Engineering reminiscences contributed to "Power" and "American machinist"

by Charles T. Porter

Now I do not think that in my limited sphere of observation at home I had ever seen a condensing stationary engine, except the engine which pumped out the dry-dock at the Brooklyn Navy Yard. In my mind condensing engines were associated with ships and steamboats. At this exhibition also there were shown only non-condensing engines. I did not think of the reason for this, that in this part of London, far away from the Thames, no water could be had for condensing purposes. I took it all as a matter of course, though I was astonished at the queer lot of engines in the company of which I found myself.

I was, of course, familiar with the development of the stationary engine in England from the original type, in which the pressure of steam below that of the atmosphere, and sometimes the pressure of the atmosphere itself furnished the larger proportion of the power exerted; but after all I carried with me my American ideas, which were limited to non-condensing engines, and had no conception of the gulf that separated my thoughts from those of the men about me.

My visitors always wound up with the same question, “How do you drive your air-pump?” And in my innocence I uniformly replied, “The engine is a non-condensing engine; it has no air-pump”; all unconscious that every time I said that I was consigning the engine to the rubbish heap. This reply was taken necessarily as a frank admission that the high-speed engine was not adapted for condensing. Of course, then, it had no interest for them. No doubt many wondered why I should have troubled myself to show it there at all. If I had thought more deeply I must have been struck by the unvarying form of this question, always assuming the air-pump to be a part of the engine, but which, of course, could not be used there, and only inquiring how I worked it; and also by the fact that after getting my answer the questioner soon departed, and I scarcely ever saw the same visitor again. But I did not think deeply. Perhaps the conditions of excitement were not favorable to reflection. All I thought was that this same everlasting question, which at home I would never have heard, was getting awfully monotonous. After a while this annoying question came to be asked less and less frequently, and also the engine attracted less and less attention. The engine had failed in a vital respect, and I did not know it. That the fact of the engine being non-condensing should have been an objection to it never once entered my mind.

But I doubt if I could have bettered the matter, however alive to this difficulty I might have been. I showed all I had yet accomplished. In the minds of my visitors it no doubt appeared impossible to run an air-pump successfully at such a speed; the water and air would be churned into foam, and the valves would not close in time. This objection I was not prepared to meet, for I had not thought on the subject at all. Moreover, it could not have been met in any way except by a practical demonstration. For that demonstration I had yet to wait five years.

There were many things connected with this season which were well worth remembering. One of these was the visit of the jury. It was the only time I ever met Professor Rankine. There were two or three Frenchmen on the jury, and they engaged in an animated discussion of the question whether the steam could follow the piston at so great a speed. I well remember the sharp exclamation with which Professor Rankine put an end to this nonsense, when he had got tired of it. “There is no limit to the speed at which steam will follow a piston.”

One day I had a call from Mr. John Penn, Mr. William Fairbairn, and Mr. Robert Napier, who came together on a visit of ceremony, and presented me their cards. In return I presented to them the cards of the engine. But their visit, like most others, closed with the same inevitable question.

It was a delightful hour that Mr. F. W. Webb spent with me. He was then assistant engineer of the London & Northwestern Railway under Mr. Ramsbottom, afterwards Mr. Ramsbottom’s successor, and the pioneer builder of compound-cylinder locomotives. He told me about the new form of traveling-crane invented by Mr. Ramsbottom for the shops at Crewe, which was driven by a flying-rope, a ³⁄₄-inch cotton cord, and also of other inventions of Mr. Ramsbottom—among these the automatic cylinder lubricator, in which the condensation of the steam was so rapid, from the locomotive rushing through the atmosphere, that only the water formed on the conical end of a bolt was permitted to drop into the oil, other condensation running into a circular trough and back through an external gooseneck pipe to the steam-chest; and of their experiments to observe the rate of this condensation. For this purpose they used soda-water bottles, which they found capable of resisting a pressure of 200 pounds on the square inch, and in which they could see the rapidity with which the condensed water displaced the oil, thus leading to the above device for limiting this action; also about the Ramsbottom piston rings, which came to be, and still are, so largely used. These consist, as is well known, of square wrought-iron rods, say ¹⁄₂ inch square, two for each piston, sprung into grooves. What is not so generally known is the way in which these rings were originated, which Mr. Webb then described to me. As sold, these are not circular rings, but when compressed in the cylinder they become truly circular and exert the same pressure at every point. The original form was found for each size in this way: A circular iron table was prepared, provided with a large number of pulleys located radially and equidistant around its edge. A ring having the section of the proposed rings, turned to the size of the cylinder, and cut on one side, was laid on this table, and cords were attached to it at equal distances passing over these pulleys. Equal weights were hung on these cords, sufficient to expand this ring to the extent desired. The form of the expanded ring was then marked on the table, and to the lines thus obtained the rings were then rolled. He told me also of the trough and scoop invented by Mr. Ramsbottom, and now used the world over, for refilling locomotive tanks while running at full speed. Being a locomotive man, Mr. Webb did not ask about the way I drove my air-pump.

Mr. Clark formed a scheme to indicate all the engines in the exhibition, twenty-four in number, all English except mine, so far as I remember, and employed my indicator for the purpose, the diagrams being taken by myself. Only two exhibitors declined to have their engines indicated. As I afterwards learned, most of the engines were bought for use there, as exhibitors would not exhibit non-condensing engines.

One of those who refused permission were Gwynne & Co., the principal partner a nephew of my centrifugal-force friend of earlier days. They exhibited a centrifugal pump supplying a waterfall. They employed Mr. Zerah Colburn, then editor of The Engineer, to investigate their pair of non-condensing engines and find out why they used so much steam. He borrowed my indicator to make a private test. Of course, I never saw the diagrams, but Mr. Colburn informed me that by making some changes he had reduced the back pressure to 7 pounds above the atmosphere, which he claimed to be as good as could be expected. No material improvement in the engines was to be observed, however.

Some of the diagrams taken on these tests exhibited almost incredible faults. The only really good ones were from a pair of engines made by Easton, Amos & Sons, also to drive a large centrifugal pump, built for drainage purposes in Demerara, and sustaining another waterfall. These showed the steam cut off sharply at one third of the stroke by separately driven valves on the back of the main slides. A mortifying feature of this work for myself was that on testing the indicator Mr. Clark found that the area of the piston, which was represented to be one quarter of a square inch, was really considerably less than this, showing lamentable inaccuracy on the part of the makers, as well as my own neglect to discover it. This rendered the instrument valueless for measuring power, but it showed the character of the diagrams all right.