Page images
PDF
EPUB

Hence we find that on the score of friction, it is highly important to make the connecting rod long, and in most cases it is equally important to increase the length, in order that the mechanical force may be as uniform as possible, although theoretically no power is lost.

To reduce these infinitesimals to positive and definite numbers, may afford employment for the industrious, but they will be of no practical utility. The proper mode of ascertaining the loss from friction, is that pursued by De Pambour; to subject the engine to direct experiment.

One of the gentlemen whose words I have quoted, refers to the defects in De Pambours formula, and shows that a uniform loss from the crank, will not remove the difficulty.

I will add, that if we reject the formula and take the experiments, we will find in them, a proof that there is no loss from the crank.

This practical demonstration, is too long and intricate for the present article, for I have found, that after reducing the most difficult part of the investigation to a tabular form, and combining several operations, there still remains upwards of thirty distinct calculations, before we can predict the pressure in the boiler, and the amount of fuel, to effect a given velocity, with a given load, under the ordinary circumstances of high speed. Of this we shall have more hereafter.

New York, June, 1840.

Yours, respectfully,

B. AYCRIGG, C. E.

To the Editors of the American Railroad Journal and Mechanics' Magazine.

ENGINEER'S CAMP, Line of the Central
Railroad of Georgia, April, 1840.

GENTLEMEN:-The frequent accidents occurring to cotton trains on railroads, from fire, has led me to bestow some little thought on a method for remedying the evil. The plan that I shall suggest, will at least have the advantage of simplicity, which is too often lost sight of.

Various descriptions of cars have been used for the purpose of carrying cotton, some close, and some open, with a canvass covering for the cotton. The latter being thought by many persons, superior to the former, from the readiness with which the fire is detected and extinguished. But as this description of car does not answer as well for other kinds of freight, and I very much question whether they are as safe for cotton, it is not probable they will be extensively used. The kind commonly in use, is the, so called, close cars; but unfortunately they have generally but a poor title to the name-however tight they may have been originally made, by tinning, tongueing and groving, and buttoning; the motion soon working the joints loose.

To open the door of the cars occasionally, while in motion, for the purpose of examining, would, it is evident, lead to the very result intended to be avoided, even if it were convenient. The object, then, is to communicate with the interior of the cars, without leaving open any space for the fire to

enter at. That fire does not spread rapidly when communicated to cotton in bales, is a well known fact. An instance lately came under my observation, where the cars ran half an hour after the cotton was on fire, in one of them (having been smelt by a passenger) without any serious result; a single bucket of water being sufficient to extinguish it. Therefore, if discovered at an early stage, it can be easily controlled; and the plan which I shall propose, will, I think, lead to an almost instant detection of it; and long before the smoke would find its way through the cracks, and diffuse itself through the atmosphere, so as to be detected in that way, in too many instances it having been discovered too late to prevent a conflagration.

The plan is, to have a hole through the top of each car, say one inch in diameter. To this hole is to be fitted a valve, attached to the end of a spring beneath the roof of the car; the spring may be a flat straight piece of steel, say nine inches long, and the valve may be of cork or wood, at tached to the spring by a screw, with a large flat head, if the former, passing through into the spring. The valve should be so made as to come flush up, when closed, with the top of the roof, to keep water out of the hole; it should be made tapering, and also the hole, so as to make the motion easy, and to insure the valve setting tight. Next there is to be a tin tube, say about four feet long, the diameter a little larger than that of the hole. A single tube will answer for a whole train. This tube is to be placed over the valve in each car, from time to time-having a point projecting about an inch to throw the valve open--and if there is any smoke in the car at the time, its levity will cause it to rise instantly through the tube, when it will be detected by the smell. One of the hands that necessarily go with the cars, for the purpose of oiling, etc., can attend to this duty when the cars are under way, so that the expense may almost be set down at nothing. It might be well to have the roofs of the cars made to project a little, so as to facilitate stepping from one to the other.

Yours, truly,

F. P. H. Assistant Engineer.

For the American Railroad Journal, and Mechanics' Magazine.

IRON VESSELS.

Though this age is often condemned for a too great desire of innovations and experiments, not only in morals, but in arts, yet it will be found upon examination, that upon this desire rests its claim, and its right, to be called "the age of improvement." Though this mania for patents, and rage for new applications of the mechanical powers, bring with them, much that is to be lamented, and much that is crude and unphilosophical, and though they tend to multiply the number of those mechanical sciolists, who regard nature and her laws of little importance in the construction of machines, and think that long continued courses of experiments, without reference to fixed mechanical principles, will supply a deficiency of knowledge, yet with this evil there is some good, with this superficiality there is some deep sci

ence, and though there are thousands of ignorant smatterers, the age has nevertheless, produced an Arkwright, a Watt, and a Smeaton.

No art which ministers to the convenience and comfort of man, is more indebted to scientific discovery and scientific improvement, than the art of navigation. When we turn our eyes to the ancients and see that weakness and imperfection of their vessels, which compelled them to creep timidly and carefully along the coast of an inland sea, to which they were almost entirely confined, and then look at the art in our day, and see the beautifu】 model of the packet "walking the waters like a thing of life," the solidity of the frigate, defying the wind and the waves-and still more wonderful, the ocean steamers "shooting backward and forward between great continents, like shuttles weaving the world into one great web," we may well be proud of our age, and with reason boast of that superiority in the mechanic arts, which has almost enabled man to make the "winds and the waves" a subjugated part of his domain.

With these trite remarks, we come to a consideration of our subject. The use of iron in the construction of vessels is comparatively a modern invention, dating back not more than eight or ten years. Little has been written upon the subject, but not a little has been accomplished. Already iron steamers are used on the Niger, the Ganges, and the coast of Great Britain and France, and one has crossed the Atlantic. Two centuries ago man might have believed that vessels could be propelled by steam, but he would have found it difficult to believe that iron would be the material of which they would be constructed. He would have supposed that only the Prophet's miraculous power, could make iron to swim.

The construction of iron vessels has been almost entirely confined to Great Britain; and there even now, the expense of building a vessel of the same tonnage of wood, is but little less than that of building of iron. Owing, however, to the novelty of the invention, and perhaps to the prejudice which favors long established usages, and rejects innovation, it has not yet come into very general use; still we are of opinion that very soon in England and France, and eventually throughout the civilized world, it will supercede the use of wood. Before we proceed to show the advantages accruing from the use of iron as a material for the building of vessels, we shall remove the chief, and indeed only objection against it, by saying that from experiments accurate and conclusive, it has been ascertained that if iron be kept well covered with tar, it will suffer no injury from the corrosive power of sea-water. At a small expense, this can be done, and thus the only cause which can produce decay in the vessel, is removed.

The numerous advantages which have appeared, even in the short time since the first trial was made, are sufficient to convince the unprejudiced mind, of the advantage of the use of iron vessels.

First. The vessel may be divided into a number of compartments, each of which is "water tight," and should the vessel sustain an injury in one or more of them, the remainder would possess buoyancy sufficient to keep it a float. This is a desideratum which cannot be obtained in the case of ves

sels built of wood, and if there were nothing but this fact to recommend iron to general use, it would be an argument strong enough and convincing enough.

Secondly-Paradoxical as it may appear, it is nevertheless true that an iron vessel is lighter by nearly one half, and consequently draws much less water, than a wooden one of the same dimensions. On the Niger and other rivers they are used where other vessels of the same size could not be, and for shoal navigation are undoubtedly superior to all others.

Thirdly. In the torid zone subjected alternately to the burning heat of the mid day sun, and the heavy night damps and rains of such climates, a vessel constructed of wood soon decays, or else from expansion and contraction of its parts soon become unseaworthy; but iron is subjected to no such decay and no such expansion from the climate.

Fourthly.- Iron vessels may be built stronger and tighter than wooden ones-they are secure from fire which so often destroys the steamer-the devouring element has no power over them and the leak at sea,” which fills every heart with terror and dismay is not to be dreaded.

[ocr errors]

Lastly. An iron vessel may be constructed and taken in pieces and conveyed to any part of the globe, and again put together, at a very little expense, compared with one of wood. Several years ago, one was built at Manchester-sailed up the Rhine as far as was practicable-was then taken in pieces and conveyed to Lake Zurich in Switzerland, at a less expense than it could be constructed for there.

In case of a war on our inland seas, a fleet might be constructed at a national foundry, secure from all attacks from the enemy, and conveyed to the seat of war at a very small expense.

Such, imperfectly sketched, are some of the advantages, attendant upon the use of iron vessels. Should we succeed in calling the attention of scientific engineers to the subject, we shall be amply satisfied. We believe that at some future day, iron will be the sole material in the construction of navies. In Europe, already the scarcity of timber is felt, coal has long taken the place of wood; and man finding the outward resources of the carth failing, has discovered still richer and more abundant internal treasures. In our own country, too, we shall experience the same thing. Our forests are daily disappearing before the industry of the backwoodsman; we are daily compelled to seek for new materials and new complications of mechanical power to minister to our comfort and our luxuries, and the time is not far distant, when here, as in the Old World, our resources must be obtained from the bowels of the earth.

To the Editors of the American Railroad Journal, and Mechanics' Magazine.

GENTLEMEN-A severe illness, which left my eyes for several weeks in a state which required me to make the least possible use of them, prevented my conplying at an earlier date with the request of "an early friend to railroads," in your Journal of November last, that I would furnish the drawings and description of the chair and rail which I have intro, duced on the Eastern railroad from Boston to Portsmouth N. Hampshire

I have now the pleasure of forwarding a drawing which presents plans and sections of the joint and centre chairs, together with the rail, key and dowel, as above requested. The chief improvement upon the old chair and rail, and the T rail, is in the greater elevation, (some three or four inches) at which it places the top of the rail; the height of chair and rail being 7 inches, and as the sleepers or ties are covered with about three inches of gravel in the centre, and two inches under the rail, the top is five or six inches above the covering. This elevation I have found to relieve the road from all interruption in three-fourths of the snow storms which have occurred the two winters' experience which we have had with it, and it is obtained without greatly increasing upon the weight of the old chair, chiefly by having the centre chairs about two-thirds the width of the joint chair, instead of having all of the same width as formerly ;— and by cutting off the inner end of the chair, and lengthening that which is to be placed outwards, to make the angle of leverage even less than with the old chair. They weigh about 23 and 17 lbs. each, giving, with six to each rail of 18 feet in length, an average of less than 18 lbs., the old chair weighing generally about 16 lbs. The rails weigh 46 lbs. to the yard, and have dowels which fit tightly at the joints, and are secured in the chairs by a single key which is bent or clenched after it is driven. — With this arrangement, and having the distance between the joint sleeper and the one next to it, a foot less than the other distances, an unusual degree of firmness is secured at the joints. Although we have experienced no inconvenience from any longitudinal movement of the rails, yet I have had check holes formed in every third or fourth rail, into which a check of five-eighths iron, two inches in length may be inserted to bear against the adjoining chair and prevent such a movement. With regard to the key which this rail requires, I have found, after several years experience, that where the sleepers are of wood, from the elasticity which it gives to the track, they do not come out, except to a very trifling extent, and are not at all objectionable. Compared with the T rail, which is very generally in use, this chair rail possesses great advantages, particularly where snow and ice, and indeed any obstacles are to be encountered. It permits a freer drainage of the track; it is much firmer, the angles of leverage being less, and the supporting base greater than with the T rail, and of course admits of greater speed without injury to the track. It allows the sleepers to be well covered, which very much improves the appearance of the road and increases also its firmness. It is more readily removed for repairs, &c., and without injury to the sleepers, as in removing the Trail. It is more easily and perfectly manufactured, and its cost is not greater.

The T rail, which is generally laid like the other with ties about every three feet, will support a greater weight without deflection, but having found this chair rail fully sufficient as to strength, running engines of from nine to about twelve tons weight, mostly at a speed of 25 to 30 miles, and more the hour upon it, I deem this additional strength superfluous.

J. M. F.

« PreviousContinue »