Читать книгу The Modern Clock. A Study of Time Keeping Mechanism; Its Construction, Regulation and Repair онлайн

45 страница из 100

The holes at the lower extreme of combination 5, 6, 7, 8, 9 are for adjustments in effecting a compensation.

The pin at 10 is the steel adjusting pin, and is only tight in the front bar and zinc bars, being loose in the back bar.

O and P show the angles in the back rod, T shows the angle in the rod at the top, m shows the pin as placed in the iron and zinc sections where they have been soldered as described.

h shows the regulating nut carried by the tube, as described, and terminating in the nut D.

l and i show the screw of 36 threads.

The nut D is to be divided on its edge into 30 divisions.

n is the angle of the back bar to which zinc is soldered.

Flat Compensated Rod.—One of the most easily made zinc and iron compensating pendulums, shown in detail in ssss1, is as follows: A lead or iron bob, lens-shaped, that is, convex equally on each side, 9 inches diameter and an inch and one-quarter thick at the center. A hole to be made straight through its diameter ½ inch. One-half through the diameter this hole is to be enlarged to ⅝ inch diameter. This will make the hole for half of its length ½ inch and the remaining half ⅝ inch diameter. The ⅝ hole must have a thin tube, just fitting it, and 5 inches long. At one end of this tube is soldered in a nut, with a hole tapped with a tap of thirty-six threads to the inch, and ¼ inch diameter, and at the other end of the tube is soldered a collar or disc one inch diameter, which is to be divided into thirty divisions, for regulating purposes, as will be described later on. The whole forms a nut into which the rod screws, and the tube allows the nut to be pushed up to the center of the diameter of the bob, through the large hole, and the nut can be operated then by means of the disc at its lower end. The rod, of flat iron, is in two sections, as follows: That section which enters the bob and terminates in the regulating screw is flat for twenty-six inches, and then rounded to ½ inch for six inches, and a screw cut on its end for two inches, to fit the thread in the nut. The upper end of this section is then to be bent at a right angle, flatwise. This angle piece will be long enough if only ³⁄₁₆ inch long, so that it covers the thickness of the zinc center rod. The zinc center rod is a bar of the metal, hammered or rolled, 25 inches long, ³frasl;₁₆ inch thick, and ¾ inch wide, and comes up against the angle piece bent on the flat part of the lower section of the rod. Now the upper section of the rod may be an exact duplicate of the lower section, with the flat part only a little longer than the zinc bar, say ½ inch, and the angle turned on the end, as previously described. The balance of the bar may be forged into a rod of ⁵⁄₁₆ inch diameter. As has been stated, the zinc bar is placed against the angle piece bent on the upper end of the lower section of the rod, P, n, ssss1, and pins must be put through this angle piece into the end of the zinc bar, to hold it in close contact with the iron bar. The upper section of the rod is now to be laid on the opposite side of the zinc bar, with its angle at the other end of the zinc, but not in contact with it, say ¹⁄₁₆ inch left between the angle and the zinc bar. Now all is ready to clamp together—the two flat iron bars with the zinc between them. After clamping, taking care to have the pinned end of the zinc in contact with the angle and the free, or lower end, removed from the other angle about ¹⁄₁₆ inch, three screws should be put through all three bars, with their heads all on the side selected for the front, and one screw may be an inch from the top, another 3 inches from the bottom, and one-half way between the two first mentioned. Now the rod is complete in its composite form, and there is left only the little detail to attend to. Two flat bars, with their ends angled in one case and rounded in the other into rods of given diameter, confining between them, as described, a flat bar of wrought zinc of stated length and of the same thickness and width as the iron bars, comprises the active or compensating elements of the pendulum’s rod. The screws that are put through the three bars are each to pass through the front iron bar, without threads in the bar, and only the back iron bar is to have the holes tapped, fitting the screws. All the corresponding holes in the zinc are to be reamed a little larger than the diameter of the screws, and to be freed lengthwise of the bar, to allow of the bar’s contracting and expanding without being confined in this action by the screws. At the lower or free end of the zinc bar are to be holes carried clear through all three bars, while the combination is held firmly together by the screws. These holes are to start at ½ inch from the end of the zinc, and each carried straight through all three bars, and then broached true and a steel pin made to accurately fit them from the front side. These holes may be from three to five in number, extending up to a safe distance from the lower screw. The holes in the back bar, after boring, are to be reamed larger than those in the front bar and zinc bar. These holes and the pin serve for adjusting the compensation. The pin holds the front bar and zinc from slipping, or moving past one another at the point pinned, and also allows the back bar to be free of the pin, and not under the influence of the two front bars. The upper end of the second iron section is, as has been mentioned, forged into a round rod about ⁵⁄₁₆ inch diameter, and this rod or upper end is to receive the pendulum suspension spring, which may be one single spring, or a compound spring, as preferred.