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

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Pendulum Supports.—Stability in the movement and in the suspension of the pendulum is very necessary in all forms of clocks for accurate timekeeping. The pendulum should be hung on a bracket attached to the back of the case (ssss1), and not be subject to disturbance when the movement is cleaned. Also the movement should rest on two brackets attached to the bracket holding the pendulum and the whole be very firmly secured to the back board of the case. Screws should go through the foot pieces of the brackets and into a stone or brick wall and be very firmly held against the wall just back of the brackets. Any instability in this part of a clock is very productive of poor rates. The bracket, to be in its best form, is made of cast iron, with a large foot carrying all three separate brackets, well screwed to a strong back board and the whole secured to the masonry by bolts. Too much firmness cannot be attained, as a lack of it is a very great fault, and many a good clock is a very poor timekeeper, due to a lack of firmness in its supports and fastenings. The late Edward Howard used to make his astronomical clocks with a heavy cast iron back, to which the rest of the case was screwed, so that the pendulum should not swing the case. Any external influence that vibrates a wall or foundation on which a clock is placed, is a disturbing influence, but an instability in a clock’s attachment to such supports is a greater one. Many pendulums swing the case in which they hang (from unstable setting up) and never get down to or maintain a satisfactory rate from that cause. This is also aggravated by the habit of placing grandfather clocks on stair landings or other places subject to jarring. The writer knows of several clocks which, after being cleaned, kept stopping until raised off the floor and bolted to the wall, when they at once took an excellent rate. The appearance of resting on the floor may be preserved, if desirable, by raising the clock only half an inch or so, just enough to free it from the floor.