Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: Compass problems

  1. #1

    Join Date
    Sep 2011
    Location
    minnesota
    Posts
    4

    Sad Compass problems

    Anyone have ideas as to eliminating residual magnetism in a rag/tube LSA? I've tried different methods but no luck. My compass likes to read east, all the time. Tried 3 compasses. All the same. Ive tried to "chase" the residual magnetism with magnets, no success. I made an ac electromagnet, nope. That did not work either.

  2. #2

    Join Date
    Jul 2011
    Posts
    1,541
    All I can say is that maybe it is divine guidance and if you follow it you'll arrive at Mecca.

    I had an a plane with a large vintage British compass, like a ships compass. For some silly reason, I tried to put a modern one in as a backup. Never could get it swung right, too much interference, and I finally removed it and realized that the old style compass was dead accurate and worked just fine, you just had to look down at the floor to read it.

  3. #3

    Join Date
    Nov 2011
    Location
    Minnetonka MN
    Posts
    122
    Funny - I've been fooling with using a large dia AC excited coil to see how much it takes to demagnetize 4130 steel. It seems to take about 30 ampere-turns in free air to generate enough magnetic flux to reset everything as the 4130 steel is pulled away slowly.

    The next step inder personal consideration is to take a 100 ft coil of 3 conductor #14 Romex wire, roll it into a 1 ft dia coil, splice the ends together so that the whole mess of wires is in series, and excite that with a Variac with a few volts to get ~ 4 amps of current thru it. Of course you could use a 500 Watt series heating element to limit the current to 3-4 amps too.

    Or a long extension cord of say 100 ft of # 16 - cobble a suicide plug system to series the three wires & bring a power cord out.

    This is all strictly not UL approved.

    Operation would be to hold it near the area to be degaussed and slowly withdraw it to at least 5 to 10 feet away before taking the power off.

    Has anyone else fooled with this sort of approach? and how much will a compass take before it becomes demagnetized? or a tachometer? or a magneto (much more I'd think).

  4. #4

    Join Date
    Sep 2011
    Location
    minnesota
    Posts
    4

    compass

    I did something like that. I took a piece of iron, a foot or so of re-rod, wrapped about 100 turns of #14 around it. I first bent the re-rod in the shape of a horseshoe. Then I connected it in series with 2 heaters each pulling about 1200 watts. When energized I moved it around the area and pulled it back, then shut the juice off. No luck so far. Sounds like were doing much the same.



    Quote Originally Posted by nrpetersen View Post
    Funny - I've been fooling with using a large dia AC excited coil to see how much it takes to demagnetize 4130 steel. It seems to take about 30 ampere-turns in free air to generate enough magnetic flux to reset everything as the 4130 steel is pulled away slowly.

    The next step inder personal consideration is to take a 100 ft coil of 3 conductor #14 Romex wire, roll it into a 1 ft dia coil, splice the ends together so that the whole mess of wires is in series, and excite that with a Variac with a few volts to get ~ 4 amps of current thru it. Of course you could use a 500 Watt series heating element to limit the current to 3-4 amps too.

    Or a long extension cord of say 100 ft of # 16 - cobble a suicide plug system to series the three wires & bring a power cord out.

    This is all strictly not UL approved.

    Operation would be to hold it near the area to be degaussed and slowly withdraw it to at least 5 to 10 feet away before taking the power off.

    Has anyone else fooled with this sort of approach? and how much will a compass take before it becomes demagnetized? or a tachometer? or a magneto (much more I'd think).

  5. #5

    Join Date
    Jul 2011
    Location
    Clarklake, MI
    Posts
    1,235
    Quote Originally Posted by 616jim View Post
    Anyone have ideas as to eliminating residual magnetism in a rag/tube LSA? I've tried different methods but no luck. My compass likes to read east, all the time. Tried 3 compasses. All the same.
    Yours is an example of where degaussing should work. Do you have a magnometer? If not, what are you using to determine the source of the magnetic interference?

  6. #6

    Join Date
    Jul 2011
    Location
    Clarklake, MI
    Posts
    1,235
    Quote Originally Posted by nrpetersen View Post
    Has anyone else fooled with this sort of approach? and how much will a compass take before it becomes demagnetized? or a tachometer? or a magneto (much more I'd think).
    Only with CRT's. All the instructions I have on degaussing says to keep it away from delicate instruments and such.

  7. #7

    Join Date
    Nov 2011
    Location
    Minnetonka MN
    Posts
    122
    616jim - How wide (far apart) were your pole pieces? I'm thinking that the loop should be maybe 1 ft in dia & maybe more if we had more wire. Do you suppose it is necessary take all the extension cords one can find, put them together & make a loop big enough to go around the fuselage? Obviously an AC current limiter within the capabilities of the extension cords is necessary.

    Otherwise we are on similar pages w similar techniques.

    Trying to do anything constructive with a DC magnet would be absolutely hopeless.

    I played w 4130N tube using a cheap compass as a polarity indicator. Just approach from the e-w direction & see what it takes to make the needle swing in the opposite direction with different materials.

  8. #8

    Join Date
    Sep 2011
    Location
    minnesota
    Posts
    4

    more

    pole pieces about 1.5" apart. I tried loops of extension cords. Did not work/help. But the current flowing in one wire would cancel out the field caused by the other wire correct? Might try again today.

  9. #9
    Hiperbiper's Avatar
    Join Date
    Jul 2011
    Location
    Shreveport, Louisiana
    Posts
    98
    http://www.sacskyranch.com/degaussi.htm

    Some of the things I've found under panels (including a magnet taped to a coax cable to "drain interference" might boggle the mind...) mean you first need to point to the section of the aircraft you need to work on. A cheap compass moved around the panel will point to an magnetic field and therefore point you to your problem.
    If I might ask for more info; what LSA, what's in the panel does the problem change if the radios/electrical system are on/off?
    Also; you say you've tried 3 compasses and none would read correctly (assuming with the compensators tweeked). What compasses have you tried?

    Chris in Shreveport
    You Tube only proves that more airplanes have crashed due to Video Camaras than any other single reason...

  10. #10
    About twenty years ago I had a Debonair with a compass which suddenly 'went loopy'.

    Took a long time to track the source (yep eventually used a cheap boy scout compass), it turned out to be our tacho cable had 'gone magnetic'.

    Removed the compass from harms way, pulled the tacho (no problems detected with it), and got the local TV repair man out with his de-gaussing coil. He activated it in the tacho hole beside the cable and circled it continuously as he withdrew to a few feet away. Repeated this twice more, then went and circled the main instrument panel once, said "try that". No more problems. Did it need the main panel circled?, he said not but did it to placate the LAME (A&P to you yankees).

    All looked very 'black magic' to me, but it worked.

    Track the source of the magnetism first, sometimes that can be just ONE hole in a bit of steel that was drilled too slowly. Yep, ever taken too long with a blunt drill bit and seen the chips attracted around the drill bit and site? One magnetic hole!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •