BULLETIN 300 ; U. S. DEPARTMENT OF AGRICULTURE. 



SWINGING DEVICE. 



The swinging device used on the different makes of dredge varies 

 greatly. In some cases it consists of a circular, double-channel frame, 

 firmly anchored to the deck, with several sheaves bolted at intervals 

 in the circumference of the frame to carry the cable that travels over 

 them in swinging the boom. In this fixed type of swinging device a 

 large diameter of circle can be used. There is also the movable type 

 of swinging circle. This generally consists of a solid iron circle 

 mounted on a pivot. The heel of the boom is over the point of the 

 pivot and the boom is braced to the circle. This type requires more 

 deck room than does the first named type. The turntable may be 

 placed on deck (PL I, fig. 1) or overhead (PI. I, fig. 2), but the deck 

 plan is generally used. 



Independent engines may be used for swinging the boom or power 

 may be obtained from the main engine to drive the swinging drums. 

 If this latter plan is followed two independent friction drums are 

 attached to the bed plate of the engine and geared so as to be driven 

 by it. If internal-combustion engines are used, independent friction 

 drums are necessary for the various operations of the dredge. The 

 common practice on large steam-operated machines is to have inde- 

 pendent swinging engines. 



Spuds are heavy timber or steel members, the purpose of which is 

 to hold the dredge in position while operating. One is placed on 

 each side near the front and the third in the center line of the boat 

 at the stern. Vertical spuds extend directly downward at the side 

 of the hull and rest on the bottom of the excavated channel. They 

 are used on deep-water dredges or for excavating large channels. 



For a dredge with a narrow hull bank spuds, which extend outward 

 and rest on the ground surface, are preferable, since they give a large 

 bearing surface and the footing is usually on solid ground. These 

 are important features, as a longer boom and a larger bucket can then 

 be used on a narrow hall. 



There are various patented types of bank spuds. One is the con- 

 vertible bank-and-vertical power spud. This type can easily be 

 changed from a bank into a vertical spud and is most convenient in 

 crossing old channels, digging cut-offs, or making a double cut. 

 Another type is the telescopic bank spud, so designed that the spud 

 is either lengthened or shortened by means of a telescopic device. 

 There are other styles of bank spuds, which, although they possibly 

 do not have as wide a range as the telescopic type, can, nevertheless, 

 be operated successfully several feet above or below the water surface. 

 Plate I, figure 1, shows a dipper dredge equipped with telescopic bank 

 spuds. 



