Improved Muzzle-Pivoting Gun.
We are indebted for the following able description and criticism of this Prussian gun to our able contemporary, The Engineer.
Viewed as a piece of mechanism, nothing can well be more beautiful in mutual adaptation of parts to the fulfillment of given and rather recondite movements, and in point of execution, than this muzzle-pivoting arrangement of Herr Gruson's; but having said this we are compelled to add, as impartial engineering critics, that it is nothing more.
GRUSON'S SYSTEM OF MUZZLE-PIVOTING APPLIED TO MONITORS.
A very few words of description, aided by the very clear engraving annexed, will suffice to make the arrangement plain to every mechanical reader. The entire structure is metallic, chiefly of cast iron or of steel. Upon the platform of the casemate, or deck of the ship, or turret, is laid the heavy bed or traverse plate, cast hollow in iron, holding the vertical pivot at its forward end, on which the gun slide traverses in azimuth, and at its rear end the segment plate, bolted down and separately adjustable as to position upon the bedplate. The slide is also a ponderous hollow casting, the upper surfaces of which, on which the gun carriage runs forward or recoils, are curvilinear in a vertical plane, so that the inclination to the horizon is greatest at the rear end. At the rear end of the slide it traverses upon two heavy cast-iron turned conical rollers, which are geared together and actuated by the winch handle and spur gear, seen in our engraving; by these the slide is practically held fast in any position on the bedplate. The gun itself--in the model, a steel breech-loader, on the Prussian regulation system, very slightly modified--is sustained between two high and ponderous cheek plates of cast iron, which constitute the sides of the carriage, and which are connected together strongly at the lower edges by a heavy base or bottom plate, and at the top by two light cross distance bolts. The muzzle and breech extremities of the piece project well beyond those cheeks. Along the bottom of the trough of the carriage, directly under the gun, lies a nearly horizontal hydraulic press cylinder, the pump and handle actuating which are seen in the figures to the proper left of the gun, and the supply of water for which is contained in the hollow bottom of the carriage. On each side cheek of the carriage is formed, by curved planing, a circular segmental race, opening inward or toward each other, rectangular in cross section and into each of which is fitted a segmental block just filling it up, and occupying a portion of its length so as to slide easily up or downward through the whole range of the arc or segment.
The center point of the length of each of those blocks carries one side of the gun, which is connected also with the two heavy radius bars seen outside the cheeks, and pivoted close to the segment races on the outside, and with a system of link work between the gun itself and the crosshead of the ram of the hydraulic cylinder, which gives motion to the gun in elevation or depression, through a vertical arc, the imaginary center of which, and of the segments of the side cheeks, is situated in the horizontal diameter across the muzzle of the gun. This is in brief the muzzle-pivoting part of the arrangement, of which, were it worth while to go into its details, we should need some further diagrams to make it quite clear. Nor is it worth while to go into the description of various minor points of refinement about the gun mounting, such as the very exposed long tangent scale seen in the figure, by which the elevation or depression is read off, nor the still more exposed and rather ricketty arrangement by which the rear sight is arranged to rise and fall with the gun, and allowance for dispart avoided. The recoil of the gun is resisted through and by the segment blocks in the side cheeks, and by the heavy radius bars, etc., and thus transferred to the carriage itself. This moves upon four eccentro-concentric rollers, in all respects identical with those brought before the Ordnance Select Committee of Woolwich by Mr. Mallet, in 1858--then rejected, after some time adopted, and brought into use in our own service, where they are now universal, and from which they have been adopted into every artillery in the world, and, we understand, without the slightest recognition of the inventor's rights. On the axle of each of these rollers is keyed a circular eccentric cam plate, those at the same side being connected together by a linking bar so as to move in concert. Adjustable tripping plates attached to the sides of the slide, are so arranged that when the loaded gun has been run forward its carriage base rests hard down, with its full weight upon the top faces of the slide, and thus the recoil is made under the full resistance due to the friction of the entire load. Arrived at the highest point, it rests there until loaded. The cam plates being then given a slight motion of rotation by the help of socket levers--the rectangular projections to be received by which are seen on the top edges of the cam plates in the figure--the carriage, by its own commenced descent, gets again upon its rollers, and runs forward upon these at once into firing position. The two elevated horns which are seen standing up at the rear part of the slide above the roller frame are designed to receive the thump of the two short buffer-blocks--seen at the rear part of each carriage cheek--in the event of the recoil not being wholly expended in raising the weight of gun and carriage, etc., along the curved racers of the slide. These buffer-blocks bear against plugs of vulcanized india-rubber secured in the bottoms of the buffer cylinders.
We have thus, though very briefly, described the whole of this mounting. As a carefully thought out and elaborated piece of elegant mechanical complication Herr Gruson's muzzle-pivoting carriage attracted much attention at Paris, in 1867, and its merits were regarded as great by those whose thoughts went little further perhaps. We should have been glad had it been in our power to have joined in its praise. We are, however, obliged honestly to say that, however highly creditable to its designer as an ingenious and capable mechanism, it shows that he has never realized to himself as a practical artillerist the primary, most absolute, and indispensable conditions of construction for a serviceable muzzle-pivoting gun for either land or sea service.
As to the general merits, or general conditions, of muzzle-pivoting, however, once in doubt at first, these are admitted now by all; and the latter resolve themselves almost into this--that system of muzzle-pivoting must be best which, while preserving the essential point of leaving the muzzle of the gun free of any direct attachment, i.e., with an imaginary, not an actual, pivot of vertical arc motion, shall be the simplest possible in its parts, have the least details, the fewest parts capable of being struck by splinters or shot, and all its parts of such materials and character as to receive the smallest amount of injury if so struck. In every one of these aspects Herr Gruson's mounting is at fault. With parts and movements far more ingeniously adapted than those of the crude and unskillfully designed muzzle-pivoting carriages of Captain Heathorn, also exhibited at Paris, and much exhibited and exposed since, the Gruson mounting is even more complicated, expensive, and liable to injury of every sort to which a gun carriage can be conceived liable. We may even venture to affirm that ponderous as was the mass of cast iron, etc., in the Paris model carrying only a 12-pounder gun, were it all enlarged in such ratio as might appear to suit for a 10-inch 25-tun rifled gun of the British type, the almost proverbial relations, between weight, velocity of impulse, and brittleness of cast iron, would show themselves, in the whole machine going to pieces within a very few rounds.