Range Dial

A Range Dial (or "Concentration Dial") was a form of concentration signal by which ships could visually indicate their present gun range.

Mr. John A. Roberts responded to an initial inquiry into their nature by the following reply:

The Concentration Dials introduced in the Royal Navy in the latter part of the First World War were arranged like a clock with a short and long hand except that 12 o'clock was replaced by '0' and the remaining numbers (Roman I to IX) stopped at 9 o'clock. The hour hand indicated 1000 yard steps the minute hand 100 yard steps. There was also an arm at the back of the dial with a disc at the end which sat at the outer edge of the dial and could be aligned with number 0, II or III indicating 10000 yard steps. This arrangement covered ranges from 100 yards to 29,900 yards in 100 yard steps and was used to indicate the gun range in use. These dials were officially described in various ways including "range dial" and "clock dial" and probably quite a few others both official and unofficial. Many ships also had a second dial which was exactly like a clock (numbers I to XII, short and long hand) which was used for passing spotting information using a numeric code. The Type 31 was also employed to pass spotting and target indication information but could be used to pass other information as well (including range if necessary) — the method was (initially at least) left to the ships to employ whatever system worked best.

Other dial-based designs are described in Manual of Gunnery in H.M. Fleet, Volume III, 1920, along with a list of ships equipped with the various models.

Type A Dial

Type A Dial

These had two dials, each four feet in diameter. The hands were positioned by transmitting arms similar to those on a Semaphore Machine. The upper dial indicated range and the lower dial was used for various purposes by different squadrons. There were several variants on the design.

• Type A.I. (Inverted) had transmitters above the dials, on the same side of the tube
• Type A.R. (Reversed) had transmitters below the dials, on the opposite side of the tube
• Type A.I.R. had transmitters above the dials, on the opposite side of the tube.
• Type A.T. (Turret) was designed for use in a turret

Type B Dial

Type B Dial

A single dial instrument similar to A, transmitting range only, and with similar sub-types, B.I., B.R. B.I.R. and B.T.

Type C Dial

Type C, E and F Dials

These had transmitted immediately behind their 4 foot dials, intended for use in light cruisers. A "New Type C" was modified to be lighter. Some installations had 9 or 10 foot dials.

Type D Dial

Type D and J Dials

These had larger 5 foot dials and were for remote use by chains.

Type E Dial

These were similar to the original Type C, but had larger 7 foot dials.

Type F Dial

Could be fitted directly to a bulkhead with a 7 foot dial.

Type H Dial

Like Type D, afforded remote control by chains, but also able to pivot its 4 foot dials 40 degrees to either side.

Type J Dial

A large 10 foot dial on a vertical standard.

Type K Dial

Similar to Type C, but with a 10 foot dial hollowed by a 5 foot inner cut-out.

Type L Dial

Similar to Types J and K, but with remote control by wire and chain and a shaft for training.

See Also

• Concentration

Bibliography

• Schleihauf, William (April, 1998). "A Concentrated Effort: Royal Navy Gunnery Exercises at the End of the Great War." Warship International 35 (2): pp. 117–139.
• Manual of Gunnery in H.M. Fleet, Volume III, 1920.