1 8 tS. 



THE CIVIL ENGINKKR AND ARCHITECT'S JOURNAL. 



161 



THE CONWAY TUBULAR BRIDGE. 



CWith Engravingx, Plate VIII.) 



The ^'eat engineeriiiff event for 1848 is the raisinsf of the Conway 

 Tubular Bridg-e, and which after so niucli fear and anxiety has 

 been effected with great success. This work derives its importance 

 not so much from its greatness, as frem its opening the way for 

 the adoption of a new system of bridge building, whereby the 

 resources of engineering are very much extended. To build a 

 bridge greater than those which have been made before, to make 

 a railway longer than those which have yet been opened, or to 

 construct a more powerful locomotive, is a great work; but it is of 

 very much greater importance to execute something entirely new. 

 Tlie engineer wlio has constructed tlie greatest lighthouse or tlie 

 greatest dock in his day, may be o\'ercome by some one else, and 

 then his claim is at an end ; whereas the engineer who extends the 

 resources of his art, has a clear and uni(|ue claim to distinction. 

 Mr. Robert Stei)Iiensoii lias the merit of carrying out tliis system 

 of tubular bridge building, and it will be a special event in his 

 career, beyond tlie many vi-orks of constructive skill he has already 

 produced. The success of the Conway bridge is none the less 

 important, because it settles the practicability of that greater 

 undertaking, the Menai Tubular Bridge. Thus progress in any 

 one direction leads most certainly to greater exertion ; and it is 

 peculiarly necessary to give every encouragement to all Jittempts, 

 wliioh open a new career for the engineer, and give him greater 

 means of exertion. 



We are glad to learn that the trials hitherto made within the 

 tube with locomotives have been successful, though we have not 

 had the opportunity of personally investigating the real progress 

 of the undertaking. We shall, however, watch it with interest 

 and attention, to see how far its continued working justifies tlie 

 opinion which has been entertained of its success : at the same time, 

 we may say we do not participate in the fears which are enter- 

 tained by some of our mathematical correspondents. 



W^e have this month given engravings of the tube, and the lifting 

 apparatus, and next month we propose to lay before our readers 

 drawings of the ingenious Jacquard machinery invented by 

 Messrs. Roberts, for punching the plates. 



The construction when finished is to consist of two tubular 

 bridges, formed of wrought-iron plates, each tube being for one 

 line of rails. AV^e shall now confine ourselves to the description of 

 one of the tubes, which was fixed in its place in March last, and is 

 shown in the accompanying engravings, Plate VIII. 



Fig. 1 exhibits a transverse section of one of the tubes and 

 the masonry of the pier, together with the lifting apparatus. 

 Fig. 2 is a side elevation of 19 feet in length of the tube, resting 

 on the masonry, and the lifting apparatus. Fig. 3 is a section 

 through 12 feet in length of the tube, and section of the lifting appa- 

 ratus. Fig. 4 is a plan of the top of the tube to the extent of 20 

 feet in length, and plan of the hydraulic press. Fig. 5 is a front 

 view of one end of the suspension girder, and fig. 6 a side view. 



The tube consists of a shell or external casing, a, a, of wrought- 

 iron plates, from 4. to 8 feet long and 2 feet wide, by i-inch 

 thick in the centre, and |ths of an iiicli tliick towards the end of 

 the tube, rivetted together to T-angle-iron ribs, placed on both 

 sides of the joints, and angle-gussets at the feet of the ribs to 

 stiffen them; a ceiling, composed of 8 cellular tubes A, each 20} 

 inches wide, and 21 inches high ; and a floor containing 6 cellular 

 tubes c, 27i inches wide, and 21 inches high. The whole length of 

 the tube is 412 feet, and 22 ft. 3| in. Iiigh at the ends, and 2.5 ft. 

 6 in. high in the centre, including the cellular tubes at to]i and 

 bottom, running the whole length, and 14 feet wide to the outside 

 of tlie side plates. The upper cells are formed of wrought-iron 

 plates, |-inch thick in the middle, and ^-inch thick towards 

 the ends of tlie tulie, put together with angle-iron in eacli angle 

 of the cells ; and over the upper joints is rivetted a slip of J-inch 

 iron, 4i inches wide. The lower cells consist of f-inch iron 

 plates for the divisions, and the to]) and bottom of two tliick- 

 nesses of plates, each 12 feet long, 2 ft. 4 in. broad, and ^1-incli 

 thick in the centre, and i-inch thick at tlie ends, and so arranged 

 as to break joint ; and a covering plate of -j-inch iron, 3 feet long, 

 is placed over every joint on the underside of the tube. Tiie 

 external casing is united to the top and bottom cells by angle-iron, 

 on both the inside and outside of the tube, as shown in fig.6. 



The ends of the tube, where it rests on the masonry, are 

 strengthened by cast-iron frames rf to the extent of 8 feet of the 

 lower cells ; 6 cast-iron transverse I-shaped girders e, on the floor; 

 6 similar girders j\ above ; and upright cast-iron stanchions </, on 

 each side of the tube, to which are bolted the ends of the girders, 

 top and bottom, and also the cross liftiug girders h. 



No. 129— Vou SI.— June, 184S. 



In order to allow of the free expansion and contraction of the 

 tube, the ends rest on 24 pairs of iron rollers ;, connected together 

 by a wrought-iron frame, and placed between two cast-iron plates 

 /, fr, 12 feet long by 6 feet wide, and 4 inches thick. The lower 

 plate is laid on a flooring of 3-inch planks /, bedded on the stone- 

 work ; and the tube is also suspended to 6 cast-iron beams m, the 

 ends resting on longitudinal bearers », 12 feet long, with a circular 

 groove on the underside, supported by 12 gun-metal balls o, 



6 inches diametei", standing upon an iron bed p, and supported on 

 the ends of the cast-iron bearers 7. The tubes are suspended to 

 the beam ;», by wrought-iron bolts }■, and spade-pieces rivetted on 

 to the sides of the tube, as shown in figs. 5 and 6. 



The lifting apparatus for raising this enormous weight was en- 

 trusted by Mr. Stephenson, to Messrs. Easton and Amos, engineeis 

 of the Grove, Southwark, to whom great credit is due for tlie very 

 successful manner the tube was lifted. The machinery consisted of 



2 steam-engines, erected in the recesses B, of the corresponding 

 tube, one on each side of the river ; and each engine has a horizon- 

 tal cylinder, 17 inches diameter, and 16 inches stroke, with piston- 

 rods working thi-ough stuflSng-boxes at each end of the cylinder; 

 eacli piston-rod has a cross-head, and gives motion by side-rods 

 and cranks to two fly-wheels ; and the ends of the two piston-rods 

 work 2 forcing-pumps with plungers, 1 ,'-j inch diameter, and 

 16 inches stroke. These pumps inject the water into the hydraulic 

 press C, shown in the engraving, through the small tube (3V 



The press was erected on a stage constructed above the level of 

 the to]) of the tube, and consisted of two cross-girders of cast- 

 iron, eacli in two heights D, D', the lower one 4 feet high, and the 

 upper one 2 ft. 6 in. high ; the ends resting upon cast-iron bearers E, 

 imbedded in the masonry of the piers. Upon the cross-girders 

 was fixed the casing F, of the ram, which is 5 ft. 2 in. long, by 



3 ft. 9 in. wide, cast with ribs ; and on the top of the cylinder are 

 fixed 2 vertical guide-rods G, G, 6 inches diameter, passing 

 upwards through the cross-head of the ram, and a cast-iron girder 

 H, nearly at the top of the tower, and 18 feet above the girders D'. 



The press consists of a cylinder (1), firmly fixed in the casing, 

 37i inches diameter externally, and 20 inches internally; and 

 the ram (2) 18g inches diameter, with a vacuity nearly | of an inch 

 all round, to receiie the water injected from the pumps already 

 described, through the tube (3), the orifice of which is | of an inch 

 diameter ; tliis tube is furnished with a lever-valve close to the 

 cylinder, for safety, in case the pipes should burst. In the event of 

 such a casualty, by an ingenious contrivance the lever- valve would 

 be instantly closed, and the weight supported by the water in the 

 cylinder. On the top of the ram is a cross-head (4), of solid cast- 

 iron, 9 ft. 10 in. long, 1ft. 10 in. deep, and 2 ft. 4 in. thick, with 

 two apertures, 2 ft. 1 in. long, by 1 ft. I3 in. wide, through which 

 the lifting chains pass ; and on the top of this cross-liead are 

 fixed two clipping vices or clams (5, 5,) each consisting of a pair of 

 wrought-iron jaws, 3 feet long, 11 inches deep, and 6 inches thick, 

 and a winch whicli turns a small pinion (6), that takes into two 

 cog-wheels (7, 7') fixed upon the heads of two horizontal screws 

 (8, 8' left and right handed) passing through nuts in tlie two jaws 

 of the clams. Thus it will be perceived, that as the wincli is turned, 

 the jaws are made to open or close, for the purpose of clipping the 

 heads of the lifting chains ; below these clams are two others (9 9'), 

 for clipping the heads of the lower links. 



The two lifting chains consist of wrought-iron flat bars, in 

 lengths of 6 feet from centre of bolt-eye to centre, and each bar is 



7 inches wide and Ig, Ij, and li inch thick, with heads having 

 shoulders fitted to the jaws of the clams. Each chain contained 

 nine links of 8 and 9 bars alternately, besides the two lower links, 

 each consisting of 5 and 4 bars. The heads of the first or upper 

 links passed through the upper lifting clams, fixed on the top of 

 the cross-head of the ram, and there secured by the jaws of the 

 clams being screwed up taut ; the second links passed through the 

 lower clam, the jaws of which were left open, and the heads of 

 the two lower links were made to abut against the underside of the 

 lifting girders, jr, h. When the pumps were set to work, the ram 

 was lifted 6 feet, its full range ; when it had attained this elevation 

 the jaws of the lower clams (9, 9'), were screwed up close and clipped 

 the heads of the third links ( 1 1 ), and there held the chain firm ; the 

 jaws of the upper clams were then opened, and the ram lowered 

 down to its original position, when the bars of the top links (lO)were 

 removed. Wlien this had been done, the jaws of the upper clams 

 (5, 5') were again brought under the heads of the second links, and 

 screwed up taut, so as firmly to clip the shoulders of the links, the 

 jaws of the lower vice (9, 9') opened, and the ram was tlien set in 

 motion to lift the tube another six feet, when the second links 

 were removed as before described, and the operation repeated as 

 above, until the tube had been lifted the height required, about 22 

 feet to 24 feet. 



22 



