DREDGING. 



141 



Dreeing 



Machine. 



Stem. 



Stcum 



| 



engine. 



I) .Ti|tiim 

 < i \.\.\IV. 



fig. 1. 



Kig. 2. 



The frame. 



at burkets. 



propriated to them on board of the barge, that carried 

 the machinery ; and it was usual to have the horses so 

 taught, that by th ringing of a bell they would im- 

 mediately stop. One of these was long employed on 

 the river H umber at Hull, and one at Port Glasgow; 

 and there have been two constructed on the principle of 

 an endless chain at the port of Greenock, the moving 

 power being communicated by men and crane-work. 

 The barges tor these two last are built very flat, and 

 square at both ends, and have an aperture up the mid- 

 dle, through which the bucket frame works, and the 

 stuff' is discharged over the end. This scheme answers 

 very well on a small scale, but would not be advisable 

 for a large machine. 



As the recent improvements on steam engines have 

 rendered them of the greatest value, particularly in a 

 country which abounds with coal, every other moving 

 power for dredging machines is rapidly giving way to 

 the steam engine. Several of these have been for years 

 employed on the river Thames, one at Hull, one at 

 Bristol, one at Suiiderland, and one at Aberdeen ; and 

 ue understand they are now constructing several for 

 dredging the entrance from the sea, and from the lochs 

 or lakes to the locks on the Caledonian canal. In one 

 of the*e, the bucket frame will project considerably 

 before the barge on which it is mounted, and be capable 

 of sloping up canal banks, or, in other words, to work 

 away high ground, and make a passage for the barge to 

 follow. 



In order to give our readers a more distinct view of 

 this important branch of hydraulic engineering, we shall 

 particularly describe one of the most powerful and 

 most improved machine* now at work on the river 

 Thaiiii--. 



< >ne of the most powerful of these machines is ex- 

 plained in Plate CCXXXIX. where Fig. I. represents 

 an elevation and partial section of the machine, to explain 

 the steam engine and wheel work contained in the 

 in-ide of the vessel. Fig. 2. is a horizontal plan of the 

 same. The machine is erected in the hulk of an old 

 slrxip of !)0 or 100 tons burden, the figure and parts of 

 which are too clearly explained by the drawing to re- 

 quire any particular reference. There are two chains 

 of bucket* to this machine, one on each side of the vessel, 

 though only one of them is shewn in Fig. 1. at EE, the 

 other beinjj omitted to make nxnri for the small Figures. 

 The endless chains revolve over rollers situated at the 

 two extremities of strong frames of timber, marked EE, 

 which rise and fall on a centre at their upper ends, their 

 weight being suspended by pulleys a a, which being 

 lowered down, permit the buckets^ attached to the 

 chain r e, to reach the bottom. 



A A are two beams projecting a short distance from the 

 sides of the vr-M'l at the *tern, upon which the two trian- 

 gular timber-frames BB are mounted, to sustain a strong 

 timber (' extended across the vessel : these, with their 

 timbers .1.1, f.rm a frame which supports all the 

 machinery that is above deck. The beam C is as long 

 as the whole width of the machine, and uj>on each end it 

 has a cast iron bracket 1)1) hanging downwards, as seen 

 at D. These brackets support the upper end of the buc- 

 ket frame's I'.K. and also the centres for the chain bar- 

 " er which the endless chains revolve by the mo- 

 tion of the machine. The bucket frames F.F. are each 

 composed of four long timbers, Ix.lted together, and 

 braced by diagonal stays d d, forming a truss frame, 

 which ha sufficient strength to prevent flexure from its 

 weight. The pulleys a <i su-| H -iiding the lower 

 end of the chain frames, hang from the beam FF, v. hich 



extends across the vessel, supported on the top of two 

 or three vertical posts erected on the deck. The upper 

 end of each of the chain frames EE, has two stout iron 

 semicircles b b bolted to the timbers, and terminating in 

 rings or eyes fitted over two tubes or hollow iron centre 

 pins, one supported by the bracket D, and the other by 

 the frame B. On these pins the frame hangs as upon 

 a centre at c , and can be raised or lowered as before men- 

 tioned. The upper roller for the endless chain, which 

 is a square barrel, revolves upon the same centre of 

 motion as the frame at c, and a similar square barrel of 

 the same dimensions is placed in bearings at the lower 

 end of the bucket frames, as seen at H in Fig. 1 : then 

 the double endless chain eee e passes round both these 

 barrels, and every other link of these two chains carries 

 one of the buckets ff, which are made of plate iron, as 

 shewn on a larger scale at Fig. 3. They are pierced 

 full of holes, to allow the water to drain out of the gra- 

 vel as they come up : their mouths are of a semicircu- 

 lar figure, which renders them less liable to stick fast 

 in the ground than if they were square, gg, Fig. 1. re- 

 presents a number of cast iron rollers placed on the in- 

 side of the beams of the chain frame, to support the weight 

 of the chains and buckets as they pass up ; for being 

 very heavy when they are full, a great friction would 

 otherwise be occasioned by the buckets dragging on 

 the timbers. 



The upper chain barrels for the frames on both sides 

 of the vessel are in a line with each other, and both re- 

 ceive their motion from the steam engine, which is si- 

 tuated in the hold of the ship. Its parts are as follows : 

 x, Fig. 2. is the boiler set in brick work, with the fire 

 place beneath it: and a wrought iron tube Y, carried up 

 to a proper height, serves for the chimney, and is firmly 

 braced by iron chains in different directions; z, Fig. 2. 

 is the steam pipe communicating from the boiler to the 

 engine, which is on Watt and Houlton's principle ; P is 

 its working or steam cylinder ; Q the working beam or 

 great lever, which is made of cast iron ; its centre being 

 .supported on the top of four iron columns UH,which stand 

 upon the floor of the engine S. The connecting rod T 

 of the engine is jointed to the extremity of the beam Q 

 at the top, and the other end to the crank on the ex- 

 tremitv of the shaft O. For a more minute descrip- 

 tion of the engine, which acts in the same manner as 

 any other made by Watt and Boulton, see STEAM 

 Engine. 



The fly-wheel V of the engine is turned by the 

 large spur-wheel W, fixed upon the shaft O, acting in 

 a pinion on the axis of the fly-wheel, to give it a greater 

 velocity than the crank, by which means a smaller fly- 

 wheel is made sufficient to regulate the motion of the 

 engine. 



The motion is conveyed from the engine to the chain- 

 barrels, by an inclined shaft L, seen more plainly in 

 the plan. At the lower end it has a bevelled wheel M, 

 receiving motion from the wheel N, fixed on the main 

 shaft of the engine. At the upper end of the same in- 

 clined shaft is a bevelled wheel K, Fig. 2. working an- 

 other, I, fixed upon a shaft, situated in a line with the 

 centre of the two chain barrels. At the two extremities 

 of this shaft, two circular iron plates, or wheels, are fixed 

 at ii ; these are received into boxes, or hollow wheels, 

 which are fixed on the extreme ends of two other shafts, 

 placed in a line with the former, and leading to the 

 chain barrels. These boxes and wheels form a connec- 

 tion between the several parts of the shaft ; and by the 

 friction of the wheels, which are accurately fitted in- 

 to the boxes, a sufficient power is communicated to tin- 



Dredginj 



PLATE 



C'CXX.XIX. 



Fig. 1. 



Fig. 3. 



The steam 

 engine. 



Fig. ?. 



The whco!- 

 work. 



Fig- ? 



Friction 

 buxet. 



