Magnetic compass for a car..

[+team lagonda]

i tried this and got different readings in different spots in the car,,i sappose becauce of the metal body of the car..hows come they sell those little bubble compasses for a car and they function....would liquid filled or regular be any difference....

Edited October 31, 2007 by team lagonda

[+CSpenceFLY]

You have to adjust those compasses for error.

[+Seasoned Warrior]

i tried this and got different readings in different spots in the car,,i sappose becauce of the metal body of the car..hows come they sell those little bubble compasses for a car and they function....would liquid filled or regular be any difference....

 

Have you ever seen the bridge on a modern ship and noticed the compass, the one with the two big iron spheres on either side of it. Those spheres are there too compensate for the magnetism of the ship. You could probably use a compensated compass in your car because of the steel in the constructin of the vehicle but it would take some serious calibration. On a vessel in the water you can calibrate a compass by using a gnomon and setting a course between two observed points and then turning to another known point such as a building on land and be able to correct the variations in the readings against a chart but it is really tough to compensate a compass in a vehicle. The one thing most people forget about using a compass in a moving vehicle is something called precession of moments which casues the compass to swing as the vehicle accellerates and decellerates. If you really must use compass in a vehicel I'd recommned one of the radio compasses that are used in aircraft, they are small, accurate and look cool besides however at a price. All the liquid does is dampen the movement and make the compass easier to read depending on the vicosity of the fluid. Good luck!

Edited November 1, 2007 by Seasoned Warrior

[+Alan2]

As long as the car is moving, any GPS on its compass page will give accurate compass headings.

[+Confucius' Cat]

As long as the car is moving, any GPS on its compass page will give accurate compass headings.

Which is FAR more accurate than any magnetic compass that i have thus far seen for automobile use.

 

To the OP question, ONLY a compass specifically designed for car use will work right in a car. It MUST have a means of compensating for the vehicle's magnetic influences.

 

My experience with car compasses has been pretty much all negative. But so far that experience has been $20 or less units.

 

You DO have to perform calibration to compensate for the car body, engine, electronics, etc.

 

The cal procedure is pretty simple, but the results haven't been very rewarding for me. The compensation seems to change in my case. But my case is special due to the sheer volume of potential magnetic field generating stuff i carry.

 

I just put my latest one in a cache the other day. It was very intermittent. It will probably work OK in a vehicle that does not have all the crap i have.

 

I would LOVE to find a good car compass, especially one that would interface to USB. It would probably have to have an external sensor.

 

(I know I will not find one for $20 at Wally World)

[+team lagonda]

Confucius cat,,searced the net and they do sell magnetic compass just for cars very cheaply but as everyone here says, i dont see how they could work..must be just another scam....is there a such thing as a electronic compass for autos....

Edited November 1, 2007 by team lagonda

[+trainlove]

i tried this and got different readings in different spots in the car,,i sappose becauce of the metal body of the car..hows come they sell those little bubble compasses for a car and they function....would liquid filled or regular be any difference....

 

Have you ever seen the bridge on a modern ship and noticed the compass, the one with the two big iron spheres on either side of it. Those spheres are there too compensate for the magnetism of the ship. You could probably use a compensated compass in your car because of the steel in the constructin of the vehicle but it would take some serious calibration. On a vessel in the water you can calibrate a compass by using a gnomon and setting a course between two observed points and then turning to another known point such as a building on land and be able to correct the variations in the readings against a chart but it is really tough to compensate a compass in a vehicle. The one thing most people forget about using a compass in a moving vehicle is something called precession of moments which casues the compass to swing as the vehicle accellerates and decellerates. If you really must use compass in a vehicel I'd recommned one of the radio compasses that are used in aircraft, they are small, accurate and look cool besides however at a price. All the liquid does is dampen the movement and make the compass easier to read depending on the vicosity of the fluid. Good luck!

 

The reason that the 2 balls on a ship compass work is that such a big object is not going to be used in any spot other than the one it's installed in, it's compensated for that location. A magnetic compass in a car will most likely be moved around quite a bit on the dashboard or the e-fields will be constantly different depending on radio, defrost, wipers... The non-magnetic compass of GPS's will work as long as you move faster than a snail.

 

I once installed an aircraft turn & bank indicator and an old gyro horizon in my car, but not having great vacuum, I used a small venturi tube vac generator, it really was only for the coolness and not the functionality. Never had access to a radio compass but have played around with synchros, servos, selsyns and resolvers, cool electro-mechanical toys. A friend might sell me his indicator for a cruise ship gyro compass, about the size of a 2 drawer file cabinet, but without the gyro I might pass up on this.

[+Seasoned Warrior]

This is a page for an aircraft surplus parts company that handles aircraft instrumentation.

 

Surplus Aircraft Stuff

 

There is a list of heading indicators including gyroscopic and radio indicators starting at around $50. These types of gyro compasses don't have many of the same problems with a cup and pin compass but the car may still have to be de-gaussed periodically to ensure accuracy. Most people don't realize it but since a car rides on insulators (rubber tires) it develops a lot of the same static problems of an aircraft. Some of these units run on vacuum and can be easily attached to your car's vacuum system to spin the gyros. Of course I completely understand if no one really cares because I get the same response in person, eyes glaze over and then roll back as the information overload reaches it's peak

Edited November 2, 2007 by Seasoned Warrior

[+sbell111]

This is a page for an aircraft surplus parts company that handles aircraft instrumentation.

 

Surplus Aircraft Stuff

 

There is a list of heading indicators including gyroscopic and radio indicators starting at around $50. These types of gyro compasses don't have many of the same problems with a cup and pin compass but the car may still have to be de-gaussed periodically to ensure accuracy. Most people don't realize it but since a car rides on insulators (rubber tires) it develops a lot of the same static problems of an aircraft. Some of these units run on vacuum and can be easily attached to your car's vacuum system to spin the gyros. Of course I completely understand if no one really cares because I get the same response in person, eyes glaze over and then roll back as the information overload reaches it's peak

Your link has too many 'http's. Try this one:

[+Seasoned Warrior]

This is a page for an aircraft surplus parts company that handles aircraft instrumentation.

 

Surplus Aircraft Stuff

 

There is a list of heading indicators including gyroscopic and radio indicators starting at around $50. These types of gyro compasses don't have many of the same problems with a cup and pin compass but the car may still have to be de-gaussed periodically to ensure accuracy. Most people don't realize it but since a car rides on insulators (rubber tires) it develops a lot of the same static problems of an aircraft. Some of these units run on vacuum and can be easily attached to your car's vacuum system to spin the gyros. Of course I completely understand if no one really cares because I get the same response in person, eyes glaze over and then roll back as the information overload reaches it's peak

Your link has too many 'http's. Try this one:

 

I'm not having a great day today ! Thank you, being the usual geeky, distrustful individual that I am I usually go back and check the functionality of my links. I realized that I needed to put my mind in gear before I just cut and past. Now if I can only find a compter with an intuitive link I'll be all set.

Edited November 2, 2007 by Seasoned Warrior

[+Confucius' Cat]

Confucius cat,,searced the net and they do sell magnetic compass just for cars very cheaply but as everyone here says, i dont see how they could work..must be just another scam....is there a such thing as a electronic compass for autos....

The cheap car compasses DO work in most cars. They are not a scam, but they are very limited in their accuracy and are not all that reliable.

 

They must be installed properly and compensated according to the instructions, then LEFT ALONE and not repositioned. Also one must recalibrate if any additional equipment is added to the car such as radio, speakers, or other electrical equipment. This is what nullifies them for me. i just got too much junk in the vehicle.

 

In my experience, even when properly calibrated, the cheap compasses still only work marginally in a car. Their bearings are perhaps good to 15-20 degrees accuracy. Basically, they will tell you if you are going East or South.

 

Most of the units I have investigated (even the electronic ones) only give the "cardinal points," which is defined as N-S-E-W in some cases and with the midpoints between in other cases. This works out to 45 degrees accuracy. Not much good for what i do.

 

Generally for my purposes, 5-10 degrees resolution is sufficient so:

 

I use the GPS compass when I'm moving and when I need a stationary bearing, I get out of the car, get about ten feet away from it and use my good ol' $10 Silva.

[+team lagonda]

Confucis..picked one up today for $12.00 ..when calibrating it says head the car directly north..does this mean the car has to be ''moving'' north or just facing north..its a car magnetic compass....

Edited November 3, 2007 by team lagonda

[+Confucius' Cat]

Confucis..picked one up today for $12.00 ..when calibrating it says head the car directly north..does this mean the car has to be ''moving'' north or just facing north..its a car magnetic compass....

Just facing north

typically you face north, calibrate one screw then turn east and calibrate another, then turn back north and correct HALF the error

 

This must be done with the car running and accessories in normal modes.

[+team lagonda]

well i 86,ed the auto compass..i found if i place my regular compass on top of the automatic shifter on the console it reads perfect north,,i drove around the block and it worked perfectly on all the cardinal points....i found i can drive easily with in in my hand while my hand rests on the shifter plus it glows in the dark for night driving....the auto compass was near impossible to calibrate and kept changing once calibrated..i,d reccomend to anyone concered to find a spot in your car where a regular compass will function....

Edited November 4, 2007 by team lagonda

[+Confucius' Cat]

well i 86,ed the auto compass..i found if i place my regular compass on top of the automatic shifter on the console it reads perfect north,,i drove around the block and it worked perfectly on all the cardinal points....i found i can drive easily with in in my hand while my hand rests on the shifter plus it glows in the dark for night driving....the auto compass was near impossible to calibrate and kept changing once calibrated..i,d reccomend to anyone concered to find a spot in your car where a regular compass will function....

Interesting that you were able to find such a location.

I think you got lucky...

 

Electronic compasses are probably better because calibration is just a matter of driving a circle- similar to calibration of the "magnetic" compass function in some GPSr's, but I cannot say from experience since I have not found one that has a remote sensor and therefore i have not actually tried one.

 

I did see one at WW, made by Bell I think (it was in the clearance Clarence aisle), but it said it would only work in the centre of the windscreen and that space is taken in my vehicle. it only gave the cardinal points anyway. I think it's "clearance Clarence" price was about $50. As usual at WW that wasn't really any markdown.

[+team lagonda]

Confucius,,only thing i can figure is that the location is at the center of the car,,i did notice though that when i use the breaks the needle drifts far off..the radio ,lights ,though dont seem to to bother....i guess if you find the right ''sweet spot'' the car itself acts as its own compensator....

Edited November 4, 2007 by team lagonda