Torpedo Director

A Torpedo Director is merely a sight for torpedo fire, more similar to a settable gunsight than to a gunnery director.

Nature and Function

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!

By 1916, the Royal Navy was clearly not happy with its directors. They were seen as flimsy, mechanically loose, and not very easy or quick to set.

Director Triangle

The Royal Navy began the 20th century with a series of sights that characterized the torpedo firing problem according to the Director Triangle formed by the path of the torpedo, the line of sight to the target at the moment of firing, and the path of the target between firing and impact. It delivered a number of sights which embodied this geometry, including the Pattern 2006 Torpedo Director.

Deflection Triangle

In 1915, the Royal Navy started to migrate toward a different geometric model called the Deflection Triangle, formed by the path of the torpedo, the line of sight, and that component of the target's speed-across attributable to its movement alone (i.e., the Dumaresq Deflection as if our ship were not moving.

Common Accoutrements

A Radiomir Fore Sight is one with a small glass tube containing radium for use in night work.

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.

A Longmore Disc was a disc that showed the inclination of the enemy to the torpedo bar. It was used on the 2380, but in 1915 or thereafter, it was to be replaced by a Robinson Disc.

A Gyro Angle Base or "angled stand" was proposed for some directors in 1911

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 was an example of the Royal Navy over-thinking the problem, and the service soon great 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. 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.

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

1909

ART1909 p. 22. The introduction of heater torpedoes with speeds above the 40 knot maximum on the radius bars of the directors in service necessitated that their scales be regraduated by 2/3rds. This gave a max torpedo speed of 60 knots .

The directors as they stand at present was;

• 1895 w/ modified rear- and fore-sights but no other alteration were supplied to torpedo craft not supplied with heaters, for their tubes only and for ships with dropping gear.
• 1895 as above, but with re-graduated scales were supplied to torpedo craft with heaters for use at their tubes

p. 23

• Patterns 1192, 1193 and 1895 directors with tangent bars and regraduated scales supplied to TBDs equipped for fore bridge firing for use at their fore bridge
• 1895, 2006 and 2391/2392 for "ships" (from the context, this appears to mean ships larger than destroyers) will not be regraduated, as their heaters will be fired at slow-speed settings at long ranges.

If it were necessary to run a fast heater from a director not regraduated, speed of torpedo and enemy were to be halved on the sights (G&T orders Feb 1st 1909)

A Harrier (gunboat HMS Harrier?) is mentioned as having double tubes demanding a double foresight -- she was not to receive night sights based on the obsolete nature of her tubes.

1910

Lt Col Chaytor's Torpedo Danger Area Instrument (Plate 10 and text)see also ARTS1909 p22

Vernon asked Bellerophon to try a modified Mark II Combined Transmitter and a Combined Receiver to see if they were suitable to convey enemy speed and relative course from the TS to the torpedo director position. She reported that the devices worked fine for this purpose, but that the TS was a poor authority on the heading and speed of the target, suggesting a topside position for the transmitter offering better overall visibility than that enjoyed by the Torpedo Control Tower.

In 1910, Indomitable, Inflexible and Invincible tested Mark I instruments and Telaupads as a means of tying the Torpedo Control Tower to the submerged aft torpedo tube. These successful tests formed the basis for the development and deployment of the B&S Mark I Torpedo Control Instrument.

Britannia suggested use of hinged director stands in the conning tower, owing to limited head room. Later classes would not require such, as their tables were not mounted on the armor.

1911

p. 43 ability to smoothly rotate the director to ascertain how far the ship must yaw to bring sights on was considered, or to set up the sight prior to the sights coming on after a yaw.

1914

p. 32 and plates 12-16 Walker's Instrument

1915

In 1915, trials were carried out to compare the "wire" and "theodolite" methods of aligning directors for submerged tubes, but results were not yet complete. Until they were available, contract-built ships were to have their directors aligned by theodolite means. Extensive description of the method is outlined in The Annual Report of the Torpedo School, 1915.

A new design of director for capital ships was being undertaken. It would not have a tangent bar, and would therefore offer a stronger design. Additionally, there was talk of using periscopes to keep personnel clear of gun blast. This blast was studied in Iron Duke when directors were placed in secondary hoods, and found to be so considerable that directors were to be placed in conning and torpedo control towers only, and no further hoods would be built. The tubes were to be dirigible from either position, with communications and firing circuits laid to both towers.

A director called Hallet's Director was tried, apparently unsuccessfully, as it was returned for disposal. Seven examples of Lambert's Attack Director were under trial at sea. Note was made of directors having been reassembled incorrectly after maintenance, resulting in poorly aimed torpedoes. One gotcha that was to be corrected was to ensure that sliders would be modified so they could not be reversed upon reassembly.

Hinged stands for directors were tried in Invincible and Hercules, but found not to be worth the expense or the possibility of errors in alignment. Henceforth, they would only be fitted where absolutely necessary.

Directors would henceforth be illuminated for use at night. An aperture with variable stop and violet glass would use a switch to turn on and off.

The director telescope Pattern 2393's 6-power magnification was criticised at sea as being too high, rendering it difficult to see in haze and rain. Six telescopes answering to a 3-power specification had been ordered for trial.

A promising wander mark telescope from the German Goertz company had been ordered before the war, but not taken before the war started. It was seen as having some promise as a director telescope or for use on the Middleton Plotter in lieu of electrical contacts.

An enterprising torpedoman aboard Blonde had added a 4-inch diameter brass disc plate to the enemy speed slider on his Torpedo Director Pattern 2390 to permit the enemy's heading to be expressed or read as an inclination to line of sight. This would especially help the adjustment of a director at a trainable tube, but no explicit recommendation was spelled out despite a supportive description of its utility.

It was concluded from practical experience that the deflection triangle was superior to the director triangle as a means of setting the director.

p 58

• A Line of Sight Indicator designed by Vernon and Portsmouth yard is being manufactured (Plate 10) It will be supplied to all LCs Blonde and later (exc LCS 1, which has similar device already), and DDs of F class and later.
• Five Walker-Bellairs TC discs are being manufactured for trial (see TCH, p. 29, Plate X)
• Robinson discs are being manufactured for issue, to be fitted by ship's artificers
• Longmore discs on torpedo bar as Patt 2380 wlll be replaced by Robinson discs
• Fitting of alternative control posns in all LCs has been approved. Vernon feels director should not be in CT, as a good view is essential (see p61, plate 14), and the CT is always cramped and busy
• Future LCs will be fitted with a 3rd RF for TC (Weymouth-Cooke sextant RFs are being supplied in lieu, the Bell station keeper is good for rough ranges -- see pamph and TCH p14)
• Voicepipes w/ electrical call-up will be used in LCs between TCPs and tubes when distance is < 100 ft and "telephones" elsewhere
• gunnery bearing graduations have been adopted for all T instruments and tubes
• a TCH has been issued (there was an 1915 edition)

plates 11-12 show submarine torpedo director 3340

p. 59

• the Line of Sight Indicator was to be mounted on the fore bridge of an LC or DD. Tube training angle is 0 to 180 red and green. Torpedo Bar is graduated up to 48 knots and slides like in a 2006, but it can be pivoted to tube's training angle. The enemy bar is graduated to 40 knots. Sight bar bears "the usual possible shot strip". A Robinson Disc shows target inclination, and a director angle disc in degrees 0 to 90.
• "Robinson Disc" (see ARTS 1914, plate 11, p. 31) enable a drector setting to be passed to the operator (particularly AW tubes) not dependent on the course of firing ship or bearing of tube, Constant director alterations unnecessary. They are being manufactured and willbe supplied for all 2390, 2390a and 2380 directors, replacing Longmore discs on the 2380 (which showed crossing inclination to the torpedo bar). See T.O. No. 124 of 1915.
• Submarine director patt 3340 is arranged to ship on the top of the periscope tube when sub is surfaced. It can be shipped in one of 4 positions for ahead, astern or broadside. When submerged, it can be used as a calculator by which to set the periscope. One disc maeasures director angle for setting on the periscope (0 to 90, right and left). Another measures crossing angle to the torpedo bar, 0 being bow-on. This crossing angle rather than inclination means of setting enemy bar is preferred by subbies owing to high bearing rates in short range attack. This is because inclination is relative to bearing (which is changing rapidly here, under control of the target and by his turning AND translational movement) whereas the crossing angle is changing more slowly by the turning of the enemy and own ship.

p. 60 Bunbury and Crace Enemy Torpedo Calculators being manufactured for trial (6 each) in 12 flagships.

Royal Navy Torpedo Directors

Pattern 1192/1192a

A large, semicircular director, presumably of the director triangle principle, not used in any modern ships as of 1912. If a 1192a existed, it was similar, but made stronger in its pivots and sighting bar. As of 1916, it was noted as being in use in the H.M.S. Pelorus class, and its semicircular nature related to its employment as a "broadside director". Some were fitted with tangent bars and regraduated to 2/3rd scale for use from TBD fore bridges and heater torpedoes.

Pattern 1193/1193a

Had a 60 degree arc, used in early torpedo craft. If a 1193a existed, it was similar, but made stronger in its pivots and sighting bar. Likely available in 1903, with a graduated sighting arm. It was sometimes called the "Right Ahead" director.

Pattern 1895/1895a

Very similar to the 1193, the 1895 had a 60 degree arc and was used in early torpedo craft. If a 1895a existed, it was similar, but made stronger in its pivots and sighting bar. It lacked graduations on its sighting arm. In 1909, those used with heater torpedoes had their scales regraduated at 2/3rds scale to allow for the faster torpedoes.

Pattern 2006/2006a

Thirty of these compact, circular directors were ordered for trial at 'Vernon and at sea in 1904. Its torpedo arm was not pivoted, and the square knob for the enemy speed pinion was geared such that each flat of the square knob was a knot of enemy speed (4 knots per turn). The sights were fine wires in sighting arches. The distance from the fore sight to the pivot of the sight bar was fixed at 17 inches.

Probably ready for service some time in 1905m it was used in conning towers and director towers of "earlier ships" (as judged by 1912) with a tangent bar, and perhaps also at times directly on tubes. The 2006a was fitted for adapting to gyro angles, sometime after 1912.

The directors had slides underneath permitting some lateral motion (3 inches?) to look around obstacles.

In 1912, a design was approved to add a central bearing disc and a Carpenter's disc sight to the director.

By 1916, displeasure with tangent bars was such that Pattern 2006 directors and later brought in for repair were sent back without their tangent bars.

Pattern 2380/2380a

Similar to the Pattern 2390a, but larger and of improved construction. By 1916 (at least), it had a possible shot scale and inclination disc. It was a 50 degree sector model designed especially for light cruisers. The enemy bar pivot was much stronger than on the 2390a. A lettered disc provided on the 2380 to set enemy heading in relation to the torpedo bar was obsolete by or before 1916. The 2380a differed by having the lettered disc removed in favor of an inclination disc and a Radiomir fore sight.

Pattern 2389/2389a

Available by 1910 at least. Same as the Pattern 2390, but fitted for use from the bridge, presumably by the addition of a tangent bar. It almost certainly was a circular design.^[Inference]

Pattern 2390/2390a

Disc added to 2390 to help set course of enemy as expressed as inclination.
Note the lack of any graduations on the sighting arm.

Available by 1912 at least, supplied to torpedo craft with heater torpedoes. Similar to Pattern 1895, but graduated for higher torpedo and enemy speeds. It was not circular, and probably a 60 degree arc like the 1895.^[Inference] It lacked graduations on its sighting arm, but by 1916 at least, they sported inclination discs. The 2390a had more rigid pivots, sturdier construction, and a sighting arm that was solid rather than slotted, and made of hard rolled brass.

Pattern 2387

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

Pattern 2388/2388a

Available by 1910 at least. Same as Pattern 1193, but fitted for use from the bridge by addition of a tangent bar. By 1916, they were considered obsolete. They may have been semi-circular.^[Inference]

Pattern 2391/2391a2392/2392a

A Pattern 2391 director similar to the 2392. The 2392 would differ by having its telescope mounted to the left of the sighting bar. The possible shot scale depicted is graduated for a Mark VI* heater torpedo (35 knots to 4,000 yards)

Additional maximum firing range scales for use on Pattern 2391/2391a,2392/2392a directors using different tupes of torpedoes.

A "right handed" director for use in conning and director towers of ships from at least 1909-1910. They had open sights as well as the capability to mount a telescope. The 2391a was fitted for gyro angling, sometime after 1912.

In 1912, a design was approved to add a Carpenter's disc sight to the director.

These were circular directors modified from the 2006.

The telescopes used initially had crosswires, a 5-power magnification, and field of view of 7 degs, 10 minutes. It was not given illumination, as the regular sights would be used at night. Improvements in moving the rear sight along the tangent bar were incorporated, and an additional scale along the sighting bar allowed the maximum firing range to be read off directly. A disc labelled 0 to 180 degrees, port and starboard was added and a pointer on the speed and course of enemy bar. This disc was fitted only when a director was mounted on its ship, as the disc was oriented to own ship's keel, with 0 degrees being forward. The intent was that enemy heading could be communicated and set on the sight as a relative heading to own ship's course.

The original telescope in use was a Pattern 2393 of 5 power and field 7 degrees 10 minutes, but in 1915, the need for the lower power scope for haze and rain was realised. A quick trial resulted in the Pattern 3341 of 2.5 power, ~25 degree field being introduced, likely sometime in 1916.

Around 1910, as on the 2006, the directors were provided slides underneath permitting 3 inches of lateral motion to look around obstacles.

Pattern 2236

Entering service in 1915 or 1916, and reflecting the disfavor 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.

Royal Navy Submarine Torpedo Directors

Handbook of Torpedo Control plate V, VI: Pattern 3340

Bibliography

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