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#11
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Compass trouble
On Apr 12, 10:07 am, Road Dog wrote:
Stealth Pilot wrote: the problem doesnt seem to be the compass but some stray magnetism in the aircraft. So he claims but what would this be that wasn't there when the plane left the factory ? Without any new equipment, how could it get so bad that it throws the compass off more than 10 degrees through mu shield ? In any case, thanks for the reply. Pipers sometimes suffer from magnetized engine mounts. I think it might have to do with the alternator ground cable terminals getting corroded so that the alternator ground current runs throught the mount tubing instead, magnetizing it and screwing up the compass. Dan |
#12
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Compass trouble
Might it be possible to kludge a degausser? I'm looking for a
volunteer to try this scheme: 1) Get a 500 ft length of 4 conductor (3 conductor plus ground) # 14 AWG Romex still in the box coil. 2) Configure/connect the ends to make it a 2000' long single wire bundle of about 400 turns. 3) There should then be enough resistance in the wire to plug it into the 110 V 60 Hz line for short periods. 4) Remove the compass. With the power on, sweep the airplane anywhere there is steel, and then step back several feet before turning power off. Reinstall the compass. No warranty. Don't wear any watches. Remove all credit cards etc from your billfold.......... If nothing else, a gun type soldering iron puts out a pretty strong field above the transformer, but of course it is small and will soon get hot. |
#13
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Compass trouble
"nrp" wrote Might it be possible to kludge a degausser? I'm looking for a volunteer to try this scheme: No warranty. Don't wear any watches. Remove all credit cards etc from your billfold.......... I wonder about the possibility of it working without some type of iron core, to form and concentrate the field. Seems to me, that there have been articles about degaussing done with a welder connected through the frame, slowly ramped up, then down. Anyone remember something like this? -- Jim in NC |
#14
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Compass trouble
The iron core is the steel in your airplane. Even with no iron, the
coil would current limit however by just the sheer length of 2000 ft of number 14 wire. Is there an electrical engineer out there? |
#15
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Compass trouble
In article nrp writes:
Might it be possible to kludge a degausser? I'm looking for a volunteer to try this scheme: 1) Get a 500 ft length of 4 conductor (3 conductor plus ground) # 14 AWG Romex still in the box coil. 2) Configure/connect the ends to make it a 2000' long single wire bundle of about 400 turns. 3) There should then be enough resistance in the wire to plug it into the 110 V 60 Hz line for short periods. With a bit over 23 amps from the resistance (5.05 ohms), you will need to hope the inductance will limit the current, or the breaker on any normal 120 volt AC source will trip pretty quickly. A bit over 2700 watts will warm it up pretty quickly, too. 4) Remove the compass. With the power on, sweep the airplane anywhere there is steel, and then step back several feet before turning power off. Reinstall the compass. You might want to remove the magneto as well. There are almost certainly other magnetic parts in the instruments that you want out of there first -- no sense destroying the instruments in the panel. Any permanent magnet motors will not appreciate it. In fact, anything with a coil to pick up energy from that field could well be damaged. The alternator and connected parts may not like this. As with old shadow mask color TV degaussing, do it fairly slowly, and step back fairly slowly. Turn the coil horizontal then turn it off. No warranty. Don't wear any watches. Remove all credit cards etc from your billfold.......... You should expect this to break something expensive. Alan |
#16
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Compass trouble
On Apr 13, 7:20*pm, Ron Wanttaja wrote:
On Sun, 13 Apr 2008 15:38:49 -0700 (PDT), John wrote: I had a similar tough time swinging a compass in a Commander 114 which has a large steel support bar just above the compass. *Couldn't find a degaussing devise but was able to get more powerful compensating magnets which took care of the problem but virtually every point had 2 to 8 points of variation.... Damn...Do you realize that a "point" on a compass is a bit over 11 degrees? *So your compass was 22 to 88 degrees off...should we start calling you "Wrong Way Dupre'"? :-) (or maybe we'll just assume you meant 'degrees') My own compass-swinging adventure is at: http://www.bowersflybaby.com/tech/hillbilly.html There are certain advantages of Experimental category..... Ron Wanttaja Remind me not to tell you about my first long solo cross country flight..... John Dupre' |
#17
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Compass trouble
nrp wrote:
Might it be possible to kludge a degausser? I'm looking for a volunteer to try this scheme: 1) Get a 500 ft length of 4 conductor (3 conductor plus ground) # 14 AWG Romex still in the box coil. 2) Configure/connect the ends to make it a 2000' long single wire bundle of about 400 turns. 3) There should then be enough resistance in the wire to plug it into the 110 V 60 Hz line for short periods. 4) Remove the compass. With the power on, sweep the airplane anywhere there is steel, and then step back several feet before turning power off. Reinstall the compass. No warranty. Don't wear any watches. Remove all credit cards etc from your billfold.......... If nothing else, a gun type soldering iron puts out a pretty strong field above the transformer, but of course it is small and will soon get hot. Radio Shack used to sell big degaussing coils as "bulk tape erasers". Their only drawback was that it had a thermal overload switch that would shut it off after about a minute. Bypassing the switch let you keep it on until it was too hot to hold, but it worked great on Mooneys and Navions. Never tried mine on a Piper. Rip |
#18
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Compass trouble
You should expect this to break something expensive. Alan I agree you are very possibly right. However, I don't think an alternator would be bothered in that it doesn't need any magnetism to start. Magnetoes might be another story & would require an experiment. Obviously remove all radios as a precaution too. Do you have any feeling as to just how powerful a degausser this might be? If it is too powerful, operating it more remotely would allow a more general degaussing. How close to a 4130 steel tube would it have to be to demagnetize for example? Another experiment...... At least the wire coil could be reused to wire a house or hangar etc as long as it isn't allowed to get too hot. A ballast such as a toaster/iron or other high current device is series could limit the current and degaussing power. |
#19
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Compass trouble
This is not rocket science.. A 120 volt solenoid can be used as a
degausser, as can the ones used for TV's... Even small ac motors will have a pretty good induction field - esp. if you can open the metal case up... The way to test is to magnetize a screw driver and then use your degausser to demagnetize it... If it will do that it will do the airframe... Start with it right against the metal and run it back and forth across the surface gradually increasing the distance away from the metal until you are at least a foot away... denny |
#20
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Compass trouble
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