1845. 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



269 



THE DRAWBRIDGE OVER THE ARUN, 



ON TUE BRIGHTON AND CHICHESTER RAILWAY. 



C With an Engraving, Plate XXI.) 



The distingnisliing cliaracteristic of niodern engineering is that it 

 never works liy general nietlioils. Now demanils on its powers are 

 being constantly made; new means of developing them are therefore 

 required ; new classes of operations arise, and these call for new me- 

 thods of effecting them. The problem of engineering is an infinite 

 one, and each of its cases requires a particular solution. Experience 

 niav, and indeed does, furnish some general ideas for the guidance of 

 the' engineer, and theoretical science will warn him from attcn)[)ling 

 physical impossibilities, but the dilTiculties of each particular case 

 with wliich he has to deal must be for the most part overcome by par- 

 ticular contrivances adapted to it alone. At present it seems quite 

 impossible to compile a general grammar of engineering. It is only 

 by recording each new case as it occurs, and by observing the degree 

 of its success that we can hope to hereafter render enginetTing a sys- 

 tematic and classified science. 



Tlie case which forms the subject of this paper is one of those in- 

 stances in v»hich pn vious rules of engineering were inapplicable, and 

 it possesses great interest, not only from its absolute novelty and ex- 

 traordinary boldness, but also from the ingenious and perfectly satis- 

 factory manner iu which the dilliculties have been grappled with and 

 overcome. 



The line at that part where this bridge is constructed, is intersected 

 bv the navigable river Arun. It was requisite in the construction of 

 the railway to provide for the uninterrupted navigation of this river, 

 which connects the important town of Arundel with the sea ; and, as 

 it would liave been impracticable to construct the railway bridge so 

 high as to allow the passage of masted vessels underneath it, it was 

 necessary to make provision for its removal when requisite. 



The means by which this object is attained may be in general terms 

 stated thus — the rai's passing over the river, and a portion of those 

 on the banks are laid on a moveable platform, which, when the trains 

 are passing, is supported on piles; but when vessels are about to 

 pass, this platform and the rails, &c. upon it are rolled back along the 

 line. In order to make room for this platform when so rolled back 

 a part of the rails of sufficient length is moved asiile, so that the plat- 

 form may occupy the space thus provided for it. It will be seen then 

 that altogether there are two moveable portions of the structure, one 

 over the river capable of being rolled back in the direction of its 

 length, the other on the ground capable of being moved laterally to 

 allow the former portion to be rolled back. These two pr^tions are 

 respectively marked in the engraving C and B. 



A is the fixed portion of the bridge G8 feet long, extending over 

 part of the river from the embankment to the opening ; and is sup- 

 ported on piles which carry four longitudinal bearers of timbers 12 in. 

 square, on the two centres of which the rails are laid: the two outer 

 carry a hand railing. 



The moveable part of the bridge from the end of A to the platform 

 C, when in use is supported on piers D and E, and on piles from E 

 to C. Ihe piers D and E are each 28 feet wide by IS feet, and con- 

 sist of piles 14 inciies square with cross beams 14 in. by 12 in. Sup- 

 ported by the pier E and the piles a is framing F, carrying transverse 

 bearers 4 14 iu. square, on which are laid four longitudinal bearers c, 

 12 in. square; the two centres of which support by a framing of two 

 other longitudinal bearers c/ of timber 12 in. by 10 in. which receive 

 the iron racks which we will explain presently. The bearers ti are 

 tied by the cross framing e, of timber (5 inches square. The moveable 

 part of the bridge B is 124 feet in length by 14 feet in width. In the 

 centre of this structure is a suspension tower. This tower consists of 

 eight vertical posts of 14 inches, two at each angle/, with a plate g, 

 at the top of them. The timbers are cased and present the form of 

 pill.isters, entablature and archway suspended from the top of the 

 tower are four irjclined ties /;, each of these ties are made of timber 

 12 inches square, in two lerrgths, and strenghtened by wrought iron 

 straps 3 inches by 1 inch. The two lengths are connected by right 

 and left handed screws at/, the purpose of which is to keep the whole in 

 a state of tension. The horizontal platform of the bridge is supported 

 by these ties, and consists of two longitudinal bearers y, on which are 

 laid transverse girders it, 12 inches square, these support the longi- 

 tudinal sleepers /, 14 inches by 7 inches, which carry the rails. The 

 hand railing is queen post trussed ; the queens m, being 12 inches by 

 9 inches, and the diagonal struts n, and horizontal plate at top o, being 

 of timber 12 inches square. 



C is the moveable pUiform which is displaced to make way for B, 

 wlien rolled back ; C is 03 feet long by 14 feet wide. 



Ko. 96.— Vol. VIH.— SEPTEuuiiR, lS-15. 



Here again we have a substructure of piles a, witli cross bearer A, 

 anil longitudinal plates c, as before. Transverse rails are laid on 

 transverse sleepers p, and on these rails run the wheels of tlie plat- 

 form when it is being moved aside. The platform consists of longi- 

 tudirral bearers 14 inches square, wliich carry the sleepers of the rail- 

 way. 



Mechanism/or moving the bridge and jjlaf/orm. 



1st. With respect to the motion of the part B. The mechanism is 

 shewn in fig. 3. Six pairs of flanged wlieels r, (J feet in diameter, per- 

 form Ihe office of rollers; their axles revolve in boxes fixed to the 

 timbers c. An inverted rail « is fixed to tin' under side of the bearer 

 ;, and runs on these wheels. Motion is communicated to the platform 

 by two men who work two crab engines at the central lower, one (m 

 each side of it. These engines consist of pinions/, 14 inches diameter, 

 working into spur-wheels ;', 7 feet diameter, keyed to their common 

 axle M, 5 inches diameter, which carries also pinions r, 12 inclies dia- 

 meter, taking into a longitudinal rack w, which extends the whole 

 length of the framing d before described. It will be seen that by this 

 arrangement the men move the bridge v\ith its tower, &c., and conse- 

 quently are themselves carried with it to the part C. The platform 

 iu its motion is guided by six friction rollers .r, with vertical axes fixed 

 on the side of the framing d. 



2nd. With respect to the lateral motion of the platform C. The 

 mechanism is shewn in figs. 5 and 5. Five pairs of flanged wheels y, 

 4 feet diameter, su[)port the platform, and run on the transverse rails 

 p. The motion is ell'ected by two fixed crab-engines z with common 

 axle at each end of which is a pinion G inches in diameter, t.iking into 

 a spar-wheel, 2 feet diameter, with pinion 1 feet diameter taking into 

 racks z'. These racks, fixed as timber shafts, 'j inches square and IS 

 feet 9 inches long, rest at one end on a roller fixed to the crab-engine, 

 and are bolted at the other end to the framing of the platform. By 

 this arrangement it will be seen that the crab-eugine communicates a 

 lateral motion lo the platform. 



Reference to Engravings, 

 F g. 1. K'cvation. 



Fig. 2. Plan uitli boanlmp; removed from one-half to show substructure. 

 FiK. 3. 'J'rinversi; section of moveable part of the bridge shuwiuj; the me- 

 chanism. 



Fig. i. Transverse section of moveable platform showing the mechanism 

 Fig. 5. Plan of the rack and crab. 



The Brighton and Chichester Railway is a continuation of the 

 Shoreham Branch of the London and Brighton Railway, and is now in 

 course of construction. The new railway will be rented bv the Brighton 

 Company : it is a single line, and at the point where the drawbridge 

 is constructed, runs about midway between Arundel and the sea. 



STUDIES OF PLAN.— No. L 



After so very long an interval, instead of returning to the subject 

 under the first title, "Episodes of Plan," we take it up again under 

 the simpler and more usual designation of "Studies," which we may 

 continue from time to time, after the fashion of what the Germans 

 call " Zwanglosen He/li," ]nst as opportunity may offer. 



In buildings of a superior kind we have a right to expect something 

 of artistic and sesthetic effect arising out of disposition and conforma- 

 tion, out of plan and section, — well managed arrangements and com- 

 binations that till powerfully, even before decoration begins to be ap- 

 plied; and which with even a moderate degree of decoration will be 

 more captivating than mere costly decoration without architectural 

 effect as a groundwork for it. Be it ever so vulgar or common-place, 

 any large room may be bedizened out any day, and in the most approved 

 fashion of the day — in all its extravagance, by the decorator and the 

 upholsterer; yet let them be ever so skilful and tasteful in their own 

 way, the work of those artists is only skin deep ; they can only clothe, 

 fill up and dress up what the architect has left naked and blank. If 

 the work of the latter be awkward and dowdy, the one may help it 

 somewhat by his professional cosmetics, and the other by the rich 

 attirings in which he deals: more than this they cannot accomplish. 

 Without at all underrating their skill, or rejecting their aid, wc may 

 yet not unreasonably require sometliii g more to charm us, dressing-up 

 will do much — we may say, a very great deal — for rooms as well as for 

 women, but as it can not bestow on the latter beauty of face and of 

 figure, nor any of the nameless graces of expression ; so neither can it 

 supply in the former the charm of architectural physiognomv and the 

 witchery of architectural effect. Well, what does it matter after a I, 

 many will say, whether there be eftect of that kind or not : — that it 



36 



