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WWII USN Instrument collection


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I recently bought this collection of WWII USN instruments I thought some of you Navy guys might appreciate. This collection consists of 32 pieces in total to include scopes, sights, sextants, signaling devices, map reading devices, clocks, compasses, gauges, etc. Many are in their original wooden transit cases. Below are a few overall photos, hope you enjoy.

 

Rob

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The small boat PELORUS, the compass rose instrument with the fold up sighting vanes is an outstanding and rare "keeper". Many commercial small vessel operator licenses require piloting using bearings to shore objects using a pelorus . Good metal instruments have not been made in years.

 

In the want to cringe department, the lifeboat compass in the square brass binnacle, as far as the CG goes, was replaced on cutter small boats with a newer version. When they arrived, we were directed to take the old compasses out onto the pier and smash them up, heave them into the dumpster and complete the paper work that they were no longer servicable..

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Rob, I see that you have a ship's bearing bar in a wood box. I picked one of those up back aways. Mine is marked "Mark IV, Mod 1, 1943. I don't have a clue what it does other than something related to bearings. Perhaps someone could educate me. It would be appreciated. It's mounted in a very nice wood box as is yours.

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Bearing bar, I'll assume is the rectangular brass bar with roller wheels at either end. If I recall that would be a roller plotter used to move course lines in a parrallel motion when measured from a compass rose on a chart. Usually this platter would be seen in the Combat Information Center (CIC) on a ship. They had a large circular 4' or so flat plexiglass template that represented the radar maneuvering board plotter sheet

 

On this plotting table, the radar operator would call our compass bearings and ranges to surface contacts and the radarman on the plotting table would mark them with a grease pencil. After two or three "marks" on a contact, The table could determine the other vessels course and speed. They could either turn to intercept or evade. The ability to move lines around the plotter table without having to lift the plotter rule off the table sped up the results with little chance for error.

 

Radar plotting entailed marking your course ans speed, your contacts range and bearing and from that, the basic plot was a triangle and you solved for the third side, the contacts course and speed. The USN put out the Maneuvering Board Manual years ago that broke the math behind it right down to 'sailor level"

 

In the day, all CICs smelled like the remnants of a reale smoky bar on Saturday night. The ashes were an excellent abrasive for cleaning the grease pencil residue off the plotting table. They always had an " El Ropo Supreme" burning..

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Thanks MastersMate for that detailed description, now I know what that was specifically used for! The bearing bar Sundance is referring to is a different instrument. Looks to be some sort of sighting device, here are a few photos of the item in question.

 

Rob

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The Bearing Bar is used for .... taking bearings. :rolleyes:

 

It is similar to Bearing Circles, Azimuth Circles, and Telescopic Alidades. The differences are the compasses to which they are mounted and the vessels on which they were used..

 

All are for taking bearings, but the Bearing Bar was used on the smaller 5" card compasses rather that the 7-1/2" "standard" compasses on which the other 3 are used.

 

The smaller, magnetic compasses were mounted on small boats - life boats, landing craft, etc., and were used for inshore/riverine navigation and determining bearing drift of other boats/ships.

 

The larger bearing devices were used on gyroscope repeater peloruses aboard ships and larger landing craft such as LCUs. These are used for the same tasks as the bearing bar - navigation (entering and departing ports) and determining bearing drift of "skunks", aka surface contacts, as well as use in station keeping in formation.

 

I'm don't know when the Bearing Bars were removed from use/inventory, but they were gone before my initial exposure to US Navy navigation equipment in 1975.

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An FYI on the bearing bar and other items.They use radium for illumination on the bearing bar and quite a few 1930s-early 1940s USN instruments have radium in them for illumination. I highly recommend you consider investing in a geiger counter and labels as needed for safety if not basic piece of mind. The bearing bar we have at the museum is rather hot.

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  • 1 year later...
Salvage Sailor
On 12/14/2019 at 8:34 PM, zzyzzogeton said:

The Bearing Bar is used for .... taking bearings. :rolleyes:

 

It is similar to Bearing Circles, Azimuth Circles, and Telescopic Alidades. The differences are the compasses to which they are mounted and the vessels on which they were used..

 

 

From my USN Navigation collection - Azimuth Circle Mark III Mod.2 1943

 

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Wooden Case

 

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USN Azimuth Circle, 1943

 

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