Gun Laying Plotter Instrument ?? OZALID

[Martin King 2Participant @martinking2]

Hi All,

My wife came across this nice instrument at a local car boot, the chap said that he had it with him in the Falklands but I did not get to talk to him to quiz him further

Not much comes up under OZALID but I have certainly heard the name before.but cannot remember the context.

Nice that it is in a custom case with a lovely little magnifier and dividers by W HARLNG, a local firm from Weymouth.

My only thoughts are that it might be for gun laying using a plane table or some such? You can locate the circle centre very precisely with the glass to align the crosshairs. Presumably you can then get a precise fix from the bearings of known objects on the map?

Any thoughts most welcome

Cheers, Martin

[Martin King 2Participant @martinking2]

[Mark Simpson 1Participant @marksimpson1]

When I was apprentice, late 1970's, Ozalid was the name of one of the two drawing print processes we used (pre CAD)

Ozalids used chemical impregnated paper, UV light and developed with ammonia. Smelt like Cat Pee, so most preferred semi dry prints which used a chemical to print and then dried (or burnt) the print at the end of the printing process…. sat next to the office print machine for a while, got some practice with the fire extinguisher when people were not paying attention

typical (american) ozalid machine pics here…

It's likely that they also made drawing and chart plotting equipment, your items look like a good way to meausre and bearing and distances on maps and charts.

[HOWARDTParticipant @howardt]

As a drawing office apprentice we all had to take alternate weeks in the print room. The worse job was replacing the gallon bottle of ammonia in the print machine. Quite a few times it would get tipped over filling the office with fumes. That added to the bottles acetone and trichloroethylene that we used to clear print areas on plastic film prints made for a very healthy atmosphere,oh yes and the smoking.

[SillyOldDufferModerator @sillyoldduffer]

I think it's a precision protractor, used for chart work or plotting maps from survey results. Here's similar:

Dave

[Mick B1Participant @mickb1]

Posted by SillyOldDuffer on 09/09/2021 16:14:09:

I think it's a precision protractor, used for chart work or plotting maps from survey results. Here's similar:

Dave

I think so too. If I'm reading it right the main scale has 1/2 degree divisions and the Vernier scale does 15 minutes either side of a 0 position by 1 minute divisions, which looks a bit puzzling to read.

It's also a pity – as indeed it is on very many linear Vernier calipers – that the Vernier scale isn't dead-level with the main one, as parallax errors can obviously result.

I share the experience of Ozalid as the main provisioner for dyeline print rooms before CAD. My father-in-law worked for them. This instrument seems quite an outlier from their usual ine of business.

[Martin King 2Participant @martinking2]

Hi All, Thanks for the helpful input, it does seem to be a general purpose precision surveying instrument,

Found this one from the USA

Cheers, Martin

[Michael GilliganParticipant @michaelgilligan61133]

Something similar mentioned here: **LINK**

https://www.moodt.org/exhibis#/measuring/

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Vernier Protractor with horn center and cross hairs

Made by T. Alteneder in velvet lined case.

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MichaelG.

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Edit: __ and a Stanley version, here:

http://www.mathsinstruments.me.uk/page73.html

P.S. __ a ‘horn center’ is used to prevent the point of the dividers piercing the paper.

Edited By Michael Gilligan on 09/09/2021 19:49:04

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin King 2 on 09/09/2021 17:51:33:

Hi All, Thanks for the helpful input, it does seem to be a general purpose precision surveying instrument,

Found this one from the USA

Cheers, Martin

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Having also seen your eMail message, Martin … I can add this reference:

**LINK**

https://www.wbparts.com/rfq/6675-00-283-0012.html

MichaelG.

[Author]

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