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Updated: May 28, 2025
These bearings must be aligned exactly parallel to the axis of the earth, and must support the polar axis so freely that it can be rotated with perfect precision by the driving-clock, which turns a worm-wheel 17 feet in diameter, clamped to the lower end of the axis.
As will be seen from our engraving, the pillar which supports the radial arm is mounted on a massive baseplate, which also carries a circular table 6 ft. in diameter, this table having a worm-wheel cast on it as shown. This table is driven by a worm gearing into the wheel just mentioned.
The plan he adopted was to fix a worm-wheel on the side of the ladle, into which a worm was geared, and by this simple contrivance one man was enabled to move the largest ladle on its axis with perfect ease and safety. By this means the work was more promptly performed, and accidents entirely avoided. Mr.
The valve-stems extend upward through ordinary stuffing-boxes, and are attached to the notched cross-heads by means of a threaded end which is prevented from screwing in or out by a compression nut on the lower end of the cross-head. The several pairs of pawls are hung on a common shaft which receives a rocking motion from a crank driven from a worm and worm-wheel by the turbine shaft.
By means of the hand-wheel, T, and worm-wheel, n, which closes or opens the levers, BB', the pressure of the boxes upon the central roller may be adjusted at will, the spring-bolt, F, allowing a certain amount of yield. The faces of the press-boxes, MM, are covered by a curved sheet of German silver attached to the point, Y. This sheet takes the place of the press papers in the ordinary process.
As this motion must be sufficiently uniform to counteract exactly the rotation of the earth on its axis, and thus to maintain the star images accurately in position in the field of view, the greatest care had to be taken in the construction of the driving-clock and in the spacing and cutting of the teeth in the large worm-wheel.
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