Crace's Change of Bearing Instrument
Crace's Change of Bearing Instrument was a Torpedo Control instrument conceived by a Lt. Crace of H.M.A.S. Australia to determine the bearing rate of a target so that the deflection can be computed to set a Torpedo Director.[2]
Instrument
It used a special telescope atop a gyro compass receiver. The telescope had crosswires and a prism in it that permitted the operator to simultaneously observe the target beneath a 5 degree arc of the gyro compass card below. The operator worked a training gear to keep the crosshairs on target and call out the bearing to a second man. This second number was equipped with a circular slide rule and also received ranges by voicepipe.
Sliderule
The sliderule had two discs:[3]
- the inner one had OwnSpeed * sin(Bearing)
- the outer one (pi * Range) / (100 * TimeIntervalBetweenBearings)
The result would be the Torpedo Deflection to passed by Navyphone to the director position.
Experience
By late 1914, it was determined that sufficient practice gave good results, but the amount of calculation required seemed worrisome.[4]
See Also
Footnotes
Bibliography
- H.M.S. Vernon. Annual Report of the Torpedo School, 1914. Copy 5 at The National Archives. ADM 189/34.
- H.M.S. Vernon. (Jan 1916) Annual Report of the Torpedo School, 1915. C.B. 1166. Copy 1025 at The National Archives. ADM 189/35.
- Admiralty, Gunnery Branch (1917). Handbook of Torpedo Control, 1916. C.B. 302. Copy No. 141 at The National Archives. ADM 186/381.
