Steam Engines at the World’s Fair (Parts 1-2)
Modified on 2015/07/15 16:01 by Joel Havens — Categorized as: Steam Engines
(Part 1)
Of all the great structures at the World's Columbian Exposition at Chicago, the Administration Building, while not the largest, is one of the most beautiful, if not the gem of the Exposition palaces. Machinery Hall, however, has been pronounced second only to this in the magnificence of its appearance. It measures 846 by 492 feet, and, with the Machinery Annex and Power House, cost about $1,250,000. These several structures together cover an area of nearly eighteen acres. The main machinery hall is spanned by three arched trusses, and the interior presents much of the appearance of three great railroad train houses. In each of the long naves is an elevated traveling crane, running from end to end of the building for the purpose of moving machinery. During the time of the Exposition it is intended to put platforms on these, so that visitors may be carried throughout the exhibition space and view all the machinery.
That with such extensive provisions for the exhibit of machinery the latter will form a most important feature of the Exposition seems almost needless to say, and that steam engines will be of the first prominence in this line of exhibits will be equally well appreciated. Interest will undoubtedly be centred in the large Corliss engine, one of magnificent proportions, built by the E. P. Allis Company, of Milwaukee, Wis., and suggestive at once of comparison with the famed Corliss engine used in Machinery Hall at the Philadelphia Centennial Exhibition in 1876, which was built by George H. Corliss.
The illustration of that engine, shown on another page, will give the reader some idea of the great dissimilarity of the two. This Corliss engine, at the time one of the finest examples of its type ever constructed, had a pair of forty-inch cylinders, of ten foot stroke, and while its full power was never developed, it supplied something like 1250 horse-power while in operation at the Exhibition. The length of the beams, between centres, was twenty-five feet, the diameter of the crank-shaft was nineteen inches, and the diameter of the fly-wheel was nearly thirty feet. The revolutions of the Centennial engine per minute amounted to thirty-six, and it may be of interest to know that the total number of revolutions made during the exhibition was 2,355,300.
The duty of the World's Fair engine will, however, be of a different nature from that of the Corliss engine at the Centennial, which transmitted its power to the main jack shaft. The Allis engine is belted by two belts made by the Page Belting Company, of Concord, N. H., to two Westinghouse dynamos, each of a capacity of 10,000 incandescent light. The speed necessary for these machines to produce 20,000 light of sixteen candle-power is 200 revolutions. The illustration shows only one belt, but when completed the second belt will be directly over the f1rst connected to the second dynamo immediately beyond. The fly-wheel is thirty feet in diameter, and at sixty revolutions, will have a periphery speed of over 5500 feet per minute. The face of the wheel is seventy-six inches, not as large as many others the Allis Company have built, but in construction it is probably stronger than any of its size ever made. It has twelve arms and the rim is made up of the same number of segments. It weighs complete 135,900 pounds, the rim itself weighing 88,000 pounds.
The engine is of quadruple-expansion arranged in the form of a pair of tandem compounds, with cylinders twenty-six, forty, sixty and seventy inches in diameter by seventy-two inch stroke. It will be observed from the accompanying illustration that a belt wheel is used instead of a rope wheel, a belt wheel having been considered more distinctively representative of American practice, and the belt also, a more durable device for power transmission. To many foreign visitors, the two belts will be a source of surprise, for most large powers abroad are transmitted by ropes. In Machinery Hall but one engine transmits its power in that way, and that is of English manufacture. This seems that notwithstanding the many advantages claimed for rope, American engineers do not think anything superior to leather belts.
The Allis engine is expected to work with a minimum economical load of 2000 horse-power, and to have an economical range of from 2000 to 3000 horse-power. The entire power of the engine, however, will, as stated, be absorbed by the two Westinghouse generators. It seems proper to state here, that while the engine is certainly one of commanding size and power, it is by no means the largest engine ever built, nor the largest built at the Allis works; compared with the Centennial Corliss engine it is much the larger machine, and also an engine of much more economical type. Under the most favorable circumstances there is thought to be little doubt that this engine would deliver a horse-power for less than twelve pounds of steam per hour.
The display of the Lane & Bodley Company, of Cincinnati, O., at the Exposition consists of three horizontal Corliss engines—a simple, a tandem compound, and a cross or twin compound. The cross compound represents their latest design. The girder is of box section and with the main box and slide support is in one casting. The slides are bored to a large radius giving a very large wearing surface for the cross-head on the slides. The design is remarkable for stiffness and has been developed to meet all the requirements of electrical engineering. The cylinders are made without the usual square corners, eliminating this unnecessary finish. The bonnets and caps are made with round flanges and the legs or pedestals under the cylinder, usually detachable, are cast with it. The steam chamber in the top of the cylinder is unusually large. The engine has sixteen by thirty-one by forty-two inch cylinders, and is designed to run at seventy revolutions per minute. The main shaft is nearly eight inches in diameter. The steam pipe is five inches in diameter, and the exhaust pipe to the condenser measures ten inches. The steam ports in the high-pressure cylinders are seven-eighth inches, and the exhaust ports 1 7/16 inches wide, and both are sixteen inches long. The steam and exhaust ports of the low pressure cylinders are respectively 1 15/16 and two and a quarter inches wide and thirty inches long. The crank pins are 4 7/16 inches in diameter and five inches long.
The tandem engine, of which an illustration is shown, is made from the old patterns. The cylinders are sixteen inches in diameter, high pressure, twenty-nine inches low pressure, and forty-two inches stroke, and are attached to an especially heavy girder frame. The main bearing of the shaft is 10 15/16 inches in diameter. This engine is furnished with the low-pressure cylinder next to the girder, and a very neat trunk connection between the two cylinders. The receiver on both the tandem and the cross compound engines is arranged below the floor. The third engine is a simple engine, having a cylinder eighteen inches in diameter and of forty-two inch stroke. The girder is made with a ribbed section forming three sides of a box. The governor on this engine is of the Hartnell type, well known in connection with this engine, and which has proven very successful in delicate regulation and durability. The engines are splendid specimens of design, having neat lines, and are evidently built for hard service. Their proportions are such as will adapt them successfully to electric lighting and railroad service.
In the way of foreign engines, an interesting type is shown by F. Schichau, of Ebling, Prussia. This engine is 22¾ x 37½, x 57¼ x 27½ inches vertical, triple-expansion condensing, with three cranks, and at 100 revolutions per minute is rated at 1000 horse-power. At a speed of 180 revolutions per minute the power runs up to 2500 horsepower. Steam is to be used at a pressure of about 180 pounds per square inch. This type of engine is built specially for marine service, but the one shown is connected direct to a Siemens & Halske dynamo. The cylinders are set on steel columns, suitably braced, and the whole makes a very light engine considering the power developed, the weight not exceeding 143,000 pounds. The shaft is of Krupp steel, twelve inches in diameter, and is one solid forging. The air pump for the engine is direct connected, and is thirty-four and one-half inches in diameter by thirteen inch stroke. The condenser is formed by the exhaust pipe running toward the air pump and the injection pipe running up into the exhaust pipe and meeting the steam. The high-pressure cylinder has two eccentrics, one working the main piston valve, and the other controlling the cutoff valve which is inside the main valve and which is rotated by the action of the governor, shortening or lengthening the cut-off by opening or closing helically formed ports in the main valve. The intermediate and the low-pressure cylinders each have one eccentric connected to balanced slide valves, and the strains on the eccentric rods are reduced by small auxiliary piston attachments. The f1rst two cylinders have steam jackets supplied with steam at boiler pressure, and the jackets have small air valves to prevent air binding, and traps for draining off the water of condensation. The low-pressure cylinder is not jacketed. The piston rods are guided at both ends, extending through the upper ends of the cylinders. The crank pin boxes are of brass lined with Babbitt metal, this being true also of the main bearing, but the cross-head ends of the connecting rods are forked and the brasses are not lined. The engine is thoroughly fitted up with gauges, counters, etc., and presents a finely finished appearance.
Another German engine exhibited and worthy of note is one of the semi-portable type built by R. Wolf, of Magdeburg, Buckau. This is a forty horse-power nominal, compound condensing engine, capable of indicating up to seventy-five horse-power. The cylinders are 260 and 430 millimeters (ten and one-quarter and about seventeen inches) in diameter and have a 400 millimeter (sixteen inch) stroke. The total heating surface of the boiler is 36.2 square meters, or about 390 square feet. The engine works at a speed of 110 revolutions per minute.
The Wolf engines have become very well known on the European continent and their export is said to be increasing every year. Quite a large number of them have gone to South America, to Africa, and even to China and Japan. They are very substantially built and, like many of English make also, are quite different from most of the engines known in the United States as semi-portable engines. In this country, as a matter of fact, the manufacture of the semi-portable type of engine has received comparatively little attention, and it can scarcely be said to have thus far appealed to the general power user as an economical or a desirable motor. In England, and on the European continent, on the other hand, semi-portable engines have for years occupied a position of prominence, and their design and construction have been carried out with much care and attention to the requirements of economy and durability.
One of the distinguishing features of the Wolf outfit is the separable character of the boiler. The latter is of the tubular form, and is so made that the whole tube system may be easily drawn out of the boiler shell for ready cleaning, examination and repairs. How important and desirable a feature this is need scarcely be pointed out; it will be appreciated at once by all steam users, and especially those who have to deal with dirty water for steam raising. In order to extract the whole bundle of tubes, it is only necessary to loosen a few nuts in the smoke-box end of the boiler which connect the front plate with the outer shell, and a few nuts on the fire-box end which hold the back tube plate to the back plate of the boiler. This having been done, the boiler readily separates into two parts.
The so-called locomotive boilers of the ordinary run of portable and semi-portable engines do not permit of such separation, as is well known, and the interior of the boiler cannot, as a consequence, begot at without much trouble, if at all. When the nest of tubes, however, can be withdrawn from the shell, the whole interior of the boiler can be laid open to daylight and all parts can be made accessible so that thorough and reliable cleaning can be insured.
Another distinguishing feature of the Wolf engine is the disposition of the cylinders inside the dome of the boiler by which long steam pipe connections are dispensed with and ample protection is afforded against loss of heat and condensation. The boiler itself is wholly enclosed by a double, non-conducting covering with an intermediate air space, so that very little loss is likely to occur from radiation. As a matter of fact, the economy of the Wolf engines has become well established abroad, and their steam consumption is claimed to be quite as low as that of many of the best stationary engines. An official test in Germany, a short time ago, of an engine like that illustrated is said to have shown a coal consumption of only two and a quarter pounds of coal per horsepower per hour.
Coming back once more to the details of the engine proper, it should be explained that the high-pressure cylinder is fitted with the Rider automatic expansion gear, while the low-pressure cylinder has simply an ordinary slide valve expansion gear adjustable by hand. The intermediate receiver as well as the two cylinders are placed inside the dome of the boiler. The condenser is an injector condenser placed vertically by the side of the engine and is connected by a horizontal tube to the air pump which is arranged underneath the crankshaft of the engine. The plunger piston of this air pump is driven directly from the crankshaft by means of an eccentric. The engine is provided with a geared Porter governor, which acts by means of an arm on the expansion slide of the Rider gear. The gears are cut by special mach1nery and work smoothly and noiselessly.
The regular compound condensing and non-condensing stationary engine turned out by the same maker is, in the main, similar in design to the engine used in the semi-portable outfit. The lubrication of the cylinders is effected by means of a mechanical oil pump, which conducts the lubricant continually, in a state of fine division, into the cylinders, and which may be regulated according to momentary requirements. Steel enters largely into the construction of the engines with the view of keeping down the weight. The fly-wheels are turned and finished, and fitted for either belt or rope driving as desired. The engines are specially designed for industrial installations of all kinds, particularly for driving dynamos, and are supposed to take the places of the large Wolf semi-portable engines where difficulty of transportation or other circumstances do not permit the erection of those. Simple automatic and throttling engines are also built by the same firm, the Rider expansion gear and Porter governor being applied in the former, while in the latter the cut-off may be varied by hand, a Buss governor being used.
A four-cylinder, triple-expansion engine, of nominally 1ooo horse-power, but able to develop about 1500 horsepower under 150 pounds steam pressure or more, is exhibited by the Buckeye Engine Company of Salem, O. It is a condensing engine, and is fitted with a Wainwright surface condenser located under the floor.
Steam is first used in the high-pressure cylinder, whose dimensions are twenty inches diameter by forty-eight inches stroke. From this it passes through a re-heating receiver to the intermediate cylinder, which is on the other engine, and whose dimensions are thirty-two and one-half inches diameter by forty-eight inches stroke. From this it passes again through a re-heating receiver, from which it divides into two pipes, each connecting with a low-pressure cylinder, one on each engine, the cylinders being thirty six inches in diameter by forty-eight inches stroke. The re-heating receivers are under the floor, and all pipes pass directly downward through the floor, making a very neat appearance.
The fly-wheel is twenty feet in diameter by seventy-five inches face, and has two sets of arms, making twenty arms in all. This is a very stiff and strong construction, noticeably so in view of the fact that a good many large wheels have been wrecked within the last year, owing to faulty construction on one hand, and running away of the engine through some sudden decrease of load on the other. The belt driven by this engine is seventy-two inches wide and has a velocity of a little more than a mile a minute.
The high-pressure cylinder is provided with a piston valve, which contains also a piston valve whose sole duty is to cut off the steam at the proper point. The other cylinders are each provided with the well-known Buckeye hollow valve, containing an independent cut-off. The engine has two governors, and is so arranged that if either half is disabled, the other half may be run independently.
Among the other engines shown by the same builders is a cross compound condensing engine of their medium speed type, having two cylinders fourteen by twenty-four inches and twenty eight by twenty-four inches, and producing about 325 horse-power under the conditions under which it is working.
They have on exhibition also a th1rteen by twenty-one inch medium speed engine, running non-condensing, of about 130 horse-power; a high-speed engine, running non-condensing, cylinder thirteen by sixteen inches, also of about 130 horse-power, and a slow speed engine of the Corliss type of bed plate, also running non-condensing, having a cylinder sixteen and one-half inches diameter by thirty inches stroke and producing about 185 horse-power. Next to this is a high speed tandem-compound condensing engine, having cylinders eleven by sixteen inches and twenty-one by sixteen inches and producing 185 horse-power.
The Buckeye Company build engines of three types: High speed (short stroke), medium speed (medium stroke), and slow speed (long stroke], so as to be able to supply engines for all possible requirements. Each of these varieties they compound in all the four ways, viz., tandem condensing, tandem non-condensing, cross condensing, and cross non-condensing. Of this variety they show at the Exposition, working with full loads, as intimated in what has already been said, simple non-condensing engines of each of the three varieties, as well as a tandem-compound condensing engine of the high speed type, a cross compound condensing engine of the medium speed type, and at cross triple-expansion engine of the slow speed type, making in all six engines, or, considering that some of these are double, making in fact eight engines.
To this exhibit they will add a small working model engine not more than fifteen inches long, complete in all details; also a sectional model, running at very slow speed, in order to show clearly the action of the valves and valve gear. This is made by cutting the cylinder and valves through longitudinally, and it will unquestionably be a very interesting; feature to engineers or men who use engines.
The large Buckeye engine, f1rst referred to, is completely equipped with U. S. metallic packing as an exhibit of the manufacturers of this packing. It should be added also that the pistons of the large engines are made of steel for the sake of increased strength and lightness. The tandem - compound, high speed engine has been running in the temporary power plant of the Exposition during the past eighteen months.
A duplex, tandem-compound condensing engine of new design is shown by the Watertown Steam Engine Company, of Watertown, N. Y. It has two nine-inch high-pressure, and two sixteen-inch low-pressure cylinders, all of fourteen-inch stroke. In the governor of this engine, unlike other shaft governors which secure a varying cutoff by shifting a single eccentric across the shaft, the movement is obtained by a mechanism which is, in effect, a double eccentric turning on the shaft. Particular attention is called to the fact that its effect is to increase the steam lead as the load on the engine is increased and as more steam is needed; on the other hand, as the load falls off, less steam is required and the steam lead is decreased, with the further result of reducing compression. The governor in this engine, it should be observed, is the same in principle and action as the regular Watertown engine governor used in the other automatic engines of the company.
The valve, of which a sectional view is given, is also of the regular Watertown design, and has port openings so arranged as to admit steam to the cylinder ports through four different openings at once, thus giving a- port opening four times the travel of the valve and securing very prompt action upon piston. The valve also exhausts steam through four openings at once. The valve is accurately fitted to its place and is carefully scraped. On the back of the valve is a pressure plate, balancing the valve so easily, it is claimed, that it can be worked readily by one hand while under steam. This pressure plate is held in its place by a small spring at the back, holding it to its position in spite of wear and acting also as a relief valve when excessive pressure from water in the cylinder throws the valve from its seat. The valves of all four cylinders are controlled by the governor, insuring an even division of the load.
All the cylinders are neatly jacketed with closely fitting iron staves. The cylinder heads also are jacketed, and the spaces between the high and the low-pressure cylinders are covered by extensions of the high-pressure cylinder jackets. The removal of a single panel at any time gives easy access to the stuffing-boxes and cylinder heads. The whole engine, which runs in conjunction with a Knowles condenser, is mounted on a neat and substantial sub-base, with an extension on which are fitted supports for the high-pressure cylinders. These supports are so made that they can be adjusted not only horizontally, but also vertically, to meet any possible movement of the high-pressure cylinders due to expansion under heat.
The frame of the engine is very heavy, with longitudinal and cross ribs securely bracing it. The working parts are placed as low as possible, bringing the centre lines at about the surface of the bed, so that all the strains are brought in line with the lines of greatest resistance. All oil from the crossheads, connecting rods, and cranks is caught in the bottom of the frame, whence it can be drawn off. The crank-shaft is slotted from a solid, forged block. The connecting rods are of forged iron with square straps and boxes, the latter being of composition metal. The cross-heads are made of crucible steel, and have large bearing surfaces, both cross-heads and guides being carefully scraped.
Besides the engine shown, the builders turn out a single-cylinder, high speed, automatic engine, a cross compound, and a plain tandem-compound. They are also prepared, however, to build triple-expansion engines of from 200 to 500 horse-power.
The Phœnix Iron Works Company, of Meadville, Pa., show one of their latest designs of tandem-compound, Dick and Church engines. Heretofore, in engines of this type, the rear cylinder, or the one farthest from the main shaft, has usually been attached to the forward cylinder, which, in turn, was suspended from the bed frame of the engine. In the engine shown, however, the low-pressure cylinder is carried on a separate bed frame, which forms the sub-base for the main engine. The cylinders thus being on separate bed frames, the overhanging of both cylinders from one bed frame is done away with. This construction is claimed to be not only more rigid, but to allow each cylinder to expand independently of the other, always preserving the alignment: it also renders either cylinder easy of access without disturbing the other. The hoods, which carry the overhanging cylinders are rigidly tied together by a rod which extends from one to the other, over the top of the high-pressure cylinder.
The valve gear is so constructed that the valves of both cylinders are controlled automatically by the one governor, a new and valuable feature in engines of this class, and which gives practically a regular receiver pressure and proper distribution of load and temperatures between the two cylinders at all points of cut-off. This peculiar feature is of special value in non-condensing engines working under variable loads. Great care has been taken in designing this engine to have ample wearing surfaces and large heavy wheels, to make the proportions such as to meet the requirements of extreme and variable loads, such as are met within electric railway service. These engines are also made in the double tandem compound and triple-expansion types.
The exhibit of the Harrisburg Foundry & Machine Works, of Harrisburg, Pa., consists of two engines driving line shafting. One of these engines is the company's standard Ide pattern, automatic, tandem-compound, side-crank engine, with outboard bearing. The cylinders of this engine measure seventeen and twenty-eight inches in diameter, and have an eighteen-inch stroke. The engine is rated at 300 horse-power, when running non-condensing, and at a speed of 180 revolutions per minute. The fly-wheel pulley is 102 inches in diameter and has a thirty-one inch face. Both the high and low pressure valves are adjustable piston valves, designed by Mr. M. E. Hershey, the general manager of the company, and each is worked by a separate eccentric. The high-pressure valve is controlled by the fly-wheel governor, while the low pressure valve is made adjustable by hand to meet the varying conditions under which the engine might be called upon to work.
The other engine shown by the company is the Harrisburg Ideal tandem-compound, with one fly-wheel pulley, 102 inches in diameter, with an eighteen inch face. A second main driving pulley is made of the same diameter, but with a thirty-one inch face, and has a special, outboard bearing. The valves are worked from eccentrics on opposite sides of the engine, the high-pressure valves being controlled by the automatic governor, and the low-pressure valve by an independent, adjustable eccentric. Both valves are of the same design as those used in the engine just described. The cylinder capacity, power and speed of the engine are also the same.
A twelve by twelve inch Ideal self-oiling engine is to be placed by the side of the larger engine, without any anchorage to a foundation. The engine is to be raised about six inches from the base plate, and is to be supported on three points. In this condition the engine will be run up to a speed of 300 revolutions per minute to show its perfect balance, and the special adaptability of this type of engine for electric light work where cleanliness, quiet running, and balance of all running parts are particularly desirable.
(Part 2)
The progress made by electricity during the past few years is exemplified at the World's Fair in many ways and places, but nowhere better than in Machinery Hall.
Beside the numerous steam engines belted to dynamos, there are various examples of electric generators directly connected and one of these, which attracts much attention, is exhibited by the General Electric Company of New York and Boston. The engine, which was designed under the supervision of J. C. Henderson, the engineer-in-chief of the company, is of triple expansion, direct acting, vertical condensing type, similar to others installed during the last two years by the General Electric Company, with the exception that, instead of piston valves, Corliss valves are used, which are equally, if not more, suitable, as the speed is but 100 revolutions per minute.
The high-pressure cylinder is 22½ inches in diameter. The intermediate cylinder measures 33 1/8 inches, and the low pressure cylinder 55 3/8 inches. The stroke of all is thirty-six inches, which, with the stated speed of 100 revolutions per minute, gives a piston speed of 600 feet per minute. At maximum efficiency the number of expansions is 12½, and at maximum power 7½. The initial pressure of steam carried is 160 pounds per square inch, and the condenser maintains a twenty-four inch vacuum.
The chief novelties in the design are, to begin with, found in the fact that the valves are arranged in the top and bottom cylinder heads, thus reducing the percentage of clearance to a minimum. Steam dash - pots are used, located in the heads and easily accessible, and the whole arrangement relieves the front of the engine of the appearance of complication. In the governor is found quite a departure from general practice, this part being made much smaller than is usual and running at a considerably higher speed than is customary, so that a finer adjustment is possible.
The design was principally intended for operation in stations using the three-wire system with the two dynamos placed on each end of the shaft, thus keeping a constant balance, never allowing the full power of the engine to be transmitted on one side alone. The end bearings are water-jacketed. The armatures are overhung, thus doing away with unnecessary extension of the bed-plate, liability of breaking shaft, besides making it more easily renewable and reducing the floor space required. The normal output of the generator is 800 kilo-watts, or 5,333 amperes at 150 volts, and the maximum output is 920 kilo-watts, or 6,133 amperes at 150 volts. The maximum efficiency is 700 kilowatts, that being the load decided upon as the load of longest duration in actual practice.
The calculated efficiency was eighty six per cent., but as the smaller generator (the 2 x 200 K. W.), fitted with piston valves did considerably better than figured, it is quite likely that this type will exceed the calculated efficiency in the same ratio. Steadiness of motion is insured by the three-throw crank design and the weight of the armature, which amounts to 39,000 pounds. The surface condenser specially designed for the engine is contained in the foundation box, which carries the bed plate as well as the feet of the dynamos. The air and circulating pumps can be worked either direct from the crossheads on the back of the columns, or independent, as in the present instance. The engine is fitted throughout with steam jackets around all cylinders, and outside, between that and the lagging, with magnesia blocks and cement. Katzenstein's metallic packing is used. The total weight of the engine, including that of the condenser and foundation box, is 320,000 pounds. The weight of the two dynamos is 165,200 pounds, bringing the total weight of the whole outfit up to 485,000 pounds. This gives a weight of about 0.6 pounds per watt.
The whole design, working drawings, etc., were prepared by the engineering department of the General Electric Company, the builders being the Southwark Foundry and Machine Company of Philadelphia, Pa.
The Stearns Manufacturing Company, of Erie, Pa., show two Woodbury automatic, high speed, tandem-compound condensing engines. The smaller engine has fifteen and twenty five-inch cylinders, with twenty-inch stroke, and the governor and driving pulleys, one on each side of the engine, are each eighty-eight inches in diameter, and have twenty-three-inch faces. The engine is to run at 200 revolutions per minute, and the indicated horse-power, at maximum economy, will be 375. The maximum load, however, runs up to 500 indicated horsepower. The larger engine, which is exactly the same in design, has nineteen and thirty-one-inch cylinders of twenty-four inch stroke, and its driving and governor pulleys are 102 inches in diameter with each 31-inch face. The engine will run at a speed of 165 revolutions per minute, and the power for maximum economy will be 600 horse-power, while the maximum load will amount to 800. The two engines weigh respectively 34,000 and 67,500 pounds.
The main features of the high-pressure valve are shown in the accompanying detail illustrations, one of which represents a longitudinal section of the cylinder and valve chest, and the other a horizontal section through the steam chest above the top of the valve. Steam pressure is eliminated from the valve
A
, by the relief-plate
B
on the back, which is supported against steam pressure at top and bottom by a forked or double wedge
C
, whose length is about equal to that of the relief-plate. It is obvious that a longitudinal movement of the wedges inward will force the relief-plate away from valve, and the outward movement of wedges will let it down toward valve. The movement of the wedges, and consequent adjustment of relief-plate, is accomplished by the two adjusting screws,
Z, I
, which fit loosely through the cross piece of the wedge and are tapped into the relief-plate. The collars
m
, which form part of adjusting screws, are notched on their peripheries, and a notch is made on the wedge opposite each screw. The collar has 100 notches, and therefore, admits of a definite degree of adjustment being made, the minimum limit of which is a very minute amount.
The device accomplishes the adjustment of relief-plate to valve in the most satisfactory manner, being at once positive and simple, and while the results of the adjustment can be extremely minute, it is very quickly done, and admits of the valve being steam tight and yet offering little resistance to movement. The movement of the relief-plate in the adjustment is exactly at right angles with the face, or in other words, it is let down equally at all points. The adjustment is made on the inside of the steam chest, and no one can tamper with it from the outside. The passage k at the bottom of the chest allows a circulation of steam under the ledge, insuring equal temperatures for ledges
i, i'
.
The screw
D
, which is operated from the outside by the handle
E
, is also used as a means of moving the wedges inward and throwing off the relief-plate for a purpose explained below.
The exact amount of inward movement is immaterial, and is regulated by the screw
f
, which forms the stop for the inward movement of the wedges. This screw taps into the relief-plate, and against its head the cross piece of the wedge strikes. When the handle
E
is turned to the left as far as it will go, the wedges are back against collars and are in proper working position. When, on the contrary, the handle is moved to the right, the screw which works through stuffing box forces the wedges inward and throws off the relief-plate. About one-half turn of the handle is all that is necessary. The handle clamps to the stem of screw
D
and is placed in such position that, when down, the wedges are back as far as the adjustment allows them to be drawn, and the relief-plate and valve have their proper working bearing.
The purpose of this handle and screw is not for adjustment, but to afford a means of separating the valve faces from the seats in case they tend to adhere together after engine has been standing over night or longer. This " sticking" of the faces is very liable to occur with any form of balanced valve, unless loosely fitted, and it is very desirable to relieve it, which this device does so that the engine starts with the valve entirely free and the driving mechanism relieved from any abnormal strain. After the parts are thoroughly warmed up, the handle is turned down, or back, as far as it will go.
The faces of valve and relief-plate are at a slight angle from a vertical position, so that they lie in place when steam is off, and afford greater convenience when adjusting inside.
In case of over pressure in the cylinder, due to the presence of water, the valve is free to separate from the cylinder face and allow the water to be forced into the steam chest and the exhaust port the same as a plain, unbalanced slide valve, with the difference that it takes the relief-plate with it. The danger of accident from water in the cylinder does not, therefore, exist in anything like the degree that it does in engines whose construction does not allow the valve to be forced from its seat under any circumstances.
The means of steam admission and distribution will be understood from the sectional view of the cylinder and valve chest. The valve
A
, besides taking steam at the ends, has supplemental admission ports
a, a
, connected at the top and bottom by passages
b, b'
, shown in the vertical section of one of the cylinders. In the position of the piston shown the latter is near the crank end. The crank end of the valve is open for admission of steam which enters the cylinder port
H'
past the end of the valve, and also through the cavity
d"
in the relief plate into the port a. At the same time steam is entering the supplemental port a at the opposite end at two points, and passes through the horizontal passages into the port a at the left hand side, and thence into the port
H'
. Admission, therefore, takes place at four points at the same time, and as the ports are very large a close approach to boiler pressure is effected. Cut-off, of course, is also made at four points simultaneously.
A double exhaust, too, is used, the valve having supplemental exhaust ports,
c, c'
. In the valve position shown, the exhaust steam passes from the cylinder port
H
into the exhaust port
I
in the usual way, and, in addition, passes through the port
c
into the central cavity
A'
of the valves, and thence into the exhaust port
I
This arrangement provides a very large area of exhaust openings, and as the opening is effected very rapidly the pressure drops promptly at release. The plate
e
, forming part of the valve on the relief plate side, serves as a shield to prevent the exhaust steam from impinging on the face of the relief plate and wearing it by attrition so as to cause leaking. This shield does not interfere with the free exit of the exhaust steam, but, on the contrary, assists in guiding the current to the exhaust port
I
. The low pressure valve is the same in all respects as the high pressure valve, except that it is not provided with the supplemental ports a, a. Both valves are controlled by the governor.
The latter has a bob on the outside instead of an eccentric and its movement is effected by weights whose centrifugal force is counteracted by a single helical spring.
The crank shafts of both engines are solid steel forgings, that is, they are not "built up." The counter weights are bolted to the crank-shaft with the regular Woodbury yoke bolts. The detail arrangements of the cylinders are such that all the moving parts of both cylinders can be passed through the low-pressure cylinder, the latter being outside, while the high-pressure cylinder is next to the frame. Thus the pistons, piston rod and inside of both cylinders, can be examined by disconnecting the piston rod from the cross-head and passing the parts out through the low-pressure cylinder without having to break the joint between the two cylinders, or removing either cylinder from its position.
Before being shipped to the Exposition both engines were set upon cast iron stands and run to their full speed and given a load of 230 horse-power, during which it was found they were so evenly balanced that the absence of a foundation was only just perceptible. The engines are being used to operate electric power generators. The steam pressure at the throttle is 115 pounds, and the vacuum at the exhaust connection twenty-four inches. The engines are worked in connection with surface condensers.
The Ball Engine Company, of Erie, Pa., show one of their 18 x 36 x 18-inch cross-compound engines. It is designed as a condensing engine, and is capable of running up to from 200 to 250 revolutions per minute with good economy. It is considered to be probably the smallest engine, in proportion to its power, in the Fair, as it occupies a trifle less space than a vertical engine of equal capacity, and has all the advantages of easy access without having to climb stairways or reach galleries to manipulate the various attachments on the engine. The particular work of the engine will be the illumination of the electrical fountains, and in its present situation it is intended to develop from 480 to 500 horse-power with a steam pressure of from 11o to 120 pounds.
The first engines of this type were built by the Ball Company a little over two years ago for the then new electric lighting station of the Edison Electric Illuminating Company of Brooklyn, N. Y. They are specially designed for heavy work, and all the parts are made unusually large and massive. The cranks are opposite each other, one counteracting the effect of the other, so that the engines are well balanced and capable of being run quietly at high speeds.
The high pressure cylinder valve in the engine shown is the same as that used in the company's single cylinder engine, and is illustrated in the accompanying sectional view. The valve consists of two parts, connected in telescopic fashion, allowing each half to adjust itself to its seat. The valve is thus really double-faced. The live steam enters the upper side of the valve, and, being enclosed by the telescopic shells, presses the faces apart with relation to each other, and against the port or passage way surface as shown. By this arrangement there is only sufficient percentage of the whole area of each valve subjected to unbalanced pressure to ensure perfect steam tightness. The combined port areas represent very liberal openings through which the steam passes to each end of the cylinder, thus giving prompt and constant admission up to very nearly the point of actual closure of the valve. The same freedom occurs for the discharge of steam from the cylinder into the chest, and thence to exhaust pipe. The valve is directly controlled by the governor, and constitutes the only automatic cut-off on the engine.
The low-pressure cylinder valve is driven independently by an eccentric which is not influenced by the governor, and hence, is not automatic in its adjustments. It is, however, adjustable by hand so that the point of cut-off in the low-pressure cylinder may be altered to suit different conditions of load. The valve itself is simply a plain slide-valve, well-proportioned, and provided with relief area rings on the back, so that, while very large, giving liberal steam distribution to the cylinder, it works easily and with little expenditure of power. The proportion of- the relief area to the total area is such that the valve is very nearly balanced. The valve has two stems connected by a cross piece and driven by one main valve rod, as shown in the view of the low pressure cylinder side of the engine. Both the high and the low pressure valves are so arranged that they closely follow up their wear and thus preserve steam tightness.
The crank shaft is made of one solid piece of steel, machined off and key-seated to receive the cast-iron counter-balance weights. These are in the shape of discs, which are slipped on the shaft and keyed up solid and tight, after which they are turned oft and polished.
The governor of the engine, as shown, has two weights and two counteracting springs running out from the rim of the governor pulley. In addition to these there is a third spring, attached at one end to one of the weight arms and at the other to the piston rod of a dash- pot, thus providing a yielding base for this spring. The dash-pot consists simply of a cylinder filled with oil, and having a piston with an aperture through which the oil passes as the piston moves in either direction. The spring is arranged for either compression or extension. When motion of the governor weights takes place this supplemental spring is put under tension for the moment and performs the function of giving stability to the governor, but the action of the dash-pot quickly releases the tension and the spring returns to its normal condition, in which it is not a factor in the speed of the engine. The speed is determined entirely by the long springs. The illustration shows the connection of the weights by means of links to a collar. The latter is supported on an eccentric bolted to the link of the governor wheel which is keyed fast to the shaft. This constitutes a point of suspension upon which the valve driving eccentric is rotated, giving a range of cut-off from 5/8-stroke down to zero.
Two engines—a high speed and a medium speed automatic—are exhibited by the Erie City Iron Works, of Erie, Pa., the latter being shown in this issue. The bed of this engine is of the well-known form first introduced by Tangyes Limited of England, and is a very strong and heavy type, thoroughly ribbed underneath. The bottom slides are separate from and are bolted to the bed. The hood on the back end of the latter forms the front cylinder head of the cylinder, and the stuffing-box is made loose and forced into the head and secured by annular ring nut, which is set up with a spanner from the outside. The cylinder is of the over-hung type, but has double exhaust passages, and the steam ports are placed close to the end of the cylinder, making the live steam passages very short. The cylinder is covered with a cast iron corrugated jacket forming an air space around the cylinder. This can be filled with non-conducting material if preferred.
The valve is the well-known Richardson valve, made double, that is with two exhaust cavities, and is held in place on the valve stem by a thick square nut inserted in a pocket cast in the valve, and secured into place on the outside of the valve by two jam nuts. These give a very short hold on the valve, and avoid any trouble by unequal expansion and contraction of the cast iron valve and the steel valve stem, and also effectually prevent this nut from coming loose. The faces of the square nut and the two jam nuts are slightly rounded, so as to allow the valve a slight vertical play on the stem.
The rocker arm is securely keyed to a rock shaft which extends across the whole bottom of the bed, having on the side next to the rocker arm a long taper bearing equal to nearly four diameters of the shaft, and on the opposite end a straight bearing of equal length. The space left for the fit of the rocker arm, is made about one-half of an inch longer than the hub of the arm itself, so as to permit the rocker shaft being drawn through the bed, thereby taking up the wear on the conical end, and allowing the rocker arm to be set further out so as not to change its position with reference to the eccentric and valve rods. The engine has an eighteen by twenty-two inch cylinder and at the speed of 160 turns per minute, at which it is running, develops 250 horse-power.
An engine which will probably appeal particularly to most visitors to the steam engine department, largely because of the rope driving gear with which it is equipped, is that shown by Messrs. Galloways, Limited, of Manchester, England. Rope-driving is essentially English in character, and was probably first used in England in 1863 by Mr. John Ramsbottom in connection with cranes at Crewe. The ropes were of cotton, and measured about 5/8-inches in diameter. They ran over pulleys with V-shaped grooves, having angles of about thirty degrees, and were supported every twelve or fourteen feet by flat pieces of chilled cast iron. Since this application rope gearing has been superseding belting and other gearing in English establishments, prominent among them cotton mills, and apparently with the most satisfactory results. In this method of driving the surface of the fly-wheel of the engine is provided with a number of parallel grooves for the ropes, the number and size of the latter depending upon the power to be transmitted.
The great advantage of rope gearing over cogs and belts has always been claimed to be the entire freedom from any risk of a breakdown. When a rope shows symptoms of giving way— and ropes always give symptoms of weakness long before they break—the weak rope can be removed in a few minutes, and another one put in its place. The width of pulleys for ropes is generally rather less than for belts transmitting the same power, but, on the other hand, the grooved pulleys for ropes cost more than plain pulleys. Still, making allowance for this, the total cost of ropes and grooved pulleys for transmitting a given power has been placed at less than half the cost of leather belting and flat pulleys. Not withstanding these and other advantages claimed, more or less correctly, for rope gearing, Americans still cling to belt transmissions, and a rope-driven plant is now probably as much as it was ten years ago, an object of special interest, if not curiosity, in the United States.
It is perhaps not so strange, therefore, that with all the thousands of horse-power in the Exposition, the Galloways engine should be the only example of rope transmission shown. The engine is a superposed compound condensing engine of 450 horse-power, and connects with a countershaft with twelve one and three-quarter inch ropes. From the countershaft a thirty six inch belt leads to a main line of shafting. The main features of the design are clearly apparent in the engraving. The main bed-plate is continuous, embracing at one end the pillow-block carrying the crank shaft neck, and at the opposite end supporting the cylinders. The low-pressure cylinder is attached direct to the bed-plate, and the high-pressure cylinder is placed on and above it at an angle.
The distribution of steam to both cylinders is controlled by an arrangement of slide valves, the high-pressure valve being controlled automatically by the governor. The latter is of the high speed, parabolic type clearly shown in the illustration.
The engine transmits its power through two connecting rods directly to one crank pin. The air pump and condenser are arranged on the double-acting system, the air pump being worked by a continuation of the low-pressure piston rod.
A very desirable and noteworthy feature of the engine is the safety barring gear with which it is provided and by means of which it may be turned to any convenient position for receiving steam to start it, or by which it may be turned round at any time when steam is not available. The gear is of very simple design. It consists of a horizontal shaft driven through worm gearing by the donkey engine. This shaft is provided with two helical feathers and carries a pinion rifled for sliding on these feathers. The pinion is arranged to gear into the toothed ring attached to the inner circumference of the fly-wheel. When the gear is put into operation, the pinion bears against the collar on the end of the shaft and is thus compelled to turn with the shaft, forcing the engine around. When, however, the engine receives steam and begins to turn faster than the pinion on the shaft, the pinion will instantly and automatically slide out of gear. The arrangement, as will be seen, is simple and direct, and entirely overcomes the laborious work of prying over large engines by levers. Galloways engines of the type shown have been employed successfully for such widely varying kinds of work as dynamo and rolling mill driving, and have found favor in many foreign markets.
Information Sources
Part 1,
Cassier's Magazine,
by George L. Clark, May 1893 pgs. 32-48
Part 2,
Cassier's Magazine,
by George L. Clark, Jun 1893 pgs. 111-126