Barr and Stroud Fire Control Instruments

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. 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.

In 1904, reports from ships were uniformly favourable, although a minor adaptation was required in the instruments in London.

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.

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.

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. By 1908 only order instruments remained in use anywhere, but they remained in service in some ships in 1914.

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.

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. 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".

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," 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)

Mark I 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. 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.

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. 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.

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.

Mark II Combined Range Deflection and Order Instruments

These devices allowed a compact grouping of 3 indications to be jointly expressed from a control to a gun position and are described in the Handbook of Fire Control Instruments, 1914..

todo: plate 20, 21 of transmitter

The Pattern 80 Combined Transmitter had 3 transmitters, placing deflection at the top, orders in the middle, and range in the bottom position. Each had a handle on the right side of the instrument for setting the desired value. The available orders were displayed in a menu-like list on the front such that all were continually visible, and a pointer moved by the order handle would move it up or down to the order desired. This design helped the operator understand which direction of handle motion would yield motion toward the desired command. A Mark II combined receiver would be placed nearby to indicate the values of all inputs. In this way, the orders were somewhat redundantly indicated.

Though the image I have for Plate 21 is not very clear, I'd say the order list looks as follows: SALVO COMM, INDEP COMM, then 6 indecipherable slots (possibly blank), CHECK FIRE, CEASE FIRE. If the intervening slots are indeed blank, I would imagine that this was to permit future additions while in the meantime creating an ample number of steps between those settings which command fire and those which command a cessation of fire! The pointer to indicate the selected command was a pair of fingers which would frame the selected command. This mechanical indicator prevented the order transmitter from rolling cyclically.

The deflection handle was geared so one revolution of the handle registered 1 knot, the order handle needed half a revolution to change to the next order, and the range handle had a clever double-geared design to allow fast or slow changes to be made. Ordinarily, a single revolution of the handle yielded a change of 25 yards, but when the handle was pressed in and spun, this quadrupled to 100 yards per spin.

The provision of the high speed gearing modification for the range data might be a nod to the weakness in step-by-step systems that large changes in reading could take time to apply. It is worth noting that even with this gearing in place, the average synchronization operation where the transmitter was driven to one limit and then the other would take 250 revolutions of the handle!

None of the range and deflection transmitters in the Barr and Stroud family had stops, but the drums in the receivers did. The order transmitter did have a hard stop at each end of the series, owing to the linear nature of the mechanical tell-tale incorporated into the design.

todo: plate 23 Curiously, the position of the indicators on the Pattern 78 Combined Receiver (orders at the top, then deflection, then range) does not match those used in the transmitter. The rightmost drum for range in this case had 8 positions, with each value (00, 25, 50, 75) occurring twice on opposing sides. The drums, and their readings, were visible through apertures on the front of the case.

Mark II Single Range Instruments

todo: plate 24 These were used in place of the Mark I instruments originally intended for use with Mark I order instruments and Vickers deflection instruments in 16 battleships as the Royal Navy was first deploying such devices, as well as between the control positions and transmitting stations in some later ships.

The Pattern 2592 Single Range Receiver was the customary Mark II cyclometric design.

The Pattern 2593 Single Range Transmitter included a receiver as a tell-tale. It was connected to 5 wires: a charging lead and 3 line wires and return main from the receiver.

Mark II Rate Instruments

todo: plate 28 + 29 These were probably used between the control positions and transmitting stations in some ships.^[Inference]

The Pattern 2594 Rate Receiver was the customary Mark II cyclometric design, and indicated range rates in yards per minute by 10s from 0 to 1990. A shutter indicated "Increasing" or "Decreasing". The Pattern 2595 Rate Transmitter included a receiver as a tell-tale. It was connected to 5 wires: a charging lead and 3 line wires and return main from the receiver.

In 1914, a number of the devices were being updated to Mark II* standards, the primary difference being to move to steps of 25 yards per minute from 10.

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.

Mark II* Bearing Instruments

todo: plate 28+29 These were similar to the Mark I. instruments, but worked in relative bearings, not compass quadrant bearings. An additional digit drum was fitted to permit angles of 0 to 180 in 1/4 degree increments, and a single remaining shutter located underneath the digital bearing drums could be in either STARBOARD or PORT position (starboard was in the higher position, and so would be visible when the shutter was lowered). I guess that this shutter was also in the raised position when the coil was off.

One small difference was that the transmitter handle had to be pushed in before would engage the drums inside. A spring would keep it out, otherwise. The degree handle was on the right side near the bottom, and the shutter setting handle on the left near the bottom. I am not sure if the degree drums and the shutter position were interconnected, or what behaviour would result if the angle was driven to (or past) its maximum reading.

The Pattern 2607 Transmitter had an integral tell-tale for angle and port/starboard. It was fed by six wires, 5 of which it passed to the Pattern 2608 Receiver.

The Mark II.* Rate of Change transmitter was fundamentally similar, with CLOSING and OPENING on the shutter.

Mark II* Combined Range Deflection and Order Instruments

Pattern 2596 Combined Receiver Pattern 2597 Combined Transmitter

Mark II* Single Range Instruments

The Pattern 2598 Single Range Receiver

The Pattern 2599 Single Range Transmitter

Mark II* Single Order Instruments

Pattern 2600 Single Order Receiver Pattern 2601 Single Order Transmitter

Mark III Instruments

With the sole exception of the Single Range Receiver, the Mark III. instruments differed from their Mark II. and Mark II.* equivalents only in their wiring interface. Whereas the Mark II. housings each required 2 or 3 individual cables to enter, the Mark III. devices each consolidated their wiring to receive just a single multi-core cable through a gland. I presume that the outward appearance and function was otherwise identical to the earlier instruments. The Single Range Receiver, however, had other features to improve its function as a reporter of discrete range estimates sent down from a rangefinder. As there is no mention of these in the 1909 handbook, we can infer that these were all introduced in 1910 or later.

Mark III Combined Range Defelection and Order Instruments

The Pattern 3141 Combined Receiver The Pattern 3140 Combined Transmitter

Mark III Single Range Instruments

The Pattern 3142 Single Range Receiver The Pattern 3132 Single Range Transmitter

Mark III Single Order Instruments

The Pattern 2604 Single Order Receiver The Pattern 2605 Single Order Transmitter

Mark III Rate Instruments

The Pattern 2960 Rate Receiver The Pattern 2961 Rate Transmitter

Mark III Bearing Instruments

The Pattern 2606 Bearing Receiver The Pattern 2607 bearing Transmitter

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.

Bibliography

• Template:BibUKARTS1903
• Template:BibUKTorpedoDrillBook1905
• Template:BibUKTorpedoDrillBook1908
• Template:BibUKTorpedoDrillBook1912
• Template:BibUKTorpedoDrillBook1914
• Admiralty, Gunnery Branch (1910). Handbook for Fire Control Instruments, 1909. Copy No. 173 is Ja 345a at Admiralty Library, Portsmouth, United Kingdom.
• Admiralty, Gunnery Branch (1914). Handbook for Fire Control Instruments, 1914. G. 01627/14. C.B. 1030. Copy 1235 at The National Archives. ADM 186/191.