Dreyer Table Mark I
The Mark I Dreyer Table was a downsized version of the earlier Mark III table, and probably first deployed in 1915. With a footprint 23% smaller than the Mark III table's, it could more comfortably fit within the smaller transmitting stations of the early dreadnought battleships and battlecruisers into which it was retro-fitted.
As no one has been able to locate a handbook for the Mark I tables produced in 1916, most of what follows is from the 1918 Handbook for all Dreyer tables, and almost certainly reflects evolutionary change and refinement from the tables' initial installed state (e.g.: manner of plotting range cuts certainly changed between 1915 and 1917).
|Width||5 feet, 8 inches|
|Depth||5 feet, 1.5 inches|
|Height of Range Rate Grid||3 feet, 4 inches|
|Height of top of dumaresq||3 feet, 9.5 inches|
A Dumaresq Mark VI* was fitted, with a manual means of setting own heading rather than the gyro-compass input used in the Mark III table.
An spring-driven Vickers Range Clock adapted by the addition of a follow-up pointer worked by an external chasing handle and by the removal of its range markings on its dial was provided near the dumaresq and acted solely as a variable speed drive. An external rate handle drove an indicator on the dial plate of the dumaresq which the operator sought to keep aligned with the enemy pointer as it set the rate on the clock. The rate handle also acted to skew the wires on the range plot's range rate grid to the proper angle.
The chasing handle drove the follow-up pointer on the clock face. This F.T.P. action passed changes in range on to the spotting corrector gearbox.
The spotting corrector in the 1918 handbook features:
- Output worm shaft for the plot range pencil holder
- Spotting handle to enter corrections
- Straddle correction hand (for corrections from a Dreyer Calculator)
- Gun range counter (on the table)
- Commutator to relay gun range to control positions and conning tower
- A flexible shaft to carry gun range to the deflection drums of the standard bearing plot
A hand-worked pedalling clutch allowed the plotted range to be tuned without altering the gun range.
The range plot ran the entire width of the table in the back, with a range rate grid positioned over it. Worm shafts from the spotting corrector carried pencils to record the plotted and gun ranges on the paper. As first created, the tables probably used a Brownrigg keyboard,[Citation needed] but by 1918 they were being replaced by the range typewriter.
|Plotting Ranges|| 2,000 - 20,000 yards|
(a +8,000 yard extended scale added later allowed plotting to 28,000 yards)
|Scale||400 yards/inch (45 inches for plotting, plus perhaps 5-in margins)|
|Paper speed||2 inches / minute|
The Handbook for Capt F.C. Dreyer's Fire Control Tables, 1918 indicates flatly that these were at some point provided with standard bearing plots, but these units received such scant service before the introduction of G.D.T. gear that it is hard to bank that many were actually fitted, not least to the humblest of Dreyer tables and the priority they would be afforded. Moreover, as the old style bearing plot seen on the original Dreyer table was so large, and the deflection totaliser pretty useless without deflection drums, it is possible that Mark I Dreyer tables in practical World War I service were range-only.
The Dreyer Handbook of 1918 lists some ships with Mark I tables, with those no longer in active service crossed out by hand at some later date, and those lost before promulgation not listed at all. Those appearing in that document are footnoted below.
In February, 1916 Dreyer was awarded £5,000 by the Ordnance Council for his contributions to fire control. A list was drawn up which indicated the "Ships in which Dreyer's Fire Control is fitted or being fitted." Those ships listed under the heading "MARK I (Simple Mechanical Table...)" in this document are footnoted below.
|Ship using Mark I table||Date equipped||Notes|
|Dreadnought||mid 1916, perhaps by May 25||installed in fore TS|
|Hercules||Replaced the Original Dreyer Table used in this ship|
|New Zealand||perhaps after Jutland?|
- Brooks. Dreadnought Gunnery and the Battle of Jutland. p. 176.
- Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 90.
- Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 13.
- Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 15.
- Handbook for Capt F.C. Dreyer's Fire Control Tables, 1918. pp. 13-15.
- Brooks. Dreadnought Gunnery and the Battle of Jutland. pp. 176-177.
- Brooks. Dreadnought Gunnery, pp. 175-6.
- Email from John Brooks, March 28 2008
- Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 3.
- "With 'Extract from Recommendations of the Admiralty Members of the Ordnance Council at a Meeting 10.2.16 concerning Dreyer's award' in DRYR 2/1." Brooks. Dreadnought Gunnery at the Battle of Jutland. pp. 175-176.
- Roberts. Anatomy of the Ship: The Battleship Dreadnought. p. 31.
- Pollen Aim Correction System, Part I. p. 12.
- 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.