Bubble in prismatic compass

This isn't the right place I guess but I'm not at all sure were would be. Anyroad since I know some serious armourers abide here I thought I what the hell.

I finally picked up a leather case for the 1943 Mk III prismatic compas I picked up for £5 when I was about 13 so I dug it out to put in it. Unfortunately the small bubble of my youth has expanded to a size that it affects the card. Can it be refilled at home or is it going to be expensive? I used it a lot in the 1980s and want to get it back into working order.

ATB

Tom

Peter did an article about servicing these... Milsurps Knowledge Library - COMPASS, PRISMATIC, Mk3 (by Peter Laidler))

There was also a lot of dicussion disagreeing with the VERY basics that I'd written. But it later transpired that the writer had a vested interest in repairing them as a profitable business. I digress. You can refill but you need isoprophyl alcohol. Otherwise, just unscrew the side mounted filler screw, allow to drain and refill with clear kerosine or methylated spirit. All the liquid is is a damping mechanism.

NEVER heard of our issue compasses being used in a leather case. Tooooooo fragile for that! A short drop in a leather case would surely snap the pivot post. Nope....., use the buffered and tight fitting webbing compass case

Added later. I seem to remember that the other man did a little pictorial essay about degassing the new fluid in the fluid bowl using the fridge overnight. Never heard of that method before and we never did it that way as we had an atmospheric depression tank. But if it works........

That's just what I needed to know! Ta!

The leather case was a Great War thing

WWI British Military Prismtic Compass by Steward with Leather Case. - Gilai Collectibles.

But the one I scored seams to be from a modern Francis Barker civy job

http://www.scientificcollectables.co...nlarge1383.htm

I'm sad enough to admit I do have the web pouches to fit, 1937, 1939 ( ok not web but same as )1944 and 1958. Also various pistol and jack knife lanyards. I've also got the lads maternal great grandads Great War era prismatic. But I've never tested it to see if its accurate still.

As it happens I get isoprophyl alchohol by the gallon jug. I use it , diluted to shrink the tissue on my silly balsa rubber powered planes, for stripping the paint off models and general cleaning jobs. Wonderful stuff! But oddly I picked up a little squirt bottle, from a surplus store of clear methylated spirits , no warning purple colour, and wondered what it was for. I assumed cleaning electrical components or some such.

Here it is

METHYLATED SPIRIT 99%
Bar code
6810 99 230 0984 UUK No. 1987
DATE OF MANUFACTURE 06
DATE OF DESPATCH. 06
CPGS2/7529. 070402
QUANTITY 100mls SHELF LIFE 3 YEARS

That suitable?

Here's a compass porn pic I was asked to take for another forum.

https://www.milsurps.com/images/impo...77a6dd08-1.jpg

If its upside down, your probably using a iPad. I don't know why.

I too have seen the leather cases...don't know where they came from though.

That compass and the leather case don't look deep enough to be the UK Military type. Ours were about 1.25" deep including the prism cover (the bit fixed to the lid that covers the prism assembly when closed down.....) Or is it camera angle distortion?

Anither bit of 'supplementary issues' for the sniper rifle CES incidentally.

I taught my son to use one while he was very young and he can still use it to orient the map, back bearings and thereafter read the map. Good and VERY useful bits of kit. Mind you, not the sort of thing that you'd ever entrust an Officer with. That and a map!

Attachment 46993
Sorry, I couldn't resist.

Haven't seen that one. But very funny! I'll send it to someone I know.......

Its the angle as it's as thick as all the otherMk IIIs I've seen and its a perfect fit in the case, not too tight but no rattling about. This case has no markings on it at all hence the conclusion its a modern civy job. It has a roll buckle to close the case and to adjust the strap lenght. but the latest ones have press stud closure.

The compass has this on the base

CKC/C
Arrow mark
16978C
MK.III
1943

The one that the boys have inherited is smaller and much thinner and isn't liquid filled has this on the base.

Inverted broard arrow
F-L:
No. 87966
1917

On this vague note a distant relation of the wife has dumped some bits on us with instructions to eBay and buy the kids something and included are her husbands dads Great War era Binos. On the front plate is a large broard arrow and on the left back plate thngy near the eye piece

Binocular Prismatic No 3 Mk I
Magnification 6
No 62152 (it fades out, not sure about the last number.)

on the right back plate is
A. KERSHAW & SON LTD
LEEDS
1918

Which was the year he was commisioned after serving as a private in the Artists Rifles i think. We got a wad of documents, training notes and Officer type bumpf with them.

ATB

Tom

Quote:

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Originally Posted by tombear

its a modern civy job

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Sort of what I thought...

Hi guys, first post.

My own WWII-era CKC MKIII prismatic compass developed an approximately 11mm wide air bubble after recent air travel. I came upon a very quick and easy way to get a bubble out of Silva compass capsules and thought I'd give it a go on my MkIII prismatic.

Here's what I did, step by step...

Step 1. Put the compass on a window sill in direct sunlight on a sunny day.

Step 2. Check the compass after a couple of hours and you'll see the bubble has either gone or reduced in size.

Worked for me.

Plan B was going to be to strip the compass and do a complete refill using purified kerosene (plain lamp oil). I haven't ever done this, but the idea is that you take the capsule out of the case and crack the filling screw carefully so as not to damage the o-ring. Remove the screw and submerge the compass capsule in purified kerosene, manipulating the capsule to (hopefully) manoeuvre the bubble out of the filling port. Replace the filler screw while the capsule is still submerged, wipe it clean and wipe some clear varnish over the edges of the filler screw. Then reassemble the compass. Once again, I'd like to point out that I've never performed that particular bubble removal technique so if anyone's compass explodes...

Try the window sill/sunny day method first.

That's a pretty case. A very Great War-looking piece of kit. It looks a little too big for the MKIII, but it's my understanding that they were also made for military engineering instruments such as barometers. I had one I picked up off ebay a while ago and discovered that it was too big for my compass by about 5-10 mm on all sides and that under the "leather" it was made from cardboard. I've also got an Enbeeco M88-ish prismatic compass which came with a similarly-constructed case, but with the correct dimensions, and it too was coated cardboard. I ended up buying some leather hide and I'm going to have to make my own for my MKIII and my US Verner's Pattern prismatic. For outdoors use, the MKIII rides in a Canadian issue webbing pouch.

I found a photo of my compass with its post-air travel bubble -

https://www.milsurps.com/images/impo...58c12500-1.jpg

And one I just took showing the mysteriously absent bubble after the sunny window sill procedure -

https://www.milsurps.com/images/impo...020f2b1d-1.jpg

Quote:

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Originally Posted by jungleisneutral

Put the compass on a window sill in direct sunlight on a sunny day.

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That works great to expand the liquid and of course will eliminate the bubble temporarily. If it appears, it'll be back. It's like electronics, it won't hear it's self. It has to be fixed eventually.

Quote:

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Originally Posted by browningautorifle

That works great to expand the liquid and of course will eliminate the bubble temporarily. If it appears, it'll be back. It's like electronics, it won't hear it's self. It has to be fixed eventually.

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I'll let you know how it goes and whether it needs to be fixed eventually or whether it healed itself.

BAR is absolutely correct. Your bubble is probably still there but trapped inside the......., er....., bubble trap! It's a small rim around the inner edge of the bowl.

Immersing the bowl into a bowl of kero is OK but BETTER if you can seal the bowl and degas the liquid. A simple way is to use a bolt-through tyre valve, evacuate the air, allow to stand for a few hours while the air is evacuated from the kero in the bowl. Release depression and then reseal compass under the liquid. New fibre or neoprene seals should be easy to find/replace

In ours, the bubble would come and go depending on how warm it was. Usually if we had any wonky compass' they would appear in the cooler climates. They don't get better, they have to be fixed. First time your compass gets cold, it'll be back.