CHAPTER XIV

Study of the Action of Reciprocating Parts. Important Help from Mr. Frederick J. Slade. Paper before Institution of Mechanical Engineers. Appreciation of Zerah Colburn. The Steam Fire Engine in England.

After the close of the Paris Exposition I devoted myself in earnest to the study of the action of the reciprocating parts of the engine, and will here give a sketch of its development. In the high-speed steam-engine the reciprocating parts were found to be a most essential feature. Besides transmitting the pressure of the steam to the crank they perform quite another office. It is their inertia, relieving the crank from shocks on the dead centers, and equalizing the distribution of the pressure on it through the stroke, that makes the high-speed engine possible. I employed this inertia before I knew anything about it. I had been occupied with the subject of balancing. I had demonstrated practically that the centrifugal force of a weight equal to that of the reciprocating parts, opposite the crank and at the same distance from the center as the crank-pin, perfectly balanced a horizontal engine, and had shown this fact conclusively at this exposition.

The problem before me was, “What is it that makes my engine run so smoothly?” I am not a mathematician, and so could not use his methods. I got along by graphic methods and study of the motion of the piston controlled by the crank. My recollection of the several steps of my progress is quite indistinct. One thing I do remember distinctly, and that is the help that I got from my friend Frederick J. Slade, who was younger than I, but who died several years ago. Mr. Slade was a mathematical genius. The firm of Cooper, Hewitt & Co. were at a later date the pioneer makers in the United States of wrought-iron beamsand other structural shapes; and all their designs and computations were the work of Mr. Slade. I had formed his acquaintance in London in ’63. I met him again in Paris in ’67. He was then in France in the employ of Abram S. Hewitt, investigating the Siemens-Martin process of steel manufacture. He took much interest in the engine. One day he brought to me a diagram representing the two now famous triangles, and a demonstration of them which he had made, showing that the ordinates, representing the acceleration or retardation of the piston motion at every point, if erected on the center line of the engine, terminate in a diagonal line, which, with a connecting-rod of infinite length, would cross this center line at its middle point.

This exhibited at once the equalizing action of the reciprocating parts in a cut-off engine, absorbing the excessive force of the steam at the commencement and imparting it to the crank at the end of the stroke. I feel myself more indebted to Mr. Slade than to any one else, and would here record the tribute of my grateful acknowledgment.

On January 30, 1868, I had the honor of reading a paper on the Allen engine before the Institution of Mechanical Engineers. The discussion of the paper was postponed until the next meeting, April 30, and the paper was ordered meantime to be printed and sent to the members. The result was that on the latter date we had a very interesting discussion. I may mention two things which occurred at the first meeting, but do not appear in the report of the transactions. When the secretary reached the statement that the acceleration of the piston was greatest at the commencement of the stroke, the president of the meeting, Sampson Lloyd, Esq., one of the vice-presidents of the Institution, stopped the reading and said to me, “You do not mean, Mr. Porter, that this isonthe commencement of the stroke, but at a point near its commencement.” I was obliged to answer him that I intended to say that precisely on the dead center, at the point where motion in one direction had ceased and that in the opposite direction had not yet commenced, at that precise point the stress on the crank was at its maximum, the crank having brought the reciprocating parts to rest, and then by a continuance of the same effort putting them in motion in the reverse direction.

Frederick J. Slade

After the reading was concluded, Mr. E. A. Cowper took the floor, and stated that I was entirely mistaken in my explanation of this action, that this had been investigated by a gentleman whose name he gave but which I have forgotten, and who had demonstrated that this retarding and accelerating action was represented by a curve, which approximately he drew on the blackboard, but which he excused himself from demonstrating there, as it would require the use of the calculus and would take considerable time. For this reason the discussion was postponed. At the next meeting Mr. Cowper did not present this demonstration, and long afterwards he wrote a letter to the editors ofEngineering, stating that on full investigation he had found the retardation and acceleration of the piston to be represented by triangles and not by a curve. At the discussion of the paper my view was supported by all the speakers who addressed themselves to this point, except Mr. Cowper. An especially careful and valuable exposition of the action of the reciprocating parts was given Mr. Edwin Reynolds, then of the Don Steel Works, Sheffield.

Zerah Colburn, the editor ofEngineering, had always taken a warm interest in my engine, and in the winter following the Paris Exposition he invited me to furnish him the drawings and material for its description in his paper. This I did, and from these he prepared a series of articles written in his usual clear and trenchant style. These will be found in Volume V ofEngineering, the cuts following page 92, and the articles on pages 119, 143, 158, 184, and 200.

Mr. Colburn’s articles inEngineeringare so interesting in themselves that I think I need make no apology for quoting from them his remarks on this subject of the inertia of the reciprocating parts, and those in which is depicted the revolutionary nature of the high-speed engine, as viewed at that time.

After a prelude, with most of which the reader is already acquainted, Mr. Colburn says:

“When a steam-engine is brought from abroad to the very spot where the steam-engine originated, and where it has received, so far at least as numbers are concerned, its greatest development, and is claimed to be superior to those produced here, and to be able to run advantageously at a speed hitherto deemed impracticable,its promoters must not expect to have much attention paid to its claims until such attention has been actually compelled, and then they must be prepared for an ordeal of severest criticism....

“In employing a high grade of expansion, especially with the considerable pressure of steam now usually carried in stationary boilers, two serious practical difficulties are met with. The first arises from the injurious effect of the sudden application of so great a force on the centers, which the beam-engine, indeed, cannot be made to endure, and the second is found in the extreme difference between the pressures at the opposite ends of the stroke, which is such that the crank, instead of being acted upon by a tolerably uniform force, is rotated by a succession of violent punches, and these applied when it is in its most unfavorable position....

“In the Allen engine the action of high speed causes all the practical difficulties which lie in the way of the successful employment of high grades of expansion combined with high pressure of steam completely to disappear. The crank receives as little pressure on the centers as we please; none at all if we like; the force is applied to it as it advances, in a manner more gradual than the advocates of graduated openings and late admission ever dreamed of, and a fair approximation is made to a uniform rotative force through the stroke. So that, in a properly constructed engine, the higher the speed the smoother and more uniform and more silent the running will be.”

After a page or more devoted to a demonstration of this action, Mr. Colburn sums up the advantage of high speed in the following illustration:

“Let us suppose that, in an engine making 75 revolutions per minute, the reciprocating parts are of such a weight that the force required at the commencement of the stroke to put them in motion is equal to a pressure of 20 pounds on the square inch of piston. This will not modify the diagram of pressure sufficiently to produce much practical effect. But let the number of revolutions be increased to 150 per minute, the centrifugal force of these parts as the crank passes the centers is now equal to 80 pounds on the square inch of piston, and any pressure of steam below this amount acts only as a relieving force, taking the strain of these parts partly off from the crank. It makes no matter how suddenly it is admittedto the cylinder, not an ounce can reach the crank; but as the latter advances, and the acceleration of the reciprocating parts becomes less, the excess of force not required to produce this becomes, in the most gradual manner, effective on the crank.

“It will be observed how completely the designer has this action of the reciprocating parts under control. He can proportion their speed and weight to the pressure of steam in such a manner as to relieve the crank from the blow on the center to whatever extent he may wish. The notion that the reciprocating parts of high-speed engines should be very light is therefore entirely wrong. They should be as heavy as they can be made, and the heavier the better.

“The advantages of more rapid rotation are largely felt in the transmission of power. Engineers understand very well that, theoretically, the prime mover should overrun the resistance. Motion should be not multiplied but reduced in transmission. This can seldom be attained in practice, but high speed gives the great advantage of an approximation to this theoretical excellence. On the other hand, slow-speed engines work against every disadvantage. Coupled engines and enormous fly-wheels have to be employed to give a tolerably uniform motion; often great irregularities are endured, or the abominable expedient is resorted to of placing the fly-wheel on the second-motion shaft. Then comes the task of getting up the speed, with the ponderous gearing and the enormous strains. Slow motion also prevents the use of the belt, immeasurably the preferable means of communicating power from a prime mover.

“But how about the wear and tear? The question comes from friends and foes alike. The only difference is in the expression of countenance, sympathetic or triumphant. The thought of high speed brings before every eye visions of hot and torn bearings, cylinders and pistons cut up, thumps and breakdowns, and engines shaking themselves to pieces. It is really difficult to understand how so much ignorance and prejudice on this subject can exist in this day of general intelligence. The fact is, high speed is the great searcher and revealer of everything that is bad in design and construction. The injurious effect of all unbalanced action, of all overhanging strains, of all weakness of parts, of alluntruth in form or construction, of all insufficiency of surface, increases as the square of the speed. Put an engine to speed and its faults bristle all over. The shaking drum cries, ‘Balance me, balance me!’ the writhing shaft and quivering frame cry, ‘See how weak we are!’ the blazing bearing screams, ‘Make me round!’ and the maker says, ‘Ah, sir, you see high speed will never do!’

“Now, nothing is more certain than that we can make engines, and that with all ease, in which there shall benounbalanced action,nooverhanging strains,noweakness of parts,nountruth of form or construction,noinsufficiency of surface; in which, in short, there shall benodefect to increase as the square of the speed, and then we may employ whatever speed we like. ‘But that,’ interposes a friend, ‘requires perfection, which you know is unattainable.’ No, we reply, nothing unattainable, nothing even difficult, is required, but only freedom from palpable defects, which, if we only confess their existence, and are disposed to get rid of, may be easily avoided. It is necessary to throw all conceit about our own work to the dogs, to lay down the axiom that whatever goes wrong, it is not high speed, but ourselves who are to blame, and to go to high speed as to our schoolmaster.

“Among the many objections to high speed, we are often told that the beam-engine will not bear it, and the beam-engine, sir, was designed by Watt. In reverence for that great name, we yield to no one. The beam-engine, in its adaptation to the conditions under which it was designed to work—namely, a piston speed of 220 feet per minute and a pressure of one or two atmospheres—was as nearly perfect as any work of human skill ever was or will be; but we wonder why the outraged ghost does not haunt the men who cling to the material form they have inherited, when the conditions which it was designed to meet have been all outgrown, who have used up his factor of safety, and now stand among their trembling and breaking structures, deprecating everything which these will not endure.

“A journal and its bearings ought not only never to become warm, but never even to wear, and, if properly made, never will do so with ordinary care to any appreciable extent, no matter how great speed is employed. It is well known that there exists a very wide difference in bearings in this respect, some outlastingdozens of others. Now, there need be no mystery about this: the conditions of perfect action are so few and simple that it seems almost idle to state them. The first is rigidity of a shaft or spindle between its bearings; but everybody knows that if this is flexible, just in the degree in which it springs, the journals must be cast in their bearings, though in actual practice this perfect rigidity is not once in a thousand times even approximated to. The point of excellence in the celebrated Sellers bearing for shafting is that it turns universally to accommodate itself to this flexure of the shaft, and the result is a durability almost perfect.

“The second requirement, when we have a shaft capable of maintaining perfect rigidity under all the strains it may be subjected to, is abundant extent of bearing surface both in length and circumference, a requirement, it will be seen, entirely consistent with the first. It is a mistake to use journals of small diameter with the idea that their enlargement will occasion loss of power on account of the increased surface velocity, as, in fact, the coefficient of friction will diminish in a greater ratio than that in which the velocity is increased. In the Allen engine it is intended to make all shafts and journals too large.

“But all is of little use unless the journal is round. High speed under heavy pressure has a peculiar way of making it known when a journal is not round, which, we suppose, is one of its faults. Now the difference between a true cylindrical form and such an approximation to it as a good lathe will produce in turning ordinarily homogeneous metal is simply amazing; but when we compare with this the forms of journals as commonly finished, the wonder is how many of them run at all at any speed. When ground with a traversing wheel in dead centers, which have themselves been ground to true cones, the only known method by which a parallel cylindrical form can be produced, their inequalities stand disclosed, and these are usually found to be greater, often many times greater, than the thickness of the film of oil that can be maintained in running. Then under pressure this film is readily broken, the metal surfaces come into contact and abrasion begins. But a true cylindrical journal swims in an oil-bath, separated from its bearing at every point by a film of oil of uniform thickness, and sustaining a uniform pressure, which cannotbe anywhere broken, and which has very little inclination to work out; and if it revolves without deflection and the pressure per square inch of surface is not sufficient to press out the lubricant, the speed is absolutely immaterial and wear is impossible, except that due to the attrition of the oil itself, which on hardened surfaces has no appreciable effect.”

From the illustrations contained in these articles, I copy only the following pair ofdiagramswith the accompanying note.

Pair of Diagrams from 18×30 Allen Engine at South Tyne Paper Mill, 108 Revolutions, Vacuum 28 Inches. Only Half Intended Load on Engine.

The winter of 1867-8 was devoted by me partly to watching the dissolving view of my engineering prospects in England. It grew more and more evident that through my difference with Mr. Whitworth all my efforts and successes there would come to naught, as they did.

But my friend, Mr. Lee, had even worse luck than I had. It will be some relief from the monotony of my reverses if I go back a little and tell of a reverse that befell another man. Curiously enough, Mr. Lee’s reverse came from the overwhelming character of his success. The English engineers had their breath quite taken away and lost their heads, with the result that Mr. Lee lost his position. He was ambitious to show his steam fire-engine doing its utmost. If he had been wiser and had realized the limit of what his judges could stand, he would have shown about one half its capacity and all parties would have been happy.

To understand how naturally this most unexpected dénouement came about, we must recall what the English people hadbeen accustomed to. In London fires were rare and trifling. Buildings were low, built of brick with tile roofs. Open grates afforded the means of cooking and of warming sufficiently for their climate. Every tenant of a building who called in the fire department was fined five pounds, which encouraged careful habits. The apparatus itself was something quite ridiculous. It consisted of little hand-engines, worked by about a dozen men. On the side of a corner building occasionally one saw painted a distance in feet and inches. This meant that by measuring this distance from this corner out into the street and digging a little into the macadam pavement, a connection would be found with the water-main. From this the water was permitted to flow gently into an india-rubber saucer some 6 feet in diameter spread on the ground. Out of this saucer the engine drew its water for a feeble little stream.

Mr. Lee’s engine, with Worthington duplex pump, was, on its completion, exhibited before a large company of invited guests, principally officials of the fire department and prominent engineers. The engine maintained a vertical column of water, delivered from a much larger nozzle than had ever before been used in England, and considerably over 100 feet high. There was also a corresponding column of sparks from the chimney of the steam-pump. The exhibition was made late in the afternoon of a short winter day, and before it was over the coming darkness showed the column of incandescent cinders to the best advantage. The few Americans there enjoyed this miniature Vesuvius hugely. The Englishmen were frightened out of their wits. Their unanimous verdict was that the engine would evidently put out a fire, half a dozen of them for that matter, but it would kindle twenty. And this where the engine had been pushed to its utmost, and had not kindled one fire. Easton, Amos & Sons instantly decided that they could never sell a steam fire-engine under Mr. Lee’s management, and they discharged him the next morning.

During the following season we had quite a steam-fire-engine excitement. Some one, I have forgotten who, but think it was the Duke of Sutherland, made a public offer of a thousand pounds sterling for the best steam fire-engine, competition to be open to all the world, the engines to be tested for six days in the park ofthe Crystal Palace at Sydenham, in the month of July following. There were a number of amusing incidents connected with that exhibition. One was the following: The common council of New York City determined that the city must have that prize, so they sent over engine No. 7, a favorite engine, one of Mr. Lee’s make, and which had been three or four years in service. A junket committee of the city fathers accompanied it. The London Fire Department received this delegation with great enthusiasm, and devoted itself to making them happy. They took entire charge of their machine and exhibited it in London to admiring crowds. A few days before the time fixed for the opening of the trial they took the engine to Sydenham, where on the way to its station it accidentally rolled down a hillside and was pretty well broken up. Mr. Lee being in London was hurriedly sent for to see if it could be repaired in time for the trial. He found that the injuries were of so serious a nature that the repairs could not be completed in less than three weeks. So that competitor was out of the way. Their sympathizing friends were full of condolence, and assumed all the cost of the repairs. They also proposed that when the engine was put in proper order they should have an excursion down the Thames to Greenwich and have there an exhibition of its powers. So a steamboat was chartered and a large party accompanied the machine to Greenwich. On arrival there it was found that the two nozzles, a large one and a smaller one for long-distance streams, which had been taken especial charge of by the members of a fire company, had been accidentally dropped into the Thames. The New York delegation were glad to get their engine back to New York without further accident.

Easton, Amos & Sons also concluded that they would like that prize. After they had taken the engine into their own hands, they found a number of features which seemed to them to need amendment, so they made some quite important changes. On the second day of the trial this engine broke down and had to be withdrawn.

I have forgotten how many competitors remained in the field, but the prize was awarded to a London firm, builders of hand fire-engines, who had only lately taken up this new branch of manufacture. This successful firm applied to the government for an orderto supply steam fire-engines for the protection of the public buildings. This application was referred to Easton, Amos & Sons, the consulting engineers of the government. This firm concluded if possible to have this order given to themselves, and applied to Mr. Lee to recommend the changes in his engine necessary to put it in proper working order. Mr. Lee replied that it was only necessary to put the engine back in the precise condition in which he left it. They finally agreed to do this, and employed Mr. Lee to direct the work. When completed the engine was tried in the gardens of Buckingham Palace, in competition with the prize winner, before a large body of government officials. The Easton, Amos & Sons engine proved its superiority on every point so completely that the government immediately purchased it.

Some time before this, however, Mr. Lee had associated himself with a capitalist for the manufacture of steam fire-engines in England, and was then engaged on plans for them. His financial associate was Judge Winter, by which title only he was known to us. He was an American, and before the war was the proprietor of the Winter Iron Works in Georgia (the precise location I have forgotten), the most prominent engineering establishment in the Southern States, in which business he had become wealthy. He will be remembered by some gray heads as having been an exhibitor in the New York Crystal Palace in 1853. He sent to it a steam-engine bearing the name of “The Southern Belle.” This stood in the machinery department, close to a Corliss engine, the two being the only engines of any size which were exhibited there. This engine was beautifully finished, polished pretty much all over, but its working features were of the most ordinary character. Mechanically it was valueless.

Judge Winter was a determined opponent of secession, and on the adoption of that ordinance by the State of Georgia, was compelled to fly from the country. He then took up his residence in London, to which he had transferred such portion of his wealth as he was able to convert into money.

He took a deep interest in the new steam fire-engine, and spent part of nearly every day in the office where Mr. Lee and Mr. Taylor, an American engineer whom Mr. Lee had associated with himself, were engaged on their plans.

The point of interest to myself in this story lies here. The old judge had no sound mechanical education, but was very fertile minded. He came almost every morning with a new idea that he wanted embodied. It was always absurd. He generally protested vigorously against being overruled. When he was furnishing all the money he could not see why he should not be allowed to havesomethingto say about it. I happened to be present in their office one morning when he got particularly excited over their opposition. He was a stout party, and on this occasion I had the fun of joining in the shout of laughter that greeted him, when, after pacing the floor in silence for a few minutes, he exclaimed, with his hand on the fabled seat of his sympathies, “I thank my God that if there is one thing I am free from, it is pride of opinion.”

My recollection of the above action of Easton, Amos & Sons and of Judge Winter contributed materially to form my imagination of the predicament in which I would certainly find myself, should I yield to Mr. Whitworth the power to make whatever changes might occur to him in my engine.

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