Bubbles in magnetic compass

Archie2009
30th October 2010, 23:55
Had a bubble the size of a thumb in the standard magnetic magnetic compass. So topped it up with a little distilled water. Got rid of the big one, but got a few very very minute ones. Just left it at that. 2/o was very keen on getting it absolutely bubble free. So let him try. But after a few attempts he gave up. Then closed the plug. Any ideas on how to get rid of these, or should I just let them be?

surfaceblow
31st October 2010, 01:26
I always thought that alcohol or mineral spirits was used in the compass. The instrument shop that I did business with would hold the instruments at 28 in Hg for 15 minutes after servicing and refilling to remove air bubbles.

I remember Isopar L being in the Exxon Mobil Products listing. It's stated use was for dampening compasses and other instruments but it was not on the ships lubrication chart.

Joe

david_crosby
31st October 2010, 02:41
Had a bubble the size of a thumb in the standard magnetic magnetic compass. Any ideas on how to get rid of these, or should I just let them be?

A constant problem on Manners tramps. We used to use Stolichnaya Vodka or (at a pinch) Tanqueray Gin. Open the plug and top up as much as possible, leave the plug open o'nite and repeat until the meniscus on the liquid inside the plug hole remained constant. Close the plug and dispose of the rest of the liquid thoughtfully :-)

slick
31st October 2010, 08:29
All,
In to the Medical Locker and 'borrow' one of the Hypos and some Gin and away you go.

Yours aye,

slick

borderreiver
31st October 2010, 09:21
You need a small bubble to allow for expansion and contraction due to changes of temp. the expansion chamber can not cope with large changes..
Have seen the mixture freeze due to using the wrong mixture and sediment in the mixture . (the gyro failed at the same time. Boat compass used) The compass had just been returned from a leading nautical instrument maker

NoR
31st October 2010, 10:22
Yes I always thought that the bubble was necessary for expansion, and the fluid a mixture of distilled water and alcohol. There were folk tales about alcoholics drinking compass fluid.

The Standard Compass was usually dry card and the steering compass fluid damped for easier steering..........I think?

mikeg
31st October 2010, 12:16
Interesting thread. Is there a recommended fluid viscosity for card damping or is the mix of distilled water and alcohol deemed sufficient. The alcohol I assume is there as antifreeze, can you not just use vehicle antifreeze or is colour/viscosity the problem there?

bev summerill
1st November 2010, 21:35
Always signed for a botle of gin from the steward for removing the bubble then drank the rest
Bev Summerill

JoK
1st November 2010, 22:04
Yes I always thought that the bubble was necessary for expansion, and the fluid a mixture of distilled water and alcohol. There were folk tales about alcoholics drinking compass fluid.


When I was a kid, there was a compass in my Grandfathers backyard, painted white. I thought it was a cool birdbath. When I got older I found out that the alcohol had been tapped out of it and drank by my Grandfather?? He had his own room in the basement where he made shine.
I must ask Mom about that compass.

Derek Roger
2nd November 2010, 00:15
I am informed by a good source that the bubble in a compass or spirit levels consists of Sardine Farts collected off the Island of Grand Mannan in the Bay of Fundy New Brunswick . It is apparently a very costly operation .

Given that fact Jo I doubt your Grandfather drank the contents of the compass.

Cheers Derek

mikeg
2nd November 2010, 13:29
I am informed by a good source that the bubble in a compass or spirit levels consists of Sardine Farts collected off the Island of Grand Mannan in the Bay of Fundy New Brunswick . It is apparently a very costly operation .

Given that fact Jo I doubt your Grandfather drank the contents of the compass.

Cheers Derek

Bay of Fundy tide range, no wonder its costly (K)

I wonder if Jo's Grandfather has a predilection for facing north?

Cheers Mike

Pat McCardle
2nd November 2010, 18:22
I used to start off a Monday morning with a shot of Compass alcohol chased down with neat brasso.............It never did me any harm. LoL

mikeg
2nd November 2010, 18:39
I prefer a shot of compass alcohol sprinkled with harpic, mind you it sent me clean round the bend. LoL