Online Encyclopedia
Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
MODERN GROOVE
Online EncyclopediaEncyclopedia Home :: MIC-MOL
del.icio.us it!
|
See also:MODERN GROOVE (latest Type but although this See also:system had certain advantages it did not fulfil all requirements. In 1863, See also:England re-opened the whole question, and after exhaustive trials of various inventions decided on the See also:adoption of the muzzle-loading type for all guns, with the See also:French system of rifling. This system was invented in 1842 by See also:Colonel Tretiille de See also:Beaulieu and consisted of a few wide and deep grooves which gave rotation to a studded projectile. At the first trials two grooves only were tried, but the number was afterwards in-creased to three or more, as it was found that two grooves only would not correctly centre the projectile. The adoption of the muzzle-loading system with studded shot was a distinctly See also:retrograde step, as a considerable amount of clearance was necessary between the See also:bore and projectile for the purposes of loading, and this resulted in the See also:barrel being seriously eroded by the See also:rush of See also:gas over the shot, and also led to a considerable loss of See also:energy. In the Wahrendorff and See also:Armstrong systems however the See also:lead-coated projectiles entirely prevented windage, besides which the projectile was perfectly centred and a high degree of accuracy was obtained. Shunt rifling was a brief See also:attempt to make loading by the muzzle easy without forfeiting the centring principle: in this the rifling varied in width and in See also:depth, at different portions of the bore in such a manner that, during loading, the studs on the projectile could move freely in the bore. When the See also:gun was fired the studs of the projectile were forced to travel in the shallow See also:part of the rifling, thus gripping and centring the projectile as it See also:left the muzzle. With See also:uniform rifling on the French system, the few studs—generally two per groove—had to See also:bear so high a pressure to produce rotation that they sometimes gave way. This subject was investigated by See also:Captain (See also:Sir See also:Andrew) See also:Noble, who showed that by making the rifling an increasing twist, commencing with no twist and gradually increasing until the necessary See also:pitch was obtained, the maximum pressure due to rotation was much reduced. Increasing rifling was consequently adopted, with beneficial results. In See also:order to prevent the heavy erosion due to windage, a gas check was adopted which was attached to the See also:base end of the studded projectiles. In some guns the number of grooves of the rifling was sufficiently See also:great to admit of rotation being insured by means of the gas check alone; in these guns studded projectiles were not employed, but the gas check, called " automatic," to distinguish it from that fitted to studded projectiles was usually indented around its circumference to correspond with the rifling of the gun. It was found that the studless projectile had considerably greater range and accuracy than the studded projectile, with the additional See also:advantage that the See also:shell was not weakened by the See also:stud holes. The introduction of the See also:plain See also:copper See also:driving See also:band for rotating projectiles with See also:breech-loading guns included a return to the polygroove system with shallow grooves; this still exists, but the continuous demand for greater See also:power has had the effect of in-creasing the number of grooves from that at first considered necessary, in order to keep the rotating pressure on the driving band within See also:practical limits. Many ingenious devices for giving rotation and preventing the See also:escape of gas past the projectile were tried in the See also:early days of modern rifling. Experiments of this nature still continue to be made with a view to improving the See also:shooting and to prevent the erosion of the bore of the gun. Briefly considered, without going into any detail of the numerous plans, all rotating devices fitted to projectiles can be divided into three classes—the " centring, " the " compressing " and the " expansion " systems. The two last named almost invariably include the " centring " type. Studded (fig. 23) and See also:Whitworth (fig. 24) hexagonal projectiles, which can freely slide in the bore, come under the first system. In the See also:compression class the coating or rings on the projectile are larger in See also:diameter than the bore and when fired the coating (or rings) is squeezed or engraved by the rifling to See also:fit the bore—the projectile is consequently also centred. The old-fashionedlead-coated shell (fig. 25), and the modern system of plain copper driving bands (fig. 26), come under this class. Most variety exists in the expansion type, where the pressure of the See also:powder gas acts on the base of the projectile or on the driving See also:ring and compresses a lead, copper or See also:asbestos ring into the rifling grooves. One of the earliest was the Hotchkiss (1865) shell (fig. 27), in which a See also:separate base end B was driven forward by the gas pressure and squeezed out the lead ring L into the rifling. The automatic gas check (fig. 28), and the gas check driving band (fig. 29), belong to this system; in the last the See also:lip L is See also:expanded into the rifling groove. In fig. 30 a copper driving band is ecR FIG. 26. FIG. 27. FIG. 28. Additional information and CommentsThere are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML. Site content, images, and layout Copyright © 2006 - Net Industries, worldwide. |
|
|
[back] MODERN ENGLISH |
[next] MODERN HIGH |