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.

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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]

Mark I 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

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

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,"[13] 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)


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.[14] 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.

Mark I 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.[15]

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]


Mark I 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.[16] 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.

Mark II Instruments

Mark II introduced the classic pattern of design for Barr and Stroud, centered on cyclometric displays on step-by-step circuits. 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.

Competitive 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.[17]

The Mark II family included a combined instruments for signaling range, deflection and orders, as well as others for communicating ranges and range rates separately. The Mark II range instruments were the ones actually used in the ships that had been scheduled for receiving Mark I range instruments.

Mark II* Instruments

These were outwardly indistinguishable from the Mark II instruments, but their internal wiring and brushes differed. The function would have been identical, and the changes were perhaps to enhance problems maintaining connectivity in Mark II, plugs-- the most common type of failure particular to that series.

The Mark II* family included combination range/deflection/order instruments as well as separate instruments for ranges, range rates, orders and bearings.

As the Royal Navy's thinking on best practices matured, the instruments kept pace: Mark II* bearing instruments differed from those of the Mark I generation by moving to relative bearings from the quaint use of Compass Quadrant Bearings, and the Mark II* rate instruments used steps of 25 yards per minute rather than 10 as had been used in the Mark II instruments.

Mark III Instruments

The Mark III family was probably introduced sometime shortly after 1909.[18].

The family included combination instruments as well as some for single ranges, orders, rates and bearings. The range instrument sported some new features that recommended its use for reporting range cuts from rangefinders down to the TS, but generally the differentiating feature was that the external wiring to the instruments was consolidated so all cores would be admitted through a single gland.

Mark III* Instruments

Mark III* Single Order Instruments

The Pattern ???? Single Order Receiver (did this exist?) The Pattern 3133 Single Order Transmitter

Mark III* Rate Instruments

The Pattern 3135 Rate Receiver The Pattern 3134 Rate Transmitter

Mark IV Instruments

Mark IV Bearing Instruments

These were nearly identical to the Mark II.* models.

The Pattern 3139 Bearing Receiver's STARBOARD/PORT shutter had a third face added to the bottom, which was blank and it had no blank/TRAIN shutter. I do not understand why this would be considered an improvement unless the digit display can go all the way up to 360 (or down to -180), and this was intended to be used with the blank face of the shutter on display.

The Pattern 3138 Bearing Transmitter had handles and a lower gearbox.


Mark IV Rate Instruments

The Rate Transmitter (of unknown pattern number) was identical to the Mark III. except the shutter coils and digital drums are fed their input from without and not directly from the transmitter and shutter switches. This allowed the tell-tale indicators to receive their data from a change-over switch, as though they were an ordinary receiver. This removed the need for a COS to have its own tell-tale indicator in cases where it was going t o be placed adjacent to the transmitter anyway.

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, 1904, p. 96.
  14. ↑ Annual Report of the Torpedo School, 1905, p. 75.
  15. ↑ Handbook of Fire Control Instruments, 1914, pp. 26-7.
  16. ↑ Handbook of Fire Control Instruments, 1914, pp. 25-6.
  17. ↑ Annual Report of the Torpedo School, 1906, p. 84.
  18. ↑ not mentioned in 1909 FCI

Bibliography

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