8 



BULLETIN" 300, U. S. DEPARTMENT OF AGRICULTURE. 



On dredges such as are ordinarily used in drainage work, the dipper 

 or bucket varies in size from one-half cubic yard to 4 or 5 cubic yards. 

 The dipper varies considerably in shape with the different manufac- 

 turers. For work in ordinary material the cutting edge is made of a 

 single steel plate, preferably of manganese steel, but if the material is 

 hard large steel teeth are used to reinforce the cutting edge. The 

 bottom of the dipper is a heavy steel plate which is hinged to the back 

 and is held in place by a spring latch on the front of the dipper. The 

 latch is operated by the craneman, who thus dumps the contents of 

 the dipper. As the latter is lowered into the ditch the weight of the 

 bottom causes it to close and latch automatically. 



The larger the dipper used, the larger must be the engine and boiler, 

 and, in fact, all of the parts, including the hull. Thus the size of a 

 dipper dredge is determined by the capacity of its dipper. 



COST. 



The cost of dredges advances rapidly as the size and capacity are 

 increased. Dredges of the same rated capacity also vary somewhat 

 in cost with the different manufacturers. All of the machinery is 

 usually made at the shops of the manufacturer. The material 

 for the hulls may also be supplied by the manufacturer, but usually 

 the purchaser obtains lumber in the open market and builds the hull 

 in the field. The cost of hauling the material and machinery from 

 the railroad to the place of erection, the local price of labor, and the 

 conveniences for housing and feeding the workmen are factors which 

 will enter into the cost of a machine of any type. It requires at least 

 two cars to transport the material for a small dipper dredge, while for 

 a machine of large size from four to six cars are required. 



The following table gives the approximate costs of the various sizes 

 of dredges ready for operation, though these would be largely 

 affected by the difficulties and expense of transporting the material 

 and assembling the machine: 



Approximate costs of dipper dredges. 



Size. 



J-yard . 

 1-yard. 

 1 J-yard 

 l'.-yard 

 2J-yard 



Cost of 



Cost of 



machin- 



wood 



ery. 



hull. 



S3, 700 



Sl,S0O 



5,400 



2,200 



6,100 



2,250 



7,100 



•1,500 



14,000 



9,000 



Total. 



?5, 500 

 7,600 

 S,350 

 11,600 

 23,000 



It requires practically a month for ten men to erect a 1-yard dredge, 

 6 weeks to erect a 1^-yard or l|-yard dredge, and 8 weeks to construct 

 a 2-yard or 2^-yard machine. It requires less than one-half the time 

 given above to dismantle a machine. A 1-yard dredge whicn cost 



