. The street railway review . here it hangsfrom the overhead travelers, which run on the top onrails over the flanges of the longitudinal lattice girders ofthe grasshopper. The gantry is sometimes, whenobstructions arise, projected forward with these pillarsremoved, the travelers being run to the rear and attachedto the next span on the trolley, which thus acts as acounterpoise, the back frame and its supporting trolleyforming the fulcrum. When the span arrives at the frontof the viaduct, the bogie carrying it, runs forward close upto the bogie which supports the back frame. The frontend of th
. The street railway review . here it hangsfrom the overhead travelers, which run on the top onrails over the flanges of the longitudinal lattice girders ofthe grasshopper. The gantry is sometimes, whenobstructions arise, projected forward with these pillarsremoved, the travelers being run to the rear and attachedto the next span on the trolley, which thus acts as acounterpoise, the back frame and its supporting trolleyforming the fulcrum. When the span arrives at the frontof the viaduct, the bogie carrying it, runs forward close upto the bogie which supports the back frame. The frontend of the span, projecting, as it does, fifteen feet overeach end of the trolle) which carries it, projects abouteight or ten feet through the back frame of the grass-hopper. It is then taken hold of and slightly lifted bythe front traveling crane of the grasshopper. Twohydraulic jacks are placed under the rear end of the span,which becomes slightly raised. The trolley being thenliberated, is run back about thirty feet, the jacks are. r^^^er x^^^^^ THE GRASSHOPPER WITH SPAN READY TO LOWER INTO POSITION. the site of their present works at Seaforth, before theconstruction of the viaduct commenced. This machine,which is known to us as the grasshopper, will lower aspan vveighing forty tons into position within half an hourof its arrival at the front. In the whole of the machine,in the tackle and the girders, the inventors have alloweda factor of safety of four, so that everything is onlystrained to one-fourth of its breaking strain. The grasshopper, in this case, consists of two main latticegirders, 15 feet apart and 86 feet long. In front thereis a cross trussed girder spreading out to a width ofabout twenty-seven feet. This cross-girder is supportedby two latticed columns, which are supported by latticedbraces, horizontally and vertically. These columns arefitted with rollers at the foot, and travel forward on shortinterchangeable lengths of rail. About sixty feet fromthe front there is
Size: 2347px × 1065px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
