compass

Chris under no circumstances add alcohol to the existing contents! I had an old and battered example of this compass which had a large bubble in it. I added isopropyl alcohol and the whole lot turned to a viscous jelly. By coincidence I bought a very good example last Sunday at the Midlands Clock Fair and am certain that it contains compass oil since it's movement is heavily damped. I gather from a friend that the compasses used in airplanes used ether as a damping medium, but am sure that for compasses intended for land or marine use a special oil is used to give a higher damping factor. At the time I did extensive Googling but was unable to come upon a source for this oil.

Regards Brian

Google now produces this US company selling it:

Greg

A google seach on groups looked helpful:

A quick scan of the posts indicates a wide variety of answers, so careful reviewing of information is probably in order.

BugBear

And you did google for "compass-oil"?

Nick

Some instruments use glycerine.. you can get this at boots. I think you may have something of lower viscosity than glycerine in your compass

It's not going to be anything very exotic given the age, time of use, and need for an available source for any maintenance. I would suspect it is something as simple as technical white oil (baby oil minus the perfume). Inert, stable, cheap, and available in a range of viscosities.

Peter

Current light aircraft use this stuff:-

I have seen reports that some compasses are filled with paraffin and that they used to use whisky...

Geo

Probably glycerine! This was standard for marine compasses in the past.

Steve R.

The modern version uses a silicone fluid (Polydimethylsiloxane) and the early ones a light mineral oil. Food grade mineral oil (better known as Liquid Paraffin BP) might be suitable but is a little heavy. Alternatively look at

He services these compasses and may tell you what the correct damping fluid is.

Be aware that the luminous paint used on the WW2 version is radium based and somewhat radioactive.

I used to use mine when talking to the public (usually older groups) about nuclear power stations. With several hundred counts per second, it's the level which would readily be detected if you tried to take it out of a nuclear power station. The regulations would not let you transport it in your car without a significant amount of paperwork. As an aside, I've been told that WW2 bomber pilots got a significant radiation dose from the lumimous paint on their instruments. At least if they survived long enough.

Well thats the nanny state summed up in a nutshell !

When you didn't know if you were going to live or die, you didn't care much for people telling you about a remote chance of something happening in the future, you would rather have a compass you could see at night and find your way home ! I know a sailor that had one of these in his yacht, it was so bright he could see his way around the cabin at night.

Now we are all so cosy, the tiniest thing is getting attention and legislation.

I have a couple of Geiger counters, and blow me I can't find the faintest radioactive thing around except for the cosmos, which is of course blatting us all the time. However I have spotted a large old ships compass in the local shop, and might try it on that. Maybe I'll be able to buy it off them cheap if its proper radium one !

Steve

I have just come across this subject.

I am following someone's suggestion and filling my Silva (Italian compass with baby oil. Cost is 5 Euros for 200 cc. in Spain and the stuff doe NOT smell.

By the way, my compass has a rubber membrane underneath it, so I have filled it to overflow in order to eliminate the bubble problem.

A word of advice..........put the fluid in the fridge for a while otherwise you'll have the membrane collapsing when it gets cold.

(32 degrees Centigrade in Madrid !)

Cheers, Mik

-- Michael6

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