Barr and Stroud Fire Control Instruments

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Barr and Stroud manufactured a large and evolving family of Step-by-Step Fire Control Instruments to convey ranges, deflections, orders and similar information throughout a ship. By 1909, 2 main generations and one minor generation had been introduced. By 1914, another 2 main generations and a minor generation had been introduced.

Prototype Design and Testing

In 1903, some Barr and Stroud (Mark I, or prototype) instruments were bolted onto plates, the backside of which were fired upon by a Maxim machine gun in bursts of 3-20 rounds in order to ascertain their resilience to shock. There were some failures, but most were simply cases of the transmitter and receiver being put out of step. In some tests, a sledgehammer was used to deliver the shock.[1] No conclusion is stated in the report, but an area of exploration mentioned in the nature of their mounting in order to absorb and reduce shock.

The early prototypes may have used pointers on dials to display the data. By the Mark I era, however, it was seen as superiour for the range receiver to have the dials rotate inside the chassis and have only the proper entry displayed through an aperture. This would have the benefit of allowing the eye to read the components of the range in proximity to each other.[2]

In 1904, reports from ships were uniformly favourable, although a minor adaptation was required in London.[3]

Mark I Instruments

The Mark I family showed promise, but none of the equipment was truly deployed except the order instruments.

The 1904 Annual Report of the Torpedo School outlined a scheme for fire control from primary and secondary control positions which would use Barr and Stroud Mark I instruments for range, deflection and orders.[4]

However, by 1905, the deflection instrument was found wanting in some fashion, as the Mark I range and order instruments were now to be paired with Vickers deflection instruments, as an "approximately correct" list of 18 ships to be so equipped reveals, although no explanation is offered.[5]

Advances and alterations were rapid. By 1908, the Mark I instruments were considered obsolete to the point that the Torpedo Drill Book explicitly declined to describe them.[6] By 1908 only order instruments remained in use anywhere,[7] but they remained in service in some ships in 1914.[8]

By 1909, dissatisfaction with the Mark I range instruments was apparent (see below), as the ships were now equipped with Mark II range instruments, Mark I order instruments, and the Vickers deflection instruments. Moreover, King Edward VII and New Zealand/Zealandia from the original list were apparently fitted with Barr and Stroud Mark II/II* instruments throughout.[9]

Mark I Range Instruments

Mark I Pattern Numbers
Single Range Transmitter unknown
Single Range Receiver unknown

Although cyclometric design (where numbers were on cylindrical drums, as in old odometers) came to characterise Barr and Stroud equipment, the Mark I range transmitter and receiver used numbered dials, with one numeric entry on each dial being visible through an aperture on the face of the instrument. The rightmost dial contained 40 3 digit entries from 000 to 975 in increments of 25 yards. The left dial was numbered 0 to 12, and denoted thousands.[10][11] The maximum range that could be conveyed, therefore, was 12975 yards.

It is not certain whether the two dials in the transmitter and receiver were mechanically connected (so that advancing a single handle to work the right dial from 975 to 000 would cause the left dial to index) or entirely separate with each being directly workable. It seems more likely that the latter case was true, as they were described as being "double".[12]

Mark I Deflection Instruments

Mark I Pattern Numbers
Single Deflection Transmitter unknown
Single Deflection Receiver unknown

Mark I Order Instruments

Mark I Pattern Numbers
Single Order Transmitter 57
Single Order Receiver 53

The transmitter The upper portion of the case had three apertures through which the indications could be read. The indications were on vulcanite sleeves on spindles which protruded out the sides of the case where handles permitted them to be rotated through 90 degrees or so to the desired command (each had just two positions). A spring pin within the transmitter grabbed the spindle to secure it within either of the two of the positions. Moving a handle to the down position completed the corresponding circuit to the receiver.

Each sleeve's face was marked with either two command indications or a command and a blank face, and the reverse side contained contacts that would complete a circuit in one position and break it in the other. When the handles were in their down position, the corresponding order circuit was energized, and they were otherwise off.

By inference from the remarks for the Mark I Order Receiver, I think the 3 channels functioned in the following fashion, top to bottom.

Mark I Rate Instruments

Mark I Pattern Numbers
Single Rate Transmitter 812
Single Rate Receiver 811

Mark I Bearing Instruments

Mark I Pattern Numbers
Single Bearing Transmitter 2591
Single Bearing Receiver 2590

Mark II Instruments

Mark II introduced the classic pattern of design for Barr and Stroud, in which cyclometric digital displays predominated. A notable improvement in thinking was to agglomerate range, deflection and order indications into a single combined receiver to simplify wiring and produce a more compact arrangement at both ends. However, standalone products for single range, single order and single deflection would continue to be produced through Mark III — perhaps with an eye to updating Mark I ships or simply to provide flexibility.

Testing

1906 Testing between: Vickers B & S F.S.C.
Wires up mast for one group transmitters to
one group receivers, any number of guns,
including repeat receivers aloft 		17 12 —
Number of Orders — 8 10
Easy to stop at required indication? Yes Yes Not so easy
as Vickers
Reliability to keep step Very Good Very Good Good
Durability in order of merit 2 1 3
Ease of repair in order of merit 2 1 3
Lowest voltage receivers will work at 12.5 10 14
Suitability for placing conveniently for sightsetter 3 2 1
Size of combined receiver, inches 7 x 5.5 x 10 10 x 6 x 6.5 4.5 x 2.5 x 3
Size of figures 7/16 inch 5/16 inch 5/16 inch

Mark II instruments were tested by Vernon and Excellent in 1906 in comparative trials with Vickers relay and some very small devices from the Facsimile Syndicate Company. The conclusion was that Barr and Stroud had the best system for heavy guns but could be improved by reducing receiver size for use at Q.F. guns.[13]


Mark II* Instruments

Mark III Instruments

Mark III* Instruments

Mark IV Instruments

See Also

Footnotes

  1. ↑ Annual Report of the Torpedo School, 1903, p. 80.
  2. ↑ Annual Report of the Torpedo School, 1904, p. 96.
  3. ↑ Annual Report of the Torpedo School, 1904, p. 95.
  4. ↑ Annual Report of the Torpedo School, 1904, p. 96.
  5. ↑ Annual Report of the Torpedo School, 1905, p. 74.
  6. ↑ Torpedo Drill Book, 1908, p. 238.
  7. ↑ Handbook of Fire Control Instruments, 1909, p. 22.
  8. ↑ Torpedo Drill Book, 1914, p. 290.
  9. ↑ Handbook of Fire Control Instruments, 1909, p. 56.
  10. ↑ Annual Report of the Torpedo School, 1904, p. 96.
  11. ↑ Annual Report of the Torpedo School, 1905, p. 75.
  12. ↑ Annual Report of the Torpedo School, 1904, p. 96.
  13. ↑ Annual Report of the Torpedo School, 1906, p. 84.

Bibliography

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