[TRANSACTIONS OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS.]

PUTTING A NEW CRANK PIN IN THE ENGINES OF THE STEAMER KNICKERBOCKER.

BY LEWIS JOHNSON.

Read at the Annual Meeting, 1880.

At

In the month of March, 1876, I was called upon to put a new pin in the cranks of the steamer "Knickerbocker," belonging to the Cromwell Line of steamers, plying between New York and New Orleans. This steamer, under command of Captain Frank Kemble, had left her wharf at New Orleans on the regular sailing day, and had proceeded so far on her voyage to New York as to have reached a distance of one hundred miles from the mouths of the Mississippi river. this time, it was discovered that the crank-pin had broken entirely in two, the fracture occurring inside of the forward crank-eye, about one inch distant from the inside face of the crank. After consultation by the officers in charge, it was determined to take the vessel back to New Orleans, as it was deemed unsafe to proceed on the voyage homeward. The vessel was headed back to New Orleans under moderate speed, and it was found that while the engine was driven ahead, the inch of solid pin projecting into the eye of the forward crank carried the crank around with security. The steamer reached her wharf under steam safely, requiring the assistance of a tug in effecting a landing only.

A brief description of the cranks and pin will give a clearer conception of the job in store for me. The cranks were of wrought iron of the balanced type, each crank fast to its respective shaft, and the pin permanently fast in the after, or main, crank only. In the eye of the forward, or drag, crank, the pin was secured by means of chocks or keys, in a manner familiar to marine engineers, and shown in the accompanying drawing. The pin was of twelve inches diameter, its length between the cranks fourteen inches, and the thickness of cranks each thirteen inches, making the entire length of the pin forty

inches. I may err in some of the dimensions, as I am trusting entirely to memory in the matter, but the dimensions do not materially affect the purpose of this paper, which is merely to describe the operation of taking out the old pin and inserting the new, an operation which presented some peculiarities of probable interest to mechanical engineers.

The first step taken toward repairing the disabled machinery was the removal of the old pin. An effort was made to dislodge the chocks in the forward crank-eye by driving, but with so little success that in view of the necessity of getting the vessel to sea again with as little delay as possible, I determined to resort to a process of heating and shrinking which had aforetime been practiced on smaller scale by myself and others. Preparations were immediately made for heating the crank-ends alternately, beginning with the forward crank, that holding the chocks. The cranks were placed in a horizontal position, with the pin on the port side. A basket or crate of iron plate was erected under the crank-end for the purpose of holding the fire for heating. The body of the crank and the surrounding portions of the frame and engine were protected from the heat by plates of iron erected and secured by wire. A fire of charcoal was then started and fanned to a glow by means of hand-bellows, kept in operation by relay of hands for about six hours. During the process of heating the crank-end, all that portion of the crank, as well as the surrounding parts of engine which might have been injured by heat, were kept cool by a stream of water directed through ordinary hose.

At the expiration of the time above mentioned, the coal was removed and fire extinguished. The crown of the crank surrounding the pin was found visibly red, this symptom of heat rapidly losing itself toward the center of the crank. The stream of water was now turned on the heated crank eye, shrinking occurring rapidly on the outside of the metal and extending gradually toward the pin, which retained its heat the longest. At a certain stage in the process of cooling, the shrinkage of the crank-eye on the pin could be distinctly heard, the sound conveying the impression of some hard substance being crushed in the jaws of a powerful vise. The water was turned off after the metal had become comfortably cool, and an examination of the chocks and broken section of pin followed. These were found perfectly loose and were easily removed by hand. The after crank with its section of pin was next subjected to the treatment that the sister crank had just passed through, with like gratifying results, the section of pin being removed without difficulty. It was noticeable, during the process of cooling the cranks, that when the hose nozzle was directed to one end of the pin the water would flow easily through

PUTTING NEW CRANK-PIN IN THE ENGINES OF STEAMER KNICKERBOCKER.

3

the eye around the pin. Of course this occurred after the metal had become somewhat cool.

A measurement of the pin and the eye of the crank, after the removal of the pin, showed that the eye had been slightly increased in diameter, while the pin had been compressed; the standard of meas. urement being the body of the pin near the face of the crank, where the crank-pin boxes had effected little or no wear, and assuming the pin to have been of uniform diameter. This assumption was justified by an examination of the spare pin on board, provided for an emergency of this kind. This spare pin had been made of the same dimensions as the fractured pin, and on trial was found too small in diameter for a proper and safe fit in the now expanded eye of the after crank.

If the old pin had been drilled out, the new pin would doubtless have been of the proper size. A difficulty was here presented, that at first gave some uneasiness. It will be remembered, that the object in taking out the old pin in the manner described, was with the view of saving time; and the probabilities were that we had defeated the very object of our desires, in pursuing the plan adopted for removing the pin. I dare not entertain the idea of making an entire new pin, as the delay involved would have been provoking, as well as expensive. A little reflection, however, suggested a way out of the difficulty, which was forthwith adopted. I concluded to turn down that portion of the new pin hugged by the eye of the after crank, to a diameter of eleven and three-quarter inches, or one quarter inch less than the body of the pin, thus making the actual difference of diameters between the crank-eye and pin a trifle more than a quarter of an inch. The length of pin thus reduced was thirteen inches (the thickness of crank), and this length embraced the two fore and aft key seats already in the pin, and which corresponded in location to those in the crank-eye. Coincident with the turning of the pin, I had five welded bands forged, of iron, one-quarter inch thick, and two and three-quarter inches wide; each of these was bored out to a diameter one-sixty-fourth scant, less than the new diameter of the pin, and the edges faced to a proper width. When the pin had been turned to this new diameter, the bands were ready for use. One of the bands was then heated in a clean coke-furnace near by, the pin removed from the centers of the lathe, turned up on end, and the hot band dropped on the pin up to the shoulder left by the turning; after cooling the band the pin was again placed between centers, and a rough cut taken off the outer surface of the band; each of the remaining bands was placed on the pin and turned off-successively in like manner-and when all the bands were on, a final cut was taken off, leaving the pin with a new diameter, a scant one-sixty-fourth larger than the eye of