Dreyer Table Mark I

The Dreyer Fire Control Table Mark I 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 dreadnoughts and battlecruisers into which it was retro-fitted.

Particulars

The Mark I was entirely hand-worked. Although the Mark III table could fall back to a hand-worked mode, with the Mark I (and Mark I* tables, this was the only means of operation.

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).

Dumaresq and Range Clock

A Dumaresq Mark VI* was fitted, with a manual means of setting own heading rather than the gyro-compass input.

Range Clock

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.

Spotting Corrector

The spotting corrector in the 1918 handbook appears just like any, with:

• 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.

Range Plot

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, 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

Bearing Plot

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.

Deployment

[TO BE CONTINUED - TONE]

Ship using Mark I table	Date equipped	Notes
Dreadnought	mid 1916, perhaps by May 25	installed in fore TS
Colossus	N/A
Hercules	???
Neptune	???
Collingwood	???
St. Vincent	???
Agincourt	???
Erin	???
Bellerophon	before Jutland
Marlborough	???
Superb	???
Temeraire	???
Australia	???
New Zealand	after Jutland[Inference]
Inflexible	???
Invincible	???

See Also

• Dreyer Fire Control Table

Bibliography

• Template:BibUKDreyerTableHandbook1918
• Template:BibBrooksDreadnoughtGunnery
• Template:BibRobertsAnatomyDreadnought