Precision Vertical Card Compass

[dlps73]

I've installed this on the top of my instrument panel but unfortunately used a screwdriver that was magnetised as it is now extremely reluctant to turn and will only move about 15 degress when rotated 360 degress.

 

Does any one know how to degauss something of this nature (the compass not the screwdriver )?

 

I've gone to the manufacturer's site but they only have a phone or snail mail contact.

 

This is the Aircraft Spruce link........

 

http://www.aircraftspruce.com/catalog/inpages/vertcard_compass1.php

 

Cheers..........Doug

 

 

[Guest Andys@coffs]

Doug

 

Did you use nonferrous nuts and bolts to fix it? brass is usual. If the nuts and bolts are ferrous (iron based) then the magnetised screw driver will have magnetised the nuts and bolts in which case it will be these that are the issue.

 

The way to test it is to remove it from the Aircraft and see if the compass still has issues. I dont see why it should as nothing in the compass build should be of a ferrous nature (excepting the magnet being used to discover mag north)

 

If it is the same on removal then I suggest its stuffed. If the link you posted was Aircraft spruce (Northern Hemisphere) , did you buy a southern hemisphere compass? There are minor differences between northern and southern hemisphere compasses.

 

Andy

 

 

[facthunter]

magnetism.

 

My experience only relates to magnetos but the principles are the same. A growler will demagnetise a magnet. It is essentially an electromagnet which is supplied with an AC. current. I would not attempt to demagnetise anything here. The active magnet in the compass may have been altered by the field from the screwdriver. CHECK THAT THE SCREWS ARE NON-MAGNETIC and that nothing else around the area is ferrous. If you can disassemble the compass and check if the polarity can be determined, (hopefully there will be enough residual magnetism left) You should be able to remagnetise it by applying a very strong magnetic field to it with the correct polarity checked first. This is usually done with a very powerful electromagnet. Nev..

 

 

[dlps73]

Hi Andy,

 

Good point. I'm not sure what the composition of the screws are that hold it - probably mild steel.

 

I'll take it off tomorrow and check whether their removal fixes it - watch this space!

 

And it is the Southern Hemisphere compass.

 

Cheers......Doug

 

 

[dlps73]

Hi Nev,

 

I'm hoping that as soon as I remove the ferrous screws it will come good. The thought of disassembling is quite scary!

 

I'll provide feedback as soon as I can....

 

Cheers.......Doug

 

 

[facthunter]

Magnets.

 

Doug, I agree with you. It should be OK as unless the magnetic field is very strong you need time and vibration to effect a change. The screws would magnetise straight away. I think I have a northern hemisphere compass here which is maybe throw-away unless someone knows how to modify it. Nev..

 

 

[dlps73]

Hi Andy, Nev,

 

It appears that the effect was on temporary thank heavens. It's working fine since I've taken the offending screws out. Now off to get some brass screws or Bluetak :)

 

Again, thanks for your assistance....

 

Cheers.......Doug

 

 

[Guest Andys@coffs]

Doug

 

Bunnings have small machine brass nuts and bolts that will probably be suitable. At least they did when I mounted an instrument that had a flux gate (electonic compass) in it. Failing that almost any avionics repair shop will have these.

 

Regards

 

Andy

 

 

[dlps73]

Thanks Andy - I'm must admit I've used Bunnings a lot whilst I'm building this aircraft!

 

Cheers........Doug

 

 

[Bigglesworth]

I was under the impression that a vertical card compass works in both hemispheres. Something to do with it not needing to be balanced horizontally. But I may be up the pole here.

 

 

[eightyknots]

Magnets.Doug, I agree with you. It should be OK as unless the magnetic field is very strong you need time and vibration to effect a change. The screws would magnetise straight away. I think I have a northern hemisphere compass here which is maybe throw-away unless someone knows how to modify it. Nev..

 

I was under the impression that a vertical card compass works in both hemispheres. Something to do with it not needing to be balanced horizontally. But I may be up the pole here.

I know this is a decade old post but I am curious about northern and southern hemisphere compasses which leads to this question: When an operator flies an aircraft in both hemispheres (e.g. Southern Asia, Central America and Africa) do they have two compasses?

 

 

[facthunter]

A vertical card is only a repeater representing information from another source like a flux gate out in a wing. A good compass will work world wide. Simple and cheap horizontal examples can't work well in both hemispheres without modification. The magnetic lines of force tilt from the horizontal more the nearer you go to the magnetic pole in each hemisphere. This throws the CARD out of balance and causes the acceleration and turning errors these compasses exhibit. Nev

 

 

[cscotthendry]

I was under the impression that a vertical card compass works in both hemispheres. Something to do with it not needing to be balanced horizontally. But I may be up the pole here.

The mechanical vertical compasses definitely do have north and south hemisphere units and are not interchangeable. The magnet in these compasses is oriented horizontally, and the position is translated to the card by gears. So these compasses require vibration to operate correctly. When swinging one of these, after you orient the plane to the heading, tap the compass gently as you adjust the appropriate compensator.

 

The compass and the compensators are magnetic and intended to be so. I would NOT under any circumstances attempt to demagnetise any compass.