degaussing for compass

Degaussing an airframe is not quite the same as degaussing a magnetic
tape or CRT.
I have "heard" of people doing it with a 110VAC line and a 100W light
bulb for a load.

AC 43.13-1 5-28


a. Demagnetization. Demagnetize between

successive magnetization of the same

part, to allow finding defects in all directions,

and whenever the residual magnetism interferes

with the interpretation of the indications.

Also, demagnetize all parts and materials after

completion of magnetic particle examination.

Test all parts at several locations and parts for

residual magnetism of complex configuration

at all significant changes in geometry. Repeat

demagnetization if there is any appreciable deflection

of the field indicator needle.

(1) AC method. Hold the part in the

AC demagnetizing coils and then move the

part slowly and steadily through the coils and

approximately 3 to 4 feet past the coils. Repeat

this process until the part loses its residual

magnetism. Rotate and tumble parts of complex

configuration as they are passed through

the coils.

(2) DC method. Place the part in the

same relative position as when magnetized and

apply reversing DC current. Gradually reduce

the current to zero and repeat the process until

the residual magnetic field is depleted.





You can make a loop of heavy insulated wire

"john smith" wrote in message
...
| Degaussing an airframe is not quite the same as degaussing
a magnetic
| tape or CRT.
| I have "heard" of people doing it with a 110VAC line and a
100W light
| bulb for a load.

(2) DC method. Place the part in the

same relative position as when magnetized and

apply reversing DC current.

What's a reversing DC current?

"nrp" wrote in message ups.com...
:
:
: (2) DC method. Place the part in the
:
: same relative position as when magnetized and
:
: apply reversing DC current.
:
: What's a reversing DC current?
:

Just opposite polarity...

opposite polarity, switch direction manually. Use less
current (amps) with each cycle. There are machines that do
this automatically, but you can rig up something to do it
from odd bits and pieces.



"nrp" wrote in message
ups.com...
|
|
| (2) DC method. Place the part in the
|
| same relative position as when magnetized and
|
| apply reversing DC current.
|
| What's a reversing DC current?
|

opposite polarity, switch direction manually. Use less
current (amps) with each cycle. There are machines that do
this automatically, but you can rig up something to do it
from odd bits and pieces.
There are machines that do
this automatically,

Isn't this the 60 Hz line? Just withdrawing the coil will fade the
cyclic magnetic flux.

BTW I had in mind a several ft diameter for the #14 wire concept, so
that a steel tube fuselage could be degaussed.

There are direct current machines for doing magnetic
particle inspection [MagnaFlux] and these machine do have a
built in degaussing procedure with DC current.

Yes, a large coil with AC can be used to degauss by
withdrawing the coil to several feet. Putting a tool or
tube in the AC field and switching OFF will magnetize
because the induced field is cut suddenly.



"nrp" wrote in message
oups.com...
|
| opposite polarity, switch direction manually. Use less
| current (amps) with each cycle. There are machines that
do
| this automatically, but you can rig up something to do
it
| from odd bits and pieces.
| There are machines that do
| this automatically,
|
| Isn't this the 60 Hz line? Just withdrawing the coil will
fade the
| cyclic magnetic flux.
|
| BTW I had in mind a several ft diameter for the #14 wire
concept, so
| that a steel tube fuselage could be degaussed.
|

That works ... sort of. How much magnetism (if any) you get, and of which
polarity is a function of where in the waveform the coil is when you switch
the current off.

Jim



Yes, a large coil with AC can be used to degauss by
withdrawing the coil to several feet. Putting a tool or
tube in the AC field and switching OFF will magnetize
because the induced field is cut suddenly.