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

by Charles T. Porter

It was found impossible to keep up steam. It fell to half pressure every day before stopping time came.

One morning, about a week after the opening, on my arrival my friend Mr. Lee, who was superintendent of the machinery department, came to me and said, “Do you know what they are all saying about here?” “No,” I replied. “Well,” said he, “you ought to know. It is that your engines use all the steam, and your boiler does not make any, and that is where all the trouble is.” I replied: “I am ready for them. You see that valve up there. I put it in expressly to meet whatever questions might arise. By closing it I can shut my system off from the general steam connections and run my two engines from my own boiler, and will try to get on without their assistance.” So a ladder was brought and I went up and shut the valve. Directly my pressure rose to 70 pounds, the pressure allowed; my automatic damper closed as nearly as it was permitted to do, and the steam began to blow off. To prevent this, the fireman had to set his door a little way open, and in this condition we ran all day. In the rest of the show the steam ran down until at noon there was barely 15 pounds pressure, but the wrath of the exhibitors of machinery driven by other engines was blowing off. After the noon hour the additional boiler was started and helped them a good deal, so that, starting with 70 pounds at 1 o’clock, at 5 o’clock they still had 25 pounds pressure.

Mr. Lee asked me several times during the day to open the valve and I refused to do it. Finally, at about 5 o’clock, he said to me, “If you don’t open that valve, I shall.” “Well,” said I, “there will be a number of the managers of the Institute here at this hour, I presume, and if you will send for them and have them come here and see the state of the case for themselves then I will open the valve.” So this was done. Half a dozen of these gentlemen came and made an inspection of the boilers and said to me: “We are quite satisfied. It is evident that you have been supplying most of the steam and using very little.” So I opened the valve and there was no further trouble. The assistance of the large boiler added that day prevented any serious fall of pressure afterwards.

A few days after the above incident a committee of the managers waited on me and said: “We have heretofore had a good deal of trouble with our steam supply, and would like next year to have a boiler that we can rely upon. What will you ask to leave this boiler here for our use next season?” I agreed with them for three hundred dollars, and so the boiler remained for the next exhibition, when there will be something more to be said about it and views of it will be shown. That winter Barnum wintered his animals in that building, and paid me three hundred dollars more for the use of the boiler to warm it. In my ignorance of business these items of good luck came in very handy. Mr. Allen said he never heard of a new thing so successful from the start.

The remark respecting my exhibit of engines and boiler at the fair of the American Institute in 1870, that there was not a drawback of any kind about it, must, however, be qualified in one respect. I was not able to run my 16×30 engine at the speed of 150 revolutions per minute, as I had intended.

A blunder had been made in the size of the driven pulley on the line of shafting. It was smaller than specified, because the contractor for the shafting put on a pulley he had, and this was not observed till we were running, when it was too late to change it. The exhibitors of machinery in motion all complained that their machines were running too fast, and after two or three days the directors ordered me to reduce the speed of my engine to 125 revolutions per minute, at which speed it was run through the rest of the fair. I was much disappointed, but consoled myself with thinking that perhaps this speed would please the general public better than the higher one, the engine even then being three or four times too large for its work.

The boiler gave me at the engine steam superheated 23 degrees all the time. This I proved by transposing the thermometers. I had two thermometers, duplicates, one on the steam-chest and the other on the first boiler drum, in which the steam was not superheated. The former indicated 23 degrees higher temperature. When these were exchanged the same difference continued to be shown.

I was greatly interested in observing in my own and other engines the relative amounts of initial cylinder condensation, as this was shown in the steam blown from the indicator stop-cocks. I had one of these on my steam-chest, and the steam blown from this was not visible until three or four inches above it. That blown from the stop-cocks on my cylinder had a very little tinge of white, showing the superheating to have been lost and a slight initial condensation to take place. As the piston advanced, the blowing steam became invisible, showing re-evaporation, through the falling of the boiling-point on the expansion.

On other engines, of which several were exhibited, the observation showed large amounts of initial condensation. From one of them I remember the blowing steam looked like a white painted stick.

I observed that the steam only lost three degrees of its superheat in passing through 25 feet of 6-inch pipe from the boiler to the engine. For this comparison I placed a thermometer on the second steam drum, in which the steam was superheated, where it showed about 26 degrees of superheat. This measured the rate at which the heat was lost through the felt covering of the pipe, and suggested an excellent method of comparing the protective value of different coverings under absolutely the same conditions.