Chapter 2

_Bell-Buoys._--The bell-boat, which is at most a clumsy contrivance, liable to be upset in heavy weather, costly to build, hard to handle, and difficult to keep in repair, has been superseded by the Brown bell-buoy, which was invented by the officer of the lighthouse establishment whose name it bears. The bell is mounted on the bottom section of an iron buoy 6 feet 6 inches across, which is decked over and fitted with a framework of 3-inch angle-iron 9 feet high, to which a 300-pound bell is rigidly attached. A radial grooved iron plate is made fast to the frame under the bell and close to it, on which is laid a free cannon-ball. As the buoy rolls on the sea, this ball rolls on the plate, striking some side of the bell at each motion with such force as to cause it to toll. Like the whistling-buoy, the bell-buoy sounds the loudest when the sea is the roughest, but the bell-buoy is adapted to shoal water, where the whistling-buoy could not ride; and, if there is any motion to the sea, the bell-buoy will make some sound. Hence the whistling-buoy is used in roadsteads and the open sea, while the bell-buoy is preferred in harbors, rivers, and the like, where the sound-range needed is shorter, and smoother water usually obtains. In July, 1883, there were 24 of these bell-buoys in United States waters. They cost, with their fitments and moorings, about $1,000 each.

_Locomotive-Whistles._--It appears from the evidence given in 1845, before the select committee raised by the English House of Commons, that the use of the locomotive-whistle as a fog-signal was first suggested by Mr. A. Gordon, C.E., who proposed to use air or steam for sounding it, and to place it in the focus of a reflector, or a group of reflectors, to concentrate its sounds into a powerful phonic beam. It was his idea that the sharpness or shrillness of the whistle constituted its chief value. And it is conceded that Mr. C.L. Daboll, under the direction of Prof. Henry, and at the instance of the United States Lighthouse Board, first practically used it as a fog-signal by erecting one for use at Beaver Tail Point, in Narragansett Bay. The sounding of the whistle is well described by Price-Edwards, a noted English lighthouse engineer, "as caused by the vibration of the column of air contained within the bell or dome, the vibration being set up by the impact of a current of steam or air at a high pressure." It is probable that the metal of the bell is likewise set in vibration, and gives to the sound its timbre or quality. It is noted that the energy so excited expends its chief force in the immediate vicinity of its source, and may be regarded, therefore, as to some extent wasted. The sound of the whistle, moreover, is diffused equally on all sides. These characteristics to some extent explain the impotency of the sound to penetrate to great distances. Difference in pitch is obtained by altering the distance between the steam orifice and the rim of the drum. When brought close to each other, say within half an inch, the sound produced is very shrill, but it becomes deeper as the space between the rim and the steam or air orifice is increased.

Prof. Henry says the sound of the whistle is distributed horizontally. It is, however, much stronger in the plane containing the lower edge of the bell than on either side of this plane. Thus, if the whistle is standing upright in the ordinary position, its sound is more distinct in a horizontal plane passing through the whistle than above it or below it.

The steam fog-whistle is the same instrument ordinarily used on steamboats and locomotives. It is from 6 to 18 inches in diameter, and is operated by steam under a pressure of from 50 to 100 pounds. An engine takes its steam from the same boiler, and by an automatic arrangement shuts off and turns on the steam by opening and closing its valves at determined times. The machinery is simple, the piston-pressure is light, and the engine requires no more skilled attention than does an ordinary station-engine.

"The experiments made by the Trinity House in 1873-74 seem to show," Price-Edwards says, "that the sound of the most powerful whistle, whether blown by steam or hot air, was generally inferior to the sound yielded by other instruments," and consequently no steps were taken to extend their use in Great Britain, where several were then in operation. In Canadian waters, however, a better result seems to have been obtained, as the Deputy Minister of Marine and Fisheries, in his annual report for 1872, summarizes the action of the whistles in use there, from which it appears that they have been heard at distances varying with their diameter from 3 to 25 miles.

The result of the experiments made by Prof. Henry and Gen. Duane for the United States Lighthouse Board, reported in 1874, goes to show that the steam-whistle could be heard far enough for practical uses in many positions. Prof. Henry found that he could hear a 6-inch whistle 7¼ miles with a feeble opposing wind. Gen. Duane heard the 10-inch whistle at Cape Elizabeth at his house in Portland, Maine, nine miles distant, whenever it was in operation. He heard it best during a heavy northeast snow storm, the wind blowing then directly from him, and toward the source of the sound. Gen. Duane also reported that "there are six fog-signals on the coast of Maine; these have frequently been heard at the distance of twenty miles," ... which distance he gives as the extreme limit of the twelve-inch steam-whistle.

_Trumpets._--The Daboll trumpet was invented by Mr. C.L. Daboll, of Connecticut, who was experimenting to meet the announced wants of the United States Lighthouse Board. The largest consists of a huge trumpet seventeen feet long, with a throat three and one-half inches in diameter, and a flaring mouth thirty-eight inches across. In the trumpet is a resounding cavity, and a tongue-like steel reed ten inches long, two and three-quarter inches wide, one inch thick at its fixed end, and half that at its free end. Air is condensed in a reservoir and driven through the trumpet by hot air or steam machinery at a pressure of from fifteen to twenty pounds, and is capable of making a shriek which can be heard at a great distance for a certain number of seconds each minute, by about one-quarter of the power expended in the case of the whistle. In all his experiments against and at right angles and at other angles to the wind, the trumpet stood first and the whistle came next in power. In the trial of the relative power of various instruments made by Gen. Duane in 1874, the twelve-inch whistle was reported as exceeding the first-class Daboll trumpet. Beaseley reports that the trumpet has done good work at various British stations, making itself heard from five to ten miles. The engineer in charge of the lighthouses of Canada says: "The expense for repairs, and the frequent stoppages to make these repairs during the four years they continued in use, made them [the trumpets] expensive and unreliable. The frequent stoppages during foggy weather made them sources of danger instead of aids to navigation. The sound of these trumpets has deteriorated during the last year or so." Gen. Duane, reporting as to his experiments in 1881, says: "The Daboll trumpet, operated by a caloric engine, should only be employed in exceptional cases, such as at stations where no water can be procured, and where from the proximity of other signals it may be necessary to vary the nature of the sound." Thus it would seem that the Daboll trumpet is an exceptionally fine instrument, producing a sound of great penetration and of sufficient power for ordinary practical use, but that to be kept going it requires skillful management and constant care.

_The Siren._--The siren was adapted from the instrument invented by Cagniard de la Tour, by A. and F. Brown, of the New York City Progress Works, under the guidance of Prof. Henry, at the instance and for the use of the United States Lighthouse Establishment, which also adopted it for use as a fog-signal. The siren of the first class consists of a huge trumpet, somewhat of the size and shape used by Daboll, with a wide mouth and a narrow throat, and is sounded by driving compressed air or steam through a disk placed in its throat. In this disk are twelve radial slits; back of the fixed disk is a revolving plate, containing as many similar openings. The plate is rotated 2,400 times each minute, and each revolution causes the escape and interruption of twelve jets of air or steam through the openings in the disk and rotating plate. In this way 28,800 vibrations are given during each minute that the machine is operated; and, as the vibrations are taken up by the trumpet, an intense beam of sound is projected from it. The siren is operated under a pressure of seventy-two pounds of steam, and can be heard, under favorable circumstances, from twenty to thirty miles. "Its density, quality, pitch, and penetration render it dominant over such other noises after all other signal-sounds have succumbed." It is made of various sizes or classes, the number of slits in its throat-disk diminishing with its size. The dimensions given above are those of the largest. [See engraving on page 448, "Annual Cyclopædia" for 1880.]

The experiments made by Gen. Duane with these three machines show that the siren can be, all other things being equal, heard the farthest, the steam-whistle stands next to the siren, and the trumpet comes next to the whistle. The machine which makes the most noise consumes the most fuel. From the average of the tests it appears that the power of the first-class siren, the twelve-inch whistle, and first-class Daboll trumpet are thus expressed: siren nine, whistle seven, trumpet four; and their relative expenditure of fuel thus: siren nine, whistle three, trumpet one.

Sound-signals constitute so large a factor in the safety of the navigator, that the scientists attached to the lighthouse establishments of the various countries have given much attention to their production and perfection, notably Tyndall in England and Henry in this country. The success of the United States has been such that other countries have sent commissions here to study our system. That sent by England in 1872, of which Sir Frederick Arrow was chairman, and Captain Webb, R.N., recorder, reported so favorably on it that since then "twenty-two sirens have been placed at the most salient lighthouses on the British coasts, and sixteen on lightships moored in position where a guiding signal is of the greatest service to passing navigation."

The trumpet, siren, and whistle are capable of such arrangement that the length of blast and interval, and the succession of alternation, are such as to identify the location of each, so that the mariner can determine his position by the sounds.

In this country there were in operation in July, 1883, sixty-six fog-signals operated by steam or hot air, and the number is to be increased in answer to the urgent demands of commerce.

_Use of Natural Orifices._--There are, in various parts of the world, several sound-signals made by utilizing natural orifices in cliffs through which the waves drive the air with such force and velocity as to produce the sound required. One of the most noted is that on one of the Farallon Islands, forty miles off the harbor of San Francisco, which was constructed by Gen. Hartmann Bache, of the United States Engineers, in 1858-59, and of which the following is his own description:

"Advantage was taken of the presence of the working party on the island to make the experiment, long since contemplated, of attaching a whistle as a fog-signal to the orifice of a subterranean passage opening out upon the ocean, through which the air is violently driven by the beating of the waves. The first attempt failed, the masonry raised upon the rock to which it was attached being blown up by the great violence of the wind-current. A modified plan with a safety-valve attached was then adopted, which it is hoped will prove permanent. ... The nature of this work called for 1,000 bricks and four barrels of cement."

Prof. Henry says of this:

"On the apex of this hole he erected a chimney which terminated in a tube surmounted by a locomotive-whistle. By this arrangement a loud sound was produced as often as the wave entered the mouth of the indentation. The penetrating power of the sound from this arrangement would not be great if it depended merely on the hydrostatic pressure of the waves, since this under favorable circumstances would not be more than that of a column of water twenty feet high, giving a pressure of about ten pounds to the square inch. The effect, however, of the percussion might add considerably to this, though the latter would be confined in effect to a single instance. In regard to the practical result from this arrangement, which was continued in operation for several years, it was found not to obviate the necessity of producing sounds of greater power. It is, however, founded on an ingenious idea, and may be susceptible of application in other cases."

There is now a first-class siren in duplicate at this place.

The sixty-six steam fog-signals in the waters of the United States have been established at a cost of more than $500,000, and are maintained at a yearly expense of about $100,000. The erection of each of these signals was authorized by Congress in an act making special appropriations for its establishment, and Congress was in each instance moved thereto by the pressure of public opinion, applied usually through the member of Congress representing the particular district in which the signal was to be located. And this pressure was occasioned by the fact that mariners have come to believe that they could be guided by sound as certainly as by sight. The custom of the mariner in coming to this coast from beyond the seas is to run his ship so that on arrival, if after dark, he shall see the proper coast-light in fair weather, and, if in thick weather, that he shall hear fog-signal, and, taking that as a point of departure, to feel his way from the coast-light to the harbor-light, or from the fog-signal on the coast to the fog-signal in the harbor, and thence to his anchorage or his wharf. And the custom of the coaster or the sound-steamer is somewhat similar.

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TREVITHICK'S ENGINE AT CREWE.

The old high-pressure engine of Richard Trevithick, which, thanks to Mr. Webb, has been rescued from a scrap heap in South Wales, and re-erected at the Crewe Works. We give engravings of this engine, which have been prepared from photographs kindly furnished to us by Mr. Webb, and which will clearly show its design.

The boiler bears a name-plate with the words "No. 14, Hazeldine and Co., Bridgnorth," and it is evidently one of the patterns which Trevithick was having made by Hazeldine and Co., about the year 1804. The shell of the boiler is of cast iron, and the cylinder, which is vertical, is cast in one with it, the back end of the boiler and the barrel being in one piece as shown. At the front end the barrel has a flange by means of which it is bolted to the front plate, the plate having attached to it the furnace and return flue, which are of wrought iron. The front plate has also cast on it a manhole mouthpiece to which the manhole cover is bolted. In the case of the engine at Crewe, the chimney, firehole door, and front of flue had to be renewed by Mr. Webb, these parts having been broken up before the engine came into his possession.

The piston rod is attached to a long cast-iron crosshead, from which two bent connecting rods extend downward, the one to a crank, and the other to a crank-pin inserted in the flywheel. The connecting-rods now on this engine were supplied by Mr. Webb, the original ones--which they have been made to resemble as closely as possible--having been broken up. In the Crewe engine as it now exists it is not quite clear how the power was taken off from the crankshaft, but from the particulars of similar engines recorded in the "Life of Richard Trevithick," it appears that a small spur pinion was in some cases fixed on the crankshaft, and in others a spurwheel, with a crank-pin inserted in it, took the place of the crank at the end of the shaft opposite to that carrying the flywheel. In the Crewe engine the flywheel, it will be noticed, is provided with a balanceweight.

The admission of the steam to and its release from the cylinder is effected by a four-way cock provided with a lever, which is actuated by a tappet rod attached to the crosshead, as seen on the back view of the engine. To the crosshead is also coupled a lever having its fulcrum on a bracket attached to the boiler; this lever serving to work the feed pump. Unfortunately the original pump of the Crewe engine was smashed, but Mr. Webb has fitted one up to show the arrangement. A notable feature in the engine is that it is provided with a feed heater through which the water is forced by the pump on its way to the boiler. The heater consists of a cast-iron pipe through which passes the exhaust pipe leading from the cylinder to the chimney, the water circulating through the annular space between the two pipes.

Altogether the Trevithick engine at Crewe is a relic of the very highest interest, and it is most fortunate that it has come into Mr. Webb's hands and has thus been rescued from destruction. No one, bearing in mind the date at which it was built, can examine this engine without having an increased respect for the talents of Richard Trevithick, a man to whom we owe so much and whose labors have as yet met with such scant recognition.--_Engineering._

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[Continued from SCIENTIFIC AMERICAN SUPPLEMENT, No. 451, page 7192.]

PLANETARY WHEEL TRAINS.

By Prof. C.W. MacCORD, Sc. D.

IV.

The arrangement of planetary wheels which has been applied in practice to the greatest extent and to the most purposes, is probably that in which the axial motions of the train are derived from a fixed sun wheel. Numerous examples of such trains are met with in the differential gearing of hoisting machines, in portable horse-powers, etc. The action of these mechanisms has already been fully discussed; it may be remarked in addition that unless the speed be very moderate, it is found advantageous to balance the weights and divide the pressures by extending the train arm and placing the planet-wheels in equal pairs diametrically opposite each other, as, for instance, in Bogardus' horse power, Fig. 31.

In trains of this description, the velocity ratio is invariable; which for the above-mentioned objects it should be. But the use of a planetary combination enables us to cause the motions of two independent trains to converge, and unite in producing a single resultant rotation. This may be done in two ways; each of the two independent trains may drive one sun-wheel, thus determining the motion of the train-arm; or, the train-arm may be driven by one of them, and the first sun-wheel by the other; then the motion of the second sun-wheel is the resultant. Under these circumstances the ratio of the resultant velocity to that of either independent train is not invariable, since it may be affected by a change in the velocity of the other one. To illustrate our meaning, we give two examples of arrangements of this nature. The first is Robinson's rope-making machine, Fig. 32. The bobbins upon which the strands composing the rope are wound turn freely in bearings in the frames, G, G, and these frames turn in bearings in the disk, H, and the three-armed frame or spider, K, both of which are secured to the central shaft, S. Each bobbin-frame is provided with a pinion, _a_, and these three pinions engage with the annular wheel, A. This wheel has no shaft, but is carried and kept in position by three pairs of rollers, as shown, so that its axis of rotation is the same as that of the shaft, S; and it is toothed externally as well as internally. The strands pass through the hollow axes of the pinions, and thence each to its own opening through the laying-top, T, fixed upon S, which completes the operation of twisting them into a rope. The annular wheel, A, it will be perceived, may be driven by a pinion, E, engaging with its external teeth, at a rate of speed different from that of the central shaft; and by varying the speed of that pinion, the velocity of the wheel, A, may be changed without affecting the velocity of S.

It is true that in making a certain kind of rope, the velocity ratio of A and S must remain constant, in order that the strands may be equally twisted throughout; but if for another kind of rope a different degree of twist is wanted, the velocity of the pinion, E, may be altered by means of change-wheels, and thus the same machine may be used for manufacturing many different sorts.

The second combination of this kind was devised by the writer as a "tell-tale" for showing whether the engines driving a pair of twin screw-propellers were going at the same rate. In Fig. 33, an index, P, is carried by the wheel, F: the wheel, A, is loose upon the shaft of the train-arm, which latter is driven by the wheel, E. The wheels, F and _f_, are of the same size, but _a_ is twice as large as A; if then A be driven by one engine, and E by the other, at the same rate but in the opposite direction, the index will remain stationary, whatever the absolute velocities. But if either engine go faster than the other, the index will turn to the right or the left accordingly. The same object may also be accomplished as shown in Fig. 34, the index being carried by the train-arm. It makes no difference what the actual value of the ratio A/_a_ may be, but it must be equal to F/_f_: under which condition it is evident that if A and F be driven contrary ways at equal speeds, small or great, the train-arm will remain at rest; but any inequality will cause the index to turn.

In some cases, particularly when annular wheels are used, the train-arm may become very short, so that it may be impossible to mount the planet-wheel in the manner thus far represented, upon a pin carried by a crank. This difficulty may be surmounted as shown in Fig. 35, which illustrates an arrangement originally forming a part of Nelson's steam steering gear. The Internal pinions, _a_, _f_, are but little smaller than the annular wheels, A, F, and are hung upon an eccentric E formed in one solid piece with the driving shaft, D.

The action of a complete epicyclic train involves virtually and always the action of two suns and two planets; but it has already been shown that the two planets may merge into one piece, as in Fig. 10, where the planet-wheel gears externally with one sun-wheel, and internally with the other.

But the train may be reduced still further, and yet retain the essential character of completeness in the same sense, though composed actually of but two toothed wheels. An instance of this is shown in Fig. 36, the annular planet being hung upon and carried by the pins of three cranks, _c_, _c_, _c_, which are all equal and parallel to the virtual train-arm, T. These cranks turning about fixed axes, communicate to _f_ a motion of circular translation, which is the resultant of a revolution, _v'_, about the axis of F in one direction, and a rotation, _v_, at the same rate in the opposite direction about its own axis, as has been already explained. The cranks then supply the place of a fixed sun-wheel and a planet of equal size, with an intermediate idler for reversing the, direction of the rotation of the planet; and the velocity of F is

V'= v'(1 - f/F).