Part 6 (1/2)
It will be apparent froures that practically the whole of the pue works may be done by means of a windmill, but it is undesirable to rely entirely upon such a system, even if two mills are erected so that the plant will be in duplicate, because there is always the possibility, although it e would accumulate; and, further, the Local Government Board would not approve the scheas, oil, or other encies In the case of water supply the difficulty e capacity, but this cannot be done for seithout creating an intolerable nuisance In the latter case the storage should not be less than twelve hours dry weather flow, nor ned reater part of the year, be sufficient to lift the whole of the sewage and storine will deteriorate for want of use to such an extent that when urgently needed it will not be effective It is, therefore, desirable that the attendant should run the engine at least once in every three days to keep it in working order If it can be conveniently arranged, it is a good plan for the attendant to run the engine for a few minutes to entirely e The bulk of the day's seill then have been delivered, and can be disposed of when it is fresh, while at the saht flow, and any rainfall whichcalled up during the night About 22 per cent, of the total daily dry weather flow of sewage is delivered between 7 p a sas or oil engine plant, so that the only advantage to be looked for will be in the maintenance, which in the case of a wind which may be obtained by the reduction of the a, a est which should be used, as when this size is exceeded it will be found that the capital cost involved is incompatible with the value of the work done by the mill, as coine
Mills smaller than 8 ft in diameter are rarely employed, and then only for small work, such as a 2 1/2 in pump and a 3-ft lift The efficiency of a windmill, measured by the number of square feet of annular sail area, decreases with the size of thethe most efficient sizes When the diameter exceeds l2 ft, the efficiency rapidly falls off, because the peripheral velocity remains constant for any particular velocity or pressure of the wind, and as every foot increase in the diath of the circureater the diaiven time; and consequently the kinetic flywheel action which is so valuable in the ser reatest efficiency will be obtained by adopting a single acting pu the liability, inherent in a long pu the use of a large nuiven out by the h soin, there are several British ly-built eneral appearance and Fig 20 the details of the type of mill made by the well-known firm of Duke and Ockenden, of Ferry Wharf, Littlehampton, Sussex This firm has erected over 400 windhly efficient Fro 20 it will be seen that the power applied by the wheel is trans of 2 1/2 ratio to a crank shaft, the gear wheel having internal annular teeth of the involute type, giving a greater number of teeth always in contact than is the case with external gears This minimises wear, which is an important matter, as it is difficult to properly lubricate these appliances, and they are exposed to and have to work in all sorts of weather
[Illustration: Fig l9--General View of Modern Wind 20--Details of Windmill Manufactured by Messrs Duke and Ockenden, Littlehampton]
It will be seen that the strain on the crank shaft is taken by a bent crank which disposes the load centrally on the casting, and avoids an overhanging crank disc, which has been an objectionable feature in some other types The position of the crank shaft relative to the rocker pin holes is studied to give a sloard motion to the rocker with aest stroke, where it is most required
In order to trans rod in coing the length of stroke bythat the pu is entirely automatic If the pressure on the heel, which it will be seen is set off the centre line of the mill and tower, exceeds that found desirable--and this can be regulated byon the fantail--the windmill automatically turns on the turn-table and presents an ellipse to the wind instead of a circular face, thus decreasing the area exposed to the wind gradually until the wheel reaches its final position, or is hauled out of gear, when the edges only are opposed to the full force of the wind The whole weight of theturn-table to facilitate instant ”hunting” of the es of direction The pump rod in the wind thethe position of the rod
CHAPTER X
THE DESIGN OF SEE OUTFALLS
The detail design of a sea outfall will depend upon the level of the conduit with reference to present surface of the shore, whether the beach is being eroded or made up, and, if any part of the structure is to be constructed above the level of the shore, whether it is likely to be subject to serious attack by waves in tiales If there is probability of the direction of currents being affected by the construction of a solid structure or of any serious scour being caused, the design ly
While there are exalazed stoneware socketed pipes surrounded with concrete, as shown in Fig 21, cast iron pipes are used in the majority of cases
There is considerable variation in the design of the joints for the latter class of pipes, soot and socket joints (Fig 22), with lead run in, or even with rod lead or any of the patent forh-water mark on account of the water which willplain turned and bored joints are liable to be displaced if exposed to the action of the waves, but if such joints are also flanged, as Fig 24, or provided with lugs, as Fig 23, great rigidity is obtained when they are bolted up; in addition to which the joints are easily e is formed all round the joint, it is necessary, in order that its thickness may be kept within reasonable liusset piece to stiffen the flange should be formed between each hole and the next, and the bolt holes should be arranged so that when the pipes are laid there will not be a hole at the bottom on the vertical axis of the pipe, as when the pipes are laid in a trench beloater level it is not only difficult to insert the bolt, but alhten up the nut afterwards The pipes should be laid so that the test bolt holes are placed equidistant on each side of the centre line, as shown in the end views of Figs Nos 23 and 24
[Illustration: Fig 2l-Stoneware Pipe and Concrete Sea Outfall]
With lug pipes, fewer bolts are used, and the lugs areto withstand the strain put upon the up the pipes These pipes are easier and quicker to joint under water than are the flanged pipes, so that their use is a distinct advantage when the hours of working are liun-metal bolts are used, as they resist the action of sea water better than steel, but they add considerably to the cost of the outfall sewer, and the principal advantage appears to be that they are possibly easier to remove than iron or steel ones would be if at any time it was required to take out any pipe which may have been accidentally broken On the other hand, there is a liability of severe corrosion of the un-metal and the iron, set up by the sea water in which they are immersed If the pipes are not to be covered with concrete, and are thus exposed to the action of the sea water, particular care should be taken to see that the coating by Dr Angus Smith's process is perfectly applied to theot and Socket Joint for Cast Iron Pipes]
[Illustration: Fig 23--Lug Joint for Cast Iron Pipes]
[Illustration: Fig 24--Turned, Board, and flanged Joint for Cast Iron Pipes]
Steel pipes are, on the whole, not so suitable as cast iron
They are, of course, obtainable in long lengths and are easily jointed, but their lightness coe in transport, is a disadvantage in a sea outfall, where the weight of the structure adds to its stability The extra length of steel pipes necessitates a greater extent of trench being excavated at one ti in On the other hand, cast iron pipes arethrown upon theency which does not frequently occur in practice
According to Trautwine, the cast iron for pipes to resist sea water should be close-grained, hard, white metal In such metal the small quantity of contained carbon is chemically combined with the iron, but in the darker or mottled metals it is mechanically coo, under the influence of sea water Hard white iron has been proved to resist sea water for forty years without deterioration, whether it is continually under water or alternately wet and dry
Several types of sea outfalls are shown in Figs 25 to 31[1]
In the exa 25 a solid rock bed occurred a short distance below the sand, which was excavated so as to allow the outfall to be constructed on the rock Anchor bolts with clevis heads were fixed into the rock, and then, after a portion of the concrete was laid, iron bands, passing around the cast iron pipes, were fastened to the anchors This construction would not be suitable beloater
26 represents the Aberdeen sea outfall, consisting of cast iron pipes 7 ft in diameter, which are embedded in a heavy concrete breakwater 24 ft in width, except at the extreht iron rods are only used to the last few pipes, which were in 6 ft lengths instead of 9 ft, as were the re s the pipes to be laid in a straight line, even if the pile is not driven quite true, and if the level of the latter is not correct it can be adjusted by inserting a packing piece between the cradle and the head
Great Crosby outfall sewer into the Mersey is illustrated in Fig 28 The piles are of greenheart, and were driven to a solid foundation The 1 3/4 in sheeting was driven to support the sides of the excavation, and was left in when the concrete was laid Light steel rails were laid under the sewer, in continuous lengths, on steel sleepers and to 2 ft gauge The invert blocks were of concrete, and the pipes were made of the same material, but were reinforced with steel ribs The Waterloo (near Liverpool) sea outfall is shown in Fig 31