Eliminating Play from the 4-Place Control Sticks

[jaredyates]

I currently have the control stick assembly removed for unrelated maintenance, but it has always had some play in pitch. The first time I tried to fix this, I purchased a .254" reamer, and used a lathe to turn a 5/16 bolt down to fit. All of that effort yielded about the same amount of play on the first stick, so I didn't do it on the other. The amount of play isn't miserable... I've been living with it for 350 hours, but I'm wondering what strategies others have found beneficial?

[schu]

Someday after I'm flying and bored I hope to remake the control system with cnc aluminum parts and bearings. It's years away if ever though.... I just don't see a way to make the existing system super tight without compromising smoothness.

[alaskabearhawk]

Russ Erb put in these bearings from the get-go: R4FF MRC BEARING. Look at his build CD for more.

[Battson]

Most of the free-play seems to come from the welded brackets which attach it to the floor.
I have no idea how to reduce the play there, apart from a full redesign and installing bearing blocks. Too hard basket.

[tf104]

I noticed this when I built my control sticks. The bolt was a little under and the tube was a little over making for a bad connection. I drilled out the bushing to accept a new tube with a smaller id, and installed it with green Loctite then reamed the hole to .250 , This worked out really well,

[jaredyates]

I asked Russ if he still liked his lss4 bearing setup and he wrote me a message about how it ended up being about the same. The bearings were still binding when he tightened the bolt if the length of the stick bushing was not exactly perfect, and the race was also prone to move in his installation. The bearings are also not cheap, about $40 each with 4 required .

[Battson]

I asked Russ if he still liked his lss4 bearing setup and he wrote me a message about how it ended up being about the same. The bearings were still binding when he tightened the bolt if the length of the stick bushing was not exactly perfect, and the race was also prone to move in his installation. The bearings are also not cheap, about $40 each with 4 required .

That is good to know - scratch the ball-bearing idea off the list.

I am also keen to solve this issue.

So we know we can get an interference fit at the main bolt, to remove play there.
That leaves the hinge blocks on the floor. I have been using heavy grease and that lasts for a short time (5 to 10 hours of active flying, longer in winter or cross-country). Maybe a thin shim made of something durable like nylon, or a greased thread, secured with an appropriate clamp or clip.

[jaredyates]

I haven't noticed any play in the hinge blocks yet, though perhaps if the roll pivot bolt fit tighter, I would.

[Battson]

I didn't notice it initially either, until I reduced the play in the main bolt. After about 400hrs flying I became more consciously aware of it and it started to annoy me.

[Nev]

I noticed this when I built my control sticks. The bolt was a little under and the tube was a little over making for a bad connection. I drilled out the bushing to accept a new tube with a smaller id, and installed it with green Loctite then reamed the hole to .250 , This worked out really well,

I'd be interested to get updates from people on this. I'm getting a reasonable amount of play at the main stick bushing on both sides and more noticeable on the left which is possibly from wear. For info I haven't noticed any play from the mounting assembly yet at nearly 200 hours.

[noema]

On my Patrol rear stick I had a lot of lateral play. Not sure if the tolerances where too big or I reamed too much. After considering doing something with bushings or lathing down a bigger bolt I got out the TIG welder. I welded the through hole shut. Then I re-drilled it. This took out the play effectively.

[Nev]

I noticed this when I built my control sticks. The bolt was a little under and the tube was a little over making for a bad connection. I drilled out the bushing to accept a new tube with a smaller id, and installed it with green Loctite then reamed the hole to .250 , This worked out really well,

Any reports on how this worked out in the longer term ? Seems like a relatively simple solution if it does the trick.

[Battson]

After more recent experience and consideration of this problem, I have halfway given up on this idea.

Once the cables are tensioned correctly (mine have been a little too tight - which can have serious consequences), I can now see the sticks appear to have an unavoidable inch or two of play on the elevator, just taking the tension out of the long cable system before the elevators start moving.

[AZBearhawk272]

Jonathan,

Can you elaborate a bit more on where your tensions were and what the issue was?
I have been tightening up turnbuckle by fingers until the deadband slop just goes out of the system, have not yet put a tension meter on the cable run.

Kevin D
#272

[Nev]

What is the serious consequence ?

[triumphantduke]

I've placed a piece of silicone "baffle" material as a dampener in-between the airframe and the rudder pedal attach point, and plan to do the same to the stick assembly - trying to isolate some vibration from that direction. My line of thought was that the cable itself is a dampener, so with dampening the airframe attach point, I may reduce the rate of play increase. 2nd line of thought is that with the areas of rotation won't be perfectly in line, (once attached to airframe) and our friendly tolerances, the dampener would allow things to line up. I've had difficulty seeing any failure modes introduced by doing that... Thoughts/feelings/concerns?

(warning: there is no reason to do what I posted, I am not a licensed professional, barely even a bearhawk builder so far)

[jaredyates]

I've placed a piece of silicone "baffle" material as a dampener in-between the airframe and the rudder pedal attach point, and plan to do the same to the stick assembly - trying to isolate some vibration from that direction. My line of thought was that the cable itself is a dampener, so with dampening the airframe attach point, I may reduce the rate of play increase. 2nd line of thought is that with the areas of rotation won't be perfectly in line, (once attached to airframe) and our friendly tolerances, the dampener would allow things to line up. I've had difficulty seeing any failure modes introduced by doing that... Thoughts/feelings/concerns?

(warning: there is no reason to do what I posted, I am not a licensed professional, barely even a bearhawk builder so far)

I have strong feelings about not doing this. I think it is fixing a problem that isn't a problem, and introducing some threats on some of the most important hardware in the airplane. The silicone will prevent you from making any reasonable torque on the mounting bolts, and over time the silicone will degrade and make the attachment loose. I'd put this in a crucial/structural category and would not make any deviations from the plan without talking to Bob first.