Category:Torpedo Director

A British torpedo director of unknown type, possibly after alteration to a deflection sight.
Images of such devices are uncommon.^[1]

A Torpedo Director, in British service, is a calculating sight for firing torpedoes, more similar to a settable gunsight than to a gunnery director.

Nature and Function

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The Director Angle is the proper angle between the line of sight to the target and the path of the torpedo. Helping the torpedo officer judge and discern this angle from data available to him by direct observation or external sources is the fundamental purpose of any torpedo director. Additionally, a good torpedo director design should offer its user a quick means of judging whether the target is near enough that the torpedo will be able to reach it.

It should be noted that the proper director angle is dependent upon a proper estimation of enemy heading and speed (expressed in one of several ways), and upon the assumption that his motion while the torpedo is underway will, on average, continue about this mean heading. It is easy to see aiming a torpedo which generally takes longer to reach its target than does a shell requires more cooperation on the part of the target!

The Royal Navy began the 20th century using torpedo directors that modeled the torpedo firing problem according to the Director Triangle — that formed by

1. the path of the torpedo
2. the line of sight to the target at the moment of firing
3. the path of the target between firing and impact.^[2]

As the war approached, the Royal Navy refined their hardware along lines they felt were important, issuing improved Marks or adding parts to existing directors.

Small Innovations

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The directors started out pretty basic. Clever torpedomen soon thought of small changes that would make them better, and these were often viewed at the Torpedo School and the best ones standardised for proper fitting and allocation.

• A Radiomir Fore Sight (or just "Radium Fore Sight") is one with a small glass tube containing radium for use in night work. It was often used on Pattern 2380A and the Line of Sight Director. They proved successful, but the luminous substance itself left a desire for looking at alternatives.^[3] Other directors had electrical lamps to illuminate their sights.

• A Compass Ring was conceived in 1911 for 2006 and 2391/2392 ... an outer ring marked in Quadrant bearings that could be attached to the base of the director and set to own ship's course. The enemy bar would be clamped to this ring. and it was thought that this ring could be adjusted manually if own ship changed course by reference to a compass near at hand or perhaps by automatic adjustment via a gyrocompass repeater.^[4] It sounds like a snafu.

• Longmore's Disc was a disc that showed the inclination of the enemy to the torpedo bar (rather than the sight bar). It was used on the 2380, but in 1915 or thereafter, it was to be replaced by a Robinson Disc.

• A Inclination Disc (or Robinson's Disc^[5]) was a disc that rode the sighting arm and marked 0 to 180 degrees left and right so that target Inclination to the line of sight was directly readable.^[6]

• A Gyro Angle Base or "angled stand" was proposed for some directors in 1911^[7] to support the proposed general introduction of torpedoes with angled gyros. It consisted of a pair of discs that could rotate up to 40 degrees either side of zero against each other and lock every 10 degrees (initially) or 5 degrees (from 1916 or so) by use of a conical spring permitted them to be clicked to the same heading a torpedo set to the same gyro angle would take upon being fired.^[8]

• A Tangent Bar was a small armature which could be added to a torpedo director to offset its rear sight a short distance to make its sighting angle converge with the track of the torpedo when the director could not be located on or near the firing tube. The idea exemplified the Royal Navy's over-thinking of the problem, and the service eventually grew disenchanted with the fragility and complexity they bestowed upon the directors. Some time during the production of directors Pattern 2391a and 2392a, some were being sent out without tangent bars and directors of Pattern 2006 and later that were brought in for repair were sent back without their tangent bars.^[9] The conclusion finally reached was that the lateral errors that would remain untreated without the tangent bars were apt to be vastly smaller than the other sources of error inherent in accurate torpedo fire except in very short range attacks. These scenarios were to be treated by choosing a suitably offset aim point on the target.^[10]

• A Central Bearing Disc "similar to those fitted in Patts. 2391-2" was considered in 1911 for the 2006 directors.^[11]

• A Graduated Sight Bar permitted the user to determine whether the target was presently within range of the torpedo to help eliminate the problem of firing when out of range.

• A Possible Shot Scale was a refinement on the graduated sight bar which allowed the firing range estimation to be resolved without resort to arithmetic.

A Change in Thinking

As the war began, the British were becoming increasingly dissatisfied with their directors, which they regarded as flimsy, mechanically loose, and not very easy or quick to set.^[12] Indeed, on the latter point, in 1911 test firings, 6% of torpedoes that missed their target were attributable to errors in setting the director properly or firing the torpedo when out of range.^[13] In 1908, the errors made at the director accounted for a full 16% of misses!^[14]

Other complaints were more fundamental. One which was not particular to the directors (as opposed to other possible sighting means) was that the directors were often poorly aligned with their tube. In 1898, the ships of the Channel Squadron were examined and many directors had significant errors in alignment. Of five in Magnificent, only one was truly "on" and the other four varied from 0.5 to 0.75 degrees out.^[15] But the tangent bar was a particular target of scorn, making the director rickety and often being wrongly set in use. More astonishingly, the very value of such a fixture as the tangent bar was finally receiving attention. Why worry about the small lateral errors introduced when the director was not located directly at the torpedo tube when these errors were apt to be tiny in comparison with those caused by the enemy manoeuvring after the torpedo was fired or a failure to accurately judge his speed and heading in the first place?^[16]

In 1912 and 1913, the Vernon was recording ideas about Deflection Plotting in such detail that it seems plain that a switch to using deflection as a means of setting the director angles was being actively considered.^[17][18]

In 1915 or so, the Royal Navy was exploring, for the first time, larger questions of torpedo warfare in fleet actions — ones that seem glaringly obvious in hindsight. For instance, discussion of the need to fire more torpedoes at once as ranges increase, and errors of estimation of speed and direction of the enemy, and likelihood that these factors will change during the torpedoes' transit appears, this editor would argue, for the first time in the Handbook of Torpedo Control, 1915 and certainly in the Annual Report of the Torpedo School, 1915 which observes that "to secure one hit at 8,000 yards, then, with 10 torpedoes, the enemy speed must be known within 1¹⁄₂ knots either way. As accuracy falls off the number of torpedoes must be increased. If the enemy is free to alter course it is very little use firing at all, and such a number as would be necessary to make certain of a hit would be hopelessly extravagant with the existing armament of T.B.D.'s."^[19]

Another aspect of this reconsideration was that the series of torpedo directors they had relied on were to be refashioned to embody the geometry based on the deflection triangle rather than the director triangle.

The deflection triangle is that formed by

1. the path of the torpedo
2. the line of sight
3. a line perpendicular to the line of sight that passed through the point of impact

This last line was equivalent to the target's speed-across if own ship were at rest.^[20][21]

The first step taken was to adapt the existing directors to a deflection aiming,^[22] a conversion process that made all above water director become T.D.S. Mark Is, and the line of sight directors T.D.S. Mark IIs. The longer term step was to build torpedo deflection sights optimised to the geometry. These T.D.S. models (Mark III et seq.) would become the late-war successors to the torpedo directors described here. It is not precisely known when these conversions took place, but mention of torpedo directors and how their enemy speed settings should be fudged by different destroyers within an attacking division to achieve a spread of torpedoes is mentioned in the Grand Fleet Battle Orders in effect at the time of the Battle of Jutland, providing weak evidence that the change really took hold after the pivotal battle.^[23]

In 1920, it was decreed that all torpedo directors except Patterns 2236 and 3340 were to be returned to store, never to return.^[24]

Royal Navy Torpedo Directors

The "Whitehead Director"

A "Whitehead Director", with deflection scale in red.^[25]

Early patterns of director may have been dubbed simply, the "Whitehead Director". There is passing mention of how practice with their use might be made in 1881, and a simple diagram seems to indicate a hemispherical shape.^[26] An important aspect of this director was to calculate the aftward deflection of a non-gyro torpedo fired over the beam of a moving vessel.^[27]

The image shows an experimental deflection scale in red from 1882, configured for firing to port. The torpedo is to be fired 22 degrees before the beam from a ship going 8 knots. The deflection scale is drawn for 1.5 degrees per knot. By bringing the red "8" to the 22 degree position, the red "0" indicates the heading the deflected torpedo will assume.

In 1896, it is implied that the director in the torpedo boats was often inside the very small conning tower, and that this might be unsuitable when conning was to be done from outside. It was urged that these ships should contrive an alternative position outside the conning tower "or other suitable place."^[28]

Pattern 1192/1192a

Main article: Torpedo Director Pattern 1192

These were large, semicircular directors intended for use directing broadside fire. They received some enhancements and alterations, but were considered obsolete by 1912.

Pattern 1193/1193a

Main article: Torpedo Director Pattern 1193

An early director with a 60 degree arc, intended for firing ahead from torpedo craft.

Pattern 1895/1895a

Main article: Torpedo Director Pattern 1895

A lighter version of the 1193, with a 60 degree arc for use in early torpedo craft.

Pattern 2006/2006a

Main article: Torpedo Director Pattern 2006

These compact, circular directors first appeared for use in armoured control towers in 1904-1905, and saw service into the great war.

Pattern 2390/2390a

Main article: Torpedo Director Pattern 2390

A 60 degree director similar to Pattern 1895, available by 1912 at least, supplied to torpedo craft with heater torpedoes.

Pattern 2389/2389a

Main article: Torpedo Director Pattern 2389

Available by 1910 at least, it was similar to the Pattern 2390, but fitted for use from the bridge.

Pattern 2380/2380a

Main article: Torpedo Director Pattern 2380

New in 1914 and similar to the Pattern 2390a, but larger and of improved construction.^[29]

Pattern 2387

Available from 1910 at least.^[30] Same as Pattern 1192, but fitted for use from the bridge by addition of a tangent bar.^[31]

Pattern 2388/2388a

Available by 1910 at least.^[32] Same as Pattern 1193, but fitted for use from the bridge by addition of a tangent bar.^[33] The 2388a was sturdier and had a solid sight bar, and was probably a 2388 that had been repaired to the new standard, as none of the type was directly manufactured, owing in part to new destroyers not being fitted for fore bridge firing in the 1911 era.^[34] By 1916, they were considered obsolete.^[35] Like the 1193, they were likely 60 degree arcs.^[Inference]

Pattern 2391/2391a/2392/2392a

Main article: Torpedo Director Pattern 2391

A family of circular directors improving upon the Pattern 2006 introduced from 1909 by adding a sighting telescope and a possible shot scale. In 1912-13, the -a models appeared which added support for gyro angling.

Pattern 2236

Main article: Torpedo Director Pattern 2236

Entering service in 1915 or 1916, and reflecting the disfavour accorded tangent bars, the 2236 was a modification of the 2391a with the tangent bar and the association telescopic member to offset the sighting telescope removed. It had an inclination disc, a Radiomir fore sight and a deflection bar.^[36]

Already in 1916, plans were being drafted to convert these directors into Torpedo Deflection Sights. ^[37] However, it was one of just two patterns of torpedo director which were to avoid being recalled as obsolete in 1920.^[38]

Line of Sight Director

Main article: Line of Sight Director

This was a circular director similar to the Pattern 2006, but with a rotating torpedo bar, intended for use on the fore bridge of a light cruiser or smaller vessel.

By mid 1917, following plans drafted in 1916,^[39] they were being converted into T.D.S. Mark II (not Mark I, as with all other directors).^[40][41]

Pattern 3340

(main article)

This director was intended for use on submarines. On the surface, it would be fitted to the head of the periscope for use on the conning tower. When submerged, it would function as a hand-held calculator to determine the periscope angle to be used for firing.

It was one of just two patterns of torpedo director which were to avoid being recalled as obsolete in 1920.^[42]

German Torpedo Directors

After the war, the British were able to examine and critique torpedo aiming equipment from some German destroyers.

Tube Director

Plate 94

The German Template:DE-S132 had a simple director atop her torpedo tube. It was extremely crude by British Torpedo Director standards. A torpedo speed arm was graduated with speeds from 22 to 45 knots and the enemy speed slider could be set from 0 to 40 knots. A Track Angle indicator was fitted to the hub of the enemy heading bar, reading the difference between the torpedo heading and the enemy heading, but there was no means of reading the Inclination. There was no sighting arm; the user had to twist the rear sight so that it roughly faced the simple pin that served as the fore sight.^[43]

Fore Bridge Firing Gear and Director

German Fore Bridge Torpedo Firing Gear and Director^[44]

The German Template:DE-G102 had a more lavish provision for her torpedoes, being equipped with fore bridge firing gear with a built-in director, one positioned on the bridge to each broadside. The device combined spring-wound magneto firing triggers for all tubes in the broadside with a director. An optional telescopic sight could be mounted if the in-built open sights were not suitable.

The ones examined supported a broadside of a single tube and two dual revolving tubes, each angled 12 degrees apart. The director was brass, with torpedo bar, enemy bar and sighting bar, mounted on a semicircular base plate, which meant that port and starboard directors could not be swapped.

The mounting onto the pedestal did not permit adjustment to perfect alignment with the keel.

Notches in the base plate allowed the director to be locked at angles of 20, 55, 70, 80, 95, 110, and 125 degrees from the bow, corresponding to the locking positions of the various tubes, whose numbers were stamped on the base plate. The locking was effected by using the hand-grip on the torpedo arm and a spring trigger.

Torpedo speeds from 28 to 45 knots could be set by locking the torpedo speed slider with a milled screw. A similar provision allowed enemy speeds from 0 to 40 knots on the enemy bar, which likewise allowed tracking angle but not inclination to be read off.

A "possible shot" strip on the sighting bar had markings for a G 7*** torpedo; one side for 35 knots to 5,000m and the other for 28.5 knots to 10,700m.

The sights were just wires within frames. A spring locking pin beneath the foresight permitted the sight bar to be locked to the torpedo bar.^[45] A bracket permitted the optional telescopic sight box to be shipped atop the director.

Each separate tube had an independent, spring-wound magneto and firing pull-handle — five of these in this case. An indicator on each read "Schuss" when its spring was fully wound, and pulling the handle would cause the tension to discharge, providing current enough to fire the circuit.^[46]

Telescopic Sight

German Torpedo Sighting Telescope^[47]

The monocular telescopic sight was manufactured by Voigtlander. A dummy second eyepiece could be swung to either side, permitting a user to choose either eye for the active optics. Both were equipped with a rubber ring for the brow.

A pair of objective lenses with caps and tinted shades were fitted, the one to use selectable by a milled head; the lower was for normal viewing and the upper gave 6 diameters of magnification. Open sights were mounted atop the housing.^[48]

See Also

Footnotes

Bibliography