Engineering Wonders of the World
Volume I

TRANSPORTER BRIDGES. 297 from the anchorage and firmly clamped, so as to form one cable. The stiffening girders project fifty-five feet beyond the towers at each end, to enable the car to enter between the tower legs. The Car ^iey are thirty-five feet deep throughout, and are hinged at the centre of the span to overcome temperature stresses. The trolley runs on the outer edge of each bottom flange of the girders, and consists of a flexible frame moving on thirty- two cast-steel wheels, four of which are drivers. Suspended from this frame is the car, 55 feet long by 24 feet wide, made specially strong to carry heavy machinery—boilers, etc.—manu- factured at the local works. (Fig. 1.) The car can take four two-horse farmers’ wagons and 300 people at the same time, and 500 to 600 passengers frequently cross at one time. On a certain occasion, just before a football match, there were nearly 800 people on board the car, packed together like sardines. The car is driven direct by two electric motors of 36 B.H.P. fixed to the trolley, this being the first instance in which rope gearing has been dispensed with. The car is fitted with a magnetic brake, and is under perfect control of the man in the cabin on the top of the car. The motors can be driven either “ in series ” or “in parallel,” the latter system transporting the car in about If minutes. The present traffic does not, however, demand this speed, and the motors are run “ in series,” the time of crossing being thus a little over three minutes, varying with, the pressure and direction of the wind. The total weight of the towers and the stiffen- ing girders is about 1,400 tons, and the total cost of the bridge, including the viaduct ap- proaches and Parliamentary expenses, was about £133,000. The approximate leading dimensions of the chief transporter bridges may be summarized as follows :— Name of Bridge. Date of Erection. Span. Clear Height above Water-level. Size of Car. Mr. C. Smith’s design 1873 G50 ft. .. 150 ft. Portugaleti 1893 528 ft.... 148 ft ...2G ft. 6 in. by 20 ft. 6 in. Rouen 1897 472 ft.... 168 ft ...43 ft. by 33 ft. 6 in. Bizerta. f898 .. 360 ft.... 149 ft ...30 ft. by 25 ft. Martrou 1899 .461 ft.... 180 ft ...46 ft. by 38 ft. Nantes 1902.. . 465 ft.... 165 ft ..39 ft. by 33 ft. Widnes and Kuncorn 1903... . ..1,000 ft. 82 ft .. .55 ft. by 24 ft. Newport (Monmouth) 1904... . 592 ft.... 177 ft ... 33 ft. by 40 ft. Marseilles 545 ft.... 165 ft . .38 ft. by 33 ft. Duluth 1904 393 ft. 9 in 135 ft ...54 ft. by 30 ft. The Designing of Transporter Bridges. In designing transporter bridges, many in- teresting points, governed by the site and other local conditions, and, as often as not, by financial requirements, have to be taken into consideration. About the advantages of this type of bridge under certain conditions there can be no doubt, although many people are still sceptical. It is generally found that those people who have never seen such bridges, and do not understand how they are worked, have most to say against them, and many good schemes have been blocked by the profound ignorance of one or two “ clever ones.” All the bridges erected hitherto have proved to be very satis- factory, so far as accommodation and creation of traffic is concerned, and most of them have also been successful financially. The methods of erection of these bridges is very interesting. The foundations are some- what similar to those of ordinary bridges, and