Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
|
See also:ANCHOR (from the See also:Greek ayrcvpa, which See also:Vossius considers is from 6yi17 , a crook or See also:hook)
, an See also:instrument of See also:iron or other heavy material used for holding See also:ships or boats in any locality required, and preventing them from drifting by winds, tides, currents or other causes
.
This is done by the See also:anchor, after it is let go from the See also:ship by means of the See also:cable, fixing itself in the ground and there holding the See also:vessel fast
.
The word " anchor " is also used figuratively for anything which gives See also:security, or for any See also:ornament or appendage which takes the same See also:form
.
Owing to a vessel's safety depending upon the anchor, it is obviously an appliance of See also:great importance, and too much care cannot be expended on its manufacture and proper construction
.
The most See also:ancient anchors consisted of large stones, baskets full of stones, sacks filled with See also:sand, or logs of See also:wood loaded with See also:lead
.
Of this See also:kind were the anchors of the ancient Greeks, which, according to See also:Apollonius Rhodius and See also:Stephen of See also:Byzantium, were formed of See also:
The invention of the teeth is ascribed by See also:Pliny to the Tuscans; but See also:Pausanias gives the See also:credit to See also:Midas, See also: 2) made of forged iron . A See also:projection in the centre of the arms See also:works in a See also:recess at the hub of the shank; the vacancies out-See also:side the shank are filled by blocks bolted through on each side, and are flush with the side plates, which keep the flukes in position . The introduction of See also:cast See also:steel in 1894 led to the improved Martin-Adelphi See also:pattern (fig . 3), in which the crown and arms are cast in one, and, with the stock, are made of cast steel, the shank remaining of forged iron . A projection in the crown works in a recess (right, fig . 3), and is secured in its See also:place by a forged steel See also:pin, fitted with a See also:nut and washer, which passes through the crown and the See also:heel of the shank . All the above anchors were provided with a stock(fig . 1, hk), the use of which is to " cant " the anchor . If it falls on the ground, resting on one See also:arm and one stock, when a See also:strain is brought on the cable, the stock cants the anchor. causing the arms to See also:lie at a downward See also:angle to the holding ground; and the pees enter and See also:bury themselves below the See also:surface of the See also:soil . To See also:stow a stocked anchor on the forecastle, it is See also:hove up close to the forefoot, and by means of a ground See also:chain (secured to a balancing or gravity See also:band on the anchor), which is joined to a catting chain rove through a See also:cat davit. the anchor is hove up horizontally and placed on its See also:bed, where it is secured by chains passing over a See also:rod fitted with a See also:lever for " letting go." The cat davit is hinged at its See also:base, and can be laid See also:flat on the See also:deck for right ahead See also:fire or when at See also:sea . Ground and catting chains have been superseded in some ships by a See also:wire See also:pendant and cat See also:hook; the anchor is then hove close up to the hawse-See also:pipe . To avoid cutting away a portion of the forecastle, in the " See also:Cressy," " Terrible " and " Diadem " classes of the See also:British See also:navy, the anchors, secured by chains, are stowed a-See also:cock-See also:bill, outside the ship, with their crowns resting on iron shoes secured to the ship's side and the flukes fore and aft .
A difficulty is experienced in stowing the anchors when the ship is pitching or See also:rolling heavily
.
Fig
.
4 illustrates an anchor with cat davit or anchor See also:crane used in the P. and O
.
See also:Company's steamers (" See also:India " class, 8000 tons); for sea the anchor is stowed on board by the anchor crane
.
Stockless anchors have been extensively used in the British See also:mercantile marine and in some See also:foreign navies
.
In 1903 they
were adopted generally for the British navy, after extensive anchor trials, begun in 1885
.
Their advantages are: handiness combined with a saving of See also:time and labour; See also:absence of davits, anchor-beds and other See also:gear, with .a resulting reduction in weight; and a clear forecastle for " right ahead" See also:gun fire or for working ship
.
On the other See also:hand a larger hawse-pipe is required, and there appears to be a consensus of See also:opinion that a stockless anchor
Anchor
.
when " let go " does not hold so quickly as a stocked one, is'more
uncertain in its See also:action over uneven ground, and is more liable
to " come See also:home " (See also:drag)
.
The stockless anchors principally in use
in the British navy are See also: Two trunnions or lugs are forged to the See also:lower end of the shank . In Byer's See also:plan (fig . 6) the flukes and crown consist of a steel-casting secured to a forged shank by a through bolt of mild steel, the See also:axis of which is parallel to the points of the flukes; one end of the bolt has a See also:head, but the other is weighing . Wasteneys Smith's anchor (fig . 7) is composed of three See also:main parts, the shank and crown which form one See also:forging, and the two flukes or arms which are See also:separate castings . A bolt passes through the crown of the anchor, connecting the flukes to it; to prevent the flukes working off the connecting through bolt, two smaller bolts pass through the flukes at right angles to the through bolt and are recessed See also:half their See also:diameter into it . Fig . 8 represents the starboard See also:bow of H.M.S . " New See also:Zealand " (16,350 tons) with lower and sheet (spare) anchors stowed . To let go a stockless anchor (fig . 9) the cable or See also:capstan holder C is unscrewed, and in practice it is found desirable to knock off the See also:bottle See also:screw-slip A, allowing the weight of the anchor to be taken by the inner slip A' (See also:Blake's stopper) . Stern, stream and kedge anchors are usually stowed with See also:special davits .
A portable anchor suitable for small yachts is the invention of Mr See also: Bitts . H . Hawse-pipes . Cable or Capstan-holders . S . Stopper-bolts . Centre See also:line capstan . R . Rollers . to withstand a certain tensile strain, expressed in tons, proportionate to their weights in cwts . New anchors are supplied by contractors, but See also:repairs are made in H.M. See also:dockyards, a See also:record of its repairs being stamped on each anchor . In the Anchors and Cables See also:Act 1899 a See also:list is given of authorized testing-establishments, with their distinctive marks and charges, and testing-houses for foreign-owned vessels are enumerated in Table 22 of See also:Lloyd's See also:Register of British and Foreign See also:Shipping . Cast-steel anchors, in addition to the statutory tests, are subjected to percussive, hammering and bending tests, and are stamped " annealed steel." (J . W . |
|
|
[back] ANCHISES |
[next] ANCHOVY (Engraulis encrasicholus) |
There are no comments yet for this article.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.
Links to articles and home page are encouraged.