CHAPTER XIX 

 DIPPER DREDGES GENERAL DISCUSSION 



THE dipper dredge can be likened to an ordinary steam shovel 

 mounted on a scow or float. This machine is very convenient for 

 dredging in shallow waters and has been extensively used along 

 the shores of the Great Lakes and in the excavation of canals for 

 drainage purposes on the flat and marshy lands along the rivers and 

 seashores of the Atlantic and Gulf coasts. It has done extensive 

 and important work at a comparatively low cost, so that to-day 

 many contractors and engineers believe implicitly in the efficiency 

 of the dipper dredge, and prefer this machine to any other type of 

 dredge. 



The hull is built with a flat bottom, so as to allow the machine 

 to float even in very shallow water. The hull is always made of 

 wood, formed with keelsons and floor planking caulked in the usual 

 way. The deck is formed by beams connected to the keelson by 

 means of verticals, supporting a heavy caulked planking. The bow 

 and stern sides of the hull are formed in the same way by beams 

 planked and caulked. In dredges of large capacity, in order to 

 support the heavy boom and its attachment and at the same time 

 to stiffen the structure so as to prevent any damage, the hull is 

 reinforced by steel trusses. Two trusses are placed longitudinally 

 along the starboard and port sides of the float, and these are well 

 braced together by crosspieces connecting the top and bottom chords 

 of the trusses. Another truss, but smaller, is placed at the bow and 

 connected with the two longitudinal ones. This is necessary to 

 support the turntable upon which the boom rests. In Fig. 43 are 

 shown the plan and elevation of the steel trusses used to reinforce 

 the hull of the dredge "Chicago/' as given in Engineering News, Vol. 

 XLV. The dimensions of the hull depend to a great extent upon 

 the capacity of the machine. 



To prevent the dipper dredge from tilting under the great strain 

 of the work, the hull is provided with three and sometimes even 



151 



