Mr. Freeland taught me the secret of producing true cylindrical surfaces by grinding with a wheel. It was to let the swiftly revolving wheel traverse the surface as it rotated, touching only the highest points, and these very lightly. This avoided the danger of errors from the springing of either the piece or the wheel, which under strong pressure is sure to take place to some extent, even in the best grinding-machines. I have found this delicacy of touch to be a most difficult thing to teach the ordinary workmen. They often manage to produce by grinding a surface more imperfect than it was before.
I took extreme pains to insure that the axes of the joint pins should intersect the axis of the governor spindle and those of the governor balls, and should be equidistant from the center of the counterpoise, these parts of the joints having been turned to true spherical forms by means of a circular tool-rest. For this purpose I employed a feeling-gauge, consisting of a cylindrical stem fitting the hole as drilled, with a curved arm projecting from this stem and terminating in a point that would rub on the external surface of the balls. By this means we almost always detected some slight inaccuracy, which was remedied by the use of a round file. The joint holes were afterwards finished with long reamers, the cutting portion of which was in the middle of their length. The front end of the reamer fitted the drilled hole and extended quite through the joint, so guiding the cutting edges as they entered, and the back end of the reamer filled the hole that had been reamed.
I finally tested their alignment by bringing the last of the five joints together after the others had been united, when the forked link should swing freely to the ball without the least tendency in either direction from its exact place. This it always did.
Some time afterwards I adopted the plan of dispensing with heads and washers on the joint pins, reaming the holes in the central portions of the joint slightly smaller than those in the arms and making the pin a hard fit in the former. There was never any tendency for a pin to get loose in the running of the governor. I also at a later date cut the counterpoise in two a short distance above the joints, so that the mass of its weight did not need to be started and stopped when the speed of the governor changed. I could not see, however, that this was of any advantage, although when the governor balls were pulled around by hand no motion was imparted to the mass of the counterpoise. The action was apparently quite perfect before.
CHAPTER III
Invention and Application of my Marine Governor.
I was anxious from the first to produce a governor capable of being used on marine engines—which the governor already described could not be, as it needed to stand in a vertical position—and also one that should be free from the limitations of the conical pendulum. I gave a great deal of study to the subject, and after worrying about it—I am ashamed to say how long, for the principle when once seen is found to be exceedingly simple, being merely maintaining a constant ratio between the compression of the spring and the radius of the circle of revolution of the balls—I finally perfected my marine governor and tried it in my shop, running it from a hand-driven pulley, and found it perfectly isochronous. It was capable of being adjusted to be as nearly isochronous as we thought expedient consistent with stability of position.
This governor is represented in the [cut] that follows. The motion imparted was small, from ³⁄₄ to 1¹⁄₂ inches in the different sizes, but the governor was very strong. The balls are shown half expanded. Before expansion their circle of revolution is 10 inches diameter; when fully expanded it is 15 inches diameter; increase in diameter, and so in centrifugal force, 50 per cent. The spring has an initial compression given by the nut of 2 inches; additional compression imparted by the expansion of the balls, 1 inch, giving an increase of 50 per cent. in the resistance. So in every position of the balls the two forces are in equilibrium, at a constant number of revolutions per minute.
My friend Mr. McLaren had the job of making repairs on the vessels of the newly started North German Lloyd Line, and feeling confident that my governor was what that line needed very much, he obtained from the agents in New York an order for me to put one on the steamer “New York” on a guarantee of perfect performance. This was the first steamship of this line. The chief engineer of the vessel, an Englishman, Mr. Sparks, told me in conversation that I could have no idea how anxious they were in the engineering department for my governor to be a success, because they had to throttle the ship by hand, and it seemed sometimes as though their arms would drop off before the end of their watch; but he was sorry to say that I could not do it, and he would tell me why. “We know when the screw is coming out of the water by the rising of the stern of the vessel, and we shut the steam off beforehand, and so when the stern goes down we know that it is going down into the sea and admit the steam to the engine beforehand. Now, your governor cannot tell what is going to happen. It cannot act until a change of motion has taken place which will be too late, and so I am sorry to say that you cannot succeed.” But in spite of his want of faith I obtained authority to attach the governor.