Trio Wing Servo install question

lostpilot28 · #1 02-03-2008, 10:40 PM

I just mounted my roll servo in my right wing. Since the bottom skin is not riveted on yet, I built a mounting plate for the servo and attached it to the rib on the outboard side of the aileron bellcrank.

I have 2 questions about this setup:

1. Is it generally bad-practice to install a servo on a rib? I used a .060" thick piece of 6061 as a doubler and extended it about an inch longer on each side of the servo (for extra surface area to keep the rib from flexing).

2. I mounted the doubler plate to the side of the rib that was flat. Unfortunately, the flat side is not in the bay with an access plate. I won't have enough room to get my hand in there after the skin is riveted on, let alone work on the servo if needed. Can I cut out another access plate in the bottom skin? Again, would this be bad form?

Thanks.

Update: added a picture.

Rockyjs · #2 02-04-2008, 07:19 AM

Sonny,
That installation sure looks robust enough. I mounted mine on the same rib on the opposite side (bellcrank side). I made a smaller diameter pushrod from the same stock as the pushrod tube if I remember correctly. To improve access, you could mount the servo on the bellcrank side using some spacers for clearance. I haven't flown, but have operated the servo, slightly loading the aileron and could not detect any flexing.

Kahuna · #3 02-04-2008, 07:32 AM

I would not mount any mechanical device in a place where it can not be serviced, and preferrable easily serviced. I recommend you cleco the skin on and completely remove and install the servo just to try out the access. My guess it after a few cuts and bruises, you will move the servo to a location where it can easily be serviced.

Best,

Sam Buchanan · #4 02-04-2008, 08:02 AM

Quote:

Originally Posted by lostpilot28

I mounted the doubler plate to the side of the rib that was flat. Unfortunately, the flat side is not in the bay with an access plate. I won't have enough room to get my hand in there after the skin is riveted on, let alone work on the servo if needed. Can I cut out another access plate in the bottom skin? Again, would this be bad form?

Sonny, you need to move the servo. It is indeed bad form to "build yourself into a corner". The Trio servo is a reliable device, but if you put it in an unaccessible location you can rest assured the maintenance gremlins are going to make a point of using you for an object lesson.!

Either move the servo so you can access it through the bay or move it to another accessible location in the wing (different access bay or the outboard wing-tip rib/spar). Adding another access plate would be your least desirable option.

By the way, your mount looks fine, just needs to be somewhere else.

You will really like your EZ-Pilot!

BlackRV7 · #5 02-04-2008, 08:41 AM

Sonny, I used a couple pieces of alum angle mounted on the side of the rib your servo is on and installed a couple of nutplates on the angles. I mounted the Trio servo on the bellcrank side of the rib............I'm with the gang......you will regret boxing yourself into a corner with the servo where it is presently mounted. My thinking is it would be much easier to reposition the servo than cut a new inspection panel.

Jamie · #6 02-04-2008, 09:01 AM

Ditto what the other guys said. I think the easiest installation for maintenence purposes is in the otherboard most bay. I used the kit from SafeAir1.

Servo Installation

Maintenance. You can easily get in there with the wingtip removed. I completely installed this servo with the wing buttoned up and it was no big deal whatsoever.

lostpilot28 · #7 02-04-2008, 10:05 AM

Thanks guys. It dawned on me after I had installed it that access would be a problem. I'll drill out the rivets and move the plate to the other side of the rib.

alpinelakespilot2000 · #8 02-04-2008, 10:10 AM

I agree that either you need to move the servo or put a new inspection panel in. I didn't put my servo there, but I did mount my Dynon pitot and mast just inboard of the bellcrank. Per tech counselor recommendation, and OK by Ken at Van's (after I showed him pictures), I added another inspection panel so that I could easily access the pitot fittings. Cutting a new access panel was very easy to do. I think I used an 0.32 or .040 doubler and modeled it on the other access panels except that I made it narrower.

Sometimes you can get different answers talking to different people at Van's, so you might run it past them just to see what they say this time around.

DanH · #9 02-04-2008, 11:59 AM

<<...servo on a rib?>>

The maximum force applied to the rib is equal to the force necessary to slip the servo clutch. It is not much, but you can test by wiring the servo to be operational, engaging it, and then overriding it with force on the big primary control pushrod. If you don't see any flex you'll feel better <g> For the test you may want to support the rib flange as the skin would do.

Minor notes. Your mount rivets are in tension, so at least use a strip doubler on the opposite side of the rib. And turn the servo pushrod bolts around.

lostpilot28 · #10 02-04-2008, 04:41 PM

OK fellas, thanks for the feedback. I was quite certain that I could've done a better job after I finished last night (hindsite being 20/20, etc). So, I rebuilt the mounting plate since I screwed the original one up removing it today. I ended up using screws and nuts to attach it instead of rivets because I had to drill the holes in the ribs oversize (since I screwed them up, too).

Needless to say, removing rivets with a 90-degree angle drill doesn't allow for perfect work.

Below is my new-and-improved mounting location. I am using a shorter control arm, and it's in the same bay as the bell crank. No need for a new access panel. Thanks for your help.