Dreyer Table Mark III*

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Fig. 1: Mark III* Dreyer Table operators, c1918
This shows a table with a Standard Bearing Plot as depicted in the 1918 Handbook but perhaps not really adopted in service. Notice how the organization of the components has changed from that in the Mark III table.

The Mark III* Dreyer Table was an updated version of the Mark III table that was being developed to equip light cruisers as the war ended. As a consequence, it saw no role in combat but likely served as an affordable and proven platform whose obsolescent design mattered less in lighter ships who were uncommonly equipped to have such amenities. By 1930, it was used in some Hawkins class cruisers in lieu of Mark I* tables originally envisioned for them.

Contents

Development

The Mark III* table was slightly larger in width and depth than the Mark III table, but somehow lower in height. A key difference in the two models is that the Mark III*'s components were rearranged, likely in an effort to make them easier to serve. The Mark III*'s late date of development also meant that it likely was never envisioned in having early-model accoutrements (e.g.: the early bearing plot or Brownrigg Keyboard).

Overall Dimensions Compared to Mark III (1918)[1]
Width 9 feet, 5.5 inches (4 inches wider)
Depth 4 feet, 3.5 inches (1.5 inches deeper)
Height of
Range Rate Grid
3 feet, 7.5 inches (2.5 inches higher)
Height of
top of dumaresq
4 feet, 2 inches (1 foot 7 inches lower)

Motive Power

As in the Mark III table, power for drawing the paper through the plots and for the the range and bearing clocks was provided by an electric motor equipped with a speed governor. Should power fail, an alternate hand-drive placed behind the table could be used. The person working this handle observed a stop-watch in a box behind an etched glass cover which revolved as he worked his handle. By keeping the etching in line with the stopwatch's hand, the correct speed to regulate the table's activity was delivered.

Dumaresq

Fig. 2: Schematic of Mark III* Dreyer Table w/ Standard Bearing Plot, c1918
An illustration of how the table would work with the automatic deflection corrector gear.

The adapted Mark VI* Dumaresq in these tables had a free dial plate rather than the fixed dial plate found on the dumaresq in the Mark III table; flexible shafting permitted the indicator along the line of bearing to show the range rate set on the clock in the lower housing. A gyro-compass linkage maintained own heading as before.[2]

Range Clock

The range clock was underneath the dumaresq and the handle for setting its range rate also moved an indicator in a slot along the line of bearing in the dumaresq's dial plate.

The range clock's output shaft fed a tuning differential which drove the carrier for the red clock range pencil across the range plot and permitted a tuning handle to quickly position the pencil to the desired range. The tuning gearbox included a resettable count-up dial, and a hand-worked pedalling clutch allowed the tuner to select whether his tuning should be negatively fed into the Spotting Corrector to keep the gun range unchanged by the tuning.

Bearing Clock

Fig. 3: Schematic of Mark III* Dreyer Table w/ G.D.T. Gear, c1918
Even though this is schematic, it helps indicate how much more compact the plotting paper on the G.D.T. was than on the Standard Bearing Plot.

As first designed for the standard bearing plot, no bearing clock was incorporated.[3][4] When the fitting of G.D.T. gear was decided upon, a bearing clock was added (see image to right).[5]

Spotting Corrector

The spotting corrector in the 1918 handbook featured:

  • the customary handle to enter spotting corrections
  • a resettable count-up dial for each incremental correction
  • a pointer to indicate the total correction in place
  • a pointer to indicate the current straddle correction to ease the interactions with the Dreyer Calculator

The final gun range from the spotting corrector was conveyed to:

  • A worm shaft for the gun range pencil holder
  • A pair of digital gun range counters; one nearby and one convenient to the Wind Dumaresq and Deflection Correction Link Gear.
  • A commutator to relay gun range to control positions and conning tower
  • A flexible shaft to carry gun range to the Range Master Transmitter on the bulkhead of the TS.
  • A flexible shaft to carry gun range to the deflection drum (the second gun range counter was driven off this).

It seems a little disappointing to me that the gun range directly worked on the deflection drum but required 2 separate manual transfers to update the wind dumaresq and deflection correction link gear.

Range Plot

The Mark III*'s range plot was typical to other well-appointed models; a large surface placed on the right, with a range rate grid positioned over it. Unlike in the Mark III table, however, the tuning handle was placed behind the table to free up space. The tables appeared so late in the war that their range plot fittings were probably always the most modern patterns found in the 1918 Handbook.[Inference]

Rate Grid Probably only the most modern pattern of range rate grid.

Plotting Range Cuts Probably only the Range Typewriters, as they had been deployed widely in 1917.[6]

Range Pencils The tables probably always had a gun range pencil driven by the Spotting Corrector in addition to the traditional red clock range pencil.

Plotting Ranges 2,000 - 16,400 yards
(a +8,000 yard extended scale added later allowed plotting to 24,400 yards)[7]
Paper width 36 inches
Scale 400 yards/inch
Paper speed 2 inches / minute

The extended range scales were likely fitted to tables as opportunity arose around the time (1915?) such a modification was made to ???? (Brooks)[Citation needed].

Bearing Plot

Deployment

Ships slated, in 1918, to receive Mark III*
Ship to be Fitted Commissioned/Completed
Cairo September 1919
Calcutta August 1919
Capetown February 1922
Carlisle November 1918
Colombo July 1919
Delhi June 1919
Dunedin October 1919
Durban September 1921

The Dreyer Handbook of 1918 indicates a number of as-yet unfinished light cruisers were being equipped with these tables (see table to right).[8] The odd aspect is that contemporary procurement initiatives were placing less-capable Turret Control Tables in other light cruisers and even Mark I* Dreyer Tables in modern heavy cruisers.[9]

Given their dates of completion well after the June 1918 promulgation of the document outlining the intention to outfit them with Mark III* tables, it seems reasonable to conclude that all were equipped with tables soon after their completion, possibly with GDT gear from the outset.

By 1930, the allocation was as follows.[10]

Ships fitted with Dreyer Table Mark III*
* = Modified Mark III* table
** = Without G.D.T. Gear
Class Ship
Hawkins Frobisher
Effingham
Emerald Emerald
Enterprise
Danae Dauntless*
Danae*
Delhi
Despatch
Diomede
Dragon*
Dunedin
Durban
Capetown Cairo
Calcutta
Capetown
Colombo
Carlisle
Aircraft Carriers Eagle**
Hermes**
Gunnery Schools Excellent
Chatham
Devonport

See Also

Footnotes

  1. Dreyer Handbook, 1918 p. 90.
  2. Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 19.
  3. Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. Plate 7.
  4. Brooks. Dreadnought Gunnery, p. 177.
  5. Brooks. Dreadnought Gunnery, p. 177.
  6. Brooks. Dreadnought Gunnery, p. 173.
  7. Dreyer Handbook, 1918 p. 17.
  8. Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 3.
  9. Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 3.
  10. Pamphlet on the Mark III* Dreyer Table, 1930, p. 1.

Bibliography

  • Admiralty, Gunnery Branch (1918). Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. C.B. 1456. Copy No. 10 at Admiralty Library, Portsmouth, United Kingdom.
  • Brooks, John (2005). Dreadnought Gunnery and the Battle of Jutland: The Question of Fire Control. Oxon: Routledge. ISBN 0714657026. (on Amazon.com and Amazon.co.uk).
  • Brooks, John (2001). Fire Control for British Dreadnoughts: Choices of Technology and Supply. Unpublished PhD Thesis. London: Department of War Studies. King's College, London.
  • Roberts, John A. (1992). Anatomy of the Ship: The Battleship Dreadnought. London: Conway Maritime Press. ISBN 085177895X. (on Amazon.com and Amazon.co.uk).
  • Dreyer, Frederic; Usborne, Cecil through Gunnery Branch, Admiralty. (1913). Pollen Aim Corrector System, Part I. Technical History and Technical Comparison with Commander F. C. Dreyer's Fire Control System. P. 1024. in Admiralty Library, Portsmouth.

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