Stick slop

[CoClimber]

My control stick has some slop in the forward backwards (elevator) direction. The play looks to be with the bolt in the center of the photo.
27322
I measure the play to be about 3/16" at the top of the stick. I have some ideas how to fix this but I wonder if it is an issue. I have yet to fly a Kitfox but I understand that they have a tight control feel. It would be a shame to lose that if this is an issue.

[taff]

From my experience, there will always be a little play, the further from the connection junction the greater the movement. (short stick =less loose travel)
If it is the bolt, maybe insert one size up? But that would need reaming the system.
Could it be the bearing?

I hope this play is not when the aircraft is airborne.
That's when to wind has things in harmony on your flying surfaces and everything should feel tight.

[Dave S]

Douglas,

I can't even begin to enumerate the number of cessnas and pipers I have had my hands on where a person would be fortunate to have as little as 3/16" slop in the controls!

It's not easy to figure out something like this if a person can't see it in person and get their hands on it; but I can venture an approach to take.

If I understand correctly, this is on a model II which has a simple bushed fitting, not small ball bearings as on the later model kitfoxes - - going with that assumption....

To determine where the slop is occurring, a person could disassemble the unit to measure the diameter of the bolt, inner diameter of the hole going through the stick pivot (both ends) and inner diameter of the holes going through the control column. If you have a dial caliper that can measure inside and outside D that will work fine even if it is not an expensive one.

Not all AN bolts will be precisely the same diameter and they can vary by a thousandths of an inch or so, if any wear has occurred that can increase the clearance - doesn't take much. One thing to check for if you haven't had the bolt out before is to be sure the bolt is long enough so the threads are not contacting the bearing surface as that will create looseness for sure.

Measuring and checking condition in detail after disassembly should lead you down the right track.

Sometimes a new bolt without any wear will help reduce the space enough to keep a person happy. While the holes in the ears of the control column can be reamed a bit larger without any appreciable reduction in strength, I am not sure the same is true of the tube going through the stick pivot.

Not to be ignored is assuring that the slop is not due to some parts further down the line all the way to the elevator.

Sure be interested what you find out.

[kmach]

There are AN oversize, tight fit bolts available that are slightly larger in diameter, if it is an actually bolt issue.

[CoClimber]

I don't need the dial calipers for this one. When I wiggle the stick, I can see that the bolt in the photo is moving and the lower assembly (the vertical plate in the photo) is not until the play is taken up. If 3/16" is too much, I'm sure I can fabricate something to fix it. There is a nice machine shop at work and they foolishly let me play in there. I'm thinking about opening up the hole in the vertical plate and pressing in a brass bushing.

[109JB]

First pull the bolt out. Could be the shank of the bolt is worn and a new standard size bolt would tighten it up significantly.

[jrevens]

I'm not familiar with how that particular assembly was originally designed, but standard good design practice would be to have a bushing of some material like bronze that is softer than the steel stick assembly, but it could also be steel and lubricated well. That would be clamped securely between the 2 ears with the bolt, and the inner surface of the stick tube would rotate on the bushing. There should be no rotation of the bolt in the holes or the bushing, and the bolt should not be used as a bearing surface. I hope that makes sense and is clear. The fact that the bolt or holes are worn indicates to me that it was not assembled or tightened properly from the beginning, but then again you see all kinds of crazy designs sometimes... even on airplanes.

[109JB]

I'm not familiar with how that particular assembly was originally designed, but standard good design practice would be to have a bushing of some material like bronze that is softer than the steel stick assembly, but it could also be steel and lubricated well. That would be clamped securely between the 2 ears with the bolt, and the inner surface of the stick tube would rotate on the bushing. There should be no rotation of the bolt in the holes or the bushing, and the bolt should not be used as a bearing surface. I hope that makes sense and is clear. The fact that the bolt or holes are worn indicates to me that it was not assembled or tightened properly from the beginning, but then again you see all kinds of crazy designs sometimes... even on airplanes.

John,

I think in this case there is a piece of bushing stock reamed to the bolt diameter on the end of the stick and this bushing stock does rotate on the bolt. Maybe not the absolute best design, but it is not uncommon in homebuilt airplanes. My Sonerai has bushing stock for hinges on the rudder and elevator that rotate on a clevis pin acting as the hinge pin. Likewise the control stick assembly also has bushing stock that rotates on bolts not unlike the one in question here. After about 400 hours with regular lubrication my hinges and control system in my Sonerai is slop free.

[jrevens]

John,

I think in this case there is a piece of bushing stock reamed to the bolt diameter on the end of the stick and this bushing stock does rotate on the bolt. Maybe not the absolute best design, but it is not uncommon in homebuilt airplanes. My Sonerai has bushing stock for hinges on the rudder and elevator that rotate on a clevis pin acting as the hinge pin. Likewise the control stick assembly also has bushing stock that rotates on bolts not unlike the one in question here. After about 400 hours with regular lubrication my hinges and control system in my Sonerai is slop free.

Good to know... thanks John. As I said, “normally” good design practice would utilize a bushing of a softer material that is replaced when worn, and a bolt, which is the primary structural part that holds everything together is never used as a bearing surface. I know that there are many times that they are used that way, like on your Sonerai, and as a practical matter work just fine. I doubt that an aeronautical or mechanical engineer would design it that way, but who knows? Bottom line, if it works and the bolt doesn’t wear, you’re happy.

[CoClimber]

I braved the cold weather and went out to the garage to examine this closer. This is a model 2. In the photo, there is the U channel made up of the sheet metal assembly. It is doubled up where the bolt goes through. The stick goes down to where there is a tube that the bolt goes through. I found two issues: the hole in the sheet metal had some play, and the tube had some play. This assembly had less than 70 hours of use so I think it was manufactured that way. I replaced the bolt although I don't think it was worn down at all. My Brown & Sharpe calipers were in the house and the cheap dial calipers in the garage are useless for this type of measurement. The new bolt was slightly longer to assure that the threads are not in contact with the sheet metal. I lightly snugged up the nut and the slop disappeared. When I move the stick left and right, the bolt stays still so the bearing surface is the bolt to the tube. I'll disassemble it and grease it up. Considering the loads on this, I'm not too concerned.
27334