[By permission from the Journal of the Royal I United Service Institution]
It is tolerably well known, through various notices which have appeared principally in the daily papers, that a new fish torpedo has been constructed by Count Adolf von Buonaccorsi di Pistoja, and we must fulfill the wishes of many of our readers who take an interest in torpedo matters if we here enter into a description of the above torpedo as compiled from five letters patent and two printed pamphlets which have been laid before us. As can be perceived from the whole tenor of the following description, we confine ourselves strictly to the employment of the above printed notices without giving any opinion whatever on the torpedo itself, its mechanism, or the qualities ascribed to it, etc. The Buonaccorsi torpedo is propelled by the reaction due to the efflux of compressed air from the blades of the propellers. This invention, as well as the special mechanism for controlling the depth, sinking the torpedo at the end of its run, exploding the charge, and also the charging and supply valves, are subjects of the letters patent above mentioned. Trials with the Buonaccorsi torpedo were carried out, to our knowledge, in 1890, at the Imperial launching station in Kiel, and further in Nussdorf, near Vienna; the results, however, have not yet been published. The fact that the "Vulcan" Company, in Stettin, has acquired the patent in Germany for this torpedo, and has established a range with a view of carrying out extensive experiments with it, proves at any rate that with them the invention is considered of the highest importance. Buonaccorsi endeavors in his torpedo to overcome the defects which, in spite of all improvements, and the great perfection of the present type, still remain in the Whitehead torpedo, viz.: (1) complexity, as a result of which constant accidents occur in the propelling, balancing, and depth-controlling mechanism; (2) limited range, by means of holding a high velocity of the torpedo in reserve. In external form the Buonaccorsi is exactly similar to the Whitehead, with pistol, charge, depth-regulator, air reservoir, rudders, and twin screws.
The following description of the internal mechanism, as already mentioned, is exclusively from the letters patent: Propelling mechanism of the Buonaccorsi torpedo. Up to the present, the propulsion of automobile fish torpedoes in general is obtained by the action of compressed air on the piston in an engine cylinder, producing the rotation of the propeller shafts, and by means of gearing the revolution of two propellers in opposite directions. This kind of propulsion is subject to the following losses of power: The air pressure during admission to the cylinder, and also on exhaust after having performed its work there, has to overcome considerable resistance during its passage, and the friction of machinery and the continual change of direction in motion of the pistons and slides of the engine cause continual loss of power. The necessity of a regulator to maintain a constant pressure, and speed of engine and torpedo during the period of its run, also causes a waste of power, and finally the wheel gearing employed to obtain the rotation of the propellers in contrary directions also requires an expenditure of power. By all these conditions the scope of the motive agent is decidedly contracted, and the obtainable speed of the whole mechanism brought into narrow limits. The system of propulsion of Count Buonaccorsi permits that the cylinder-engine, pressure regulator, and wheel gearing may be dispensed with, with the possibility of simplifying the mechanism of the torpedo considerably, and also increasing the useful work obtained from the compressed air. The principle of this system consists in developing the energy, by applying the reactive force of compressed air, allowing it to escape freely, immediately to the propellers and causing them to revolve, instead of employing the statical pressure of the air on a piston when confined in the cylinder of an engine.
Of the annexed figures, Fig. 2 shows a longitudinal section of the after part of the torpedo with both propellers; Fig. 3 and Fig. 4, sections through x—x and y—y of Fig. 2. The air, which is compressed to 70 or 90 atmos. into a cylindrical reservoir slightly smaller in diameter at both ends, is led out of the reservoir through a fixed tube, a, which is connected by an air-tight connection with another tube, b, the latter capable of revolution on its axis, and enclosed by the tube c; on these tubes the propellers A and B are fitted, of which A is a right-handed, and B a left-handed screw. The boss of each of these propellers contains a conical chamber A' and B', which surrounds the tube c, and into which the compressed air has access through the tubular shafts b and c, and the slits b’, c' and b2, c2, which are cut through them. The air is led out of these chambers (which form a sort of pressure reservoir, and by means of which, in conjunction with the propellers, which act as governors, the speed of the torpedo can be regulated) through the channels A2, A2, B2, B2 formed in the blades of the propellers, to the surrounding atmosphere or water, as the case may be; and the rotation of the propellers in the opposite direction to the issuing air is thus obtained by the force of reaction. The speed of revolution of the two propellers is regulated by the size of the openings through which the compressed air is admitted to the chambers A and B, and the speed of the propellers may be quite different, as by this means the unequal effect of the propellers, which up to now has had to be counteracted by means of rudders, etc., is obliterated, and the adjustment of the torpedo effected; the inventor has found by experience that, with the increase or decrease of the speed of propeller, its directive effect on the torpedo increases or decreases, and consequently it is only necessary to make the difference in speed of the propellers of such a magnitude as to exactly balance each other in directive effect on the torpedo.
Again, as before mentioned, the speed of the propellers depends on the size of the openings through the two tubes b and c, through which the air pressure is admitted to the chambers A’ and B'; it follows, therefore, that by changing the size of these openings, changes in the revolutions of the propellers, independently of each other, may be obtained, and consequently a resultant steering effect on the torpedo. The variations in the size of these air supply orifices is obtained in the following manner: The inner tube b. Fig. 2, side view and section, is provided with the longitudinal slits b1 and b2 , Figs. 3 and 4, in section, in the wake of the propellers, and these openings communicate with similar openings of half the width in the outer tube, c, and it can be so arranged that the compressed air may be admitted to the chambers A and B, through the full area of the openings c1 and c2, or these areas can be reduced by altering the relative positions of the inner and outer passages. The two openings c1 and c2 can never come at the same time in coincidence with their corresponding openings b1 and b2 in tube b, and it is by revolving the pointer b2 fixed to the tube b, in direction of the arrow 1 (Figs. 3 and 4), that it is possible to throttle the air admitted to propeller A; or vice versa, by moving the pointer b in direction of arrow 2.
For registering the number of revolutions of the propellers throughout the run, the two worm wheels w, and the toothed wheels w' (Fig. 2) are fitted. In this after part of the torpedo there is also a part of the depth-steering apparatus, viz., Fig. 2, the diving rod d worked by the steering engine, and connected rigidly to the tube c by the arm f, so that, as the latter tube is movable in an axial direction to the tube b, the movement of the arm d can be transmitted without change to the rod d' , in the after end of the tube c. This rod d', by means of the connecting rod and lever, t, t, is connected to the horizontal rudders and communicates to them directly the movements of the diving rod. The most important novelties claimed by the inventor in his patent are: (1) the propulsion by means of the reaction of compressed air on the propeller blades; (2) the means of governing the direction of the torpedo by variation of speed of the propellers through varying the supply of air pressure to the same; (3) the mode of transmitting the movement of the depth regulator to the horizontal rudder arms by means of the hollow movable propeller shafts.
With regard to the construction and dimensions of the new propelling apparatus, the following calculated results are taken from an article by the inventor. The air is compressed to 80 atmos. into a reservoir of a capacity of about 0.12 cub. m. = 4 ¼ cub. ft. This air flows through a straight tube of the same effective area as the outlet orifice in the reservoir by the shortest course to the hollow tubes of the propeller shafts. On these shafts, in the usual position, not keyed on but movable on their shafts, are the two-bladed propellers of 0.32 m. diameter (12 5/8 in.). The boss of each propeller contains the conical air chamber already described, and each is fitted air-tight, both at its forward and after sides. The air pressure passes out from the before-mentioned conical chambers by four channels of rectangular section, 30 mm. by 1 mm. in width, into an outlet opening of 0.00003 sq. m. in area, bored through each of the propeller blades, leading out to the point of the blade. The radius of curvature of these channels is constant, and equal to 0.1 m. The angle at which the concave surface of the channel is met by the issuing air is 10°, the bend of the channel is 90, the whole length of the surface acted on by the pressure in each channel is therefore 0. 15 m. By the calculation of the inventor, his propelling mechanism, with an initial pressure in reservoir of 80 atmos., and using up all the energy of the air to the final pressure of 20 atmos., obtains a useful effect of 100e (= H. P.), which gives the torpedo a velocity of 34 knots, or in two minutes it would cover a distance of 2000 m. The charging and air-supply valves of the Buonaccorsi torpedo have, in the view of the inventor, particular advantages: whilst in the other fish torpedoes worked by compressed air the air supply valve is a lift valve, in the Buonaccorsi a cock is used, and the plug is held in position by a flat spring, which bears against a square on the plug both in the "open" and "closed" positions. The key which opens and shuts this cock is connected to one arm of a three-armed lever, the other arm of which projects through the shell of the torpedo, and serves to open the cock in the same way as the air lever of the Whitehead torpedo, that is, by means of the tripper of the launching tube. The automatic closing of the starting valve is obtained by the action of the propelling mechanism on wheel work which releases a spring which has been put into compression on opening the starting valve, and which is connected by means of a link to the third arm of the lever on the plug of air cock. The charging pipe is fitted directly on the after end of the air reservoir, immediately in front of the air supply valve and connected to the same pipe, the valve itself being fitted on the upper end of the charging pipe, so that when it is compressed by the charging nozzle a direct communication is opened up to the air reservoir. The depth-controlling apparatus is on the same principle as in the Whitehead torpedo, a combination of a hydrostatic valve and spiral spring and heavy pendulum, the spring adjustable to the pressure corresponding to the required depth of the torpedo during its run. This apparatus is placed immediately in rear of the explosive chamber, and the action is communicated to a servomotor by a rod passing through a tube through the air reservoir. There is also an arrangement for fixing the horizontal rudders in any desired position for a certain time, and for bringing the rudders up when the torpedo is stopped, and so bringing it to the surface. A sinking valve can also be opened at the same time, if desired, to sink the torpedo by admitting water to the after chamber. The safety pistol, to prevent a premature explosion of the charge, is of the "fan" pattern. The material of which the torpedo is constructed is, with the exception of the steel air chamber, Austrian delta metal.
From a pamphlet by the inventor, it appears that it is proposed to make the air chamber also of delta metal, the experiments on a shortened air vessel of this metal having shown that there would be no technical difficulty. The inventor claims for his "reaction" torpedo, as against the automobile fish torpedo: 1, increased speed; 2, increased range; 3, greater reliability in direction; 4, simpler mechanism; 5, more perfect action of the steering apparatus; 6, increased range of depth, as well as a simpler and more certain adjustment of the same; 7, larger range of action of the explosive; 8, more exact adjustment of the controlling gear of horizontal rudders; 9, more reliable action of the stopping and sinking gear.
Further, the fish torpedoes of former types may with comparatively small expense be easily converted into the Buonaccorsi type, as the explosive chamber, air chamber, buoyancy and balance chambers, etc., are not interfered with to any great extent by the new fittings, and a good many of the internal parts also may be utilized in the conversion.