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Seat Belt cable magnetism with ADAHRS...need a fix.

hesty

Member
I'm wondering if anyone knows if there is a process to reduce the magnetism of the seat belt cables? I am having a bit of interference with my Dynon D6 and a much less extent, my Skyview. I have mounted the ADAHRS and D6 compass on a cross bar aft of the baggage compartment. The seat belt cables pass about 5 inches from them. I am getting some heading swing if I move the cables around. I am in the build stage of my 7A still, so I am looking for an easy solution if there is one. I have wrapped the cables in two layers of plastic shield, but no help.

Thanks for any ideas.

Chad
 
Yeah ahve to find a NDT shop and have the person run them through their degauss machine.

I did that with my RV-8 rollbar and it worked great!
 
Wrapping in plastic is a waste of time.

If you can find an old bulk magnetic tape eraser you can degaus the cables. These are typically 6" in diameter and 4" tall, and plug into the wall. I used one of these to degaus the roll bar in an RV-8A.

The other option is to find a real SS cables and replace what you have.

Carl
 
An option is to constrain the cables so they can't move around the area of the AHRS. I've seen people use Nylon cable clamps and clamp the cable to the cross bar. We can calibrate out a fixed error, so as long as the cable doesn't move it will be fine.
 
The NDT shops also have a 120V hand held degaussing coil that will demag that cable. I had one at one time and loaned it to an A&P who said it worked perfectly to demag an engine mount that was effecting the onboard compass. If you can locate one you can do it yourself in about 3 minutes. They also have a small meter that will tell you if the magnetism is still there.
 
Had the same problem. On the passenger side a loose or tight belt would cause 10 degrees or so change. As Dynonsupport said, clamping the cable tight at the baggage bulkhead allowed a good calibration and fixed the problem.
 
Found this out on a goggle search. Get a pistol grip type solder gun, the type that has the wires that extend out and loops at the end. Run the cable through the loop of the two elements. It will demagnetize it. I have done this with drill bits and screwdrivers and it works. Slowly run it through a couple times and done.
 
shelf

Mount a shelf on one side of the floor under where it located now and move it there.
Bob
 
Mount a shelf on one side of the floor under where it located now and move it there.
Bob

I don't like this idea. The rudder cables are there and they move. I prefer to just leave it on the upper shelf and do something to hold the seat belt cables there. As Dynon said, as long as they don't move they should be fine.
 
A small "buzz box' welding machine makes a good degausser. Needs to be an AC welder ie not the DC type used for good welding results! Wrap several turns two or max three of the welding lead around the part and connect to the ground. Need to minimize the time and use in a low amp setting if you have that option. It will get hot and eventually burn up a cheap welder if you leave it for minutes. Its like a stuck rod when you were learning how to weld. Wont take but seconds to do what you need to do. If you ever practice welding you know how bad an AC welder will stick the rod to your work.
 
They used to make a "thing" used by radio/tv stations that would erase recordings on magnetic tape, I don't know what it is called but one of those may work well as a degausser.

It was about the size of a package of CD dics.

Someone with more experience with broadcasting may be able to clarify.

Glenn Wilkinson
 
I had a compass that wouldn't swing because my autopilot was too close to it. I wrapped the autopilot in nickel sheet metal... Compass swings perfectly now. You can get a roll of nickel sheet metal pretty cheap on Amazon.
 
Can it be that easy?

I had a compass that wouldn't swing because my autopilot was too close to it. I wrapped the autopilot in nickel sheet metal... Compass swings perfectly now. You can get a roll of nickel sheet metal pretty cheap on Amazon.


sounds like a great solution...
too good to be true?
Thanks for all the ideas!
Chad
 
Go to amazon!

I used one of these and rubbed it along the cables. http://www.amazon.com/gp/product/B008NNQ6P4?keywords=degausser&qid=1452279720&ref_=sr_1_17&sr=8-17 It worked on the cables but I then had an issue with the elevator control horns, I couldn't get this device in and around the control horns well enough, or it just didn't work well enough, so I had to move my (garmin) magnetometer from back by the aft surface near the stabilizers forward to a bracket across the fuse, close to the static ports and away from the control horns. No more interference with the cables though. There deffinately was some to start because I could see the numbers swing during calibration when I would cycle the rudder back and forth.
 
Brilliant

I used one of these and rubbed it along the cables. http://www.amazon.com/gp/product/B008NNQ6P4?keywords=degausser&qid=1452279720&ref_=sr_1_17&sr=8-17 It worked on the cables but I then had an issue with the elevator control horns, I couldn't get this device in and around the control horns well enough, or it just didn't work well enough, so I had to move my (garmin) magnetometer from back by the aft surface near the stabilizers forward to a bracket across the fuse, close to the static ports and away from the control horns. No more interference with the cables though. There deffinately was some to start because I could see the numbers swing during calibration when I would cycle the rudder back and forth.

Excellent Derek! Great price too!
Thank you.
Chad
 
The guts of a $8 big box store bathroom exhaust fan can be useful.

The outer part of the shadedpole motor has the plug.

Rudder cables fit through the center to degauss.

Do not plug it in near any magnetometers or a compass.

Two passes, not allowing the cable to touch the motor housing worked for me.

1 foot in 10 seconds.

Felt like bomb squad meets "Operation" the wacky doctors game.

GRT magnetometer was then easily calibrated.

Found the problem with a compass slowly moved around the magnetometer installation.

It was obviously the rudder with the copass, but did not show up as easily moving flight controls and looking at the EFIS setup pages as instructed.

Annoying video at times,but the inspiration:

https://www.youtube.com/watch?v=8kKTJQTyX-w
 
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flux

Chad man I'm not sure that my I dear of moving it away from the cable was a bad idea as with 90%/of the others sounds like a life or death and a good Chance of burning a hole in your plane or getting shocked! Good luck and be safe
Bob
 
The guts of a $8 big box store bathroom exhaust fan can be useful.
snipped
Two passes, not allowing the cable to touch the motor housing worked for me.

1 foot in 10 seconds.

Felt like bomb squad meets "Operation" the wacky doctors game.
snipped.

Hey Rich, you do know you could just cut a donut of paper, wood, etc & put it in the motor frame to keep the cable centered, right?

Charlie
Lazy redneck improviser in MS
 
That was the plan for pass number 3. Was not needed. The donut idea would not fit the end buckle easy enough and center the cable. A padded vise and two free hands did it.

Rubber gloves helped. Seemed a bit more dangerous than the $10 watch demagnetizer, but worked great. I figured I needed the extra oomph of a loop.

Can make a magnetized item also, If needed, just watch the video.
 
I used a vinyl tubing that I slit and slipped over the cable. It reduced it quite a bit, although not totally. I wonder if you can double up the tubing to shield it ever better. You can buy it at home depot or lowes for a couple dollars.
May be worth a try.
 
The "easiest" fix

I had the same problem, used stainless steel cables and see no effects on ADAHRS.

I did check out stainless cables at the local nationwide boating store and they attracted a magnet as bad as the Van's cables.

I did what I have rarely done in my build it seems...took the "easiest" suggestion and implemented it with successful results. I riveted a zip tie anchor to the adahrs mounting crossbars under each cable and this resulted in no further relative motion and no strong interference. The Skyview and D10 differ by about 8 degrees now and I'm sure I can adjust that with the software during a compass swing after the build is complete.



Thanks for all the suggestions folks.
 
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