Page:Collier's New Encyclopedia v. 09.djvu/503

TOBFEDOES 441 TORPEDOES Immediately abaft the head is the air- flask, B, a large compartment charged with air under high pressure and fur- nishing the motive power for the engine, D. In a pipe leading from the air-flask to the engine is the starting-valve, con- nected with a small lever on the outside of the torpedo which is tripped auto- matically when the torpedo is fired. The engine in the latest American tor- pedo is a turbine, but reciprocating en- gines are still used abroad. The shaft runs through the after-body, E, to the propellers, of which there are two, RR, in tandem, one being keyed to the shaft and the other to a sleeve around the shaft and connected with it by a beveled gear. The propellers turn in opposite directions, one right, the other left, and must be balanced perfectly, as the slight- est difference in their action would cause the torpedo to diverge from its initial course and might make it run in a circle and, in an extreme case, strike the ship from which it had been fired. The rudder, R, abaft the propellers, is placed horizontally, not vertically, its pedo. The essential feature of this de- vice is the utilization of the pressure of the water, which varies with every varia- tion in the depth, to actuate the horizon- tal rudder already described and so steer the torpedo up or down, as may be neces- sary. The figure sliows the immersion- chamber (water-tight), and the engine compartment (open to the sea), sepa- rated by a water-tight bulkhead. In the immersion-chamber is a sleeve carrying the hydrostatic-piston, which is held by a spring in contact with a flexible dia- phragm forming a part of the water- tight bulkhead. The tension of the spring can be varied to correspond with the pressure of the water for any desired ■depth. If we suppose the spring to be given a tension equal to that of the water at a depth of 15 feet, the piston will remain at rest when the torpedo is run- ning at that depth. If the torpedo rises, the pressure of the water on the flexible diaphragm will be less than the tension of the spring and the piston will move to the right, carrying with it a rod which is attached to the rudder, and steering AIR FLASK IMMERSION CHAMBER RUDDER COMPARTMENT DIAGRAM OF TORPEDO — FIG. 1 PROPELLERS purpose being to steer the torpedo up and down^ not to right and left. Very small vertical rudders are used in con- nection with the Gyro gear, described later, but these are not shown in the drawing. The brains of the torpedo are in the iminersion-chamber, C, between the air- flask and the engine compartment. Here is placed the mechanism by which the torpedo is governed in many ways. A gyroscopic device opposes any tendency to deviate from the initial course. A depth-regulator insures running at a pre- scribed depth, usually from 15 to 20 feet. A soluble plug opens a valve after a certain time and causes the torpedo to sink if it has missed its mark. An auto- matic throttle-valve keeps the air pres- sure constant during the discharge of the air-flask, insuring a uniform speed throughout the run. Of these devices, only the depth-regulator, Figure 2, will be described, this being, perhaps, the most characteristic feature of the tor- the torpedo down. If it dives too deep, the balance of pressure is disturbed in the opposite direction and the torpedo is steered up. And so on, until the tor- pedo becomes steady at the depth for which the spring is adjusted. The range of the most powerful tor- pedoes in use in 1921 is approximately 12,000 yards (six miles) and at this range a stationary target of the length of a dreadnaught can be struck three times out of four. Naturally the condi- tions are greatly modified and the ac- curacy enormously reduced when both the firing ship and the target ship are moving at considerable speed. The ships sunk by German torpedoes during the war were all attacked at short range, usually less than a thousand yards. While torpedoes may be launched from battleships, all of which are fitted with elaborate arrangements for the purpose, they are more effectively fired from small- er craft — destroyers and submarines — the high speed of the destroyer and the