Chapter 6

The machine which we illustrate has lately been constructed by Messrs. Merryweather & Sons, of Greenwich Road, with the view to combining the advantages of both horizontal and vertical steam fire engines. Hitherto the horizontal engine has been considered by some firemen to be less handy of access than the vertical, and the vertical engine has had the undoubted disadvantage of not being stoked from the footplate. By shortening the length of stroke and constructing a special pump, the makers have been able to keep the engine sufficiently high in relation to the boiler to enable the firedoor to be placed directly in the rear of the boiler and underneath the engine, thus enabling the boiler to be stoked en route, and allowing access from the footplate to the starting valve, the suction and delivery connections, the whole of the boiler fittings and feed arrangements. This enables one man to drive and stoke the engine, and to attend to the suction and delivery hoses, and it does not interfere at all with the stability of engine in traveling or at work, as the center of gravity is well below the top of the side frames. Another feature is the absence of a main steam pipe, a bracket being arranged on the cylinders containing the steam passages, to bolt directly onto the top of the boiler. The close proximity of the engine to the boiler renders it peculiarly suitable for cold climates, and times of frost, reducing the chances of the pump or feed arrangements being frozen up. The pump valves are arranged between the barrels, and are all accessible by the removal of one cover, which weighs but 12 lb. The engine, we understand, may be stopped, the cover removed, a damaged valve replaced, the cover put on again, and the engine restarted in two minutes. A slotted link is used with a crankshaft for regulating the length of stroke. All the bearings have large wearing surfaces, and substantial eccentric straps are used, the whole of the motion being simple and accessible. There are three different methods of feeding the boiler, viz., by feed pump driven by the crosshead of the main pump, by forcing water directly into the boiler from the main pump, and by an injector taking its water from a tank either supplied from the main pump or by a bucket when pumping dirty water. All the feed pipes are fitted with strainers where attached to the main pump. Drop feed lubricators are fitted on the cylinders, and an efficient system of lubrication is provided for the rest of the working parts. The carriage frame, hose box, etc., are of the same design as usually employed for engines of this class, with the exception of the fore carriage, which is fitted with a cross spring in the rear, as well as the two longitudinal springs. This arrangement makes the engine run more lightly, and removes much of the strain on the side frames when traveling rapidly on a rough road. The wheels are fairly light for the weight they have to carry, and have gun metal stock hoops with diamond pent rims to prevent the men slipping when mounting in a hurry. The engine and boiler work is brightly polished where-ever possible, and the whole machine has a handsome appearance.--Engineering.

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APPARATUS FOR OBTAINING THE CUBATURE OF TREES.

In the exploitation of forests it is an important matter to be able to measure the cubature of trees, and the process most generally employed consists in determining their height and mean circumference, the apparatus used for this latter measurement being compasses having the form of the calipers used by mechanics. The figure indicated is read upon the graduated rule and is called off in a loud voice to another person, who at once writes it down. There are several causes of error: it is possible that the reading may be incorrectly made or improperly called off, or be misunderstood or incorrectly noted. Finally, it is a somewhat fatiguing operation that is often dispensed with and the measurement made by estimate. In order to do away with all such causes of error, M. Jobez, a mining engineer, has had M. Peccaud construct an apparatus that automatically registers all the measurements upon a paper tape analogous to that used in the Morse telegraphic apparatus.

The registering mechanism (Fig. 1) is fixed to the movable branch that forms the slide of the instrument. It is so arranged that when this branch is slid along the rule carrying the graduations, a gearing causes the revolution of a wheel, D, which carries figures corresponding to such graduation. At the same time, two feed rollers, E, cause a small portion of the paper tape (which is wound upon a spool, A) to move forward and wind around a receiving spool, B. After the apparatus has been made accurately to embrace the trunk of the tree to be measured, it is removed and a pressure given to the lever, H, which applies the paper to the type wheel, D. A special button permits, in addition, of making a dot alongside of the numbers, if it be desired to attract attention to one of the measurements, either for distinguishing one kind of a tree from another or for any other reason.

With this apparatus one man can make all the measurements and inscribe them without any possible error and without any fatigue. It is possible for him to inscribe a thousand numbers an hour, and the tapes are long enough to permit of 4,000 measurements being made without a change of paper. There is, therefore, a saving of time as well as perfect accuracy in the operation.

In order to make the calculations necessary for the estimate, M. Laurand has devised a sliding rule which facilitates the operation and which is based upon the method that consists in knowing the height and mean circumference of the tree. The circumference taken in the middle is divided by 4, 4.8 or 5 according as one employs the quarter without deduction or the sixth or fifth deduced. This first result, multiplied by itself and by the height, gives the cubature of the tree. As for the value, that is the product of this latter number by the price per cubic meter. It will be seen that there is a series of somewhat lengthy operations to be performed, and it is in order to dispense with these that has been constructed the rule under consideration, which, like all calculating rules, consists of two parts, one of which slides upon the other (Fig. 2). Upon each of these there are two graduated scales, or four in all, the first of which is designed for the circumference and the second for the height of the tree, the third for the price of the cubic meter and the fourth for the total result, that is, the value of the entire tree. The arrangements are such that, after the number corresponding to the circumference of the tree has been brought opposite that corresponding to its height, the result will be found opposite the price per cubic meter.

Thus, in the position represented in the figure, we may suppose a tree having a circumference of 2.5 m. and a height of 3.2 m.; then, if a cubic meter is worth 25 francs, the tree will be worth 20 francs.

In order to simplify the calculations and the construction of the rule, no account is taken of points; but this is of no importance, since the error that might be made in misplacing one would be so great that it would be immediately detected. A 2 franc tree would not be confounded with a 20 or a 200 franc one. As an approximation, the first two figures of the result are obtained accurately; and that suffices, because, since the whole is based upon an approximate measurement, which is the mean circumference of the tree, we cannot exact absolute precision in the results. The essential thing is to have a practically acceptable figure.--La Nature.

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EGYPT'S POPULATION, according to the census taken last June, is 9,750,000, more than double the population in 1846. The foreign residents are 112,000; of these, 38,000 are Greeks, 24,500 Italians, 19,500 Britishers, including the army of occupation, and 14,000 French subjects, including Algerians and Tunisians. Twelve per cent. of the native males can read and write; the other Egyptians are illiterate. Cairo has 570,000 inhabitants, Alexandria 320,000, Port Said 42,000, and Suez 17,000.

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MACHINE MOULDING WITHOUT STRIPPING PLATES.[1]

[Footnote 1: Paper presented at the New York meeting (December, 1897) of the American Society of Mechanical Engineers, and forming part of volume xix. of the Transactions.]

BY E. H. MUMFORD, PLAINFLELD, N. J.

(Member of the Society.)

Moulding machines may be classed under three heads. First, machines which only ram the moulds, and, when the ramming is done by means of a side lever, by hand, are generally called "squeezers." Second, machines which only draw the patterns, the ramming being accomplished by the usual hand methods. Third, machines which both ram the moulds and draw the patterns, ramming either by a hand-pulled lever or by fluid pressure on piston or plunger and drawing the patterns through a plate called a "stripping plate" or "drop plate"--till recently the usual method--or without the use of this plate fitting everywhere to pattern outline at the parting surface, the patterns being effectively machine guided in either case.

It is to the third class that the machine which is used to illustrate the subject of this paper belongs, and which would seem to have enough that is novel in the application of machinery to the foundry to merit the attention of the society.

At the risk of appearing pedantic, but with a view to developing an appreciation of the true function of the method of pattern drawing used in this machine, attention is called to the following sectional views of moulds and ways of drawing patterns occurring in machine moulding. Fig. 1 shows an ordinary "gate" of fitting patterns being drawn from the drag or nowel part of the mould by means of a spike and rapper wielded by the moulder's hand after cope and drag have been rammed together on a "squeezer" and cope has been removed. Frequently the pernicious "swab" is used to soak and so strengthen joint outlines of the sand before drawing patterns, in such cases as this. In this case, before cope is lifted, these patterns must be vigorously rapped through the cope; an amount depending (and so does the size of the casting) upon the mood and strength of the moulder.

Fig. 2 shows the stripping or drop plate method of drawing patterns.

In this method the patterns are not rapped at all and are drawn in a practically straight line so that the mould is absolutely pattern size.

The stripping plate is fitted accurately to every outline at the joint surface of the patterns, obviously at considerable expense, and, of course, at the instant of drawing the patterns, supports the joint surface of the mould entirely. This is, at first sight, an ideal method of drawing patterns, and it has for years been the only method practiced on machines. It has two disadvantages. The patterns are separated from the stripping plate by the necessary joint fissure between the two. Fine sand continually falls into this and, adhering to the joint surfaces more or less, grinds the fissure wider. This leads to a gradual reduction of size of patterns on vertical surfaces and a widening of the joint fissure often to such an extent that wire edges are formed on the mould, causing, on fine work, "crushing" and consequently dirty joints. A nicely fitted but worn plate of twenty-four pieces which had cost, at shop expense only, $250, was recently replaced by a plate of twenty-eight pieces, fitted ready for the machine under the new system about to be described, for not more than $25.

The stripping plate method has another drawback, not always appreciated, probably because accepted as inevitable. Stripping plate patterns are not rapped, and there frequently occur on surface of patterns, remote from the action of the stripping plate, rectangular corners just as important to mould sharply as those at the parting line. Such corners have either to be filleted or "stooled" in stripping plate work, and neither method often is practicable. When the entire pattern and plate are vibrated so that the corners where the pattern joins the plate draw perfectly, as they do in the machine to be described, it is obvious that similar corners anywhere on pattern surface will draw equally well.

The vibrating of patterns, or rather of moulds, during the operation of drawing the patterns possesses little of novelty. Ever since a bench moulder's neighbor first rapped the bench while he lifted a cope or drew a pattern, the thing has been done in one way or another. In fact, machines are now and then found on the market in which a device like a ratchet or other mechanical means for jarring the machine structure during pattern drawing renders the working of easy patterns without stripping plates possible.

The idea of applying a power driven vibrator directly to the plate carrying the patterns to thus vibrate them independently of other parts of the machine and the flask and sand has been the subject of the issue of patents to Mr. Harris Tabor, and the various figures shown will serve to illustrate the mechanism.

Briefly, the operation of the machine is as follows: The ramming head shown thrown back at the top of the machine is drawn into a vertical position after flask has been placed and filled with sand. The 3-way cock shown at the extreme left is then quickly opened, admitting compressed air of 70 to 80 pounds pressure to the inverted cylinder shown at the center of the cut. The cylinder, with the entire upper portion of the machine, is thus driven forcibly up against the ramming head, flask, sand and all. Often a single blow suffices to rain the mould--often the blow is quickly repeated, according to the demands of the particular mould in hand. Gravity returns the machine to its original position, as the 3-way cock opens to exhaust. After pushing the ramming head back and cutting sprue, if the half mould is cope, the operator seizes the lever shown just inside the 3-way cock at the right, and, drawing it forward and down, raises the outer frame of the top of machine containing the flask pins, with flask and sand thereon, away from the patterns, thus drawing them from the sand. Just as he seizes the pattern drawing lever with his right hand, he presses with his left on the head of a compression valve shown at the left side of top of machine, thus admitting air to the pneumatic vibrator already referred to.

Fig. 3, a rear view of the machine, shows at the top center, with its inlet hose hanging to it, this vibrator, which is shown in section in Fig. 4. It consists simply of a double acting elongated piston having a stroke of about 5/16 inch in a valveless cylinder and impacting upon hardened anvils at either end at the estimated rate of 5,000 blows per minute.

The method of communicating the rapid yet small oscillations of the vibrator to the patterns and yet keeping them from being transmitted to the rest of the mechanism is this:

A frame, called a vibrator frame, to which the pneumatic vibrator is bolted and keyed, is shown in Fig. 5. To this frame the plate carrying the patterns, often, in cases of patterns having irregular parting lines, forming one and the same casting with the patterns, is fastened by the four machine screws, the small tapped holes for which are shown in the corners. In fact, in changing patterns, the process consists of simply removing these four machine screws, taking up the pattern plate and screwing to the vibrator frame the new pattern plate. The vibrator frame itself is secured to the machine structure by the four larger bolts, the holes for which are shown in the inner corners. These bolts are, as shown in Fig. 7, surrounded by thick bushings. These bushings are elastic to such a degree as to absorb the sharp vibrations of vibrator frame and patterns, while so firm and well fitted as to hold patterns accurately to their position.

The action of the vibrator is such as to give to the entire pattern surface an exceedingly violent shiver, making it impossible that any sand should adhere to this surface, while the magnitude of the actual movement of the pattern is so slight that it is found to fill the mould so completely that it is impracticable to draw it a second time without rapping. Yet, so truly are the patterns held and so little disturbed from their original position, that it is perfectly practicable to return patterns to a mould having the finest ornamental surface in the ordinary practice of "printing back."

In cases where deep pockets of hanging sand occur, which cannot be held during lifting off and rolling over, machines are arranged to roll the flask over in their operation and draw the patterns up under the influence of the pneumatic vibrator, though, owing to the time consumed in the rolling over process (and each operation counts in seconds on a moulding machine) this style of machine is not usually as rapid in its working as the simpler type, in which the flasks come off in the same way they go on.

Fig. 6 shows a set of patterns as they are ordinarily fitted to plates for this machine. Round holes will be noticed at places in the plate surface. These are openings for the insertion of what are called "stools."

When it is found necessary to support the sand surface at any point, or generally, round holes are drilled through either plate or pattern surface and loose cylindrical pieces are dropped into these holes, their upper end surfaces being flush with the plate or pattern surface and their lower ends resting on the plate called, from this use, a stool plate. This plate appears in Fig. 7 at A and is hung solidly by the brackets shown at B from the frame which carries the flasks, so that it has the same upward motion as the flasks, and the upper ends of the stools remain in contact with the sand of the mould until same is lifted from machine. Fig. 7, showing a vertical section through a machine, will make perfectly clear the position and action of these stools.

As illustrating the importance of being able to work without stripping plates on a line of work which is much more extended than that possible with them, we may say that a machinist with a drill press supplied with split patterns and planed pattern plates has matched and fixed five sets of from four to eight pieces in a day: and wooden patterns fitted for temporary use in the same way are of frequent occurrence when it is not thought wise to go to the expense of metal patterns on account of the relatively small number of castings to be made from them.

It is not perhaps too much to say that pattern expense is not the final evil of the costly and not durable stripping plate patterns.

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ARTIFICIAL INDIA RUBBER.

One of the most recent important events in the history of chemistry was the discovery by an English professor that a substance corresponding in every respect to India rubber may be produced from oil of turpentine.

Dr. W. A. Tilden, professor of chemistry in Mason College, Birmingham, began a series of experiments with a liquid hydrocarbon substance, known to chemists as isoprene, which was primarily discovered and named by Greville Williams, a well known English chemist, some years ago as a product of the destructive distillation of India rubber. In 1884, says The New York Sun, Dr. Tilden discovered that an identical substance was among the more volatile compounds obtained by the action of moderate heat upon oil of turpentine and other vegetable oils, such as rape seed oil, linseed oil and castor oil.

Isoprene is a very volatile liquid, boiling at a temperature of about 30 degrees Fahrenheit. Chemical analysis shows it to be composed of carbon and hydrogen in the proportions of five to eight.

In the course of his experiments Dr. Tilden found that when isoprene is brought into contact with strong acids, such as aqueous hydrochloric acid, for example, it is converted into a tough elastic solid, which is, to all appearances, true India rubber.

Specimens of isoprene were made from several vegetable oils in the course of Dr. Tilden's work on those compounds. He preserved several of them and stowed the bottles containing them away upon an unused shelf in his laboratory.

After some months had elapsed he was surprised at finding the contents of the bottles containing the substance derived from the turpentine entirely changed in appearance. In place of a limpid, colorless liquid the bottles contained a dense sirup, in which were floating several large masses of a solid of a yellowish color. Upon examination this turned out to be India rubber.

This is the first instance on record of the spontaneous change of isoprene into India rubber. According to the doctor's hypothesis, this spontaneous change can only be accounted for by supposing that a small quantity of acetic or formic acid had been produced by the oxidizing action of the air, and that the presence of this compound had been the means of transforming the rest.

Upon inserting the ordinary chemical test paper, the liquid was found to be slightly acid. It yielded a small portion of unchanged isoprene.

The artificial India rubber found floating in the liquid upon analysis showed all the constituents of natural rubber. Like the latter, it consisted of two substances, one of which was more soluble in benzine or in carbon bisulphide than the other. A solution of the artificial rubber in benzine left on evaporation a residue which agreed in all characteristics with the residuum of the best Para rubber similarly dissolved and evaporated.

The artificial rubber was found to unite with natural rubber in the same way as two pieces of ordinary pure rubber, forming a tough, elastic compound.

Although the discovery is very interesting from a chemical point of view, it has not as yet any commercial importance. It is from such beginnings as these, however, that cheap chemical substitutes for many natural products have been developed. Few persons outside of those directly connected with rubber industries realize the vast quantities imported yearly into this country. Last year there were brought into United States ports, as shown by the reports of the customs officers, no less than 34,348,000 pounds of India rubber. The industry has been steadily progressive since the invention of machinery for manufacturing it into the various articles of everyday use. The wonderful growth of the India rubber interests in this country will be seen from the statistics compiled in the tenth census.

In 1870 there were imported 5,132,000 pounds at an average rate of $1 per pound; in 1880 the imports were 17,835,000 pounds, at an average price of 85 cents per pound; in 1890 31,949,000 pounds were imported, at an average price of 75 cents per pound. The present price of India rubber varies from 75 cents per pound for fine Para rubber to 45 cents per pound for the cheapest grade.

It will be seen that, notwithstanding the increase in importations, the price of the raw material remains at a comparatively high figure. Many experiments have been made to find a substance possessing the same properties as India rubber, but which could be produced at a cheaper rate.