Dreyer Torpedo Control Table

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Wiring for Hood's Dreyer Torpedo Control Table[1]

The Dreyer Torpedo Control Table was a device adapted from the Dreyer Fire Control Table to meet the needs of torpedo control. They were similar in concept to the Torpedo Control Plotting Instruments.

It was to feature the dual-instrument bearing plot that a critique of the Torpedo Control Plotting instruments had suggested for that device.

Trial in Ramillies

The first one was almost completed at the end of 1917, and was to be fitted in Ramillies. A second was already on order for Hood, and a pamphlet for the device was being written.[2]

By mid 1919, Ramillies was able to report on the device, which it had used in a manner slightly different than designed. Rather than use the dual bearing plot for plotting 2 bearings, one side was used to plot the gyro compass repeater data so that the lag of its influence will be made apparent. Somehow, this was found to permit the trend in bearing from the single observing instrument to be discerned.[3]

The Annual Report of the Torpedo School, 1918 offers limited hope, panning the device on general terms that reflect a wholesale shift from aiming torpedoes against a ship as the target as opposed to considering the enemy battle line the target:[4]

"The decision to fit a Dreyer table for torpedo control was made at a time when it was thought that the source and speed of the enemy could be obtained with such an instrument, and that such information was required for torpedo control. Experience and development of ideas have since shown us that what is now required is the trend of the enemy's line, together with their direction of advance, and that, with constant alteration of course on the part of the ship observed, the Dreyer table will not produce any information of alue when worked on a range and bearing plot. It is not therefore recommended in its present form.

The occasions when the table could be used have not been numerous; in many of them the T.C.T. rangefinder would not bear and could get very few ranges, and the necessity for an additional rangefinder with forward bearings was clearly brought out."

Hope was offered in the form of adaptations that might permit the Dreyer to work with inclinometers so it might plot the range and help judge the mean course of the enemy. Under this plan, the bearing plot would converted to an inclination plot with wider paper and slower traction so that 10-15 minutes of history could be visible, and the gyro-rectified bearings to the target would be added to this to come up with the enemy's mean course. The dumaresq would also be set by inclinometer and so "should be able to maintain the range with far greater accuracy than at present," and the inclinometer would transmit bearings rather than the rangefinder.[5]

Hood

By mid 1919,[6] the results of the trial in Ramillies led to sweeping changes in plans for Hood's table, exchanging the bearing plot for an inclination plot. This necessitated difficult adaptations to the Electrical Dumaresq, as the existing design was intricately tied to range rate and bearing rate, not inclination.

There was to be a double Range Plot, so as to permit all the 15-foot torpedo control rangefinders to contribute data,[7] and the outputs to the control positions would be:

  • Mean compass course of enemy
  • Speed of enemy
  • Bearing of enemy
  • Inclination of mean line of advance (by separate transmitter)
  • Range (from the table's range clock)

The inclination-measuring instrument was to be Barr and Stroud Horizontal Angle Measurer Type S.F. 2 passing down to receivers in the torpedo TS

  • length of enemy (in feet, to be applied on the inclination plot)
  • horizontal angle (in units of 5 arc seconds,[8] to be applied on the plot)
  • bearing of torpedo target (to be set on the dumaresq)

See Also

Footnotes

  1. Annual Report of the Torpedo School, 1917. Plate 67.
  2. Annual Report of the Torpedo School, 1917. p. 196.
  3. It seems that gyro compasses were still not ready for real fire or torpedo control use
  4. Annual Report of the Torpedo School, 1918. p. 167.
  5. Annual Report of the Torpedo School, 1918. p. 167. The editor wants to see some source that explains why anyone thinks inclinations would truly be the most reliable observations to take at long ranges.
  6. Annual Report of the Torpedo School, 1918. p. 168.
  7. I thought Hood was to have three such RFs? — TONY LOVELL, Editor.
  8. Annual Report of the Torpedo School, 1918. p. 174.

Bibliography

  • Admiralty, Gunnery Branch (1917). Handbook of Torpedo Control, 1916. C.B. 302. Copy No. 141 at The National Archives. ADM 186/381.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1917. Originally C.B. 1474. Copy 7 at The National Archives. ADM 189/37.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1918. C.B. 1527. Copy 20 at The National Archives. ADM 189/38.