Note:  Still being edited, photos and drawing to come.  This is a long document.

It was during a club diving weekend in October 1977 that the skipper of our hired boat received a request from a local fisherman friend asking if we would mind searching for some lost prawn pots on the Portland Harbour wall. This we readily agreed to do since diver/fisherman relations can always do with a boost. Several divers, including myself, took part in the search. My allotted depth was about eight metres and for several minutes I carefully searched amongst the huge boulders which make up the wall. Suddenly I spotted several greenish coloured metal items scattered amongst the rocks. All thought of prawn pots disappeared as I filled my bag with all manner of unidentified copper, brass and bronze items. Several other divers joined in, and when back on board, we soon had quite a haul. I think that the general consensus of opinion at that point in time, amongst my colleagues, was that the best thing to do was to take it all to the scrap yard. Fortunately, I insisted that everything returned home for further inspection.

During the weeks that followed the various items were meticulously cleaned, yielding all manner of intricate mechanisms, made, primarily of bronze. Nearly every item was clearly stamped RNTF 21" Mk. VIII No. 698 and after limited research I realised they were all parts of torpedo, (RNTF being the abbreviation for the Royal Naval Torpedo Factory). Date stamping on some items indicated that it had been manufactured in 1936 and had probably been lost from the test tower on the Portland Harbour wall.

This very fascinating find was the start of my current interest in historic torpedoes, the more I researched the subject, the more I have been amazed at the general lack of interest in such a significant weapon.

The inventor of the most successful design of torpedo was Robert Whitehead 1828 - 1905. He was clearly one of the greatest British inventors of the 19th Century. The type of torpedo that he invented exerted more influence over the tactics of naval warfare than all the worlds? top admirals and naval architects put together. Yet, although he was honoured by many other nations, he received minimal recognition from the country of his birth. Even today, apart from current and past members of the Royal Navy, his name remains virtually unknown.

There has also been a tragic lack of appreciation of the engineering skills that have gone into the development of the torpedo since Whitehead produced his first prototype in 1866. Of all offensive arms, the workings of the torpedo are probably the least understood. Until recently even the administrators of the Royal Navy seemed to have had very little respect for the weapon. In the 1950?s a superb collection of torpedoes on display at the Torpedo Experimental Establishment at HMS Vernon was scrapped, despite the pleas of the engineers who had built up the collection. I have a feeling, that divers like myself may be destined to put things right, since the first find in 1977 I have personally discovered the remains of three very historic torpedoes and have rescued parts of another seven from the scrap yard.

With the help of Edwyn Gray and Mr Geoffrey Kirby this article is merely a pr?cis which I hope will accurately discuss the development and history of torpedoes up to the end of the Second World War.

I have decided to detail the technical advances made to the various torpedo components, since Whitehead first prototype in 1866, rather that discuss the various torpedo designs in date order.

Robert Whitehead was born in Little Bolton in 1823 and came from a family of engineers. Maintaining the tradition, he served a long apprenticeship with a well-respected engineering company, Omerods of Manchester, and left in 1840 to seek his fortune abroad. In Victorian times British Engineers were at a premium. He managed to make a good living, working initially in a shipyard in Toulon and setting up as a consultant engineer in Milan. He was, however, forever trying to avoid the numerous European wars and, as a result of boundary changes, lost many of his important patents. He moved on to Trieste on the Adriatic coast, again working for a shipyard where he was credited with producing the first screw propeller and cylindrical marine boiler to be built in Austria. In 1864 he decided to except the job as manager of a major engineering company based in Fuime near Trieste. The company undertook work for the Austrian Navy. Whitehead who had an excellent reputation by now was approached by an Austrian Navy Captain, Giovanni de Luppis and ask to enter into a partnership to build an unmanned, self-propelled surface boat packed with explosives which could be directed at blockading warships. It was referred to as the ?Der Kustenbrander? (Coastal Fire Ship), it had been turned down by the Austrian Navy on basis it needed further development. Whitehead tried for several months to assist Luppis with his invention but between them they failed to perfect a viable weapon, there were major problems with the clockwork engine and the tiller controlled steering.

The partnership ended, but the project left Whitehead with the gem of an idea. He reasoned that a weapon, like they had tried to develop, would be at its most effective if it detonated below the waterline. Better still, if it could travel beneath the surface throughout the attack. Remembering his ?lost? patents, Robert with only his son John to assist him, spent months in secret trying to perfect his own idea. His invention when it appeared in 1866, and later perfected, has since been described as the work of a genius. Fortunately for the World?s Navies the Austrian Government failed to except the exclusive contract, that was offered by Whitehead in 1868, leaving him free to offer his product to whom he saw fit. In 1870 he brought two of his weapons to England for trials with the Royal Navy. The larger two was 14ft long, range 3000ft, diameter 16" with a charge of 67lb. of gun cotton and the smaller 13ft 10?inches, range 2000ft, diameter 14" and charge 18lb. of dynamite. The Royal Navy were very impressed and bought the manufacturing rights for ?15,000 in 1871. One of the important provisos of this purchase was that modifications could be made and fitted if they so wished. This proved the be of benefit to the Whitehead Company as well, since the Woolwich engineers made some significant improvements of their own.

Whitehead's experience with the ?Kustenbrander' made him realise that the power of clockwork was totally unsuitable for his new weapon, instead he decided to use the power potential of compressed air. Detailed drawings of the prototype torpedo are sadly unavailable because of Robert Whitehead's obsession with secrecy. However the following information give us rough idea;

Performance was said to be 6-8 knots for 200-400 yards. It was 11ft 7ins long with a pointed nose and cylindrical body. There were large vertical fins to prevent the weapon from rolling over (or spinning), a single propeller and a simple rudder. Inside there was the head containing dynamite and a simple detonator (or pistol). There was the air chamber containing the compressed air fuel at approximately 700psi, a compressed air engine, which drove the single drive shaft. A simple hydrostatic valve operated the rudders.

Trials of this prototype in Austria were reasonable successful, however, to depth keeping was erratic.

Between 1866 and 1868 he returned to the drawing board and produced his ?MK 2? which proved to be far more reliable. The oldest surviving example of one of Robert Whitehead?s early torpedoes can be seen in the Maritime Museum in Vienna, Austria.

The engines used in the prototypes were purpose designed and built. They were said to consist of two oscillating cylinders set at right angles. A constant engine speed on a rapidly failing air pressure was aimed at by an automatic regulating valve.

In about 1875 Whitehead completely redesigned his product, producing a 14" diameter weapon, capable of 18 Knots over 600 yards. In this he used a three-cylinder radial engine ( Photo) designed by Mr. Peter Brotherhood?s Company in Peterborough, England. In this engine, air is admitted to space above the pistons (cylinder head being integral with the cylinder) by cam operated piston valves (Photo). This produces the power stroke, forcing the piston down. When the piston approaches bottom centre, the exhaust escapes through ports in the cylinder walls, uncovered towards the end of the power stroke. As the piston returns to top centre, compression prior to the introduction of further compressed air, which would cause power loss, is avoided by having a slot in the piston. This slot is uncovered, during what would be the compression stroke in a petrol or diesel engine, by the relative movement of a semi-hemispherical gudgeon. Exhaust air from both cylinder ports and the gudgeon valve, leave via the crankcase, the big end and then through the hollow propeller shaft. This method of exhausting the air, added significantly to the speed of the torpedo. All the components that make up this engine are various types of bronze. To complement this superb engine, the air vessel pressure was increased to 1000 pounds per square inch (psi). The Germans used a similar three-cylinder engine (Photo) in their Type G torpedo developed in 1906 and used in the First World War. This was basically a crude copy of the Brotherhood engine with the slide valve cam outside the crankcase.

The three-cylinder engine remained in use till about 1900 when a four-cylinder version was developed in 1899. This engine apparently had poor balance. The extra cylinder increased the power marginally from 50 brake horse power (bhp) to 56 bhp. With the advent of heater systems the increase in inlet temperatures up to 1000 ?F and resulting power required improvements to the engines. The piston type slide valves were replaced with cone seated types (Photo) and extensive modifications were made to the lubrication system, which on the earlier engines was very primitive. One fact that would horrify many engineers was the practice of spraying salt water into the crankcase to aid cooling. An early engine of this type (photo) circa 1909 for an 18" torpedo is a bronze four-cylinder unit in which like previous engines had integral heads, bores and manifolds. Air consumption was up to 12 lb. per bhp per hr.

A more advanced engine of this pattern (Photo Caton Engineering Company Lancaster 18" torpedo) for an 18" torpedo weighs about 120 lb. and can be made to yield 180 hp. One of the major limitations was that of piston stroke, which was set by the diameter of the torpedo, often caused seizure in the lower part of the cylinder, because of a large thrust on the side wall. The arrangement also restricted the area of the big end bearings on which pressures in the order of one ton per square inch were not uncommon. Counterweights needed to bring any four cylinder radial engine into correct balance could not be used due to lack of space, Figs. X shows diagrammatically the engine shown in the photograph.

Many other types of engines were experimented with and many gained favour in foreign built torpedoes. However in Britain the majority were Brotherhood type radials although these engines were considerably unreliable, inlet valves frequently leaked and had a very high consumption rate.

Following the Armistice in 1917, the RNTF at Greenock and several outside firms investigated possible improvements in torpedo propulsion. Many of the experiments involved the use of improved fuels such as hydrogen peroxide and oxygen enriched air.

A very significant advance was made in the late 1920s with the invention of the Peter Brotherhood, Burner Cycle engine. The remarkable success of this engine compared with foreign turbines was due to its superb power/weight ratio and weight of fuel consumed per bhp per hour. The Burner Cycle or semi-internal combustion is a four-cylinder radial engine (photo) which was not integral in its construction like its predecessors, the crankcase was bronze (photo) but the manifold, cylinder heads and bores are steel. Early forms of the engine used air as the fuel oxidant that was fed at about 840 psi via a reduction valve from the main air vessel. A small quantity of fuel e.g., paraffin, is atomised into the air and burned (see igniter *). This raises the air temperature to about 1000 ? C and only slightly depleted the oxygen content. This hot gas is then fed into the engine through the poppet valves. More fuel is then injected into each cylinder a little before top dead centre. Spontaneous ignition occurs and supplies the driving force. Like its predecessors the exhaust gases leave through four main ports in the cylinder liner and two auxiliary ports in the piston crown (photo). By the end of World War II this engine had, with minor modification, achieved a power of 465 bhp.

In Whitehead's prototype, a simple hydrostatic valve acting directly on the elevator controls, was intended to hold the torpedo at a pre-determined depth underwater. In practice however the depth control was erratic, sometimes running along the surface, sometimes plummeting to the depths and often acting like a porpoise.

The prototype was demonstrated to the Austrian Navy as early as 1866, the trials proved impressive but as mentioned earlier, the erratic depth keeping of the weapon made it apparent that the torpedo was not as yet in a sufficiently advanced stage of development. The Austrian Government did admit that the weapon had considerable possibilities so Whitehead returned from the trials to continue his development work. The problem took Whitehead many months to solve but when he did, it was certainly an ingenious mechanism. For many years it was referred to as the 'Secret' since he did not patent it and would always ensure that only a few specialists were admitted to its mysteries once the contracts for orders had been placed. The 'Secret' was as simple as its title was dramatic and there was little doubt that Whitehead got it right from the time he introduced it in 1868. It remained unchanged in its basic form until the end of World War Two, some 75 years. A tribute to Robert Whitehead's remarkable genius.

The mechanism was housed in an airtight compartment within the torpedo called the ?Balance Chamber?. It was originally situated behind the warhead but this arrangement was changed in 1875 to the familiar layout of the balance chamber behind the air chamber and in front of the engine. Two mechanisms are combined to make up the depth keeping apparatus, the original hydrostatic valve and a heavy pendulum. The hydrostatic valve is mounted in the shell of the balance chamber in contact with the water and consists of a movable disc that is made watertight by a flexible rubber joint. The balance chamber will be at atmospheric pressure and depending on depth the water pressure will move the disc inward. It is a relatively simple matter to pre-set the disc for a certain depth of water using a spring so that at equilibrium, via a series of connected levers, the rudders are horizontal. If shallow, the rudder will tilt down taking the torpedo deeper, likewise if too deep the rudders will tilt up. The heavy pendulum, responding to gravity only, acted as a damper (see diagram) and reduced the depth control tolerance to as little as plus/minus 6 inches. On these early models the depth could be varied from 5 to 15 ft.

No significant propulsive improvements were made before the end of the 19th century since the uncertain directional accuracy made it pointless to strive for greater range. The accuracy of torpedoes depended on scrupulous adjustment of the vertical rudder and various trim tabs on the tail over many test firings. There were always large angular errors caused by varying conditions of discharge from the ships and adverse surface conditions of the sea that would cause a torpedo to deviate from its set course. Robert Whitehead was probably the first engineer to realise the potential of the gyroscope and started experimenting with a device designed by a Russian called Petrovich in about 1890. The device however was crudely engineered and the Whitehead Company finally opted for a precision built instrument invented by Ludwig Obry in 1895. This device could achieve the required rate of high rotation speed necessary for both accuracy and duration. The mechanism consisted of a 1? lb. wheel about 3" in diameter held in gimbals with its axis along that of the torpedo. The wheel was spun up to a maximum of 2400 rpm by means of a pre-tensioned spring and could develop a force of about 20ft lbs. (This force could be utilised when the torpedo started to deviate from its course.) A two-way valve was mounted to the gyroscope frame activated by the vertical gimbal. The gimbal would be turned one way or the other by the force applied to the gimbal by the rotating ball trying to maintain its rotational axis. The two-way valve in turn directed a measured amount of air to correct for course deviations for port or starboard. This supply of air was fed to the steering engine connected to the vertical rudders to apply opposite helm to any deviation of the torpedo?s course. It was an ingenious solution to a problem that had bugged the torpedo ever since its birth in 1866. The Obry apparatus increased the accuracy of the torpedo's course to a mere ? a degree over a distance of 7000 yards. A little academic in 1900 since the best torpedo could only manage 1000 yards. It did however, lead the way to significant increases in performance and range.

The Royal Navy at first refused to adopt the gyroscope on the grounds that its Woolwich built weapons were sufficiently accurate for all likely operational requirements. This claim was in fact quite reasonable because the Royal Navy made a fetish or recording and averaging the results of hundreds of trial runs so the characteristic of each individual torpedo could be calibrated and analysed. From 1883 each torpedo had its own log-book in which was entered details of every test run, all the relevant data on deflection angles, speeds, strength of wind, and direction of tidal flow. The loss of a torpedo was a very serious event that could result in a Court of Enquiry.

It was soon apparent that the Obry gyroscope gave an even greater degree of accuracy than the entire logbook data and subsequent performance analysis. It also got over on erratic running due to deflection of the torpedo on entering the water, dents or damage, particularly in the tail area, also one propeller overcoming the other due to an imperfect balance.

In 1898 the Royal Navy reversed their decision by agreeing to manufacture their own gyros on payment of a ?25 royalty to the Whitehead Company for each unit built. It has been suggested that the Royal Navy were also a little reticent to adopt the gyro since at that time they possessed more than 4000 Whitehead based torpedoes. Many of these were on board ships serving in the farthest corners of the globe, to convert then would be a massive undertaking. Once the decision was taken? however, every torpedo in service was converted by 1900. This was a considerable achievement and indicates the efficiency of the Royal Navy at that time.

The German Company Schwartzhoff also adopted the gyroscope when it was realised the advantages that Whitehead had achieved with the Obry device. With the Obry rights bought out by Whitehead they had to search for another design which, by good fortune, they found fairly quickly.

They opted for a more promising type of gyro designed by a Mr Kaselowski. This worked on similar principles, but the wheel was spun by a short blast of pressurised air from two nozzles acting on blades mounted on the periphery. (Photo). Although a wheel with blades loses speed more rapidly than a smooth one, the disadvantage was offset by the added energy that the air blast imparted to the wheel compared to the spring.

The gyro does have certain limitations: pitch and rolling of the torpedo strains the gimbals and can cause directional errors. Another problem with the gyro is the effect of latitude. When the gyro is balanced and adjusted on a testing stand so as to maintain an apparently fixed orientation, it has been adjusted in fact to compensate for the Earth?s rotation in the latitude of the place of adjustment.

The increased range and speed derived from the adoption of heater systems of propulsion soon led to a demand for better performance from the Whitehead and British made weapons.

The Obry gyroscope was improved on the lines of the Kaselowski by the fitting of air jets to the vertical gimbal ring and by cutting bucket-like grooves in the wheel. The air was fed continuously thereby maintaining the wheel spin indefinitely. The major drawback with the modification was that the initial spin conferred by its spring start was not nearly high enough. The acceleration imparted by the nozzles was insufficient to bring the wheel to an adequate speed until half a minute or more had elapsed. This resulted in poor directive control during the early part of the run. One further problem was that nozzles, mounted on the vertical gimbals, resulted in small opposite reaction that could also cause inaccuracies.

The next stage of development, to overcome these inadequacies, was circa 1910. A turbine rotor was connected to the gyroscope wheel and set in motion by a jet of air at full air vessel pressure for a short time only. In fact, in one design the valve controlling admission of the air blast only remained open for 0.35 sec, the energy imparted to the wheel was over 500 ft lb., a considerable increase over the 20 ft lb. of the original Obry type. It was now possible for the gyro to take charge of the torpedo during the critical period immediately following discharge, the wheel speed still being maintained by low-pressure jets acting on buckets cut in the periphery of the wheel. The mechanisms that were developed to transfer the relatively small force of the gyro to the rudder are covered under ?servo motors?.

Although there was always the threat of competition, Whitehead continued to develop and improve his torpedoes. A very important innovation was the servomotor, which fitted between the balance-chamber mechanism and the rudders. This mechanism, very like that fitted to the modern automobile brake system, amplified the small force from the hydrostatic valve and pendulum linkages, sufficient power to control the horizontal rudders far more efficiently. The amplification in power was reported to be in the order of 5500 to 6000 times! This device first appeared in the 14 inch Fiume Mark 1 circa 1877.

The Whitehead torpedoes needed compressed air to power the engine. In the prototype we mentioned a supply of 700psi. What we are not sure about is the capacity and the construction of the air vessel. Since in Whitehead?s early designs the balance chamber containing the ?Secret? was in front of the air vessel (see above), there was a tube through its centre to house the rudder control rod. In about 1875 (14 inch Fiume MK1) the balance chamber was re-sited behind the air vessel removing the need for the central tube. Both the capacity and the working pressure (1000psi) of the air vessel were increased significantly. Capacities and working pressures continued to increase as metal technology improved and in many cases, as the torpedoes became larger.

A mentioned elsewhere torpedo engineers constantly strove for increased performance and the introduction of the gyro made it far more worthwhile. Whitehead based torpedoes between 1866 and 1900 were driven solely by compressed air and so were many other experimental engines of that period e.g., cold air turbines. Although design modifications incorporated some small additional improvements, the experts were only tinkering with existing ideas. What was needed was a significant breakthrough, this came, as many discoveries often do, quite by accident. In 1901 the Woolwich torpedo factory chanced to find that the warming effect of seawater on the cold air supplied from the compressed air chamber increased the speed of the weapon by half a knot. As capacities and working pressures of the air vessels had increased, the cooling effect produced when the air expanded, was obviously affecting the torpedo performance. Although it was only a minute increase, it was highly significant, it started the era of the heated torpedo, the most significant step in torpedo development in almost forty years. Early experiments involved warming air by coiling the air pipe around the engine room thereby obtaining a slight warming effect from the seawater circulating the compartment. Marginal improvements were noted. In 1904 Sir W. G Armstrong (Whitworth Company) patented the Elswick Heater. In this the contents of the air vessel are warmed by a spray of liquid fuel, injected by compressed air, locked in the upper parts of the fuel bottle and ignited by the firing of a cartridge. With a single fuel bottle arrangement, the quantity injected, will be roughly proportional to the inverse square of the pressure in the main air vessel, hence an irruptive and possibly dangerous influx will occur when the system reaches its last gasp. The twin bottle arrangement was designed to avoid this.

This heater system was tried at Weymouth in an 18" Whitehead/Fiume Mark III torpedo before British and Japanese Naval representatives in 1905. The result was an increased speed of 9 knots over 1000 yards compared to the same weapon cold. The heating was very uneven and soot built up in the air vessel and there was still a significant loss of heat between the air vessel and engine once again due to the reduction of air pressure.

The next major improvement was the ?Fiume? heater Fig X made by the Whitehead Co., who had not been building torpedoes for the past 40 years merely to pass the time. In this system the fuel is sprayed into a combustion pot or generator on the low-pressure side of the pressure reducing valves. Since the most liquid fuels injected in this way would create a temperature too high for the currently used engines, water was also injected and converted into steam. The resulting mixture of hot air, burnt fuel and steam significantly increased the torpedo performance yet again. Fig shows that the feeding head for the fuel is obtained through the water supply bottle, thus avoiding a burn out if the water supply should fail or become blocked. A choker constricting the main air passage into the generator induces this feeding head. Torpedoes with this type of heater were nicknamed 'steam torpedoes'.

The Admiralty, who felt that the system was over complicated, did not adopt the Fiume heater. Instead they used a system invented by Engineer Lieut. S. U. Hardcastle (Photo) and generally known as the R.G.F. Heater. It was first used in an 18" Mk. VII Fig X ?Woolwich? torpedo of 1908. The liquid fuel and the air are swirled in opposite directions to obtain thorough vaporisation of the fuel. An igniter, or incendiary cartridge, fired by a hammer system (Photo) which is tripped by gearing turned by the engine. The mechanism is arranged so that the igniter is not fired until there is something for it to ignite. In fact the engine runs on cold gas for a few revolutions before gaining full power when ignition takes place. The outside combustion chamber is cooled by seawater circulation. The petroleum fuels used with this heater require approximately 14 times their weight of air for complete combustion. The proportion of water injected modifies the temperature of the fuel gases. A mechanism (Photo) can be included to vary the amount of water and hence the temperature of the fuel gases.

Up to the development of heater systems 'fuel' was obviously solely compressed air, and range was therefore dependent on the capacity of the air vessel and consumption of the engine. The charged air vessels of torpedoes, circa 1925, weighed about one third of the total weight of the weapon and the largest part of its bulk. Since atmospheric air contains only 21 percent oxygen (79% nitrogen) torpedo designers frequently experimented with alternative oxidants. Once the heater systems were introduced, small quantities of fuels like petroleum and alcohol were used.

Hydrogen peroxide was studied as a low-pressure oxidant that had the advantage of high density, the need for a low weight container and catalytic decomposition into oxygen and water with the release of appreciable heat. In the UK studies were made of enriched air as an oxidant; although a heavy pressure vessel was still needed, a greater weight of oxygen could be carried. A 21" Mk. VII of 1928 was designed to run on air with 57% oxygen, its performance was 33 knots to a range of 1600 yards. This weapon was fitted to the ?London Class? cruisers and was several years in advance of similar development in other countries. They were, however, unpopular on account of the capricious nature of the enriched air and the rapid corrosion in the pressure vessel. A significant advantage apart from the superb performance was the reduced ?track? due to the low proportion of insoluble gases like nitrogen in the exhaust. This is primarily an advantage for submarines attacking convoys because without the obvious track, the first indication of an attack is the explosion. The Mk. VII, however, was not fitted to submarines! The thing that killed the enriched air torpedo was the invention of the Brotherhood Burner Cycle engine (see above). The early weapons fitted with this engine used Broxburn Lighthouse Shale Oil and later, paraffin as fuel. A significant advantage with this engine was that it did not need a diluent and could receive its oxygen supply from an alternative source such as hydrogen peroxide. Hydrogen Peroxide was, however, not available in Britain in sufficiently stable or concentrated form before the Second World War, so the Burner Cycle Engines were generally run with compressed air.

(see G Kirby page 53)

The prototypes on all the early models had a single propeller, spinning being avoided by large vertical fins. It was the Woolwich engineers who made one of the most significant modification to torpedo design; the use of contra-rotational propellers. The number of propeller blades also changed as torpedoes developed.

The main pipe from the air vessel passes through a screw-down stop valve, which if not opened resulted in a wasted shot and possible loss of the weapon. Some manufacturers omitted this valve. Woolwich made torpedoes that had a stop valve from which the spanner could not be detached unless the valve was fully open.

After the stop valve (if fitted) there is the starting valve that is thrown open, as the torpedo is discharged, by a stud or ?trip? mounted on the discharge apparatus. In early torpedoes this valve was usually cam operated (Photo). As the air vessel pressures increased, it became more difficult to open the valve. This was overcome by a double valve of which only the small member has to be pushed open by the first movement of the lever, the action equalising the pressure on both sides of the large member. Fig. X. This type of valve forms part of a larger assembly described next as the ?Counter Mechanism?.

Photograph X shows a range of counter mechanisms 1909 - 1944. Apart from the starting valve already mentioned, it also incorporates other functions. There is a spring-loaded check valve on the discharge side to prevent seawater from flowing into the air vessel and then to the generator and engine at the end of a practice run. A counter that can set to cut off air after a given range has been run. A plunger mechanism then operates the valve to start the gyro.

The main reducing valve was used in the earliest of torpedo and cuts down the air vessel pressure to the working pressure of the engine (about 500 lb. per sq. inch).

The Whitehead Company never built electric torpedoes but many that were produced used many of his ideas.

The electric torpedo made its first appearance in about 1873 and was the brain child of John Ericsson . It was a wire-controlled weapon that was powered by an electric current passing down an umbilical cable to the shore base or mother ship. A direct development of the Ericsson was the Sims-Edison that was similarly powered down a trailing wire. A speed of 10 knots was attained using a Siemens motor drawing 30 amps at 600 volts. Several versions of this weapon were built, all carried under a large float. They were very similar in external appearance to the weapon shown in Fig X. The last version built in 1889 carried a 400 lb. warhead to a range of two miles.

The Swedish Engineer, Thorsten Nordenfelt, took the idea a stage further in 1888 when his giant 29" torpedo, the largest ever built, was driven by an 18 BHP electric motor fed by 108 storage cells carried inside the shell of the weapon. Guidance was by means of electrical impulses transmitted down a wire paid out from inside the weapon. C Sleeman in his book "Torpedoes and Torpedo Warfare 1889" describes the weapon Fig X as being buoyant and held down by the heavy fins. It is difficult to see how the weapon could have remained upright. The sloping edge to the fin was supposed to assist the weapon to pass under the torpedo nets. This design was the forerunner of electric weapons that contained their own propulsive energy in the form of batteries, and the generation of wire guided weapons, which are in use to the present day. At the time these weapons were being developed circa 1890, their performances were comparable with compressed air weapons. At the turn of the century however the electric torpedo was left far behind in performance. Insert?

Some work took place in the United States, resulting in an experimental battery driven torpedo in 1915. The weapon was only 7.25" in diameter and six feet long. Its specification was to carry a warhead weighing a few pounds to a range of 3800 yards at 25 knots. It is unlikely that such a performance would have been achieved however. By 1918 this work, carried out by the Sperry Gyroscope Company, had come to a halt. The United States Navy was still maintaining an interest however and a design study in 1918 gave rise to an 18" diameter weapon in 1919. This work carried on slowly without much official support until 1931 when it ceased altogether. It was not until World War Two and the success of the German electric torpedo that American interest was revived.

It is not hard to discover why many countries pursued the electric version of the torpedo with vigour. There was the obvious tactical advantage of complete tracklessness and the fact that electric weapons remained at a constant weight during the run. This meant that ?list? and inclination did not vary. Torpedo manufacture is a highly skilled art that I am hoping this article shows. Not only is considerable engineering expertise required, but also, a vast amount of sophisticated machinery to build them. By 1914 the construction of a single torpedo used up a tremendous number of man-hours. The cost per weapon was enormous at about ?1000. Most of the labour and cost was tied up in the production of air vessels and engines and by its very nature, work had to be restricted to highly specialised workshops backed by years of experience and know-how. The electric torpedo by contrast, was a far simpler piece of machinery and it was possible to sub-contract much of the work to non-specialising firms using only semi-skilled labour. The only disadvantage was that their performance did not match many of the new thermal weapons. With the increasing use of the submarine, however, the success of the electric weapon was assured.

The Germans had produced a successful electric weapon in 1917 that was issued experimentally to some boat units in the G fleet. They were not fired in anger however due to the timely intervention of the Armistice. The weapon was capable of 28 knots to a range of 2000 yards. Further developments continued between the wars and to circumvent the restrictions imposed on torpedo manufacture by the Treaty of Versailles much of the work and testing was carried out in Sweden. The work began in 1923, ten years before Hitler came to power, and was concluded in 1929 when after successful trials the designs were frozen and carefully stored away ready for full scale production at the appropriate time. The weapon became the Type G7e, and during World War Two appeared in three forms. The earliest type, the T2, was in service at the start of the war and had a range of 5400 yards at 30 knots. The T3 and T3a had a range of 8000 yards and a speed of about 29 knots. The weapons had to be kept warm (approx. 30?C) for maximum range since, if fired cold, the range would be significantly reduced. The batteries were, in fact, heated when the submarine was on patrol. The batteries were lead acid types and 26 cells each of 18 plates were used; the total battery weight being about 1500 lbs. The cells in each of two batteries were connected in series. The motor was an 8-pole series wound direct current (DC) device rated at 91 volts, 950 amps at 1755 rpm which weighed about 250 lb., it was used with only small modifications in all the German electric weapons.

The G7e was a very successful weapon as the terrible shipping losses in World War Two only go to prove. It was of a design that owed much to Whitehead's basic principles and all his various inventions and developments since the prototype. It was also identical in shape and, apart from the power unit, the internal layout was similar. The depth-keeping and steering mechanisms still used the pendulum device, the gyroscope and the servomotor. It strangely had the ?Woolwich? type tail i.e., the propellers abaft of the rudders. This was strange decision by Germany's designers since Whitehead's original layout was proved to be more hydrodynamically efficient. The output of electric torpedoes in Germany achieved the astonishing rate of 1000 weapons per month and approximately 7571, of all torpedoes fired by Hitler?s U-boats were electric. The production rate of thermal weapons was much slower, information suggests that British torpedo production started at about 80 per month in 1939 rising to a maximum of 500 per month during the war.

From 1875 - 1917, Whitehead?s Fiume factory turned out 12,000 weapons, i.e. less than one per working day. The German G7e required only 1255 man-hours of semi-skilled labour, the equivalent thermal engined weapon needed 1707 man hours of highly skilled engineers. A significant difference especially during war time.

The British and United States Navies had lost interest in electric weapons prior to World War Two because of their relatively poor performance. The British navy had no particular use for trackless weapons. The success of the G.7e probably spurred renewed interest by the US and a development programme re-started. The General Electric Company produced a 90hp electric motor suitable for torpedo use based on batteries manufactured by the Exide Storage Battery Company. Progress was, however, slow and it was only after a German Type G7e had been captured intact, that a really successful electric torpedo was produced. One German electric weapon was recovered in 1939 from the child evacuee ship ?S.S. Volendam? which had fortunately been a 'dud', and later in the early days of 1941 from the captured submarine U.570. The weapon became the US Mark 18 and was built by the Westinghouse Company under contract to the Bureau of Ordnance with the assistance of the Navy Torpedo Station at Newport (see US History. EG page 229 Subscript).

The Mark 18 was a success, 65% of all submarine torpedoes fired by the US submarines in the last six months of the Pacific War were Mk. 18's.

The first British work on electric torpedoes started soon after the first pieces of the German G7e arrived at the Royal Naval Torpedo Factory at Greenwich in 1940. Only a low priority was given, however, because of the lack of tactical requirements for slow weapons. In 1912 the available drawings and hardware were sent to British Thompson Houston Ltd. (BTH) at Rugby with instructions to investigate the possibilities of building a similar weapon. This renewed interest only resulted from the requirement for trackless torpedoes in the Meditteranean. The prototype was received for trials in May 1943 and after successful completion BTH eventually managed a production rate of 25 weapons per month. It was numbered the Mark II and was about to enter service in the Meditteranean when the Italians capitulated. Stocks were then moved out to the pacific arena where they arrived just too late to be used against the Japanese. Thus the first British electric torpedo failed to be fired in anger.

There is more to the story of electric weapons and several other developments are to be found in the paper by G Kirby. In addition to the advantages of the electric torpedoes already mentioned they had another significant advantage over their thermal cousins. This was silent running, a characteristic which led to other important development, the acoustic homing torpedoes and the multitudinous variants that have since followed.

? E M CUMMING 29-3-2000

References:

Torpedo History Articles, Parts 1 to 4 (J.R.N.S.S. Vol. 27. No. 2)
G. J. Kirby.

The Devils Device - Edwin Gray.

Development of the Torpedo - Engineering, May 1945 - March 1946 - (Parts 1 to 7) Commander Peter Bethell.

The Whitehead Torpedo and Engineering Works - Doug Hollins - Shrubbery Lane Local History Publications.

The Development of the Whitehead Torpedo
E M Cumming (Unpublished Manuscript).