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

by Charles T. Porter

EXPOSITION UNIVERSELLE, PARIS, 1867.
DIAGRAM FROM THE “ALLEN” ENGINE, EMPLOYED IN DRIVING MACHINERY
IN THE BRITISH SECTION, AND MANUFACTURED BY
THE WHITWORTH COMPANY, LIMITED, MANCHESTER.
ENGINE, 12 INCHES BY 24 INCHES, REVOLUTIONS PER MINUTE, 200.
SCALE, 16 LBS. TO THE INCH.

I took to this exposition five engines. One of them was 12×24 inches, making 200 revolutions per minute. I advanced the speed from 600 feet to 800 feet per minute, to show what both the engine and the condenser could do. After all, however, I did not show one half of what with proper port areas the high-speed system was capable of. The ports were insufficient, having been adapted to a speed of 150 revolutions per minute. I took great satisfaction in showing the condenser to my old friends, Easton, Amos & Sons, who were all there, at one time or another, during the exposition. Before the exposition opened we had on hand at the works four condensers, one for an engine the Whitworth Company were building for themselves, two for the parties already mentioned, and the one for the exposition engine. As this was the first one required to be running, I had to make the first test of the condenser in this public way, which I immensely enjoyed doing.

Through the influence of Mr. Whitworth, we received an order from Trinity House, which is the British lighthouse board, for two engines to drive the machinery of an electric light. The English and the French governments each made an exhibit of such a light, at the summit of a high tower. The current was produced by rapidly revolving magnets, a large number of which were set in a wheel.

Everything in this English exhibit was in duplicate. The requirement was that either engine should drive either or both electric machines. This involved the use of four clutches and a lot of gearing. I measured the power required by one machine, at the works in London where they were made, indicating their shop engine with the light on and with the light off. To make sure I repeated this three times. I found that one of my engines, 6×12 inches, non-condensing, at 300 revolutions per minute, would drive the two machines, with the steam pressure we were to have, I think 70 pounds, and cut off at one quarter of the stroke, while it was capable of following five eighths of the stroke. So two of these engines were furnished. The exposition was well advanced before this machinery was ready for its trial. A large crowd had assembled to witness it. With both machines on, the engines could only crawl along. The superintendent of the British mechanical section ordered one machine taken off. There was very little improvement. Then this royal engineer, detailed from the army, and whose qualifications for his position consisted in absolute ignorance of anything mechanical, declared the trial finished, and strutted off with the remark, “There has been a great blunder made here in providing the power.” The men in charge of the machinery looked at me quite speechless. I asked them to throw off the other machine also. This was done, when it appeared that both engines, with steam following five eighths of the stroke—for I had indicators on both of them to show it—could not drive the gearing, except at a snail’s pace. They were then driven to examine the gearing for resistances, and found the teeth wedged in the spaces throughout. This gearing was removed and proper running gears substituted for it, and after ten days’ delay away went the engines at full speed. On this second trial one engine could drive both machines, cutting off at one-quarter stroke, precisely as my measurement of the power had shown. They then ran perfectly through the exposition and were accepted by Trinity House. Did the superintendent apologize to me for his hasty judgment or congratulate me on my success? He never made the slightest allusion to it.

My fourth engine, of the same size, had been spoiled for practical use by having the upper half of the cylinder and steam-chest planed off, to show the cylinder and valves in section. It was belted from the large engine to run very slowly, and thus exhibited the valves and gear in motion to the end of the exposition. Mr. Whitworth wanted his friend Mr. Owen to purchase this model for the South Kensington Museum, but it appeared to Mr. Owen that Mr. Whitworth ought to present it to the museum. This I learned from Mr. Hoyle. What was finally done with it I have forgotten, if, indeed, I ever knew.

My fifth engine, of the same size, 6×12 inches, I got up to show what the capabilities of high speed really were, so far as smooth and safe running were concerned. The reciprocating parts, which weighed altogether only 40 pounds, were exactly balanced. I did this by rolling the crank-disk on a boring-table, with 40 pounds hung on the crank-pin, and cutting out the lead from the hollow disk opposite the pin, where I had purposely put it in somewhat in excess, until the pin came down to the horizontal position. This brought the inertia of the reciprocating parts of the engine, at every point in the revolution, into equilibrium with the horizontal component of the centrifugal force of the revolving counterweight. The vertical component of this force, or rather its upward stress, for downward it would be resisted by the whole mass of the earth, remained to be dealt with. To prevent the whole engine from being lifted at the crank end by this stress at every revolution might have been accomplished by putting on a heavy fly-wheel; but for my use I wanted a very small one. The fly-wheel I put on the shaft was a solid disk, 18 inches in diameter and ¹⁄₂ inch thick, with a rim 1 inch square. The bed of the engine I filled with lead, and set it on a block of Caen stone 3 feet thick and wide and 5 feet long. To this stone it was firmly bolted, and I was ready for business. The governor was speeded to hold the engine at 500 turns per minute. As it might be difficult for some persons to count this speed, I put a little pinion on the end of the shaft, engaging with a larger wheel, one to ten. Fifty revolutions per minute could be accurately counted, and the speed was put beyond dispute. I was guilty of one oversight: I did not protect this gear. A French gentleman had the skirt of his frock-coat caught in it, and I thought it never would be got out. The engine had been running only two or three days, but the speed being then well established, I took off the gear. I ought to have protected it instead, and have had it to substantiate the big story I am going to tell, but it never occurred to me.

The engine running idle, I commenced very soon the exhibition for which I had made all this preparation. That was to hold the governor down by pulling the end of the lever up and letting the engine fly; which it did without a jar or a sound, only phantoms of the cross-head and connecting-rod being visible. That was my daily amusement and must have been repeated many hundred times in the course of the exposition, and of course always attracted a crowd.

We had no means of counting the speed, but I judged it to be more than 2000 turns per minute. When I released the governor and the speed fell gradually to 500 turns, it appeared to every one as if the engine were going to stop. But the governor never reacted, and soon the eye became accustomed to the slower speed. This presented quite a curious phenomenon. The connecting-rod was especially adapted to this enormous speed, by being made of the form already [shown], and which I afterwards adopted for all my engines. This engine never gave any trouble, and was sold, I think to Ducommen & Co., the purchasers of the large engine. The electric light with its engines was installed at the South Foreland Lighthouse, on the Shakespeare Cliff, east of Dover, if I remember rightly. We brought nothing back to England with us.

I went to Paris a few days before the opening of the exposition, and found my main engine already in running order, installed next to the Whitworth exhibit of tools, and selected by the imperial commission as one of the engines employed to give motion to the machinery exhibited.

By an imperial decree, the opening ceremonial of the exhibition was to take place on Monday, April 2, at 2 P.M., and everything was to be absolutely completed before that hour. The engines were to have been tested the previous Saturday. Every engine in the building was ready, but the imperial commission itself was behind. There was no steam. The first interview I had with the superintendent of the British machinery department was on this Saturday, when he came around to notify the several English engine exhibitors to be in readiness to run their engines the next day, Sunday, in order to make sure that there should be no hitch on Monday, I told him I should not run my engine on Sunday. “Very well,” said he, “we will run it for you,” and stalked off. Before going away I took out the pin at the end of the governor lever connecting the governor with the valve motion and put it in my pocket. Never heard any reproof, put the pin back on Monday, and when they gave us steam the engine started off as if it had always been running, and continued to do so until the signal for shutting down at 5 o’clock. I had my hand on the wheel of the stop-valve to close it, when suddenly all the valve-rods of the engine bent and tangled up, and the exclamation was heard on all sides, “The high-speed engine has come to grief the very first day.”