Will a magnetic compass work well in a semi truck?

I was thinking about putting a magnetic compass in a semi truck, but I am concerned about all those masses of steel in it, like the engine
and so on. Does anyone know if any such compass would work, any experiences?
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There are magnetic compasses designed for use in magnetic bodies such as trucks or steel-hulled ships. One installs the compass, and then makes a number of maneuvers so the compass can calibrate itself.
I have one in my car (came with the car), and it indicates 8 directions of the compass.
.<http://www.manualslib.com/manual/187875/Volvo-Xc70.html?page 3>
If the candidate compass does not come with calibration instructions, look for better choices.
Joe Gwinn
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wrote:

That is an electronic "flux gate" compass. Magnetic compasses are used in steel hull ships. Compensating magnets are used to calibrate the compass.
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Not so. Compensation was invented long before electronics, like 1784.
..<http://en.wikipedia.org/wiki/Magnetic_deviation
Joe Gwinn
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wrote:

You don't read well, Joe. He said "so the compass can calibrate itself". That's a flux gate. Compensating magnets are required on "magnetic" compasses when used in or near large metal/magnetic objects like ships, airplanes, and vehicles.. There is a big difference between "flux gate" and "magnetic" compasses.
One thing you may experience that compensating magnets don't help is magnetic deviation from heavy intermittent current draws - like running the heater blower or WSwipers if the high current wires run too close to the compass. Sometimes when starting an airplane the compass will "spin" as well due to the magnetic feild around the starter cable.
Back when guys were running "boots" on their CB radios, some experienced their compass spinning when they keyed the mic too.
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wrote:

Why bother with a compass? Spend $5.00 like I did for a GPS unit!, then you can verify that your dashboard clock is correct.
--

Gerry :-)}
London,Canada
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On Sunday, February 22, 2015 at 8:36:04 PM UTC-5, snipped-for-privacy@yahoo.ca wrote:

I'm with you there, Gerry.

Its great that you're thinking all "digital" and modern, but I think most of this crowd just doesn't want to emerge from the transistor era.
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On 2/23/2015 3:42 PM, snipped-for-privacy@hotmail.com wrote:

I'm curious...does your compass always point "TRUE LEFT"? ;>)
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wrote:

And his IQ "false positive".
--
A sound mind in a sound body is a short but full description
of a happy state in this world.
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On 2/22/2015 6:29 PM, Joe Gwinn wrote:

As Joe saw they can calibrate out the effect of the vehicle, although I suspect there is a limit. I had a compass in a Camry years ago, My trip to work took me across a 1/2 mile bridge. As I crossed this bridge the compass would make a 45* swing and then come back to normal. Mikek
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snipped-for-privacy@rahul.net (Edward A. Falk) fired this volley in

As it will any time there's a substantial current flowing in a line close to the compass.
Magnetic compasses are tricky bastids, but they can be got a lot closer than one-two-three-deviation adjustment procedures... just depends on how much time (and fuel or trolly-hauling) you want to do.
Flux-gate compasses can also be fooled by mains busses. They don't measure attraction, but fields... but they do measure ANY field, and even can be made in error by 'bending' of clean fields by large masses of ferro-magnetic materials!
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> fired this volley in

I should have said, "D.C. current...."
LLoyd
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On Tuesday, February 24, 2015 at 8:41:31 PM UTC-5, Lloyd E. Sponenburgh wro te:


Retired from it now since last year, but I did many compass calibrations on airliners. We had a compass rose on the field where I worked, and ships u sed to be scheduled through for compass cals. Had to be done when you repl aced the whiskey compass if the calibration card had been lost. If I rememb er it correctly, there were certain electrical loads that had to be drawing current before the cal. If it was a cal. for a gyro compass, always must check to see if somebody had put a steel screw on the cover of the flux val ve at the wingtips. That was a common problem. You could align one gyro com pass to the other system, but the compass system had to be cal. checked on a compass rose within 30 days. Gyro compasses a thing of the past now, with the Inertial ref. systems. Pretty much useless information nowadays.
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Try googling 'Flinders Bar' and 'Flinders Balls' for more about how it used to be done on shipboard.
Jim H.
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Again, not to belabor the point, but to make it clear. All you're doing with those _nearby_ lumps of iron is making the attraction load of more distant 'lumps' of iron equal in all directions. Then the only thing left is the attraction of the magnetic pole.
It's not magic, but might be non-intuitive to someone who's never actually calibrated a compass.
Lloyd
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On Thu, 26 Feb 2015 17:34:29 -0600, "Lloyd E. Sponenburgh"

And on an aluminum plane you don't have magnetized steel structure like in a rag and tube, which may require degaussing - not a trivial endeavour. A magnetized fuselage is more likely with a mig welded fuselage than with a gas welded one. (particularly if welded with a DC welder)
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snipped-for-privacy@snyder.on.ca fired this volley in

Eh... magnetization has little to do with it. This method was perfected in the day of riveted iron vessels, not welded.
The simple matter is that the compass pointer itself is THE magnet, attracted to whatever iron masses may be near enough.
Make those _apparent_ masses equal in all directions, and the pointer would be equally attracted in all directions, leaving only the earth's magnetic pole to control its pointing.
And... where have you found a _powered_ aluminum aircraft that did not have sizable masses of ferrous metal inside and around the engine(s) (aluminum blocks/heads nothwithstanding)? And, at least in single-engine planes, that those masses weren't pretty close (relatively) to the dashboard, console, or windshield where the compass was mounted?
LLoyd
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On Thu, 26 Feb 2015 19:19:07 -0600, "Lloyd E. Sponenburgh"

And hot rivets are magnetized too. The proximity of iron, magnetized or not, will have some effect on the compass, but magnetized iron or steel has a whole lot more effect.

And the magnetized roll cage on an RV8 causes the compass to be off by 20 to 60 degrees. Degaussing the hoop knocks the compass back to within 2 dgrees - easily compensated for with the compensating magnets.
Google " degauss roll cage "
The attraction of the compass needle to unmagnetized ferrous metals is insignifficant compared to the attraction/repulsion of a magnetized ferrous metalfuselage (or even a small portion of the fuselage, as in the RV8 windsheild hoop, or roll cage.
Clare Snyder, technical director Recrational Aircraft Association of Canada (RAA)
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snipped-for-privacy@snyder.on.ca fired this volley in

Ok, so, talking to a pilot, now -- you're claiming that the engine mass has no significant effect on an aircraft's magnetic compass. That only steel tube welded fuse frames are to fault. Right?
And, you're saying that aluminum fuselages with iron-bearing engines don't suffer from that, because they're not 'magnetic' in character?
And, that any of this has anything whatsoever to do with using a magnetic compass in a semi truck-trailer combo?
Right?
Are you sure you don't work for the US FAA? <G>
(I know of a Super Viking owner who might argue your points, unless spruce and mahogany have become magnetic during my inattention)
Lloyd
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On Thu, 26 Feb 2015 21:42:34 -0600, "Lloyd E. Sponenburgh"

That is not what I said. I said the the attraction of the iron in the nose mounted engine - if not magnetized, is insignificant compared to the effect of magnetized metal in the fuselage.

I didn't say that.
You remind me of the story of two brothers.Bill and Bob. Bill was a scoundrel. He had been in just about any kind of trouble you could imagine, leaving bedlam in his wake - ex wives and illigitamate offspring and a criminal record as long as your arm. He died. His brother Bob went to the pastor who was in charge of the funeral service and offered him $1000 extra if he told everyone his brother was a saint. Small-town pastors are not terribly well paid - he figured he could really use the money. At the funeral service, the pastor said "As you all know, Bill was a scoundrel, a theif, and a womanizer,There really isn't a whole lot of good I can say about him, but compared to his brother Bob, Bill was a saint!"

We don't know what kind of Semi he's talking about installing it in. Aluminum cab, steel cab, or mostly fiberglass. A set of non-sheilded stereo speakers in the dash of an aluminm cabbed Pete are going to cause more havoc than a 400 Hp Paccar up front, compass-wise

Emeraude and Jodel too. The compass can be compensated to within a degree or two with no problem Starter current can spin the compass on the jodel.
Can't compensate for a magnetized loop. Particularly if the compass is mounted to one side or other of the panel.

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