ADAHRS mounting
- Thread starter TexasRV8
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- Mar 23, 2005
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Small bits of static, non-magnetized steel tend not to be a problem, but your milage may vary.
If "the world" is really jiggling on account of the shimmy, and the attitude indicator is just reflecting that, then you're fine. If you're seeing errors that accumulate and end up giving you a wrong attitude picture that doesn't fix itself quickly, you could try damping the ADAHRS, but might it be easier to look at the shimmy itself?
If "the world" is really jiggling on account of the shimmy, and the attitude indicator is just reflecting that, then you're fine. If you're seeing errors that accumulate and end up giving you a wrong attitude picture that doesn't fix itself quickly, you could try damping the ADAHRS, but might it be easier to look at the shimmy itself?
Thanks to help from Mike at Dynon support, we figured out that the STAINLESS STEEL, #10 screws that I used to mount my ADAHRS were magnetic enough to throw the magnetic heading off by more than 30 degrees and prevent it from ever passing a compass calibration! And I had checked them before installation and they showed no attraction to a magnet whatsoever.
I'm going to try brass screws tomorrow. I sure hope it's non-magnetic brass.......
I'm going to try brass screws tomorrow. I sure hope it's non-magnetic brass.......
As a follow up, I replaced all of the SS hardware on the ADAHRS with brass from the local hardware store and it calibrated on the first try! It was so nice to have accurate magnetic headings for the first time. I'm still not sure how or why the SS hardware was magnetic but it certainly was. Nice flight this morning but it was B-U-M-P-Y so I was only up for 1/2 hour.
Thanks for the post. I too have SS bolts mounting my dual ADHARS. I am not in a position to calibrate yet, but had a question. It you boot up the system and wave your SS bolts near the ADHARS, does the heading change? I had 6 extra SS bolts like I used, I did this test and the heading was rock solid. I'm wondering if I will have the same issue as you describe or if I will be ok?!?!?! Maybe my SS bolts are made of less ferrous material?!?!?
Thanks
-Mike
Thanks
-Mike
I was curious about exactly that question so I checked, and yes, there is a change in the indicated heading when you hold one of my "SS" screws near the ADAHRS. This was really surprising because they don't exhibit any other evidence of magnetism.
Note too, that I was using several SS washers as shims so there was actually a lot of metal there but it was all stainless. But for new installations, there is no reason not to use brass, just like you use for magnetic compass mounts and other instruments, so that's what I would recommend.
Also note that my airplane is particularly difficult when it comes to ADAHRS mounting. It's a canard-style, centerline thrust twin so, with engines on both ends and no tail, the options are pretty limited so mine ended up under one of the rear seats.
Note too, that I was using several SS washers as shims so there was actually a lot of metal there but it was all stainless. But for new installations, there is no reason not to use brass, just like you use for magnetic compass mounts and other instruments, so that's what I would recommend.
Also note that my airplane is particularly difficult when it comes to ADAHRS mounting. It's a canard-style, centerline thrust twin so, with engines on both ends and no tail, the options are pretty limited so mine ended up under one of the rear seats.
gerry.vandyk
New Member
Stainless steels may or may not be magnetic, it depend on the grain structure of the steel. Austenetic stainless is essentially non-magnetic but there are plenty of grades that are not austenetic.
http://www.azom.com/details.asp?ArticleID=1140
This link has a good description. To quote one passage:
"After substantial cold working Grade 304 may exhibit quite strong response to a magnet, whereas Grades 310 and 316 will in most instances still be almost totally non-responsive."
Keep in mind threads are typically rolled into screws, that's cold working. What is the grade of steel in the screws you're using? I wouldn't have a clue, the package rarely tells you.
It would probably be best to stick with brass or nylon screws and nuts just to ensure the totally non-mag environment near the ADAHRS.
Gerry
http://www.azom.com/details.asp?ArticleID=1140
This link has a good description. To quote one passage:
"After substantial cold working Grade 304 may exhibit quite strong response to a magnet, whereas Grades 310 and 316 will in most instances still be almost totally non-responsive."
Keep in mind threads are typically rolled into screws, that's cold working. What is the grade of steel in the screws you're using? I wouldn't have a clue, the package rarely tells you.
It would probably be best to stick with brass or nylon screws and nuts just to ensure the totally non-mag environment near the ADAHRS.
Gerry
- Joined
- Mar 23, 2005
- Messages
- 13,226
It nominally isn't anywhere near it, as the ADAHRS is usually well away from the panel (magnetic interference avoidance), but the battery is near the screen (it connects to it). If they somehow are near each other, at least 1-2 feet is the separation you're going to need.
This is a pretty old thread but I'm hoping someone from Dynon will see it! Question is - the manual says within 12 ft longitudinally of th cg. That seems quite a way. Is it really going to be 100% fine out at 12 ft or would closer be better? (I'm looking at mounting it under the fin on my RV6 which is 9 or 10 ft back from the cg).
Strikes me that the g will be quite different that far back from the cg, especially during pitch accelerations.
Advice much appreciated!
Strikes me that the g will be quite different that far back from the cg, especially during pitch accelerations.
Advice much appreciated!
Closer to CG is better, yes. In particular, idea autopilot performance can be harder to achieve when you get too far off the CG.
Reviving an old thread. I've fabricated a shelf and mounted it to the upper J-stringers. A hardware is aluminum or brass. Aluminum floating nut plates and brass screws, washers, etc.
Question is what about the D-sub? Isn't the D-sub made of steel? What about the D-sub on the Dynon harness?
Question is what about the D-sub? Isn't the D-sub made of steel? What about the D-sub on the Dynon harness?
Raymo
I love aviation!
The main concern is that anything ferous is not moving around once you calibrate the compass within the ADAHRS unit. Hence the reason we put them in the tail cone in most RVs.
Some have reported issues when no passenger is along and the seat belt cable moves around. One fix for that is to clamp the cable at the baggage bulkhead such that it will not move around.
Some have reported issues when no passenger is along and the seat belt cable moves around. One fix for that is to clamp the cable at the baggage bulkhead such that it will not move around.
E
ed.meyer
Guest
ADAHRS can now be mounted behind panel IF a remote magnetometer is used. Dynon did not have this option when this thread was started but it is available now. We installed one out near the end of the wing in our steel tube fuselage airplane and it works fine with the ADAHRS behind the panel.