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[TRANSACTIONS OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS.]

FRICTION AS A FACTOR IN MOTIVE-POWER EXPENSES.

BY PROF. JOHN E. SWEET, SYRACUSE, N. Y.

Read at the Annual Meeting, 1880.

The honor of reading the first paper before this Society having been conferred upon me, my greatest regret is that I am not better prepared to do honor to the high compliment.

The two classes of papers that will prove most valuable to the Society are those that present new discoveries or inventions, and those that call forth general discussions upon subjects of universal interest.

Not having anything new of sufficient importance to form the subject of a paper, a topic has been selected that must, more or less, interest all; and which, it is hoped, will call forth some discussion, or bring out the thoughts and experiences of those who have spent a lifetime in the study of steam engineering.

Friction as a Factor in Motive Power Expenses, has been taken as the title of this paper. Not that you are to be treated to an essay upon the subject, but simply as an excuse for presenting my thoughts and experience in steam engine experiments, which have all tended toward economy by reducing friction, and consequently, maintenance and repairs.

Great economy in the use of fuel has been accomplished within the last twenty or thirty years by following, in a proper way, the paths laid out by the engineers a half century before.

Increased pressure; increased expansion-cut-off controlled by the governor-compounding; surface condensation; the steam jacket and high-speed. Many of these improvements were predicted. years before, but remained unperfected till recent times.

Notwithstanding the fact that two or three of the old slide-valve engines of our forefathers are still running to every one of all other kinds, yet we must honor George H. Corliss for the great revolution he has been, more than any other one man, instrumental in creating. And, too, we must sooner or later, and Mr. Corliss with us, bow reverently to Charles T. Porter for proving that sound engi

neering and perfection of workmanship render high speed possible, safe and profitable.

Without aspiring to the advancement of any new principle, or assuming to possess full knowledge of the principles that govern the action of steam, I have expended a good deal of thought upon the steam engine, but always as a machine. Accepting the principle that an automatic cut-off and high speed were settled advantages, I have worked to design an engine as I would to design any other piece of mechanism.

That is, to use the fewest necessary parts; to put them in the best form, and to make the machine durable, which of itself implies, as free as possible from friction.

Having worked up to this friction question from the other way, and becoming biased in my convictions, I now state boldly what to many may probably appear absurd.

Of two roads, one offering a saving of ten per cent. by a reduction in friction, and the other a saving of twenty per cent. in the use of steam, I should take the road which leads to a saving in friction; which of necessity implies an additional saving in maintenance, attendance, repairs, and, above all, saving the loss occasioned by delays.

The percentage of loss by attendance, repairs and delays, is far larger in small engines than in large ones; and it is to the small engines that I have directed my own, and to which I wish to call your attention.

Generous wearing surfaces, accurately fitted and properly lubri cated, are pretty commonly supposed to be all that is necessary to secure freedom from friction; but absolute alignment is a factor of equal importance, and absolute alignment implies many considerations, some of which never occur to many designers of machinery.

A shaft, set in perfect line, when at rest, and deflected by the strains put upon it while at work is not in line. And a journal that is so long as to spring within its own length has not only its own alignment destroyed, but its generous wearing surface also.

It will be seen by the sketches of details that I deviate in many particulars from what is believed to be the best practice of the best engineers; but in no particular so radically as in making certain portions rigid and weak, rather than strong and elastic. These may seem contradictory terms, but they are not.

Fig. 1 shows a plan of engine framing that promises to secure perfect alignment during the life of the engine.

The strain is resisted by the diverging arms, running in a direct line from cylinder to the main bearings. The main bearings being equally loaded, cannot wear down unequally, and the whole structure resting upon three self-adjusting supports, stands a fair chance of remaining true for all time, if made so originally.

The fly-wheel is split through from side to side, and the crank placed between the two halves (the bosses of the two half wheels making the throws of the crank). Thus making a built up crank, which locomotive and steamship practice has proven to be a better method than that of cutting them from a solid forging. Aside from this manner of construction, there is an advantage in thus putting the wheels within the frame.

The power is applied to the wheel without going through the main bearing, and the counter weight, acting directly, does not tend to bend the main shaft. To explain: Imagine the main wheels to be outside the framing, and counter weighted to balance the crank and reciprocating parts. Then the force of the steam acting in one direction, and the counter-weights acting opposite, the strain tending to bend the shaft in the bearings would be greatly increased. Again, if a counter weight be used in a disc crank of the overhanging kind, the shaft will at each revolution be lifted from its seat; or, in other words, the disc crank, tending to revolve around its center of gravity, will cause the shaft to be worn wholly on one side; while in the form shown, the entire weight of the shaft, crank and wheels tends to hold the shaft down, and the engine would run without danger, if the shaft was mounted in the classical crotched sticks, if they were only strong enough to sustain the weight.

Fig. 2 shows a section through the cylinder and throttle valve. The throttle valve is the invention of John Coffin, and has these meritorious points. A straight-way opening; an opening that has a good form when full open, half open, or nearly closed; and neither the valve nor the seat is exposed to the action of the steam when open, nor the action of corrosion when closed. It consists of a circular disc A, turning upon a circular seat B, with a like opening through each. A segmental rack on the disc, a pinion and shaft within the casing and hand wheel outside, complete the device. The piston, as will be seen, is very long and light, which gives a large wearing surface in proportion to the weight; prevents the piston from ricocheting through the cylinder, and requires less severe packing to prevent the leakage of steam. This form leaves but a narrow wall of metal in which to secure the piston rod, and that is made fast in a novel manner. The hole is conical at each end, and has a parallel thread in the center; into this hole the rod is screwed, while the piston is red hot. The conical shoulders prevent the rods being forced in, the thread from being drawn out, and the shrink fit from unscrewing. The rod, instead of being parallel, as is usual, is reduced at each end; for the same purpose cylinders are counter bored. This reducing the ends of the rod serves another purpose. Whatever spring may occur will be sure to take place within the

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