Control Binds in roll

[RVG8tor]

I am just installing the control column and connecting the push rods. When I tighten down the two nuts holding the bearings that the control column hangs on my controls bind in the roll axis. If I move the stick left or right and let go is stays there an does not move back to center. If I loosen the nuts it moves freely. What could be my problem, I set the bearing according to the plans so I am not sure what could be causing the binding. Anyone have any ideas on how to proceed. The plans don't call for washers between the bearing and the weldmount but maybe I need some.

Thanks

 

[jsharkey]

If it's like my -6 there is a brass bushing in the control column roll axis joint. This bushing should be a tad longer than the steel tube that it passes through so that when you tighten down the nut the bushing forms a stop and the tube with the control column welded to it is not pinched in the clevis and is still free to move around the bushing.

Jim Sharkey

 

[Kevin Horton]

I am just installing the control column and connecting the push rods. When I tighten down the two nuts holding the bearings that the control column hangs on my controls bind in the roll axis. If I move the stick left or right and let go is stays there an does not move back to center. If I loosen the nuts it moves freely. What could be my problem, I set the bearing according to the plans so I am not sure what could be causing the binding. Anyone have any ideas on how to proceed. The plans don't call for washers between the bearing and the weldmount but maybe I need some.

Thanks

I had problems here too. The distance between the two bearings was not exactly the same as the distance between the fore and aft bearing areas on the weldment (builder error). The result was that a side load was placed on the bearings when I tightened everything down, which put a lot of friction in the system. I recall that I slotted the four bolt holes in the large aluminum angle that the aft bearing hangs from. That allowed me to move it slightly to remove the side load on the bearings.

 

[Guy Prevost]

I had the same problem as Kevin, even though I have a matched hole fuselage. In my case, tightening all of the fasteners tried to squeeze the two rod end bearings together. If memory serves me correctly (I'm on a business trip at the moment and can't look), the forward bearing hangs on an L shaped bracket mounted on the front face of the center section. I made a .020" shim to go between the bracket and the center section. That got rid of the preload.

Guy

 

[jthocker]

Same thing happened to me. Try shimming either the front 2 bolts or the rear 2 bolts on the aft control column hanger with AN960-10 or 10L washers.
Or elongating or slightly enlarging the holes will work also.

 

[Webb]

Bushing Length

The bolt puts the compression on the bushing, not the steel tube. If the tube gets any pressure, it will bind.

Make sure the bushing is longer than the steel tube it goes in. This goes for the aileron bellcranks also. Also make sure the flang that is welded to the steel tube does not extend beyond the steel tube. You don't want that to drag either. If memory serves, there are 4 bushings. One on each stick and 1 on each aileron bellcrank.

I had this problem on the left belcrank and it was very hard to move the stick from side to side. Once ground down slightly, the stick was easy to move from side to side.

 

[Guy Prevost]

The bolt puts the compression on the bushing, not the steel tube. If the tube gets any pressure, it will bind.

Make sure the bushing is longer than the steel tube it goes in. This goes for the aileron bellcranks also. Also make sure the flang that is welded to the steel tube does not extend beyond the steel tube. You don't want that to drag either. If memory serves, there are 4 bushings. One on each stick and 1 on each aileron bellcrank.

I had this problem on the left belcrank and it was very hard to move the stick from side to side. Once ground down slightly, the stick was easy to move from side to side.

RV8's are different from the side by sides in this regard. In fact, they're exactly opposite. The stick bushings are on the pitch axis on an RV8, not the roll axis.

 

[RVG8tor]

Great ideas

Thanks for all of the input, I think I will try the slotting idea, as I have one nut plate for the aft control mount that is not lined up well. I did get a better fit, I forgot the front floor panel goes under the front two holes of the aft control mount. I may also try to shim the front mount. When I look at the bracket it seems to be just off from 90 degrees, like the bracket was not bent correctly. Thanks again for the input, the stick bushing make for a feather touch in the pitch axis, I do need to work the aft stick bushing, I have a little too much side to side play but the front stick has non slop at all. . Thanks guys, you have been very helpful as usual.

Kevin,

Just to make sure I under stand, slotting means you oblong the 4 holes that attach the aft mount so you can move it around for best fit then tighter down the bolts?

Cheers

 

[Kevin Horton]

Kevin,

Just to make sure I under stand, slotting means you oblong the 4 holes that attach the aft mount so you can move it around for best fit then tighter down the bolts?

Yes. You could either do that, or use shims somewhere else in the system. I honestly don't recall which I did, and I am on a different continent than my aircraft right now, so I can't got look at it.

 

[John Collier]

I ran into this two weeks ago

I tried everything.... shims and enlarging holes etc. In the end, what I found was that when I was trying to tighten down the two bolts that hold the control column bearings, I was turning the bearings ever so slightly with the bolt and jam nut. I ended up taking a small shim and placing it between the bearing and control column mount. After I tightened down the bearing i removed the shim and the tightened bearing was straight. I was nervous about damaging the bearing...but it turned out OK in my case.

Good Luck
John

 

[Webb]

Thanks Guy

RV8's are different from the side by sides in this regard. In fact, they're exactly opposite. The stick bushings are on the pitch axis on an RV8, not the roll axis.

Opps - Good advice for the 7, not 8. Thanks.

I assume the wing bellcrank info is still valid.

 

[nucleus]

Ditto...

I had this exact same problem. I pried the ears apart just a bit and it eliminated the binding.

Hans