File:The Civil engineer and architect's journal, scientific and railway gazette (1839) (20466355458).jpg

Title: The Civil engineer and architect's journal, scientific and railway gazette
Identifier: civilengineerarc04lond (find matches)
Year: 1839 (1830s)
Authors:
Subjects: Architecture; Civil engineering; Science
Publisher: London : (William Laxton)
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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414 THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. TDeckmber,
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ON CONSTRUCTION. It is our intention to give occasionally some examples of construc- tion which will be found useful to the student. The annexed engrav- ings show the construction of the Roof over the Polytechnic Institution at Vienna; unfortunately the work (the AUgemehie Bauxeitmig), irom which we take the drawing, contains but a meagre description of its construction, without any reference to the scantling of the timbers ; we can therefore only form out opinion of what they ought to be from the geometrical view before us. It is stated that the roof stands remark- ably firm ; the span is 56 feet, and the rise of the arch 18 ft. 6 in. above the chord bar; the curvilinear ribs or principals are placed 12 feet apart, and are 12 inches in depth, of pieces of timber ia 4 feet lengths which are laid side by side in thicknesses so as to break joints; we should apportion three thicknesses of two inches each; upon their ribs are laid the purlins 6 by 5 inches, which carry the rafters 4 inches deep by 2i inches placed 3 feet apart; upon the rafters is laid the copper covering. The roof is very much stiffened by the braces 6 by 3 inches on each side of the ribs, and horizontal ties of the same scantling bolted to the ribs and feet of rafters; and also caulked down to the pole plates, there are two plates G inches square, one lies on the wall, and the other is supported by vertical posts under each rafter; there are also two wall plates each 5 by 5 inches, the wall plates and the foot of the curved ribs ought to be well secured to a cross tie either of timber about 12 by 4 inches, or a wrought iron tie li inch diameter. The tie beam would also answer the purpose of girders to carry the floor—if it be desired to continue the curvilinear form throughout the roof, horizontal ceiling joists 4 by 2 and 12 inches apart might be notched and nailed on to the front edge of the ribs, the laths could then be easily bent to the form of the curve and plastered in the usual way; to give the room a pleasing effect, it may be lighted by means of sky-lights in the upper part of the roof, and the centre of the curved ceiling formed into circular sashes and glazed with ground, stained or embossed glass. Fig. 1 is a section of one half of the span of the roof drawn to a scale of a quarter of an inch to the foot. Fig. 2 is an enlarged view of the purlin secured to the ribs by the iron straps Fig. 3. A NEW SAFETY VALNE, Sir—It appears to me that the comer in your Journal which was last month occupied by " Funnel," has been filled up but in an indifferent way; I really can see no object in attempting to arrive at a simple end by means of a very circuitous route; what possible advantage can the complicated arrange- ment of compensating bars, cylinders and radiating arms have over the beau- tiful, and I may say perfect inveation already in use ? Mr. Funnel should have fixed a cog-wheel at the end of each arm, and a cam to each leg by way of giving his safety-valve a truly eccentric character, and on such he might have grounded its merits, as it is one feels greatly at a loss to ascertain the object of this funny discovery : however, as I hope to spared being levelled to a Caudidus, so must I eschew the ways of that worthy, and by setting all banter apart, must merely venture to suggest that Mr. Funnel would do well to enter into such an explanation of his valve as would tend to estabhsh its superiority, or else by screwing it down to oblivion, would acknowledge tacitly or otherwise, that after all his invention is nothing more than what our mutual friend of the Fasciculi might coll " a mare's nest." Believe me. Sir, to be, with respect, Pluc. .Voiemier 22. 1841.

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