Carpentry made easy, or, The science and art of framing, on a new and improved system : with specific instructions for building balloon frames, barn frames, mill frames, warehouses by Bell William E

Author:Bell, William E
Language: eng
Format: epub, pdf
Tags: Carpentry, Bridges
Publisher: Philadelphia : Howard Challen
Published: 1857-03-25T05:00:00+00:00

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Plate 15.

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PLATE 15.

CIRCULAR CENTRES.

Plate 15 exhibits several designs, more or less convex, for the construction of centres, which are skeletons used by stone and brick masons to build an arch upon, but which are to be taken away when the arch is sprung and the mortar set.

First, draw the line AB upon a floor, two inches less than the width of the skeleton required, and take OA as a radius, and describe the semi-circumference. Inch boards are then to be fitted to this curved line, and their ends beveled to fit each other, as represented in the Plate. The bevel is determined by simply drawing a straight line from any point of the curve to the central point 0. Other boards are then to be nailed over the joints, on the inside of these ; and the long brace AB nailed at each end at the bottom.

Uaving prepared the other end of the skeleton in the same manner, strips of boards, an inch thick, two inches wide, and of a length equal to the thickness of the wall, are nailed upon their convex edges, as represented.

Should the arch have more than 12 feet span, it would be proper to use thicker boards; but for any thing less than 12 feet, inch bv.arda are amply sufficient.

(67.

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