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Can you identify this instrument

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Can you identify this instrument

Old 27th Nov 2015, 18:44
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Wageslave,
This instrument is not connected to a compass. It is a separate instrument, could be located within the instrument binnacle. It allows the helmsman to steer under orders from the Captain without any compass. Think of it as a rudder indicator.
This one is a repeater, could be located below or on the bridge wings and can work without a compass in sight.

The descriptions are from the Admiralty Manuals of Seamanship - not my words.
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Old 28th Nov 2015, 04:21
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I still like the idea that it is a Wind Over Deck Indicator or Repeater. From a user's point of view, you would want to know that the ship was steaming into wind in a direction that was useable by the pilots. Thus the Island would have to be taken into account in any display as any wind in a direction that would take you into it would, by definition, be useless. Wind Over Deck is a relative measurement - so any instrument would require, at a minimum, ship's heading & speed as well as wind speed & direction. On a modern ship these might all be derived inertially but in WW2 you would need individual sensors for all four and then combine them through a summing circuit. The directional sensors would be 360 degrees but the combination as displayed would only be useful in sectors where aircraft could land or takeoff - hence the asymetric presentation.

Last edited by ICT_SLB; 28th Nov 2015 at 04:36.
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Old 28th Nov 2015, 14:58
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I think you might be reading a bit too much into it, ICT.

As a former mariner (merchant, not naval), I must admit I'd not previously encountered such an instrument.

Like most who've been following this thread, I too, have been intrigued by the possibilities.
A Wind-over-Deck indicator is high up there on the list, but OzBob's post, citing the Admiralty Manuals, has tentatively won my vote.
The apparent asymmetry still has me scratching my head, though.

No doubt, someone will be along soon with the definitive answer (including the name of manufacturer - and date) so that we can sleep at night.
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Old 29th Nov 2015, 11:45
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A wind instrument makes no sense because of the missing sector. You need to know it all the way around the compass especially on a carrier where you have to turn into it - how do you do that if you can't see it in a certain sector? No, it isn't that. Arguing that the dead sector is because of the island makes no sense because the island is on the stbd side, not port. You can't "use" wind from astern on carrier air ops either so why would it be calibrated all the way to astern on one side and not the other? You can't "use" the wind 40' either side of dead ahead in a sailing boat but the wind instrument still shows it because you still need to know it.
All the rudder position indicators I've seen have been clearly annotated as such and only range 30' or so either side of ahead. No rudder can turn 180', so why annotate it?
It could indicate logically as a repeater for a rotating power-pod type thruster but they're far too modern for this instrument, aren't they? Even so a rotating thruster is a bit handicapped of it has such a large dead sector on one side.
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Old 23rd Jan 2016, 14:08
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It's an Azimuth indicator for a Leigh Light. The arc of movement suggests it would be for a light installed on the starboard wing, e.g. Catalina.
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Old 23rd Jan 2016, 16:09
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682al
It's an Azimuth indicator for a Leigh Light. The arc of movement suggests it would be for a light installed on the starboard wing, e.g. Catalina.
That sounds good to me especially given its range of movement highlighted below in bold would make a perfect match.

Anti-submarine operations - The Leigh Light. | Military History Forum

THE LEIGH LIGHT FOR NIGHT ANTI-SUBMARINE OPERATIONS

The Leigh Light was a carbon arc searchlight carried on an aircraft and used in conjunction with A.S.V. to illuminate surfaced submarines at night. The searchlight operator was situated in the nose of the aircraft from where he could control the searchlight beam in both elevation and azimuth. Indicators were fitted which showed the direction in which the beam would shine. The operator was thus able to train the searchlight in approximately the right direction and distance before the light was exposed. A lens giving a spread of 10° in either a horizontal or vertical plane was provided which made search¬ing for the target easier, but some expert operators prefer to use the light without the lens. The maximum effective range in ordinary -weather was about two miles.

The arc lamp was fully automatic in operation, the rate of feed of the Carbons being automatically controlled. Power for the arc, which ran at 120 to 150 amperes, was obtained from seven 12 volt 40 ampere hour type D accumula¬tors and a-trickle charge fitment -would maintain them fully charged provided the arc was not run for more than three half minute periods per hour. Fully charged accumulators \?would maintain the arc for about six minutes without re¬charging.-

There were two types of Leigh Light in service:-

(1) The Turret type, fitted on Wellington aircraft; in this a 24 inch
searchlight was mounted in a retractable under-turret and the controls were
hydraulic. The maximum beam intensity was 50 million candles without the
. Spreading lens and about 20 million candles with the lens. Total weight of the installation was 1,100 Ibs.

(2) The Nacelle type, fitted on Catalina’s and Liberators; in this a 20
inch searchlight was mounted in a nacelle 32 inches in diameter slung from
the bomb lugs on the wing. The controls were electric and the maximum beam
intensity was 90 million candles, without the spreading lens and about 17
million with the lens. Total weight of the installation was 870 Ibs.

The trickle charging current for the accumulators was obtained from an engine-driven generator on the Wellingtons, windmill driven generator on Catalina’s and a motor generator set on Liberators.

The control system on the Wellington was similar to that used for turrets. The turret itself was rotated by a Vane oil motor for movement in azimuth and the projector was moved by a ram inside the turret for movement in elevation.
The maximum speed of rotation when the control column was turned to the limit was 40 degrees per second, the limits of movement were 60 degrees to Port and 180 degrees to Starboard.
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