ANCHOR 



ANCHOR. 



tit. . 



A c produced in r ; tlu n it r represent the tension / of the cable, I p 

 will be the perpendicular re-action of the fluke, and P p the force which 



tend* to drive it into the ground ; 

 draw P H perpendicular to c A, then 

 H p is that purl of p r which is per- 

 pendicular to the horizon, or is the 

 effort of I to link the fluke : let 

 I p r a, then P P( cos a, uid 

 PBPPina~( coi anna, which 

 it a maximum when a = 46* ; or the 

 fluke should be placed At 45 to the 

 shank. Now, it U remarked by 

 seamen, that when an anchor U once 

 started, it u difficult and often impossible to get it to hold again, and 

 as this cue U the most urgent of all, it i apparently the one to v hi. h 

 the position of the fluke should be calculated. 



It would appear, since the weight of A large anchor beam a much 

 higher ratio to any given tension of cable than the weight of a smaller 

 one, that the solution of the problem ought to involve the weight of 

 the anchor, which would give a different angle for anchors of different 

 weight* ; but it appears from numerous experiment* which Lieut. 

 Rodgers has made on the qualities, as well as on the strength, of 

 auchon, that an anchor, when dragged, always tends to rise out of 

 the ground, thus following the direction in which the loosened soil 

 affords a free passage ; since, therefore, it will not sink till it rests, 

 and since its weight becomes leas effective in pressing it farther the 

 de|<er it sinks, while the tension of the cable remains the same, it is 

 thus constantly tending to the most favourable angle (when = 45) till 

 the arm is entirely buried. 



It appears from .*;/. 2, that in shortening the shank, the fluke, making 

 already in most anchors the angle with the shank, or F r i in >;/. 3. 

 too great, will become still more nearly perpendicular to the horizon, 

 la many such cases the pull of the cable will produce scarcely any 

 tendency whatever to sink the fluke ; besides which it is to be observed 

 that by lessening the horizontal distance A F, while rg remains the 

 same, the pressure on the fluke is diminished, and thus on both 

 accounts the qualities of the anchor impaired. 



We now come to considerations relative to the strength of the 

 anchor. It is obvious we have not the means of determining the 

 amount of any of the forces concerned, but long experience has marked 

 pretty nearly the limits beyond which the dimensions of anchors need 

 not be earned. With these we can determine satisfactorily the pre- 

 ference which should be given to one form over another. The h'rst 

 strain that comes on the anchor when the cable is strained falls on the 

 ring, which had been often broken or distorted, till its dimensions v., i . 

 of lite years increased. This pull is conveyed along the shank to the 

 lower arm, which it tends to break off at the greatest distance from the 

 fluke, and therefore the thickness of the arm should increase towards 

 the throat The crown, which formerly was a circular arc, of late 

 years formed an angle, till changed by Mr. Pering. The force to break 

 the arm c F (fg. 3), is the re-action perpendicular to the fluke, or F I, 

 against the tension of the cable. And the moment of this force to 

 break the arm c F at c, is aa the perpendicular from c on F t. If the 

 arm p c be straightened into F p meeting A c in r, then the moment of 

 the same force is as P F, which is considerably greater than before. 

 It would be curious, therefore, to know what reason led to change 

 from the curved to the angular form. In lifting or weighing the 

 anchor, the cable acting perpendicularly to the end of the shank tends 

 to break it, and hence the thickness of the shank should increase with 

 ita distance from the ring ; also the breadth of the arms and the shank 

 should be downwards. In order to obtain increase of length without 

 either increase of weight or loss of strength, Lieut. Rodgers constructed 

 his patent hollow-shanked anchor. The principle on which a hollow 

 rod or bar is stronger than a solid one of equal sectional area is well 

 known. Since the fluke from its breadth opposes greater resist- 

 ance to being disturbed in weighing than the arm does, the axis of 

 rotation will be towards the fluke, and accordingly the ground dis- 

 placed by the angular motion of weighing being less than that displaced 

 by fair pull, and moreover the fulcrum or axis being near the throat 

 in direct pull, it seems that the force to lift an anchor out of the 

 ground will be considerably leas than the force sufficient by fair pull 

 to bring the anchor home. 



Before noticing the recent improvements in anchors, we v. ill l icily 

 detail the chief processes in mulfing those of ordinary construction. 

 Whether we view the forging of an anchor under the old state of 

 things, or now that Nasmyth's steam-hammer works such wonders, it 

 is a striking exhibition of industrial skill and labour. The shaft of a 

 fint-claas anchor, nearly twenty feet long by ten or twelve inches t hiek, 

 is too ponderous to be worked out of one piece of metal ; and it has 

 consequently to be built up of many pieces. Forty or fifty bars are 

 sometimes Uid together in a group, to be welded into one mass by 

 powerful blows while at a white heat ; but in modern times a smaller 

 number of wider bars are more frequently used. The bundle of bars 

 is brought to a highly-heated state, in a kind of oven formed wholly of 

 coals, which completely surround the iron ; but as the length of the 

 shank is so great, only so much of it is heated at once as can be forged 

 before it cools down too low. The tire i* urged by ten or 

 men; and when the mass U brought to a white heat, it i< drawn out 



of the fiery furnace, swung round by means of the crane by which it 

 has been suspended, and brought to bear on a Urge anvil. The men 

 arrange themselves in a circle around the heated mat* ; and, guide,! U 

 a foreman, they wield their ponderous hammers of sixteen or twenty 

 pounds weight, and produce a rough iniwic ly their equal-timed ' 



But this was in the old times. If we now visit the government 

 anchor Kmitheries, such as that in Deronport IWk;. that 



steam has driven away something of the "M pMoreaqneoeai 

 replacing it by a grandeur of its own. Tin- 

 buried In a mere heap of blazing fuel, but is lu-at< d \'. 

 constructed fumacv ; the bellows are no longer worked by liand, lmt 

 by the powerful blast of a steam-engine ; the forgers need no ! > 

 confine then- operations to one small length, at a time, for a much 

 greater length can now be managed before it cools down too low; and tin- 

 circle of anchor-smiths leas frequently wield their hammers, and < 

 their strength in blows which were once called powerful , but which nave 

 been superseded by something much more effective. Mr. Nasinyth'* 

 steam-hammer is a contrivance in which a powerful hammer or weight 

 is allowed to fall by ita own gravity, but is drawn up by tin- op, 

 of steam-power ; and this alternation of rising and falling occur* 

 tunes in a minute much faster indeed than a man couh) wield . 

 sledge-hammer. The white-hot anchor-shaft is placet I u|>on an anvil 

 immediately beneath the steam-hammer; and the blow- which follow 

 are so powerful and so quickly repeated, that the heated mam l 

 forged in a wonderfully short space of time. Let the anchor-smiths 

 group themselves as thickly as they may, and wield hammers tin- 

 heaviest that human muscles can command they cannot approach 

 the amount of work which the steam-hammer effects. KM n the 

 Hercula which formed an intermediate stage between the sledge- 

 hammer and the steam-hammer, and which consists of a heavy mass of 

 iron worked by ropes, must yield in efficiency to Mr. Nasmyth'n 

 remarkable machine. 



It would be impossible to notice all the improvements introdi-,. 

 suggested hi the form of anchors; but the chief novelties ma 

 Histently pass under review. 



Mr. Pering introduced the plan of forming the shank of flat 1 > 

 breadth equal to the depth of the shank. His greatest improvement, 

 was, however, that of forming the anna and part of the shank t 

 effected by splitting or dividing the bars, and throwing tin- 

 back in opposite directions to form the arms; over the owning or 

 angle thus formed is fixed a truss, and then to this are joined the 

 flukes, and at the other end the remaining part of the shank. 



Lieutenant Rodgers introduced the hollow-shanked anchor; thn- 

 disposing the metal in the form which engineers know to be m -' 

 profitable in proportion to its weight. The shank is, correct i 

 not hollow in effect ; for the square interior is tilled up with a bl 

 hardwood, to keep the iron bant or plates in their places; the principle. 

 nevertheless, is that of a hollow shank, so far as strength is concerned. 

 The shank is bound round with hoops at inter \ 



In 1888 Mr. Meggitt patented an anchor in which the wide flukes or 

 palms are dispensed with, the flukes being very little broader than the 

 arms; while at the same time there is an increased width 

 crown by the addition of a triangular piece of iron. About tin- 

 same period another form of anchor was introduced, in which the 

 several parts were formed of .1 that it mi. 



stowed away with great facility, or conveyed piecemeal by a boat 

 which could not carry the whole anchor. The arm mod of 



one piece, the shanks passing through the crown; the stock w 

 separate and secured to the shank when required ; and tin- who! 

 BO adjusted as to be put together in a short space of time. 



Mr. Porter's invention relating to anchors has, through \ 

 circumstances, led to very important results, and to a curious legal 

 decision. The objects designed to be attained by this 

 are mainly the two following: the avoidance of "fouling," by the 

 cable (Kissing over the exposed fluke of the anchor when 



swinging in a tide-way; and the axoidam f injury to the vessel 



itself, in the event of falling upon her anchor. The ,.f the 



plan consists in giving to tl. 



round a pivot or fulcrum at the end of the shank : ' ling at 



once from the rigidity usually observed in tin 



The arms and flukes are forged wholly in. f the clunk, and 



have a hole (hilled transversely through 



of the iron bolt which conned- them with the shank. To . 



familiar illustration, the joint may be described as of that kind which 



u the wires of an umbrella with the ribs, HU as to gi\ 

 of motion round the pin or 1x>lt as an axis. When an am hr thus 



dropjied from the vessel, it descends swiftly anil 



against the bottom of the sea with great mom I. with 



an anchor of ten hundredweight and a depth of twenty four f.i' 1 

 at 45 tons). When the anchor resU fairly on [the ground, i- 

 p".-ition (A) is with the lower peak, or tip, in contact with the 

 surface of the shank, the upper ];ik being as far an p. . il.li u-mi the 

 shank. Then tin -li.uh' ' the cable suffices to d 



ition, and to bring the lower peak into a dilution Ii- 

 ti; the ground (B). T! n continues until the U)>JHT 



peak touches the U|>|KT cur face of the shank, and the lower peak is 

 directed almost |K.r|H-ndicularly : a p, i-ition very favourable for pene- 

 tration, which then take* place. Tin- h.-mk and stock then lie flat on 



