Question about Trio Servo w/ SafeAir1 kit

[IowaRV9Dreamer]

I'm installing a Trio gold roll servo in the wing of my 9A. I have a question for someone who has installed one of these using the SafeAir1 installation kit.

It looks like the SafeAir1 pushrod attaches to the bellcrank using the same bolt as the control stick pushrod (hereafeter called the "bellcrank bolt"). My question involves the maximum control swing at this point.

The Trio manual specifies a maximum of 2.4 inches (peak-to-peak) control movement, less if you use one of the inner servo arm holes. I don't have my wings attached, but it looks to me like the bellcrank bolt will move more than that. I moved my aileron over the range Vans specifies and I got about 3 inches of swing at the bellcrank bolt.

To get under the 2.4 inches it seems to me that one would have to drill a new hole in the bellcrank, about 3/4 inches closer to the pivot?

Am I all wet here? If someone has a 9/9A and could measure the swing of the bellcrank at the control stick pushrod attach, that would really help.

I want to make sure that the maximum control swing will move the servo arm less than +/- 50 degrees (Trio maximum).

Thanks for any help,

dave

 

[Sam Buchanan]

To get under the 2.4 inches it seems to me that one would have to drill a new hole in the bellcrank, about 3/4 inches closer to the pivot?

Dave, the distance from the bellcrank pivot to the servo pushrod attachment on the bellcrank needs to be the same as the distance from the servo shaft to the servo arm pushrod bolt. I suspect you will be drilling another hole in the bell crank to attach the servo pushrod.

I have not seen the instructions for the SafeAir1 installation kit but the above is generally how Trio wants their servos installed.

 

[N908RV]

Safeair Crank Arm for Trio/Navaid Servo

Safeair has a bolt on crank arm (comes in the kit) that replaces the Trio/Navaid arm on the servo and this provides a 1:1 relationship in terms of the pivot distances.

 

[IowaRV9Dreamer]

Dave, the distance from the bellcrank pivot to the servo pushrod attachment on the bellcrank needs to be the same as the distance from the servo shaft to the servo arm pushrod bolt.

Hi Sam - I don't see this 1:1 requirement in the Trio manual... but I believe it would be highly desirable. How critical is it? You would certainly need a larger servo crank arm to get there.

FYI - here is a good link to a SafeAir1 install (bottom of page)
http://www.kit-panels.com:80/rv9a/qb_ApInstall.htm

The SafeAir kit attaches to the spar at the outboard rib bay - I'm interested in the same kind of attachment but with the servo mounted to the spar in the bellcrank bay. Has anyone else done this (please don't tell me to contact Vans...)

 

[hydroguy2]

............The SafeAir kit attaches to the spar at the outboard rib bay - I'm interested in the same kind of attachment but with the servo mounted to the spar in the bellcrank bay. Has anyone else done this (please don't tell me to contact Vans...)

Check this thread post #3, might be what you are trying to do.
http://www.vansairforce.com/community/showthread.php?t=21819

I mounted my Navaid servo in the bellcrank bay. Haven't tested it yet, but did match the strokes to ensure aileron hit the stop before the servo hit it's stop.
http://www.mykitlog.com/users/worklog_image_popup.php?user=hydroguy2&project=294&log_id=43048&photo_number=1

 

[Sam Buchanan]

I don't see this 1:1 requirement in the Trio manual... but I believe it would be highly desirable. How critical is it? You would certainly need a larger servo crank arm to get there.

Dave, here is a quote from the installation manual for the Trio EZ-Hold:

"If your aircraft employs an elevator bell crank, you should ideally attach the pushrod to the bell crank at a distance from its pivot point equal to that of the servo crank arm radius (distance from crank arm pivot point to pushrod attach point)."

I guess that is where I got the suggestion to keep the 1:1 ratio. I do recall that my EZ-Hold system worked better after I rerigged it to have the 1:1 ratio.

Having said that, I don't know how critical, if at all, this rule is for the wing leveler servo. The Navaid servo in the wing of my RV-6 that is now driven by the EZ-Pilot most likely does not have a 1:1 ratio. You might just go ahead and install per the SafeAir kit and if necessary (probably won't be) you could modify the installation after you have flown the system.

By all means make sure the control surfaces hit their stops before the servo goes over center or hits its stops. Your installations looks very good and I bet it will work fine.

You are going to enjoy your EZ-Pilot!!

 

[IowaRV9Dreamer]

Check this thread post #3, might be what you are trying to do.

Hi Brian - that's close but not quite it. On the 9 wing, there is just enough room to put the base of the flat against the spar web. There are no spar doublers in that area. I'll try to post a picture of what I'm considering.

The install should consist of 4 mounting holes, an extended servo crank arm (to get the 1:1 ratio described above) and would use the existing bolt on the bellcrank.

I'm sure I'm not the first one to consider this?