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slide and the commutator revolved at the proper speed either by turning over the engine or by other power conveniently applied. Only very fine cuts should be made and great care exercised in the performance of the work. A finish is made at higher speed with carborundum or sandpaper and a dead smooth file. There are also grinding tools on the market which are used for a similar purpose to that of the usual lathe tool. These are built up for use on a lathe or for attach. ment to a generator bearing.

If the proper care is exercised when a commutator is first put in service, it will not be difficult to get its color and polish. The first consideration is perfect contact between the brushes so that they bear uniformly, then keep the commutator clean and use just enough vaseline or lubricating compound to keep it running smoothly and quietly.

Boilers.

J. W. READING.

assembling commutator segments or the working loose of some of the nuts or screws which are used to hold the parts in proper form will bring about a flat segment. A commutator may run eccentric because the armature shaft becomes loosened from the commutator shell in some way. On account of the high rotative speed and the brush pressure the commutator would tend to wobble. The whole armature might chatter as a result of the irregular brush contact. If the mica insulation between adjacent commutator bars is harder than the metal, the copper will wear down a little faster and as a result, the brushes will be caused to vibrate and lose contact.

When a commutator is in good condition, its surface will have a deep bronze polish seeming as though glazed. It may have such a polished appearance and yet one or two bars may show that something is wrong. If we touch the commutator with the finger-nail lightly held against it when running, it will be possible to detect any roughness or irregularity in the surface. Similarly in the case of an eccentric commutator, if it be turned over slowly, the brushes can be seen to move up and down, whereas the usual rotative speed will cause the brushes to chatter. Eccentric running or high and low bars may even be so pronounced as to enable one to see through between the brushes and commutator. In examining railway motor and generator commutators, care must be exercised in handling when the line voltage is on the machine. In such equipment one side of the circuit is always grounded and it is a good precaution to see that one's self is effectively insulated from the ground.

In general, when sparking is due to any of the causes just mentioned, there is no effective remedy other than a removal of the armature from the motor and giving it proper attention in a lathe. Large generator or rotary converter armatures do not lend themselves to such methods. For machines of this class, a slide rest or bracket arrangement is available for fastening to the outboard bearing. The commutator turning tool is placed on this

(Continued from February JOURNAL.) James Watt, by his genius and perseverance, exercised more influence over the development of steam power than perhaps any other individual. Newcomen had taken steps in the right direction when he built his atmospheric engines, and the progress that he made was greater than is usually imagined; yet his engine, as he left it, was clumsy and far from being economical.

James Watt started where Newcomen quit, carried the development much further, and when he left the steam engine it was a far more reliable machine than it was when he started to improve it; he made it capable of being used as a motive power for all the requirements of the times.

Watt's first attention to the steam en. gine came about by a very happy circumstance. He had returned to Greenock, after having worked some time in London, and was appointed mathematical instrument maker to the University of Glasgow. He was allowed to open a shop within the precincts of the university, for

the reason that trade jealousy prevented that advocated them. He was, apparenthim becoming a regular instrument ma- ly, so much occupied with his work upon ker in the city. A model of Newcomen's the steam engine that he did not regard engine, belonging to the university, hav- the more passive boiler with the respect ing failed to act promptly, it was given to and attention due it. Watt for repairs. At a meeting held in The well-known wagon boilers—a few the university later, June 10, 1766, a sum that are still in existence-were introduced of £5 11s. was granted Watt for making by Watt, or rather by his firm. He did alterations as well as repairs to the model. not introduce the internal furnace flue, as The choice of James Watt for this work all his early drawings of engines are was an exceedingly fortunate one and shown with wagon boilers under-fired. just the very thing to develop his fertile Later, however, in one of his specificabrain.

tions, dated 1785, he shows a wagon boiler James Watt took out his first patent on with an internal flue and an improved the steam engine January 5, 1769. His fireplace. new engine was entitled, “A new method In a specification dated in 1782 Watt of lessening the consumption of steam and says, “I have not described the boilers fuel in fire engines.” This patent inclu- that supply any, or all of these engines ded the use of a separate condenser and with steam, because I use such as are comthe expansive power of steam. From his monly applied to other steam engines." having been the inventor of this use The first steam engine made by the firm of steam pressure acting directly of Boulton and Watt seems to have been upon the piston, instead of only using the made in 1776 for the collieries of Bed. steam to produce a vacuum, it would nat- worth. There is no record of the kind of urally have been expected that he would a boiler used on this occasion. Dr. Robhave increased the working pressure of inson, a great friend of James Watt, says his boilers; but it seems Watt was preju- of the boiler, “This has received great imdiced against high steam pressure. This provements from his (J. Watt’s) comprejudice was not shared in by Watt's plete acquaintance with the procedure of partner, a man by the name of Matthew nature in the production of steam. In Boulton, who wrote him in July 1776 urg- some engines the fuel has been placed in ing him to adopt higher pressures, saying, the midst of the water, surrounded by an "As to boilers and steam pipes, let them iron or copper vessel, while the exterior be as strong as cannon; let it be applied was made of wood which transmits and, in copper spheres within the water, and therefore, wastes heat very slowly." then four or five atmospheres will not In Dr. Robinson's work there is a very compress such forms. The great boiler interesting footnote by James Watt himmay be framed with scantlings of cast self, which reads as follows: “The exte. iron well screwed together with plates rior part of large boilers was never exehalf inch thick, well fitted and screwed cuted in wood by me. This relates only to within; and then the greater the elastic some of my models and one or two very force of steam the closer will they be small engines which I made of Newcomen's pressed together, as the lid of a digester kind. They conveying the flame through is.”

flues in the inside of the water had been The above description of Boulton is not practiced by others before my time, and very explicit, but he evidently saw the were common in Cornish engines. The advantage of placing fire in copper fire- inventor is unknown, but a person of the boxes surrounded by water. Both Brind- name of Swaine was a great propagator ley and Smeaton had proposed methods of the practice. However, I somewhat of a similar nature.

improved the forms and adjusted the proWhile Watt was possessed of an amia- portions." ble disposition, yet his dislike for high According to Trevithick, Charles Swaine pressures led him to speak harshly of those worked as a rivet boy in making his

(Trevithick's) cylindrical wrought iron boilers.

James Watt, for some unknown reason, never was friendly with Trevithick and is said to have made remarks of a decidedly bitter nature against him, and may therefore have neglected to give the credit of the internal flue boiler to him. Smeaton's efforts as far back as 1758, also Brindley's about the same time—and while they were crude affairs-were undoubtedly the first steam engine boilers made with internal fireboxes.

There is some dispute as to who was the originator of the cylindrical boiler with internal flue, now universally known as the Cornish boiler. The honor, however, by some is given to Oliver Evans, an American inventor, and by others to Richard Trevithick, Sr. Trevithick's first cyl. indrical boilers were made so early that Swaine as a rivet boy could hardly have been old enough to have an insight into boiler construction and design at the time inentioned by Watt.

Murdoch, the right-hand man of Messrs. Boulton and Watt, made a model of a steam carriage in 1781, with a small copper boiler, the source of heat being a spirit lamp; the flames passed through a chamber in the boiler and out at one side of the top through a small chimney. The original is preserved in the art gallery at Birmingham, and is an interesting relic of one of the first carriages propelled by steam. The cylinder is partly within the boiler, which was the common practice in the manufacture of the early Trevithick engines.

As early as 1782 a steamboat was constructed by Marquis de Jouffroy, of Lyons, France. This boat, it has been said, ran for 15 months on the River Saone. It had a horizontal single cylinder engine, the cylinder being placed partly within the boiler for warmth, an idea that was subsequently followed out by Trevithick. A sketch of this boiler is exhibited at the South Kensington Museum, but no description is given.

Oliver Evans, an American millwright and engineer, sometime about the first of the eighteenth century, made a light

pressure engine. The boiler was cylindrical with a flue. In fact, it was built upon the same principle as the Cornish boiler heretofore mentioned. This boiler, however, was bricked up, the fire was placed underneath, the products of combustion passed along underneath the boiler and returned to the stack through the single flue. A diagram of this boiler is given in “Evans' Own Book.” It is thought that the title of Evans' book was suggested for the reason that he did not think the world paid sufficient attention to his work as an engineer. In Article V of his work he describes boilers for high pressures, up to 120 pounds per square inch. They were plain cylindrical under-fired boilers about three feet in diameter and from 20 to 30 feet long, and were recommended for use where fuel was cheap. For great economy in fuel he recommended a double cylinder boiler -two cylinders-one inside the other, the inside boiler being placed a little below the center of the outside one, which calculated to give room for steam on the upper side above the surface of the water. The water covered the inside boiler, inside of which fire was created. The barrel of these boilers was made of the best rolled iron. In Evans' description he says: “The ends may be made of soft cast iron, provided the fire be kept from

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R. H. Thurston in his work gives a description of a boiler made by Evans which had a cylindrical shell and flue, as in the Cornish boilers, but under-fired, the flames first passing under the shell, then back through the tube to the stack. Thurston further remarks that this form of boiler was in use by both Evans and British engineers about 1800. If the date is correct, Evans must have been using cylin. drical boilers at the same time or a little before Trevithick.

Luke Hebert, writing in 1835, says: “Next to the wagon shaped boilers of James Watt, those of cylindrical form have been most used, especially for highpressure engines. They are usually known in this country as Trevithick boilers, from the supposition that Trevi.

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thick invented them. We, however, ob- Bainsford Bridge, and exposed to public serve that Mr. O. Evans described them view as a wreck for many years. She was as being used by him for his high-pres- abandoned on account of injury to the sure engines prior to Trevithick's patent, canal banks from the wash caused by her and as Evans does not claim them we paddle wheels. may suppose that they were in use before It is recorded that Nathan Read, of his time."

Salem, Mass., took out a patent for a In the year 1786 a man by the name of tubular boiler in 1791. The boiler was Fitch tried to solve the problem of pro- vertical in design, and of a construction pelling boats by steam. He appears to which appears more recent than implied have built a steamboat, but unfortunate- by the date. Tubular boilers are reckoned ly, the only thing known about the to belong to a much later date than 1791, boiler is the fact that it was not strong yet a few isolated designs may be found enough to do its work. In this same year recorded in various books and papers, William Symington submitted a working this boiler of Read's being one of them. model of a steam carriage to the inspec- Read's boiler was intended for use with tion of a body of scientific men in Edin- fire engines. burgh. No description of this boiler can Count Rumford, under whose direction be found.

the boilers for heating the lecture room In October, 1788, Symington fitted a at the Royal Institution were made, boiler and engine to a pleasure boat which adopted another method, that of dividing seems to have been fairly successful. Mr. the water up in a number of small cylinScott Russell says of the boiler in this ders, around which the flames circulated. boat: "It was compact and contained the This boiler was designed in 1796 and is of fire wholly within it." Here again special interest as a link in the chain of knowledge is lacking of particulars. It development of the modern water to be may have been a flue boiler of the kind and sectional boilers. Although this afterwards used in marine work. In one boiler was used only to supply steam to description of this boat the chimney was heat the building, yet it is worthy of note said to have been built of brick.

as being the first of its kind recorded. In 1803 Symington was employed by Probably no man contributed more to Lord Dundas to fit up a boat with a steam the use of high pressure and the developengine. This, the first practical steamboat, ment of the steam boiler than Richard was named the “Charlotte Dundas." Trevithick, Jr. He was a man of large From figures given of this boat the boiler inventive genius, but of somewhat erratic may have been of wagon shape or possi- habits, and was never given the credit bly cylindrical, and the stack appears to due him. His son, Francis Trevithick, have been at the same end as the fire collected a large amount of information door. An engraving of this boat was and published an interesting story of the made bat no detail of the boiler is shown. life of his father. Richard Trevithick, The engine is described as being double- Jr., seems to have inherited the genius of acting, the earlier ones of Symington his father, Richard Trevithick, Sr., who being single-acting atmospheric engines. about the year 1775 made history in boiler Fincham, in his “History of Naval Archi- development. tecture,” gives a good description of the Richard Trevithick, Jr., made a number boat, but not of the machinery. If of improvements in designs for high presthe engine was of the double-acting type, sure boilers, and on Christmas eve, 1801, it would imply the use of a higher pres- tried a road locomotive at Camborn. Little sure of steam than was required for the is known of this engine except that it acatmospheric engine, and it would be of tually ran upon the wagon road and was decided interest if a description of the the first locomotive that took a load of boiler could be found. The “Charlotte passengers-some seven or eight-men, who Dundas” was laid up in a creek near were with difficulty persuaded to ride

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apon it. Eventually, it seems to have Tydfil in South Wales. A drawing, met the fate accorded to many more steam taken from a model, shows the boiler to road carriages of later and better design. have been six feet long and four feet A figure is given of this steam carriage in three inches in diameter, with return the life of Trevithick, and the boilers ap- flue. There is some dispute as to the pear to have been of cast iron with a re- material used in this boiler, some claim. turn flue. A model of this engine can be ing that it was of wrought, others that seen in the South Kensington Museum. it was built of cast iron. However, the

In the history of the life of Richard facts are that the shell was of cast iron Trevithick, Jr., he is credited with the and the return flue of wrought iron. building of a number of various designs Another of Trevithick's locomotives, of cast iron boilers, one of which is de- made for use in the north at Newcastlescribed as being four feet in diameter and on-Tyne, about the history of which there

and one-half inches thick, and is considerable obscurity, had apparently capable of withstanding a pressure as a wronght iron boiler with a return flue. high as 145 pounds to the square inch. Two extremely valuable and interestHe was certainly a bold or reckless man, ing relics of old boiler work are preserved or probably a combination of both, which in the South Kensington Museum, both has often been found in great inventors of Trevithick's make. One of these has a and pioneers into new fields of research. cylindrical cast iron shell, with wrought Among his many inventions he seems iron return flue. The other has a shell to have devised the fusible plug and the of cylindrical form, with a pocket for lockup safety valve.

the engine cylinder at the back end, and About the time Trevithick, Jr., in is of one-inch thickness of metal. The England and Oliver Evans in America front plate is of wrought iron in two were struggling with boilers for high pieces, riveted together and bolted on pressure, we come across isolated cases the flange of the shell. The bolt holes of the use of wooden boilers of very low in the front plate are remarkable large pressure, as mentioned in the February and of square shape. The return flue JOURNAL. A cut of these wooden boilers was made of several small plates, and shows a horizontal section just above the was riveted to the shell by means of fire grate, also longitudinal and cross angle irons and rings attached to the sections. There was a flat combustion front plate. The construction of this rechamber at the back of the firebox, the turn flue, which was made of five-sixtop and bottom of which were stayed by teenths, of an inch plates, must have been short tubular castings forming water a matter of great difficulty with the aptubes, and from the back end of which

pliances then in It might be an oval uptake smoke fue was carried mentioned that the shell of this last de. by a bend and a return bend forward and scribed boiler was of wrought iron. back below the water line.

The relics of old boilers which have was three feet by five feet, giving a been handed down are so few that these surface of 15 square feet. The total heat- two of Trevithick's make are of especial ing surface was given as nearly 300 square value for giving us an insight into the feet. The construction of these boilers workmanship and methods of the early was highly ingenious, but with such ma- boilermakers. terial as wood could not have been very In 1808 Mr. James Linaker, master durable. Yet some of them seem-as in millwright at the Portsmouth dockyard, the case of the Philadelphia boiler-to made some experiments on propelling have lasted for years. In the history of vessels by machinery. He proposed pumpthese wooden boilers the kind of wood ing water in at the head and discharging used was not named.

it at the stern. He had an engine and In 1803 Trevithick had a locomotive boiler made for his boat, but the results running upon the railroad at Merthyr of his experiments are not recorded.

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