this interesting experiment.

I am, Sir,

Your obedient servant,

HENRY HANDLEY.

26, Pall-Mall, June 13.

Steam-Ploughs.

The adaptation of inanimate power to the tillage of the soil must evidently have been considered by practical men to present almost insuperable difficulties, or steam would, probably, long since have been substituted for horses and oxen, as the motive power of agricultural implements. Certain light operations of the farm, such as thrashing, churning, chaff-cutting, &c., which could be performed by fixed power, have partially occupied the attention of inechanics, and suitable machinery driven by water, wind, or small steam-engines, has to some extent been advantageously used for such purposes. But the idea of a "steam farm," of a farm to be altogether cultivated by steam, in lieu of animal power, has hitherto been treated as visionary and absurd, except by a few individuals, and one or two agricultural societies, who have enforced, in their publications, the practicability and importance of applying steam to effect the more laborious operations of agriculture.

This desideratum is at length accomplished. Mr. Heathcoat, M.P. for Tiverton, the ingenious and well-known inventor of the lace machinery, has the merit of having conceived and planned this additional and remarkable contribution to science, and to the wealth of his country. The invention, after years of costly experiment, has been matured and perfected through the enterprising libe rality of Mr. Heathcoat, assisted by the mechanical ingenuity and perseverance of Mr. Josiah Parkes, civil engineer, whom he selected to carry his designs into effect. The first machine has been constructed expressly for the cultivation of bogs, and has, for some months, been practically and successfully worked in Lancashire, on Red Moss, near Boltonle-Moors.

During the Whitsuntide recess of Parliament, a numerous assemblage of gen

227

tlemen from different parts of the country attended to witness an exhibition of this novel and interesting invention; amongst whom were Mr. M. L. Chapman, M.P., Mr. T. Chapman, Mr. H. Handley, M.P., Mr. J. Featherstone, of Griffinstown. house, Westmeath (an enterprising and successful bog-reclaimer), Mr. F. Brown, of Welbourn, Lincolnshire, Mr. James Smith, of Deanston, near Stirling (well known to the mechanical world by his ingenious inventions, applied both to agriculture and manufactures), Mr. B. Hick and Mr. P. Rothwell, engineers, with other experienced judges of mechanical contrivances. These gentlemen were unanimous in pronouncing the invention to be the germ of great improvements in the science and practice of agriculture, as well as eminently fitted for the particular purpose to which it has, in the first instance, been applied. Two ploughs of different construction were put in action, to the admiration of the spectators; particularly the one last invented, which is double-acting, or made with two shares in the same plane, so that it returns at the end of a bout," taking a new furrow, without loss of time. The perfect mechanism of this plough→ the action of the working coulters and under-cutting knives, which divide every opposing fibre of the moss-the breadth and depth of the furrow turned over→→→→ the application of a new and admirable means of traction, instead of chains or ropes-together with the facility with which the machine is managed, and the power applied to the plough, especially interested and surprised all present. The speed at which the plough travelled was 2 miles per hour, turning furrows 18 inches broad by 9 inches in depth, and completely reversing the surface. Each furrow of 220 yards in length was performed in somewhat less than three minutes, so that in a working day of twelve hours, this single machine would with two ploughs turn over ten acres of bog land!

66

The machine which bears the steam... engines is itself locomotive; but as the ploughs are moved at right angles to its line of progress, not dragged after it, the machine has to advance only the width of a furrow, viz. eighteen inches, whilst the ploughs have travelled a quarter of a mile; in other wo ds, the machine has to be moved only eleven yards, in the

« iepriekšējāTurpināt »