GAS-HOLDERS.
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Five secondary bearing-bars, 3 inches by 3 inches by f-inch T-iron, to be fixed at one end to theouter angle-iron curb with 1-inch bolt and nut, and at the other end with a T-end formed by twopieces of flat iron riveted on to the end of the bar with three f-inch rivets and butting against the4-iuch by 3-inch bracket-bar, to which it is to be secured by two f-inch bolts.
One ring of 2f inches by 2f inches by f inch bracket-iron to be secured to each main andsecondary bearing-bar by 2f-inch bolts at each end, and one strong ring of bracket-bars 4 inches by3 inches by f inch, bolted at each end by two f-inch bolts to the main rafters. The whole of thebrackets and bars to be cambered so as to set the crown full out.
The above comprises the framing for supporting the roof of the gas-holder, which roof is to becomposed of one crown-plate of f-inch boiler-plate 3 feet 6 inches diameter. The inner and outerrings of plates to be of No. 12 gauge and the rest of No. 14 gauge. The top and sides to beattached to each other by a ring of angle-iron 4 inches by 4 inches by f inch. The top and bottomrows to be of No. 12 gauge, and the rest of No. 17 gauge. Five vertical bars of T-iron 2f inchesby 2f inches by f inch to be secured to the main bearing-bar and bottom curb. The bottom of theangle-iron to be formed of two bars of 3 inches by 3 inches by f-inch angle-irou riveted back to back,with f-inch rivets one foot apart, with the bottom of sheet-iron in between. The whole of thesheet-iron, where attached to the angle-iron or to the crown-plate, to be riveted with f-inch rivetsnot farther apart than If inch from centre to centre; the remainder of the sheets to be attached toone another by rivets yV inch diameter, for the Nos. 12 and 14 gauge sheets, and f inch diameterfor the No. 16 gauge. None of the sheets to exceed 3 feet 6 inches in length by 2 feet in width, allto be perfectly sound and free from cold sheets and scales. The No. 12 gauge plate not to weighless than 43 lbs.; the No. 14 gauge not less than 323 lbs., and the No. 16 not less than 262 lbs.per square foot.
A hempen string to be placed between the joints of the plates and between the joints of the platesand the angle-iron. The whole of the wrought-iron work to be well done over with boiled oil, andall the joints to be painted twice with red-lead and oil. The gas-holder to be provided with twoman-boles in the roof, each one to be 2 feet square and to have a 2-inch gun-metal cock fixed in thecrown-plate.
The guides for the gas-holder to consist of five cast-iron columns, each 22 feet long, 7 inches out-side diameter at the bottom and 5f inches at the top; the metal to be uniformly -j-f inch thick. Atongue to be cast on of uniform thickness and quite free from any inequalities or windings, as it isfor the guide-wheels to run against. The base of each column to be secured by four wrought-ironbolts, of If inch square iron; with screws 9 inches long at the top and If inch diameter, andhexagonal nuts and washers for tightening them down ; they are to be each 16 feet long.
There are five open sand foundation-plates If inch thick with four bolt-holes to correspond withthose in the base of the columns. These plates to be 3 feet 6f inches by 3 feet 6 inches square.Five guide-wheels in sliding-carriages, each bolted to the top angle-iron curb with two f-inch bolts,and secured to the main bearing-bars with a piece of flat iron 5 inches by f-inch and two f-inchbolts. Also five diagonal strutts of angle-iron 3 inches by 3 inches by f inch, attaching the fivevertical T-iron bars to the five main bearing-bars, each to be fixed with two f-inch bolts. Eachstrutt must be blocked out with a washer so as to clear the tie-bar. The tops of the guide columns,to have each a small cast-iron ornamental vase. They are also to be connected to one another byfive bars of T-iron 3 inches by 2f inches by f inch, forming in plan a regular pentagon, and se-cured at each end to the column by a 1-inch bolt tapped into it. To the lower curb of angle-ironthere are to be attached fixteen cast-iron rollers and wrought-iron carriages placed equidistant roundthe curb, and each to be bolted thereto by two f-inch bolts and nuts; the rollers to be 4 inchesdiameter in the centre and 4 inches long.
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