I got lots of helpful responses to Planning BD-4C Autopilot Servo Installation and have decided to attach the autopilot servos in my Bede BD-4C airplane to the horizontal stabilator and to the rudder. Over the years, many people have experimented with autopilots in BD-4s and controlling the rudder seems to work better than controlling the aileron.
My current thinking is the mount the servos inside the main landing gear box. I had already decided to bolt the center section of the box top on, instead of riveting it, so access will not be a problem. The structure is plenty strong enough to support the servos. And there is just the right amount of space.
Here is a photo with the servos set into position. I mocked up control rods and attachments with aviation grade blue masking tape.
The servo on the left in that photo is attached to a rudder cable. Since the cable only moves about 1.5 inches, I plan to attach the control rod to the cable with a single clamping block, forgoing a capstan drive.
I fabricated brackets today. I used .125 aluminum angle for the main brackets underneath the servos. I used .063 aluminum angle for secondary brackets on the tops of the servos to help stabilize them.
What do you think?
Looks good. I’ve looked thru my old BD stuff and don
t find any references to auto pilot install.
I think you’re becoming an expert aluminum hacker, Art.
(eh, editorial note, the title to this posting is “Mounting Autopilot Servers in the BD-4C”. Shouldn’t it be “Servos”?)
Oops! Indeed it should be “servos” and not “servers.” Thanks!
— Art Z.
Art
Curious if you have tested the set up on the stabilator tube?
Also will you have a trim hook up or are you going to trim the plane and then start the auto pilot?
I have not tested it, yet. Soon though.
I plan to trim the plan before engaging the autopilot. That’s what I did in my previous planes (Archer and Arrow) and it worked well.