AHRS installation?? -help please

[wingnutzster]

I know this has been asked before, sort-of, but I am struggling to find an example of specifically the MGL SP-6B and SP-7 magnetometer and AHRS installations....I found what research suggested was a good location for the magnetometer (SP-6B) just under the keel, up in front of the F-707 bulkhead, I fabricated a 'tray' of sorts which can be pulled out for servicing - the unit is mounted on a rubber mat and the all attachment points are vibration dampened but where would be the best location for the AHRS (SP-7) unit?
It has to line up with the SP-6 on 3 axis and obviously has to avoid all vibration and heat/cold....I initially thought to mount it right next to the SP-6 on the same tray (there is adequate room for it) but after reading the notes and the forums it appears I am too far from the center of rotation?? It was suggested by Rainier that best theoretical location would be the center of the roll and pitch axis.

If someone can post a picture of their installation that would help a ton, lining it up with my mounted SP-6 might be a task though. :roll: :roll:

Also, without slamming my build quality (because I do my best) or scrutinizing every rivet in the region of the subject could you please comment on my servo installation - will this do? With some force the keel itself - to which the bracket is secured - can be pushed 15-20mm from left to right but there is no play back and forwards or twist.

http://www.avcom.co.za/phpBB3/download/file.php?id=157186&mode=view

 

[wingnutzster]

Ok I just spoke to the aircraft owner and Rainier and it seems I really do need to get closer to the pitch and roll axis convergence....so, a discussion with the owner has a possible location for the SP-7 as here:

...my concerns with this location are numerous, firstly I do not like the unit being mounted right on top of a rather large flap motor - I know the SP-7 isn't succeptible to magnetic fields and ferrous metals as the compass but the vibration of the motor and in the metal surrounding the motor I think could be a problem, then being open in the cavity behind the seat which is essentially baggage area, it would be sucseptible to being knocked by baggage and if I were to enclose it to keep it safe it might be in the way of what could be usable space behind the seat and at the seat brace?

What do you think?

 

[brad walton]

Location

Hello Wingnutzster

I have the older model MGL AHRS and magnetometer (maybe SP-2 and SP-4) on my RV-8. I looked at numerous locations and decided to try the easiest first. It works well even though it may not be optimal according to Rainer, But I have not noticed any erroneous indications. I put both side by side on a piece of aluminum angle riveted high and to the right side of the rear side of the bulkhead that forms the rear of the forward baggage compartment. In other words, on the back of the bulkhead that is about 20 inches forward of the instrument panel. Makes for short cable runs, is out of the way and works just fine. They are about 3 feet forward and 3 feet above the CG and offset 1 foot to the right.

 

[scootwoot]

I put my AHRS under the pilot?s seat just to the left of the tunnel. and the Magnetometer in the upper section of the fuselage just in front of F-607
So far seems to be working fine.

 

[GrayHawk]

A little dated but:

http://www.mglavionicsusers.org/files/magnetometer&ahrs-installation.pdf

I am re-building the forward part of an RV-6A using mostly RV-7 parts. To adapt the RV-7 center tunnel to the RV-6 wing spar, I've designed a small console for the fuel valve , etc & hope to put the AHRS in there as close to the spar as I can (close to centers of rotation). Then for the magnetometer, just aft of the baggage bulkhead up high.

However my units will use the CAN bus, so I need to think about that & probably test before finalizing the locations.

GH

 

[wingnutzster]

Thanks for the replies guys, scootwoot, re your installation - how do you avoid the known problems with cabin floor skin drumming in flight?
Thanks Gray Hawk - will read through that

 

[scootwoot]

What I did for the AHRS is to not mount it directly to the floor.. I put an angle on each floor rib, as a standoff, then a .040 plate between them. That way you can drill the plate to the AHRS, and use plate nuts for mounting,, then should you need to adjust the planer alignment,, it is easy shimming.

 

[Smilin' Jack]

Check out my build pictures where I put a shelf in, might be an idea for you
Around the 93 page on the webshot site
Smilin Jack