Torpedo: The Complete History of the World's Most Revolutionary Naval Weapon

^{Early Whitehead torpedo at the Vienna Military Museum. (Photo courtesy of Mr Peter Enne)}

The drawing of Whitehead’s first exploder model shows the rearward inclination of the long arming lever. When lever ‘1’ is thrown rearwards on leaving the launch cradle, the exploder cap ‘2’ is free to operate on contact with the target. It moves to the rear, overcoming the pressure of the spring ‘3’ and hits the percussion cap ‘4’, firing the exploder ‘5’ into the main charge. On later torpedoes the arming lever would be inclined forward. This long lever also formed a useful safety feature for anyone brave enough to retrieve a fired live torpedo which has missed its target. By pushing the lever forward the exploder is disarmed.

Note that in the drawing of the complete torpedo ‘of 1868’ the vertical lever is missing (although this could be due to the poor quality of the drawing), but that three horns now project from the exploder, to ensure detonation even from a glancing blow.

The success of the 1868 prototypes was guaranteed by incorporation of Whitehead’s ‘Secret’ which controlled the depth-keeping. Put in simple terms, to even out the varying depth responses obtained from the hydrostatic pressure sensor, he had interposed a vertical pendulum. When the valve called for a reduction in depth, too rapid a reaction could cause the torpedo to broach, followed by a corrective signal, causing it to dive. The pendulum sensed the change in inclination of the torpedo and imposed a corrective force of its own, thus dampening down the over-rapid signals from the depth-keeper. Variations in depth were thereby reduced from several feet to just a few inches. All that was now required would be to await the arrival of the Obry device — but that is getting ahead of the story.

^{Here, in a plan from the 1908 Austro-Hungarian navy maintenance manual, is the mechanism for the exploder ‘whiskers’. Not shown is a small rectangular plate on a lever which fits into the circular lug on the underside of the cone. On leaving the tube this plate strikes a projection, and arms the exploder mechanism. It is still set to safe, however, until the flat paddle blades have been screwed backwards along the central thread. In so doing, they push on the pivots of the two pairs of ‘whiskers’, bringing them forward where they will set off the exploder, even if the torpedo strikes a glancing blow. At the same time, the central firing pin can now move backwards when its nose hits the target. (Drawing courtesy of Erwin Sieche)}

^{The tail of a US Navy 18in Whitehead torpedo of 1898, showing the hydrostatic depth valve ‘V’ and the pendulum ‘D’, together forming Robert Whitehead’s ‘Secret’. (From the Bureau of Ordnance 1898 handbook)}

Robert Whitehead’s 1868 models were tested by the Austrians and approved for use by their navy, but as a result of the financial crisis in the Austrian empire following the Seven Weeks War with Prussia they were unable to purchase exclusive rights, and Whitehead was free to launch his invention on the world stage.

The next year Royal Navy representatives visited Fiume, and Whitehead travelled to England to demonstrate his 14in and 16in models. The British government paid him the paltry sum of £15,000 to purchase the ‘Secret’, and also for the right to begin manufacturing their own versions of the Whitehead in the Royal Laboratories (RL) at Woolwich. A fortuitous clause in the contract allowed for improvements made by the engineers in Woolwich to be shared with the Fiume factory, and vice versa.

Robert Whitehead purchased the bankrupt Fiume factory in 1872 and renamed it the Silurifico Whitehead, and events moved rapidly forward. In 1874 the Royal Laboratories engineers fitted contra-rotating two-bladed propellers, which took away the need for the stabilising fins top and bottom, the torque from one propeller counteracting that from the other. Naturally, they shared their work with Fiume, who immediately adopted the same arrangement. In the meantime, Fiume had experimented with a pair of two-bladed propellers set side by side with a horizontal control surface set between them. (This experimental design is displayed in the museum in Split.) But the RL design was clearly superior, and the twin tandem propeller system was dropped. The next year saw the change to a three-cylinder radial engine designed by Peter Brotherhood, and this design would have an extremely long life.

^{On the left, the Brotherhood three-cylinder engine in a USN 18in Whitehead (Bureau of Ordnance 1898 handbook); on the right, the four-cylinder engine of an Austrian 18in Fiume torpedo of 1908. (Plan courtesy of Erwin Sieche)}

A strange development by the Royal Laboratories changed the position of the vertical and horizontal control surfaces, moving them to the conical rear body, ahead of the propellers. From detailed examination of the contemporary plans, it is clear that this move was carried out in order to simplify production, and especially the control connections which no longer had to pass around the propellers. It would also have significantly reduced the cost of production. Fiume was reluctant to copy this move, and it is a reliable recognition feature to determine from which factory subsequent models originated. Hydrodynamically, the Fiume arrangement of control surfaces positioned behind the propellers was more efficient.

By 1882 the pressure contained in the air flasks had reached at least 1500psi, and other countries which had obtained a manufacturing licence for the Whitehead found it extremely difficult to produce air vessels able to withstand such pressures. The Whitehead factories accordingly supplied the air vessels. This problem was particularly acute in the United States in the last quarter of the nineteenth century, with no manufacturer capable of undertaking this work. The Fiume air flasks of the period prior to the Great War were formed from straight tubes, with internal end caps screwed in front and rear.

In 1883 Dr Froude’s work on hydrodynamics led to the introduction of a semi-rounded nose replacing the sharply tapered cone. This not only allowed the carrying of a larger warhead, but also surprised everyone by adding at least one knot to the torpedo’s speed, much in the way that the bulbous bow aids surface ships. The Split Museum holds a strange Whitehead torpedo head that is bulb-shaped, probably an attempt to increase the payload without increasing the overall length. It might be thought this could have improved the speed, but since it was not proceeded with, it obviously did not.

Five years later the first 18in torpedo appeared, which would prove to be a popular size over many decades. Then in 1890 Robert Whitehead opened his own factory in Weymouth in southern England, and a third factory at St Tropez in France. Back in England in 1893 the manufacture of the British versions of the Whitehead was transferred from the Royal Laboratories to the Royal Gun Factory. The same year three-bladed contra-rotating propellers were introduced, followed in 1897 by the four-bladed variety.

^{A Whitehead in the Vienna Military Museum. (Photo courtesy of Mr Peter Enne)}

In the meantime, in 1895 Whitehead introduced a startling new innovation: the gyroscope patented by Obry and designed to control a torpedo in azimuth. At a stroke, this application produced two major improvements. First, the torpedo’s steering would no longer depend on preset rudder adjustments based on empirical practice with each individual torpedo. Now every production torpedo had the ability to keep on a straight course under the control of its gyroscope. Second, the gyroscopic control could itself be preset to continue straight ahead for a short distance after launch, and then to take up another course for the torpedo at the angle fed into the device prior to launch. The Whitehead was now controlled automatically and continuously in both the vertical and horizontal planes.