1849.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



57 



TUBULAR BRIDGES. 



Description of the Tabular Beam Bridge on the Carmvnnock Boad, 

 over the Polloc and Goran Railway. Erected by Andrew Thomp- 

 son, Esq., Eiiffineer, of Glasgow, in ISIO. — (Paper read by T. L. 

 Donaldson, Esq., at the Royal Institute of British Architects, 

 January 22nd.) 



The Carmunnock Road, near Glasgow, passes over the Polloc 

 and Govan Railway, askew, by means of a beam bridge. The 

 width from outside to outside of parapet is 25 ft. 6 in. ; the total 

 length from one extreme to the other of the abutment-walls about 

 93 feet. The aperture for the railroad is 30 feet in the clear, taken 

 at right-angles to the axis of the railroad ; but taken on the face 

 of the bridge is 31 ft. 6 in. The walls which support the iron gir- 

 ders are 3 ft. 6 in. thick, constructed of stonework, faced with fair 

 ashlar of hammer-dressed course-work, ^th of the facework being 

 headers. The ends of these walls are strengthened by the wing 

 retaining-walls ; and there are four intermediate abutments or 

 counterforts, 2 feet wide, and projecting 3 ft. 3 in. One coming 

 under each girder, these walls rise to a height of 19 feet ; and im- 

 mediately under the beams is a course of ashlar 3 feet broad in the 

 bed, and 1 foot thick. There is a wrought-iron plate bolted down 

 to the course of ashlar just mentioned, to receive the feet of the 

 tubular beams, which are six in number, being 5 ft. 1^ in. apart 

 from centre to centre, and 35 ft. 3 in. long. They ai;e constructed 

 of the best boiler-plate, f inch thick, and measure 3j inches wide 

 in the clear at top, and 6 inches in the clear at bottom, and are 18 

 inches deep (as shown in the annexed engraving, drawn to a scale 

 of I inch to a foot). The upper and lower plates are 6 inches 

 wider than the beam, the 3-inch projection on each side being for 

 the purpose of receiving the angle-irons of f plate, with a bearing 

 width of 3 inches against the side and upper and lower plates, to 

 which they are attached by rivets ^ inch in diameter, square-headed 

 on one side and rivetted over on the other, spreading to 1 inch in 

 diameter. They are Ig inch apart from centre to centre. The 

 beams are filled in solid with concrete to render them unyielding 

 and rigid, and are tied together by § cross-bars of Low-Moor iron, 

 3 inches wide, attached by bolts to x -irons, which are rivetted to 

 the sides of the tubes. 



Fig. 1. — Shotting two of the Girders and Brick Arch between. 



Fig. 2.— Plan of Girders andTye. 



The beams being thus framed together, the spaces between them 

 were filled in with two 9-inch courses of arched brickwork, having 

 a rise of 1^ inch at the centre in a space of 3 ft. 2 in. The crown 

 of the arches was paid over with hot tar, upon which was a layer 

 of well-wrought clay puddle, well rammed down. Over the clay 

 there was a coating of Whinstone metal, to form the road, covered 

 with a binding course of engine-ashes, 2 inches thick. The hori- 

 zontal rusticated arch-faces are of cast-iron plates, f thick, bolted 

 to the outside beams, and cast in three lengths. The parapets are 

 of hammer-dressed stonework, each alternate course going through 

 the whole thickness. There is a foot pavement on each side of 

 the bridge, 4 feet wide, with gutters laid between it and the road- 

 way. 



This bridge was constructed for AVilliam Dixon, Esq., the emi- 

 nent iron-master of Glasgow, to whom the raiLoad belonged. 

 That gentleman has the most important foundry called the Govan 

 Ironworks, at Glasgow. The communication between the furnaces 

 is by means of platforms resting on tubular beams, slightly differ- 

 ing from those just described. The bearing between the furnaces 

 is 33 feet. The beam is composed of f plate, the depth 19 inches 

 in the dear ; the width, which is the same at top as at bottom, is 

 7 inches in the clear. The bottom plate is secured to the side 

 plates by inner angle-irons with ^ inch rivetted bolts, 25 inches 

 apart from centre to centre. The side plates rise 2^ inches above 

 the top plate, for the purpose of receiving the outside angle-irons, 

 which secure the top plate to the sides, and to which it is rivetted 

 in the same manner as the bottom. Each side of the angle-irons 

 is 2i inches wide. Two or three of these beams form the supports 

 for the platform, which connects the summit of one furnace with 

 the other. 



There have been recently brought before the notice of the pro- 

 fession so many schemes for the construction of beams for support- 

 ing floors, in order to avoid the various casualties to which cast- 

 iron is liable, and at the same time to produce less depth in the 

 flooring and greater lightness in the weight, that the considera- 

 tion of' the construction of the above-described bridge, which 

 was erected nine years since, is at once instructive and interest- 



FREE-ACTION PUMP FOR COFFERDAMS. 



We copy the following description of a pump from the Railway 

 Chronicle. It has been tried lately in one of the cofferdams at the 

 bridge over the Trent, now in the course of construction upon the 

 Great Grimsby and Sheffield Junction. The principal features in 

 the invention are — that the action of the pump i: independent of 

 the contact of any two solid rubbing substances: — that it is not 

 subject to the derangement to which other pumps are liable, 

 in which water-tight joints of one kind or another are required, 

 and upon the perfection of which, universally, their effectual 

 working, and in many cases, their actual working depends: — that 

 it can he used in engineering works where ordinary pumps would 

 be choked: — and that it can be constructed wholly of wood, in a 

 short time and at a trifling cost. The accompanying sketch shows 

 a section of the one that was tried, and 

 which discharged as much water (working 

 at fourteen strokes per minute) as a 12- 

 inch circular suction-pump. The working 

 part was below the surface of the water 

 on starting the pump, although when once 

 at work it would continue to draw water 

 until the surface fell below the bottom of 

 the main. The bucket, which was a square 

 wooden tube, closed by a common flap- 

 valve at the top, was suspended by a 

 wooden rod connected with the rocker 

 above, and worked within another wooden 

 tube 10 inches square inside, open at the 

 top and constituting a main 26 feet long. 

 The bucket worked clear of this main, 

 about l-16th of an inch on every side, 

 and was 3 feet long. About 8 inches or 

 10 inches from the bottom of the main, 

 another valve was inserted, which, toge- 

 ther with that in the bucket, opened up- 

 wards. The stroke of the pump was 4 feet. 



The mode of action is clear. As the bucket rose, the water 

 rushed in at the lower valve, and by this means every up- stroke 

 raised the surface within the main, a certain amount — the motion 

 of the bucket and the supply through the lower valve being too 

 rapid to admit of the escape of any significant quantity of water 

 between the bucket and the main. The experiment was exceed- 

 ingly satisfactory. The pump lifted sand and gravel in considera- 

 ble quantities, and though scored by the same in the immediate 

 neighbourhood of the bucket, its action was not in the least im- 

 paired. 



