Barr and Stroud Mark I 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 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.

It appears that the early prototype instruments 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 the instruments in London.[3]

Adoption

The Mark I family showed promise, but little of the equipment was widely deployed for long 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]

1906 saw complaints arise about flimsy dials on the Mark I range receivers. A fix was issued and tested in Exmouth, but the entire model was presently stricken in favor of Mark II range instruments.[6]

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.[7] By 1908 only order instruments remained in use anywhere,[8] but they remained in service in some ships in 1914.[9]

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, 4 ships from those listed in 1905 were apparently fitted with Barr and Stroud Mark II instruments throughout and 2 others with Vickers equipment and Barr and Stroud rate instruments.[10]

Range Instruments

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.[11][12] 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".[13]

The Mark I range instruments proved immature and were replaced in service by Mark II versions soon after first installation or possibly before widespread adoption.

Deflection Instruments

These were described as a planned part of initial orders and installation, but by 1905 planning soon shifted in favour of Vickers instruments for this. The instruments probably had pointers on dial faces or numbered dials with an aperture. It could handle deflections "from 0 to 50 knots, right or left,"[14] which I interpret as meaning 3 possible basic forms, the first appearing most strongly implied:

  • a dial with 51 positions and a 2 position (Left, Right) shutter
  • a dial with 101 positions
  • a dial with 50 positions and a 3 position shutter (Left, None, Right)

Order Instruments

TODO: plates 17 and 18 from 1914 FCI handbook

As Described in 1905 As Described in 1914
Handle Down
(power on)
Handle Up
(power off)
Handle Down
(power on)
Handle Up
(power off)
Slot 1 blank "Cease fire" blank "Cease"
Slot 2 "Controlled" "Independent" "Indep." blank
Slot 3 "Commence" blank "Fire" blank
Receiver
Gong
Rang when any command changed Rang when shutter 3 went to "Fire"

The upper portion of the Pattern 57 Order Transmitter's 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 up or down through 90 degrees or so to on of two commands. 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 and moved a different command into view on the transmitter to reflect the order being sent.

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.

The Pattern 53 Order Receiver required four wires to control its 3 separate shutters and provide a return. It outwardly resembled the transmitter, but lacked the handles and included a single-stroke gong which was criticised in 1905 for being too quiet.[15] Although the outward appearance of the windows was similar, the shutters had just one command written on them which was either swung up out of view to allow a fixed command underneath to be seen, or drawn down by electromagnet to cover the fixed command.

In 1906, it was realised that the order receiver's use of a gong to draw attention whenever an indication changed was creating confusion with the widespread use of single-stroke fire gongs. It was decided to alter the function so that it would act in the same way as the fire gong — only when an instantaneous salvo was being ordered. This alteration may have coincided with the change in the labeling of the orders detailed in the table. The wiring change that effected this had a minor fault, however. If the "Cease" command on the top slot were moved to its blank state while "Fire" was showing in the lowest slot, the gong would ring. The workaround employed was to train those men working the transmitters to always establish "Cease"/blank/blank when a cessation of fire was being ordered.[16]

Rate Instruments

TODO: plates 31 and 32 of 1914 FCI

The Pattern 811 Rate Receiver and Pattern 812 Rate Transmitter are described in the Handbook of Fire Control Instruments, 1914.[17]

The devices resembled each other strongly, as the transmitter had a receiver within it to act as a tell-tale. 4 wires (one being a return) were required at the receiver and 5 at the transmitter. The receiver display had two concentric cylinders with the outer one noting "Open" or "Close" and the inner one designating the Royal Navy's old means of expressing range rate, in number of seconds required to alter range by 50 yards. This implies that the instruments were installed relatively early. They would sorely have desired replacement or rework when the move to yards/minute was made c1905.[Citation needed]


Bearing Instruments

TODO: plates 25-7 of 1914 FCI

The Pattern 2590 Bearing Receiver and the Pattern 2591 Bearing Transmitter are described in the Handbook of Fire Control Instruments, 1914.[18] The instruments conveyed compass bearings in quarter-degree granularity.

The receiver had 3 receiving elements to express the bearing according to the old Compass Quadrant Bearing system. The first of these was a digital cyclometric display with 3 drums able to convey bearings in 2 digits and 1/4 degrees, up to 893/4. The other 2 elements were 2 position shutters positioned at each end of the cyclometric drums, the left one indicating N. or S. and the right one E. or W.

The transmitter had two transmitting elements and a tell-tale receiver as described above. One transmitter was of the Mark II type and the other a simple commutator connected to a switch handle on the face of the device indicated the quadrant (N/E, N/W, S/E, S/W). The transmitter received 7 wires, one being a positive supply and the other 6 going to the receiver. The transmitter handle to work the cyclometric display was geared so that a quarter rotation of the handle advanced the display by a quarter-degree.

It is not clear to me how this display would signal due East or due West unless the description is a bit off and the cyclometer could go to 90 degrees.

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, 1906, p. 80.
  7. Torpedo Drill Book, 1908, p. 238.
  8. Handbook of Fire Control Instruments, 1909, p. 22.
  9. Torpedo Drill Book, 1914, p. 290.
  10. Handbook of Fire Control Instruments, 1909, p. 56.
  11. Annual Report of the Torpedo School, 1904, p. 96.
  12. Annual Report of the Torpedo School, 1905, p. 75.
  13. Annual Report of the Torpedo School, 1904, p. 96.
  14. Annual Report of the Torpedo School, 1904, p. 96.
  15. Annual Report of the Torpedo School, 1905, p. 75.
  16. Annual Report of the Torpedo School, 1906, p. 79.
  17. Handbook of Fire Control Instruments, 1914, pp. 26-7.
  18. Handbook of Fire Control Instruments, 1914, pp. 25-6.

Bibliography