UNlVtHbl i Y ur 



PARTMENT O?.CV!L ENGINE 

 HYDRAULIC DREDGES FOR CHANNELS 129 



which has been arrived at through the correction of defects of earlier 

 designs. The pump has a cast-iron shell with cast-steel runner and 

 blades. The suction and discharge pipes are both 20 in. diameter. 

 The blades of the pump runner are faced with renewable steel 

 blades at points of greatest wear and the pump is so designed that 

 it can be readily taken apart and the pump runner removed with- 

 out taking down the pump shell or discharge-pipe connections. 

 The internal passageways of the -pump-are- of large -area, -so as -to 

 pass freely any stones or solid bodies that may enter through the 

 openings of the suction head without injury or liability to choke it. 

 It will readily be seen that if the passages of the pump were of 

 smaller size than the openings through the cutter head that stones 

 or other obstructions might lodge in the pump, but by the foregoing 

 precaution this liability is obviated. 



By referring to the plan it will be seen that the entire suction 

 pipe projects in front of the dredge and swings thereupon, its lateral 

 movement being accomplished by means of a block and tackle on 

 each side, the hauling parts of which are carried to the drums of 

 the auxiliary engines. The suction pipe has a universal movement 

 on the hull so that it can raise and lower as well as swing. This 

 movement is provided for by a section of rubber suction hose where 

 it passes over the deck, the suction pipe being attached by hinges 

 to a revolving base plate on the bow of the dredge. 



The material is excavated by means of a rotary cutter head, 

 which is formed of a cast-steel hollow shell and removable cast-steel 

 blades. These blades are arranged on a spiral and so as to give the 

 maximum effect with the least liability of choking. The action 

 of the cutter is such that the blades slice off or excavate the material 

 and feed it into the interior of the shell through the openings, 

 whence it is removed by the pump suction. The cutter head with 

 its shaft, gearing and all connections are of ample strength to stall 

 the engines which drive them. Thus, in case of an immovable 

 resistance being encountered, nothing worse can happen than the 

 stoppage of the engines, and by slacking off the feed of the cutter 

 a little, they are enabled to proceed and try again. It is worthy 

 of note that since this dredge has been in commission she has worked 

 in all kinds of material, including roots, stumps, hardpan and stones, 

 and that no breakage or injury has occurred to the cutter head or its 

 driving gear. 



It will be observed that the suction pipe when swinging on the 



