De gaussing, and stuff of science.

Wolfie, have a look at gyrocompasses here for the shipping question for the up to date answer. You obeviously need another room in your Kayak for a bigger compass.

Compasses do work in steel vessels, although they need 'correctors' aptly named "Flinders Balls" which are positioned either side of the compass & adjusted to compensate for the surrounding steelwork.

With a normal compass you have either a Northern or Southern hemisphere model as one does not do both, as discovered by people buying them of ebay ... lmao!

I believe that they would work in mines, but not in space.

Why is it so...Pity ole Julius Sumner-Miller isn't around any longer....but there must be lots of luminaries around.....lol

1. Dunno....... Most cars are built of plastic these days. Maybe it is picking up forces from the engine compartment.

2. JohnR answered the question

3. I would guess that once you left Earth's gravitational pull the compass would be of little use to you

Mostly guesses so early on a Sat eve.........

Cheers

So many words, so little time..... Ships used to carry out an exercise known as 'boxing the compass'. Sightings were made on known points and and a chart of the errors made. With any errors plotted, large chunks of iron (usually in the shape of a ball) located on bars each side of the compass box were moved closer or further away from the compass to counteract the effects of the mass of iron in the ship. On an old aircraft type compass, small screws were adjusted on the side of the caseing. Then along came the fluxgate compass and the RMI (remote magnetic indicator) A very sensitive compass was situated at some place on the vehicle / plane / ship well away from engines, electrical generators, radios etc. and the position of the compass pointer was relayed electronically to a read out at the navigating position. Most Japanese vehicles that have a built in compass use a fluxgate compass.

A compass needle simply points along the direction of the earths magnetic field at that point on the earth. As the magnetic lines of force travel around the globe and dive into the earth at the poles then as you aproach the magnetic pole the needle will tend to point downwards (the z component). This 'dip' effect and the unbalanced compass needle makes a magnetic compass rather useless as you approach the magnetic poles.

To counteract the downward deflection of the compass needle a small weight is added to one end of the compass needle. This weight adds a small mass to the needle which has inertia so when accelerating or deaccelerating the inertia turns the compass needle even though you are not turning. Try facing east or west and move a compass forward or back and watch the needle move even though you are pointing straight ahead and not turning.

Will a compass work in a mine? Depends how much shielding of the earths magnetic field there is arround the compass, same as being in a wooden box or a metal box.

How much more do you want (trying to keep it simple) ? Space gets a bit technical - short answer is no it will not work unless you are in synchronous orbit, stationary in relation to a spot on the earths surface, and then the compass needle should align it self with earths magnetic field.

Part the three:
The earth's magnetic field does venture into space but diminishes with the square of the distance.
If a compass is sensitive enough it will continue to work.
The earth's magnetic field in space is indicated by the aurora lights.

Part the fourth:
Really deep mines - of course! The magnetic field is not stopped by earth. metal bearing earth will concentrate the lines of force but will not stop it.

wOLFIE, a DECENT CAr compass will have adjusting screws so you can compensate for the affects of surounding metal. If it doesn't then it's not a car compass irrespective of what the manufacturer calls it.

Wolfie.
A compass has a small magnet attached to the needle, if the pivots are good quality that small magnet can be very weak, conversely if the pivots are crap the magnet has to be stronger, a strong magnet is more inclined to lock onto any bit of steel.
Eric.

And in the ruuly early days, people used to get stuffed because they had their small ships compass sitting next to the radio speaker.

The Fluxgate compass sensor in the Pajero is located on top of teh dash in the centre - well inside the steel shell.

It is useless without calibration - just drive in a circle twice.

wolfie, its bloodyamazing that inquistive mind of yours...do you stay awake all night thinking what makes things tick?

Guys,

I think you should give Michael Carey's post another read.

Dont know what he does for work, but, i'd love to work in 'that' field.

If you were at the the center of the earth, you would be weightless, free to move around but a little uncomfortable (Squashed and Cooking), so where would be your North and South then?
Answer: Nowhere.

To MC, does the Sun have polarity? If so, then do other 'Stars' have polarity? If so, then does that mean the Solar system has a universal sort of Norths and Souths?
If so, does that mean that there is after all a UP and DOWN to the whole universe?

Holy crap!, sorry i got carried away there, this a 4x4 forum....

Love forums....

Alan.

Hi,

I showed this post to my father-in-law and, well, he has a b it of a background in this area and thought you guys might be interested in his repsonse.

Regards

Graham

* * * * * * * * * * * * * * * * * * * * * *

Answer.
First part
The subject is a complex one and in terms of marine magnetism (Ships Compass) involves some 10 weeks of lessons for people completing the Master 1 Certificate. Total course 11 months at TAFE Sydney, NSW

We can equate a compass in a car to that placed in a vessel
The compass is placed in the middle on the fore and aft line of the vehicle.

This ensures that the permanent magnetism (hard steel) used in the construction gives the compass a permanent error equal 9all most) on either side but of an opposite pull.

The soft iron has a variable value as the car/vessel moves to various latitudes; this is strongest at the magnetic equator and lowest towards the magnetic poles. (Dip). This means that there is a variable error as the car moves being the combination of the permanent and variable errors.

We know the positions of the earth’s magnetic poles, checked daily by US and Britain,

From these positions we can draw the lines of direction of the earths magnetic fields, known as lines of variation. Named east or west of true north.

On vessels we can determine the deviation of the compass caused by the soft iron of the vessel (one way) by taking bearings of celestial bodies and comparing to the known true bearing. This error is called deviation.

The car/vessel is seen as a total magnet and there will be a certain field on one side (red say) and therefore (say blue) on the other, these will cancel each other out. (think about it). So there will, usually a low value error in the compass when placed in the middle (fore and aft). If the compass was place on one side or at the extremity there will be a large value error. A magnetic compass on one side as in an aircraft carrier (bridge on one side usually starboard) will have a large value error on two opposite quadrants.

If you approach a car with a magnetic compass, you are approaching a magnetic, and therefore you will great changes of magnetic influence. Go to one end on the centre line and see what is the fore and aft direction.Then go to the other, your will see a different direction shown. Similarly check along the sides.

Second part.
Prior to or on departure, the ships magnetic standard compass, (there are two compasses placed on a vessel for navigation, the standard which the accurate one and the steering which is for steering only), is checked by taking a bearing and comparing that bearing to a true bearing or compare the magnetic heading to the gyro heading, the error of which is known.
There is usually little error from container position allocation or their contents. Vessels loading steel, particularly steel beams loaded for and aft and or across the vessel can caused dramatic errors.

Remember a ship’s magnetic compass (standard) is checked at least once a watch or when there is a major change of course during the watch. All of which are recorded in an official document.

Third part.
Satellites orbiting the earth are subject to earth’s magnetic field, but there are complex arrangements of gyrocompasses fitted to give accurate direction indications. The moon is a magnet and therefore when satellites approach they will induce its field on a compass should they have one.

Fourth part.
Compasses do work in mines but are subject to induced magnetic influences cause by the nature of the surrounding material eg hard rock soft rock, minerals etc. For those people lucky to have been near the Flinders Ranges in South Australia and walking with a magnetic compass, as one might do, will see great variations of direction. These ranges record the various changes of the earths polarity, remember about each 9 million years the polarity of the earth changes, north becomes south. In terms of these change we are again close to such a change.

The south magnetic pole (near South Africa) has been recording noticeable changes in recent years.

I suggest that you obtain a book on ships magnetic compasses from your library; they may have to order it in.
Happy attractions and repulsions! Mick Costelloe. (Mariner) (Licenced Compass Adjuster)

And not a word about presession ! :-))