Beware of perilous flips by magnetic compasses

by tonytran2015 (Melbourne, Australia).

#compass, #flip, #reversal, #compass reversal, #compass flip, #re-magnetize, #navigation, #survival

There has been warning by a Mountaineering expert that many people got into perilous situation when their compasses unexpectedly flipped direction prior to critical use. The Mountaineering Council of Scotland has issued warning on this danger.

This posting gives a method to re-magnetize and set at will the direction of any compass needle. The basic steps in guarding against unexpected flipping of magnetic compasses are also shown.

One possible cause of flips by magnetic compasses.

When a magnetic compass is stored its needle can not swing or cannot swing fast enough to follow the change in magnetic field.

If a strong magnetic field is forced through the needle from one end to the other, the needle will be magnetized by this strong field.

Therefore when your compass is stored in your bag and a strong magnet approaches it faster than the needle can rotate to adapt to change, the new field may be able to force a magnetic flux from one end of the needle to the other end and re-magnetize the needle. This occurrence is not rare.

Proof and applications.

 

compassflipMEDIUM

Figure: The reverse-magnetized needle of the compass with clear case

The first pictures shows that the needle of the clear based compass is pointing in the opposite direction to that given by the reference, metal cased compass. The needle has been magnetized into the flipped condition.

Re-magnetize the needle again

compassRestoredMEDIUM.jpg

Figure: The re-magnetized needle of the compass with clear case.

The compass needle was then successfully re-magnetized back into normal condition. It again points in the normal direction.

So I have been able to re-magnetize (in any direction of choice) the needle of a compass (the clear based compass with a mirror) as shown in the first two pictures. The magnet I used costs me under $0.30USD and is shown in the third, composite picture.

Re-magnetizing the needle of any compass

CompassToolsMEDIUM

Figure: Tools for Re-magnetizing the needle of any compass.

1/- To re-magnetize a compass, it is preferable to have a single pole P of a strong magnet far away from its other poles. Lay the compass up-side-down. Find out the end A of the needle that is repulsed by P. Push that pole P to the center of the needle, then move P towards that end A. When P has reached the end A and attracted that end, the needle has been re-magnetized.

It is even better if you can supply another single pole Q of opposite polarity to also touch the other end B of the needle. Otherwise, just use the compass just re-magnetized by the single pole P.

2/- The above re-magnetization shows that it is preferable to have long, observable needles for compasses.

3/- If you carry any strong magnets make sure that they are closed by closing irons to keep their magnetic lines within the vicinity of the magnets and the lines do not affect your compass.

The magnet I used is a fridge magnet of the rare earth type, it costs under $0.30 USD.

Avoidance and detection of flipping of a magnetic compass.

On acquisition of a compass, you should

1/- inspect it for any damage,

2/- count the swing, roll, and pitching vibration frequencies of its needle and make a written record,

3/- check the pitching of the needle and make a written record.

Before packing the compass for each field travel, you should

1/- inspect it for any damage,

2/- compare its swing, roll, and pitching vibrations of its needle with the written record made on acquisition,

3/- check the pitching of the needle and compare against the written record made on acquisition.

4/- have the polarities of the strong magnets on your phone case marked on a sketch (showing which magnets attract which ends of the needle). A copy of the sketch should be carried with the compass.

Before each field use, you should

1/- inspect your compass for any damage,

2/- carefully check the pitching of the needle (If a flip has occurred, the pitching also changes as the North pointing end usually balanced to point horizontal. If the North end pitches in any other way, the needle may have flipped.),

3/- slightly and slowly move the compass towards the phone case to see if the attraction pattern is still the same.

4/- If the vibration patterns are noticeably different the compass may have been damaged or may be in a stronger or weaker than normal (abnormal) magnetic field. You need to think about possible causes and effects.

5/- The above steps only help to detect any unexpected flipping, you still has to carry out all other procedures recommended by the maker of the compass.

Your compass usage should be more reliable with these extra precautionary steps.

Reference.

[1]. Heather Morning, Calling ALL Hill Walkers,The Mountaineering Council of Scotland, http://www.mcofs.org.uk/navigation-reversed-polarity.asp, posted on April 2013.

 

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