This section is for builder's Tips and Tricks for Controls, as well as one-off modifications.
Control Stick Enhancement
The aileron torque tube in the keel is 3/4" O.D. aluminum. The factory has produced a couple designs for attaching the control stick to this tube. The original design simply used a bolt connecting the control stick to the torque tube. The later design uses an arm welded to the control stick to capture both sides of the torque tube. With the arm the factory also installed a brass insert bushing in the torque tube.
The arm and bushing helped, but the original problem was not solved. The torque tube is aluminum. The control stick has significant mechanical advantage and over time the aluminum will yield and waller. The result is slop in the aileron controls.
Here are some of the modifications owners have made to address the control slop.
This tip for improving the way the standard center control stick mounting/support again comes from Jim Agnew. Jim_agnew_2 at yahoo dot com
While flying with Sam I commented on the stick play (side to side) and he said that it was caused by the limited support in the lateral direction caused by the two round pieces of tubing having almost no bearing surface. He mentioned the new velocity saddle type mount and said that he had made some microglass bearings to provide more support. This intrigued me so back at the hanger I grabbed a 1 1/4” piece of 6061-T6 aluminum rod and chucked it up in the lathe. I trued the surface and the exposed end and lathe drilled a ¼” axial hole in the rod. Next I used the mill to precision mill a ¾” hole at right angles to the axial hole and centered on the rod.
You now have a rod with a ¾” hole thru it and a 90 degree intersecting hole down the center of the rod. Placing the rod back in the lathe I lathe drilled the ¼” axial hole to 3/8” on one side of the ¾” intersecting hole. The bushing in the aluminum torque tube is this size so one side must be 3/8” & the other ¼”. Next I faced the end of the rod until the metal at the axial hole was only .040 thick measuring out from the ¾” hole. At this point I cut the rod on the inboard side of the ¾” hole and reversed the piece in the lathe. Face the new end to the same .040 thickness and then you cut the rod in half thru the center of the ¾” hole. You now have two round aluminum washers with a ¾” half round grove and a hole (one ¼” & one 3/8”) perpendicular to the grove and centered in it.
Next I polished the flat sides on 400 grit emery paper to a very smooth finish. I then made a round bearing washer to fit the flat sides out of .002 brass shim stock and with a ¼” center hole. Almost done, I removed the through bolt from the stick and placed the 3/8” drilled washer on the bolt with the ¾” with grove against the torque tube If made correctly this “saddle” will be a very tight fit and actually stick to the torque tube. Next coat the brass washer on both sides with NeverSez (the same stuff you use on spark plug threads) and place over the bolt. Next comes the ¼” drilled washer with the groove facing the stick. Install the stick on the bolt and tighten firmly to seat the saddles. Then back off the tension slowly testing the elevator action to make sure you don’t have too much friction. When you are happy with the action install the stick locknut and lock the bolt. You will find that the elevator action is butter smooth and there is no aileron side play other than the bending of the torque tube that is slight. You will find that aileron reaction is much faster. There is far less strain on the torque tube and pivot bolt and the expected life of the piece is probably well beyond the aircraft by a factor of ten.
Jerry Brainard took a slightly different approach. He saw the problem as a matter of attaching to the torque tube. Instead of depending on the brass bushing inside the tube he fabricated a clamp. The clamp positively grabs the torque tube and provides a larger, flat surface for the control stick to ride against.
Millin/Dugas ASSES (AntiSlop Stick Extra Support)
Andy Millin created a support block based upon the Dugas solution. The block captures the bushing and clamps to the torque tube. It is made from 2024 aluminum. The supports are re-purposed 3/4" aluminum double split shaft collars.
To install the block, first remove the AN4 Through Bolt. This will free the stick from the aileron torque tube. It is possible to complete the install without disconnecting the grip, wiring and the elevator. It will probably be easier if the stick is completely removed as it needs to be modified.
The stick comes with a U shaped saddle. See picture at the top of this page. The top and outer leg of the saddle must be completely removed to install the block. Leave the flat piece of steel welded to the side of the stick. The flat steel will work against the aluminum block -- flat against flat.
The area inside the keel is a bit tight for working space. The block goes on the stick side of the torque tube. The two half collars go on the opposite side. It all gets screwed together with the 4 socket head screws.
A couple long (2" or so) AN4 bolts can be helpful. Put the bolts through the top holes of the block and start them into the two collars.
Place the block and collars over the torque tube. Slide the Through Bolt through the block and torque tube to maintain alignment.
I installed the socket head screws with a drop of blue Loctite. The long bolts will hold the clamps in place and allow you to start the lower screws. Once the lowers are started, remove the long bolts and install the upper screws.
Note: the block is meant to clamp onto the aileron torque tube. There is supposed to be a gap between the block and the half round collars. Do not attempt to draw them into contact.
Evenly tighten the clamp screws between 50-70 in-lbs.
- Lubrication is up to you, the owner.
- Section 6.4.5 - Control Stick Assembly of the Construction Manual does not call for lubricant on the Through Bolt.
- In the original configuration the steel saddle works against the bronze bushing. I believe this is an Oilite bushing and is self lubricating. With the block in place the stick will be working against the aluminum. The aluminum is softer than the steel and could gall over time.
- I used a small amount of anti-seize on the Through Bolt and on the stick to block interface.
If you need to, re-connect the elevator to the stick.
Re-install the stick. Adjust the Through Bolt torque to allow easy elevator control with minimal slop.
The following .pdf is a hand drawing of the Dugas solution.