Fluid for Compass?

Hi,
Not exactly a model engineering problem but I'm sure it is just the sort of problem model engineers can probably advise on.
I've a military compass which was fluid filled. It seems to have "lost" its fluid and so the disk no longer "rides" on its pivot.
I'd like to refill it.
Any ideas on what the fluid would have been?
Compass is a handheld beast, a "marching compass", about 3cm in dia. and the "capsule" is about 1cm deep, so about 7 cm^3
Regards Brian
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Try this link
http://www.ybw.com/forums/showthread.php?t=79643
Hope it helps
John H
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On Mon, 21 May 2012 12:32:55 -0700 (PDT), John H

Take care, any dust or debris you get out of it is likely to be radioactive and possibly harmful to health, especially if inhaled.
Russell
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"Brian Reay." wrote in message

I topped mine up about ten years ago with white spirit, and it's been fine ever since. Shame it's calibrated in military 'grads' rather than degrees though !!!
AWEM
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Don't you mean "mils"? 6400 to the circle. That is the norm for the military.
A "mil" is the angle subtended by 1m and 1km. It is a very easy unit to work with when "gun laying" etc. It is close the true milli-radian (2Pi/1000, about 6280 to the circle).
(I used to work in military navigation systems.)
The Grads is 1/400 of a circle and is (or perhaps was) used in surveying.
OK on the White spirit, probably the most "available" liquid. Thank you.
Regards
Brian
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Brian Reay. wrote:

I'd be cautious using white spirit - in fact I wouldn't use it at all. The "proper" fluid is alcohol, either ethyl alcohol or isopropyl alcohol - I'd be worried that white spirit might dissolve the paint/ink on the markings etc.
Isopropyl alcohol (IPA) is both cheap and widely available - many chemists stock it, as do some of the better electronics and computer shops: or you can get IPA from eBay for a few pounds delivered, eg
http://www.ebay.co.uk/itm/IPA-Isopropyl-Alcohol-99-9-Pure-50ml-Dropper-Bottle-/140573765857?pt=UK_BOI_Medical_Lab_Equipment_Lab_Supplies_ET&hash=item20bad970e1 http://www.ebay.co.uk/itm/ISOPROPANOL-IPA-Isopropyl-Alcohol-99-9-Pure-250ml-/390302507918?pt=UK_Computing_Thermal_Compounds_Supplies&hash=item5adfd7a38e
or if you are really stuck send me your snail mail address and I'll send you enough for several compasses.
Also, you can probably use rubbing alcohol (which is about 70% IPA and 30% water) instead,
-- Peter Fairbrother

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Peter Fairbrother wrote:

http://www.ebay.co.uk/itm/IPA-Isopropyl-Alcohol-99-9-Pure-50ml-Dropper-Bottle-/140573765857?pt=UK_BOI_Medical_Lab_Equipment_Lab_Supplies_ET&hash=item20bad970e1

http://www.ebay.co.uk/itm/ISOPROPANOL-IPA-Isopropyl-Alcohol-99-9-Pure-250ml-/390302507918?pt=UK_Computing_Thermal_Compounds_Supplies&hash=item5adfd7a38e

this chap seems to know what he's talking about:
http://www.trademarklondon.com/Compass-Fluid/index.html
-- Peter Fairbrother

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Peter Fairbrother wrote:

http://www.ebay.co.uk/itm/IPA-Isopropyl-Alcohol-99-9-Pure-50ml-Dropper-Bottle-/140573765857?pt=UK_BOI_Medical_Lab_Equipment_Lab_Supplies_ET&hash=item20bad970e1

http://www.ebay.co.uk/itm/ISOPROPANOL-IPA-Isopropyl-Alcohol-99-9-Pure-250ml-/390302507918?pt=UK_Computing_Thermal_Compounds_Supplies&hash=item5adfd7a38e
I second that.
My prismatic compass still has its original alcohol - and that's been there approaching seventy years.
Mmmmmm! Should be mellow!
--
Old Nick

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On Mon, 21 May 2012 19:59:35 +0100, Brian Reay. wrote:

Whiskey or vodka wood be a place to start.
--
Neil
Reverse ‘a’ and ‘r’
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Isopropyl Alcohol is the fluid of choice, used in many compass damping systems. 'Maplin' sell it by the litre. Or maybe your local chemist will supply lesser amounts. Its been in my mark III for years.
Ray
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Thank you for all the replies.
I've now several ideas to explore.
Every time I "visit" I seem to get a positive response here, it is most refreshing.
Regards
Brian www.g8osn.net
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Brian Reay. wrote:

But that may not apply to the damping fluid...
--
Old Nick

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In addition to the problems of chemical compatability with paints, glues, and seals that others have pointed, it is worth considering the viscosity of the fluid. Low viscosity liquids such as the various alcohols will give little damping; while higher viscosities such as oil or glycerol will damp the motion more. I imagine that a hand held compass for use on the move would need more damping than one for static use.
Cliff Coggin.
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Cliff Coggin wrote:

I would think he reverse is true, especially as all the good quality hand-held (and costly) instruments I know contain alcohol.
--
Old Nick

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