Control System Slack

[Tacco]

During my annual, I noticed there is some slight play in the control sticks when moved fore and aft. When I hold one stick and move the other side to side, there is zero play, which is what you would expect given the linkage between the two. But when I hold one stick static and move the other fore and aft there is about a 1/16 inch of free play between the two. Since the elevator is connected with a tensioned cable, I think the play is from the WD-1210 control column attachment to the control sticks (bushing, AN4 bolt) or the attachment of the control column to the floor structure brackets. It's slight and maybe has always been that way, maybe I just never noticed it before.

So...some help. Could some please check their stick play as well? If nothing else, it will confirm what my wife has always said - I'm just too anal about some things.

Thanks

[RFSchaller]

I have some play. I made the mistake of reaming the stick bushing to get it to move with little resistance. Problem is it introduced a small amount of dead band. I only notice it on the ground as you describe. In the air I never notice it. I have tried adding thin washers at each end of the bushing and tightened the nut on the pivot bolt which helped, but I still have a little bit of wiggle. The airframe now has 9 years and about 1050 hours. It has never caused any issue.

[Piper J3]

I bought new bronze bushings and knurled them in a lathe to increase OD. Then I cut the OD for tighter slip fit into the stick. Also fit the length of the bushings and added thin washers on each end as mentioned in post above. Bottom line is I still have ~ 1/16” relative motion between control sticks. It was a good exercise and I ended up with a slightly knurled surface on the bushing that hold grease.

[Tony_T]

In case some are wondering what this is about, here is a picture.



I have the same slight fore and aft slop. All the other control stick connections are ball bearings with no clearance. As Rich said, I never notice it in the air.

[DaleB]

I just went through this exact same thing. I had never noticed any slack or play in the sticks, but one of my partners did and asked about it. Since I didn't have an explanation, into the floor we went. Here's the email I sent afterward:

I pulled up the floor and took a look at where the play was coming from. The castle nuts on both AN4-25 bolts were in place and properly secured with cotter pins, but tightening them up by about three flats removed the play from the sticks. What we had was the ends of WD-1210 were not snug up against the ends of the bushing, allowing the stick to wobble a bit. The bolt is a snug fit in the bushing, and the bushing is a decent fit in the stick weldment, but not a snug fit. If I tighten the pivot bolts any further it will add drag to the aileron motion. In my opinion, the bushings could stand to be about .005 or .010 longer, but I'm not going to sweat it. Next condition inspection I'll remember to take a stone to the ends of the WD-1212 tubes and just remove a few thousandths of powder coat -- that should make it even better.

There is now essentially no play in either axis.

[AeroDog]

I re-made the bushings on a lathe, used the thin washers on the ends, still had the slight play. Careful measurements revealed that the tube which is welded into the control column was very slightly warped, probably by the welding. At this point I could have re-reamed the ID of the tube, re-made the bushings and maybe eliminated the play. Maybe. I decided to live with it.

Jerre

[lr172]

Originally Posted by AeroDog

I re-made the bushings on a lathe, used the thin washers on the ends, still had the slight play. Careful measurements revealed that the tube which is welded into the control column was very slightly warped, probably by the welding. At this point I could have re-reamed the ID of the tube, re-made the bushings and maybe eliminated the play. Maybe. I decided to live with it.

Jerre

Their all like this. SOmeone once said that they are reamed after welding, but I don't believe it. The interiors are simple not round. They need to be using thicker stock and properly ream them after welding. I even made slightly tapered bushings on the lathe to match and still had slop. Just too much out of roundness that is variable across the length.

Larry

[rvbuilder2002]

Originally Posted by lr172

Their all like this. SOmeone once said that they are reamed after welding, but I don't believe it. The interiors are simple not round. They need to be using thicker stock and properly ream them after welding. I even made slightly tapered bushings on the lathe to match and still had slop. Just too much out of roundness that is variable across the length.

Larry

They are reamed (for all RV models) after welding.

[rcarsey]

I think I had the issue that you described. When holding the WD-1210 firmly against one of the control stops, I can still wiggle the stick a little bit fore/aft.

This confirmed to me that there was play in the control stick-to-WD1210. I thought of a few possibilities: 1. i trimmed the bronze bushing too short 2. the bushings weren't the right diameter somehow. 3.the hole in the WD1212 (control stick) was too big.

In an effort to troubleshoot, I bought new bushings. Diameter was correct (0.375), but this time I was more careful to trim to exactly 2" (+/- 0.001). It did not help (but there was a more snug fit between the WD1210 and the bushing).

In the end what I decided was that brass was soft and that if I tightened the AN4-25 enough (i used a sacrificial bolt), the brass would compress and deform just enough to eliminate or reduce that play. I was then able to put a AN4 in and torque to spec.

[Tacco]

Thanks guys. So I’m not crazy! Think I’ll live with it for now. Might fiddle with at next annual.