Chapter 16 Control System

Autopilot servomotor install for a Dynon Skyview system
(doubleclick any image for large view)


It's cold weather and so it is a good time to do some autopilot servo work. The Dynon folks sent a good install guide for several of the RV versions and I was able to adapt the installs to the Cozy layout. I was glad to move the roll servomotor up to the CS cutout area and make room for an Al Wick type central fuel sump tank/dual fuel pump setup.


Pic#1: This setup shows left to right: CS124-boston bearing-1.5 inch piece of 6061T6 3/4" tubing-Dynon converter to Dynon arm of servomotor. I marked lines on the plastic on the table to check for alignment. This setup is lined up and then the pieces of the converter are tacked together with a little 5 minute epoxy. The converter is made from hardpoint material. The base of the converter encircles the bolt that secures the Dynon arm to the shaft of the servomotor. The base is also bolted to the Dynon arm with two AN3 bolts. Then the base is secured to the tubing with 5/8ths inch wide pieces of hardpoint material and two AN3 bolts with flox. The alignment is critical to non-binding movement.
Pic#2: This is the control linkage aft of the firewall. See the supply list for the components. I did not trim down the CS-124 piece, so that I could change the rotation point, if needed.
Pic#3: The converter has been floxed and trimmed.
Pic#4: This is the CS124 projecting into the centerspar.  

Pic#1: This is the servomotor base being tacked together with 5 min epoxy. The alignment is set with the triangle piece.
Pic#2-5: Pic#2 shows the base. Pic#3 is a 1/4th inch thick piece of foam with 10-32 Tee nuts (waxed on the ends and placed on the underside). The  Tee nuts flushed out with the top of the foam. The base has to be removable by sliding forward after being unscrewed and allow the servomotor to slide forward off of the CS-124 tubing and then be lifted up and out. This base is screwed onto the CS via a glassed on foam piece with Tee nuts (which are glassed over to secure them). 
Install steps: 
1. After making the base, I drilled out holes for the machine screws and then drilled through those holes down through the bottom foam piece.
2. I inlarged the holes in the foam base and tapped in the Tee nuts on the underside with a hammer and added a little wax.
3. I installed the servomotor onto the CS-124 tubing and placed the base around it and on top of the foam piece on the CS and hand screwed the MS-24694-S54 machine screws through the servo base into the foam piece. Move the roll controls to check for any binding action of the servo arm.
4. I marked around the foam base for position and mixed up some 5 minute eopxy to tack it in place. After 5 minutes, I disassembled everything. I added small squares of duct tape over the Tee nut holes and marked the hole position with a Sharpie and glassed over with a 3 ply BID layup.
5. A trial fit is done to check the alignment by placing the base over the foam piece and lightly inserting the MS-24694-S54 machine screws. Move the control arm for roll and see if the servo motor moves off center.
6. After cure, then everything is reassembled with the base screwed down and the four holes are marked with mustard through the servomotor onto the base side pieces. Disassemble and drill for the AN525-10R10 machine screws to go through the servomotor and secure it to the base.  IF you have an alignment problem and the servomotor binds at the end of travel, then you can expand the holes some and switch to AN3 bolts that prevent rotation, but leave some slack to allow the servomotor to shift the center of rotation.

This pic shows the final aft FW install. I moved the moment of rotation from the hole marked with blue hatch marks to give more of an in line travel to the main alileron controls. I may need to move it back. I will have to fly with the autopilot to see if the amount of course corrections is sufficient. What I don't want to do is hinder the control motion and make a different resistance in a right turn motion as compared to the left turn motion.
Material list for the roll servomotor work:

Boston bushing
6061T6 3/4 OD aluminum tubing (1.5 inches long)
CS-124 (AN3 size hole drilled at "point A" distance off center of rotation)
CS201 (made these by using tube cutter on some alum. tubing scrap)
Steel tubing (mine was 5 inches long)
CS1 insert with AN315-3 jamnut
(CS1 insert with AN315-3 jamnut)
AN3-14 (replacing the plans AN3-7A)
Note: the placement of CS201 on the inboard side is to account for the outboard CS-124 not being parallel to the aft of the firewall and so not being parallel to the servomotor CS-124 and the placement of two CS201's on the outboard setup is to space the added 5 inch servomotor steel tubing away from CS-125L (aka-aileron FW tubing)

Transition piece:
AN4-14A (two) (through hardpoint side pieces & 3/4 tubing & CS-124 tubing)
AN4-7A (two) (through hardpoint base arm & servo arm)
AN960-416 (eight)
MS21042-4 (four)
1.5 inch piece of 6061T6 3/4 OD tubing

Foam piece for securing the servo base to the CS:
Tee nuts-10-32 (four)
AN525-10R8 machine screws (four)
four lock washers

AN525-10R10 (four) holds servo to base
lock washers (four) 

Pitch Servomotor

 I took out the AN4-11 and replaced it with an AN4-20(drilled). The head of the AN4-20 will have to be like this (inboard). This is a modification of view B-B of page 16-4. From left to right the order is: MS-21042-4, AN970-4, CS-201, MM4, CS-201, NC-12 lift tab, AN970-4, CS-201, MM4, CS-201, AN970-4, AN4-20(drilled). I plan to add a safety wire through the AN4-20 after the final install. The picture does not show the addition of the AN970-4 to the right of the lift tab ( I added that for snugness). If that washer interferes with the lift tab weight, then drill out a smaller washer to the AN4 size and substitute.
As per plans for the controls to the lift tab, you use 2024T3 1/2 inch tubing and connect to the servomotor like view B-B of 16-4 and use an AN4-11A at the servo arm. When you cut the tubing, go for a 90 degree angle of servomotor arm to the tubing. 
Pic#1: This is the hanging position of the servomotor. Now, I just need to make a bracket to hold it there.
Pic#2: The servo in on the mount.
Pic#3: The mount is finished.
Pic#4: This is a top view. Earlier, I took off a hinge from the FHC (canopy) and checked for interference.
Pic#5: Bottom view.
Pic#6: Another bottom view, that shows the control connections.  
Supply List:
CGProducts (CozyGirrrl.com)
4        CS-201
1        MKCS-124L (drill your own center hole)
2        CS-1A insert (drilled for MM4)

Aircraft Spruce
1        MM-3 Aurora Bearing (for CS-125, you need smaller there)
2        MM-4 Aurora Bearing
2        AN316-4R Nut, thin check
3        MS21042-3 Nut, Stop
1        MS21042-4 Nut, Stop
1        AN4-5A Bolt undrilled    
3        AN970-4 Washer, Flat
1        AN970-3
6        AN960-10
1        AN4-20
3        AN-14A
2        AN-16A
1        AN-11A
3        AN-7A
1        03-32500-2 2024T3 Alum Tube 1/2 X .035, Two feet
2        MS24694-S54 (for the rear pad)

10        #10-32 X 5/16 Tee nuts
2         #8-32 X 1/4th Tee nuts
10        #10-32 Comboround bolts 2.0 inches

Chapter 16
Dec-2007 to Feb. 2008 (see chapter 24 for armrest during this time period) 

As I put in the controls, I did some chapter 24 work ( armrest and then seats) and some chapter 21 work. I ran the fuel lines from my fuel selector to the strakes area and to the FW. This rewrite is after the strakes are done and the sumps fit around the fuel line exit points.

The phenolic blocks (CS-108 and CS-118) get bad press. The problem lies with alignment of the blocks at a 90 degree to the control tubing. If the control tubing goes smoothly into the phenolic block at the lab bench, but then the controls are stiff after install, then loosen the bolts on first one side of the block and move the phenolic. If the binding is relieved, then add a washer there. If the binding worsens, then it is the opposite side that needs the washer. Track down the binding points and these will work smoothly.
The second picture shows the two pieces of "C" channels that I glued together ( you have to cut off a little to make the rectangular shape). There are three reasons for these. The first is that you get even platform to install the rudder cable conduit and fuel line(at the aft section). They are more flame resistant, and they are easier. The BID sample ignited at about 30 seconds with the propane torch and the grey C channel did not ignite and flame even after 90 seconds. The heat was applied to the opposite side shown in the pic.
The height of the entry of the rudder cable into the electrical conduit at the LG determined the water line for these gray conduits. I used the 5 minute epoxy to tack down the rudder cable conduit, and then placed BID strips around the conduit to secure it. I enlarge the hole where the electrical conduit meet the front seat.

Lay out all the tubing pieces in order on you table. In the later pics, you will see the red dashed line on the top side of the control tubing and you will see left and right marked on each piece. Every time, that you drill a hole it will be lined up from top to bottom evenly. The fuselage is to the left in the first picture on carpeted saw horses screw down onto a sheet of plywood. I did some work with the fuselage like this, but most of the work was done with the fuselage turned on its side (I tied it to secure). I used the side position for the armrest fabrication ("glass down"). Back to the controls. I got out some baggies and a sharpie and bagged all of those little parts for the area where they go. Later as I did the wing install, I was able to pull the relevant baggie back out of the chapter 16 plastic shoe box and install the parts. I keep this setup on the table until, I finished chapter 16. The second and fourth pics show the aileron control function being locked in the neutral position.
The picture in between those is showing the little inset on the workbench for drilling rivet holes. Drill the first and place a finishing nail in the first hole before drilling the second. Rivet the second hole and then remove the finishing nail from the first hole and rivet that one.
The last picture shows the extra birch supports with a BID glass overall. You have to make CS-109 and CS-118 (left and right) and install them first with the control tubing, ect.

The question of removable or fixed armrest has been a point of discussion. I say that you can have fixed armrest and have access to the controls by cutting out panels and still maintain the fuselage reinforcement that the armrest were intended to have (as per Nat Puffer).
Pic#1: This shows a later work of making the drip rail (chapter 18), but if you click the pic, then you can see the access panel that is necessary to remove the aft FW controls. I was able to remove and reinstall the AN3 bolt through this panel. I would stuff a rag under the control while you are taking the nut on and off to catch the nut during that process.
Pic#2: In the second picture you see the armrest supports. The strakes with the 300-400 pounds of fuel plus any baggage are supported by the CS aft and the side of the fuselage where these armrest go, so the armrest are a part of the support system. Also when you crawl (fall) into the back seat, then you've got to catch yourself on these armrest. Having emphasized the support feature, you still don't want to add any width to the armrest. I made paper templates for each F.S. point (you know). Since the fuselage curves more than the inner surface of the armrest, each set is different and I labeled each set and left and right. The fuselage is shown on its side raised up on the saw horses. It really helps for the work.
Pic#3: The "F" is where the fuel line will exit (see the later pic). The wood pieces assemble like this. The bottom piece slide on first and then the top piece overlaps that and you tape them together and add the triangle support. Make sure that they don't interfere with the controls and then 5 min epoxy and then add small BID pieces later.
In the first picture, notice that the small triangular support for CS-109 has a notch cut out. This was needed for the manual roll control action. The Strong's pitch control is shown. It is a great product, but since I have a servomotor for pitch on the autopilot, I wanted and installed the plan's manual pitch control for my initial climb, and then again for the descent to land. I don't want a "over controlled" feeling on the pitch controls. So I have a Strong's pitch control to sell for one third off. I will remove the previous sentence when it sells. My e-mail is on the first page of the site.
The last picture shows the fuel line installed. The "F" mark was about 1/2 inch below the bottom surface of the CS-121 tubing. Take this picture on left and right to guide you when you cut out the access panel for the AN3 bolt removal. I really, really suggest that you run your fuel lines right here at this point. The fuel line from the selector back to the FW taps in on bottom port on the plans control valve. The back port is just plugged. Also notice the ugly pull strings for electrical wiring. There was room for rear pockets in the armrest. I went on at this point to chapter 24 work and did the rest of the armrest and the seats, while I could still easily turn the fuselage on its side. See chapter 24.