Steam gauge

“ For it requires some force, and by no means an inconsiderable portion, to move the engine itself, even when unloaded; all this, therefore, which is spent in overcoming friction, &c. is to be left out of account, and only the balance set down as the effective working power.
From what we have stated, it appears that in order to estimate the effective force with which the piston is urged, it is necessary to refer to both the barometer and the steam-gauge. This double computation may be obviated by making one gauge serve both purposes. If the end C of the steam-gauge (fig. 38.) ”

“ From the engine the exhaust pipe leads to the nose of the figure, whence the steam escapes when the machine is in motion. Through the head the smoke flue is carried, and the products of combustion escape from the top of the helmet. The steam gauge is placed by the side of the neck. The skirts of the armor open like doors, so as to give free access to the engine. The main body of the figure is made of heavy tin. By reducing gear the engine is made to drive the walking mechanism of the figure at reasonable speed. ”

“ Suppose the dial vacuum gauge shows 10 lbs., the steam gauge 120 lbs., and the barometer 15 lbs., and we may find the total pressure or pressure above vacuum of the steam in the boiler is as follows:
To make the correction necessary because there is not a perfect vacuum in the condenser, we then proceed as follows:
Then
Racing means a sudden acceleration of the engine speed, and occurs when the propeller is not fully immersed in the sea, as by reason of the pitching of the ship. ”

“ The principle of construction of the dial steam gauge is, that the pressure may be indicated by means of a pointer in a divided dial similar to a clock face, but marked in division, indicating pounds pressure per square inch instead of hours and minutes. ”

“ It is unsafe to trust to the glass gauges altogether as a means of ascertaining the water level, as sometimes they become choked, and it is necessary, therefore, to have gauge cocks in addition; but if the boiler be short of steam, and a partial vacuum be produced within it, the glass gauges become of essential service, as the gauge cocks will not operate in such a case, for though opened, instead of steam and water escaping from them, the air will rush into the boiler. ”

“ Gas is used as fuel, but they can be made to burn either coal, wood, or oil. The construction and method of generating steam are such that an explosion can not occur, and the steam-gauge, water-gauge, and safety-valve are therefore dispensed with, with the advantage of considerably lessening the cost. The idea carried out in the construction of this engine is that of converting the water into steam in small amounts at a time. In the steam-engine, large or small, the whole body of water is exposed to the action of the fire, and a considerable quantity of steam is constantly generated. ”

“ The glass gauge tubes should always be fitted with a cock at each neck communicating with the boiler, so that the water and steam may be shut off if the tube breaks; and the cocks should be so made as to admit of the tubes being blown through with steam to clear them, as in muddy water they will become so soiled that the water cannot be seen. The gauge cocks frequently have pipes running up within the boiler, to the end that a high water level may be made consistent with an easily accessible position of the gauge cocks themselves. ”

“ The total heating surface is 940 sq. ft.; steam pressure, 120lb.; weight of engine in working order, 221⁄2tons. There is no dome on the boiler; but some modern attachments have been fixed on the upper portion of the round fire-box, the steam pressure gauge being very noticeable. The tender is supported on four wheels of 3ft. diameter, the wheel base being 8ft., capacity of tank 1,000 gallons, and coal space 100ft.; weight in working order, 141⁄2 tons. The tender has outside frames, and the brake actuates blocks to both sides of the four wheels. ”

“ The engines of these elegant ships were arranged in the manner already indicated so as to avoid having unnecessarily large cylinders, the two high-pressure cylinders driving one crank, being arranged tandem fashion, the intermediate cylinder driving one crank, whilst the two low-pressure were also put the one above the other like the high-pressure, and by an ingenious contrivance it is possible to prevent the screws racing; for when the number of revolutions begins to exceed its proper limit the supply of steam is automatically cut off. ”

“ It will be about 150 feet in length, 20 to 40 feet diameter of the gasometer, with propelling blades on each side of the centre, describing a radius of about 16 feet. The propellers are shaped like a steamship’s, with two blades, each very light. They will be driven by a steam-engine of five-horse power, weighing, with boiler connections and water, 430 pounds weight. The planes on each side for floating the machine will be about twenty feet wide at the centre of the machine, and made in sections, so that they can be depressed or elevated at pleasure with the rudder or tail. ”

“ The bossing out of the stern, as in the Teutonic and Majestic, permits the screws to work without any exterior overhanging bracket, as in other screw steamers. The central boss of the propeller is made of steel; the three blades, weighing eight tons each, are of manganese bronze. A new feature in the machinery is what is called an “emergency governor,” which, in case of the shaft breaking, or the screw racing from any other cause beyond a certain speed, is designed to act automatically on the reversing gear and stop the engines. These gigantic engines are started and reversed by steam. ”

“ Imagine the effect on an engine which is putting out its whole strength and getting full charges of fuel, if the belt suddenly slipped off and it were "allowed its head." A burst fly-wheel would be only one of the results. The steam-engine is easily controlled by the centrifugal action of a ball-governor, which, as the speed increases, gradually spreads its balls and lifts a lever connected with a valve in the steam supply pipe. Owing to its elastic nature, steam will do useful work if admitted in small quantities to the cylinder. ”

“ Pressure gauges are supplied to indicate the pressure in the steam pipe, the various receivers, and the vacuum in the condenser. Revolution counters are attached, which automatically record the number of revolutions of the engines. A water service is supplied, consisting of a system of piping by means of which sea water can be circulated through such parts as the thrust bearing and crosshead guides, or sprayed on various other bearings where heating is likely. ”

“ By drawing down a chain or rope acting over a pulley, the piston would in its descent (omitting the consideration of friction, &c.) raise a weight of 2160 pounds a foot high. Since 2160 pounds are nearly equal to one ton, it may, for the sake of round numbers be stated thus:—
"A cubic inch of water, being converted into steam, will, by the condensation of that steam, raise a ton weight a foot high." Such is the way in which the force of steam is rendered practically available in the atmospheric engine. ”

“ There were two large bath rooms for the use of the after saloon passengers, and one three times as large as either of these two for the use of the ’tween deck passengers. She had seven watertight compartments and tanks capable of holding 64,000 gallons of water.
The Royal Charter, independently of her steam power, was a full-rigged ship, and was the first English vessel to adopt the American plan of double topsails on each mast. On her trial trips she averaged a speed of nine knots per hour with her propeller; and under canvas only, with a light N.N.E. wind, made fourteen knots per hour. ”

“ Horse and hand powers are limited in their extent, and are moreover very expensive. The first attempts at a steam-engine were those in which the steam was only used that by its condensation a vacuum might be formed in a cylinder under a piston, so that the weight of the air should cause this to descend with considerable force—15 lbs. on the square inch. The piston was balanced by a weight, so that the steam might raise it with scarcely any pressure; the steam beneath the piston being condensed by a stream of cold water, the weight of the air again forced down the piston into the vacuum. ”

“ If a weight were hung to the other end of the rope it would be raised as the piston was forced down. In that way the air pressure did the work of lifting the weight, and the necessary vacuum was obtained by forming steam and then condensing it in the cylinder. This was a very primitive device, requiring several minutes for the engine to make one stroke, but it was the beginning of the practical use of steam as a motive power. ”

“ The steam-engine itself, which supplies us with such unbounded power, owes its present perfection to this most admirable means of giving to metallic objects the most precise and perfect geometrical forms. How could we, for instance, have good steam-engines if we had not the means of boring out a true cylinder, or turning a true piston-rod, or planing a valve face? ”

“ IT will help us to appreciate the work of the men who first experimented with steam-driven ships if we recall the fact that James Watt, working at Soho, near Birmingham, England, invented the engine which used steam on both sides of the piston in 1782, and that it was for many years after that date an enormously heavy and cumbersome machine. From this fact we see the state of the mechanic arts in England at the end of the eighteenth century, when practical experiments in steam navigation were first begun. ”

“ Near the top of each chamber is a small air-valve opening inwards, which allows a little air to enter each time a vacuum is formed. When any steam is condensed, the air mixed with it remains on the cold surface and forms a non-conducting layer. The pulsometer is, of course, far from efficient as a thermodynamic engine, but its suitability for situations where other steam-pumps cannot be used, and the extreme simplicity of its working parts, make it valuable in certain cases. ”

“ An inner cylinder similarly constructed, corresponding to the hold of a ship, remains stationary while the other is supposed to be rolling over the surface of the water, regardless of wind and waves, at railway speed. The modest calculation of the inventor is that a steam vessel so constructed of 700 feet in length and 150 feet in diameter, ought to cover the distance between New York and Liverpool in forty-eight hours! This model was built at a cost of $10,000. The results of the trial trip on Toronto Bay have not been made public. ”

“ This is what the engine-power meter does, and it shows the continuously growing result on a dial. When the piston moves, it drags the cylinder along; where the steam presses, the wheel is inclined. Neither action alone causes the cylinder to turn, but when they occur together the cylinder turns, and the number of turns registered on a dial shows with mathematical accuracy how much work has been done.
In the steam-engine work is done in an alternating manner, and it so happens that this alternating action exactly suits the integrator. ”

“ The condensing pipe being again allowed to play upon the vessel V, and the further supply of steam being stopped, a vacuum will be produced in V, and the atmospheric pressure on L will force the water through the valve A into the vessel V, which it will nearly fill, a small quantity of air, however, remaining above it.
Thus far the mechanical agency employed in elevating the water is the atmospheric pressure; and the power of steam is no further employed than in the production of a vacuum. ”

“ The now well-known principle of a steam-engine is this: there is a cylinder with its rod fixed to one end of a lever, which is worked by the combined pressure of the atmosphere and the steam upon a piston, a temporary vacuum being made below it by suddenly condensing the steam, which had been let into the cylinder where this piston works, by a jet of cold water thrown into it. ”

“ If the engine does not start when the regulator is opened, which will occur when the high-pressure valve covers both steam ports, the driver pulls the additional small handle, which closes the passage from the receiver to the low-pressure cylinder, and also admits a small amount of steam to the low-pressure steam chest, so that the two cylinders together develop additional starting power. ”

“ You must remember that in high-class workmanship these gauges are constantly being used. As time goes on, the "limit of error" allowed in many classes of machine parts is gradually lessened, which shows the simultaneous improvement of all machinery used in the handling of metal. James Watt was terribly hampered, when developing his steam-engine, by the difficulty of procuring a true cylinder for his pistons to work in with any approach to steam-tightness. ”

“ In the year 1800 Watt retired from business, leaving the steam-engine in much the same condition as we find it now. The application of steam-power for locomotion on both land and water followed, and now stationary, locomotive, and marine engines, driven by steam, are distributed all over the civilised world.
The varieties of model engines are in many cases indicated by their names. Stationary engines are intended to be fixed, as those used for driving machinery. Locomotives are those which are intended to travel by steam, and are self-moving. Marine engines are those used to propel ships. ”