RudiGreyling

RudiGreyling

Well Known Member
Hi Guys

I want to check your experiences.

I'm bussy assembling the center section and bolted the control coloumn and stick to it.

If I keep the control column stationary, and I move the stick forward and back, I get 1/8 - 1/4" play on top of the stick (Yellow Arrow).

The play orginate between the brass bush and the control stick housing (Red Arrow). It is NOT the bolt or bolt hole in the bush or hole in the control coloumn. It looks like the hole in the control stick bush is just too big to fit the brass bush decently?

This sounds like a lot of play to me, since it will only get worse as you add linkages all the way to the elevator.

Is this amount of play normal?

control_column_play.jpg


Thank You,
Kind Regards
Rudi
 
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With both sticks installed, I can move one relative to the other a tiny bit. It might be 1/8".

You're saying the outside diameter of the bushing is not as large as the inside diameter of the tube welded to the control stick?
 
This may be worth a shot

I guess that little bit of play translates to 1/8 - 1/4 with the long moment of the stick.

I wonder if putting some bearing grease around the brass bushing would help? It seems like it would work in the short haul but I am not sure if this would be a long term solution. I'm sure others will chime in to let us know. Good luck.
 
This is a common problem

Rudi,

I found there to be quite a bit of play on the left stick and very little on the right. After further investigation, I noticed the was too much in the left stick bushing tube. I measured the inner diameter of the bushing tube with gauge pins and found the hole was tappered and oversized compared to the right stick bushing tube.

I called Van's about this and was told that "they were all that way" so there was no need to send it back for a replacement.

My understanding is that the inner diameter of the tube is whatever the stock tubing diameter is. All they do is run a reamer through the tube after welding to clear out the diameter if there is any warpage due to the welding.

My plan is simple. I am going to purchase the closest reamer size to the largest inner diameter of the bushing tube. Ream the tube until the inner diameter is no longer tappered and then machine a new bushing to properly fit in the new diameter.

For clarification, the control sticks pivot around the bushing. The bushing is fixed to the lower weldment with the 1/4" bolts securely tightened down. The bushing should not be free to rotate around the bolt once tightened down.

I hope this helps.
 
You want as little play in this area as you can get. My original setup had a bit of play as my bushing was tight and I drilled out the tube to fit. I ended up over doing it and had play in the setup. I could feel it in the elevator as a clicking sound and play when bouncing it back and forth. It worked fine for 450hrs, but finally bugged me too much this year.

So at my 3rd condition inspection I ordered a new pilot stick and bushing and remade the parts. The new stick and bushing were pressed together tight and would not move without a drift punch. After removing the bushing and reaming with a straight reamer until I just had a smooth fit with no play, I was good to go. I put some wheel grease on the bushing, reassembled everything and now there is NO play in the elevator. While flying now the slightest nudge of pressure on the stick starts a climb or descent just as it was designed to be.

To me it was worth redoing the part to make it right.

Lastly, I would think 1/4" is quite a bit of play. I'm talking less than 1/16 for my original one that bugged me.
 
Ditto guys,

The play originate from between the brass bush outside diameter and the inside diameter of the welded stick bush.

I contacted Vans, they say this is normal, and should be like that +/- 1/8" play. They also say you'll never feel it in flight. But here we hear at least from 'akarmy' that he did notice it during flight.

Now I can understand a final play of 1/8" after everytihng is installed and linked up, but 1/8-1/4" on only one hinge-point??? I don't like it.

While everything is appart I think I'm going to try and fix it. Better now than later while flying..wishing I did it. Looks like I will end up sending my control stick assembly to some machine shop to redo a brass bush slightly bigger diameter with a better slip fit. They can also check the play before handing it back. The cost should not be that much to turn 2 brass bushes that fit perfect. At least it will give me peace of mind.

Regards
Rudi
 
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FWIW, I have a good 1/8" of play in my pilot's stick on my RV-7. Been like that since day one. Yeah, you sure can feel it when the plane is not flying. But in the air, you don't even notice it. It's there, but it has no effect on flying qualities.

It's on my list of things to fix at some point, but it's very low priority.

I also have a trim tab that has about 1/8" of play at the trailing edge. Everybody says both of these things will keep me from being able to trim the plane for level flight. Whatever. The thing flies hands-off. And I have 258.1 hours in formation with no ill effect. It's not like it's causing a problem.

My message here is -- just don't sweat it. Fix it if you want to, that can't hurt, but as Van's said, it's normal. Press on!
 
Tighten control stick attachment nut

I had approximately 1/8? play on the left-hand stick since day one and it too was annoying on the ground, but was not perceptible in the air. I was ready to replace the bush during annual last month, but after close inspection, determined the play was created in the bracket through hole (perhaps a few thou? oversize). I applied a fair amount of bearing grease to the bolt, bush, bracket then tightened the castle-nut maybe one additional ?flat?. The very slight tightening seems to have done the trick without creating unwanted friction in the joint. I suggest trying this before cutting metal.

Steve Campbell
N601SC, RV-6 140 hours
 
DO NOT Secure the bushing in the bore

IGNORE THIS SUGGESTION. I MISUNDERSTOOD THE FUNCTION OF THE COMPONENTS. THE BUSHING IS SUPPOSED TO BE FIXED BY THE CLAMPING FORCE OF THE BOLT THAT HOLDS IT IN PLACE. THE CONTROL ASSEMBLY IS SUPPOSED TO ROTATE AROUND THE BUSHING. DO NOT USE LOCKTITE IN THIS ASSEMBLY.

DAVE COLE

If the play in the stick results from a loose fit between the bushing and the bore of tube that holds it, a simple answer is to use a retaining compound to secure the bushing to the bore. Loctite makes retaining compounds that are intended for this purpose. The following is from the Loctite website:

?Loctite Corporation, the pioneer of anaerobic adhesives, has applied this technology to create retaining compounds that increase the shear strength of cylindrical, non-threaded assemblies. Finding wide acceptance as a standard method for assembling press and slip-fitted parts, Loctite? Retaining Compounds fill the "inner space" between components and cure to form a strong precision assembly. Formulated in a selection of viscosities, gap filling ability, flexibility and strength characteristics, Loctite? Retaining Compounds can be applied with automated process equipment or dispensed manually.?

The use of Loctite retaining compound is an accepted industrial practice that improves the integrity of slip-fitted assemblies.

Dave Cole
RV-7 wings
 
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Dave Cole said:
If the play in the stick results from a loose fit between the bushing and the bore of tube that holds it, a simple answer is to use a retaining compound to secure the bushing to the bore. Loctite makes retaining compounds that are intended for this purpose. The following is from the Loctite website:

?Loctite Corporation, the pioneer of anaerobic adhesives, has applied this technology to create retaining compounds that increase the shear strength of cylindrical, non-threaded assemblies. Finding wide acceptance as a standard method for assembling press and slip-fitted parts, Loctite? Retaining Compounds fill the "inner space" between components and cure to form a strong precision assembly. Formulated in a selection of viscosities, gap filling ability, flexibility and strength characteristics, Loctite? Retaining Compounds can be applied with automated process equipment or dispensed manually.?

The use of Loctite retaining compound is an accepted industrial practice that improves the integrity of slip-fitted assemblies.

Dave Cole
RV-7 wings
Click to expand...

Dave, the control assembly rotates around the bushing, which is is held firm by the bolt. Your technique would work if the bushing rotated around the bolt, which it is not supposed to do.

I worried about freeplay as well... I had 1/32" total play, but it was not perfect. Vans told me that up to 1/4" was fine, and my inspector says that he had to loosen his linkage up slightly to prevent oversensitivity to elevator control in the flare.

The only significant problem to too much freeplay is the danger of flutter... and that's why I called Vans. If it was a safety problem, I'm sure they would be concerned.

Vern
 
Cool a product made for this problem

Dave, the control assembly rotates around the bushing, which is is held firm by the bolt.
Click to expand...
Agreed

Your technique would work if the bushing rotated around the bolt
Click to expand...
Disagree: The retaining compound is basically a product that is for filling very small voids between rotating, non-threaded surfaces. That is the exact situation we have with the stick barrel and bushing, rotating surfaces. I suggested bearing grease for this same purpose but holy smoke there is a product made specically for the job (thanks Dave!). Whoda thunk.

Put some of this compound in the barrel as well as on the outside of the bushing. I think you will see the stick slop disappear. The question I have is for how long. Since this is a product specifically made for the purpose, I would guess years but that is a guess.

Here are the options as I see them:

1) Van's says that "they are all that way" so I don't seem Vans sending a new one. Do nothing and live with the slop.

2) Get an oversize bushing and have it machined down. Best solution but that is a lot of time, money and resources.

3) Use some retaining compound. Cheap and easy. If the results are not what you want, do option 2. The results using the compound will certainly be better than option 1.


Good luck and let us know what you and what your results are.
 
Retaining compound

Dave Cole said:
If the play in the stick results from a loose fit between the bushing and the bore of tube that holds it, a simple answer is to use a retaining compound to secure the bushing to the bore. Loctite makes retaining compounds that are intended for this purpose. ...
Click to expand...
This is one of the things I really love about these lists. Even if I had thought there was something that does what retaining compound does, I would have never known what it is called. I just checked McMaster-Carr, and they have several different types. I put one of each in the shopping cart - I'll trim it down later. Excellent info, thanks Dave!
 
Retaining compound is intended to, well, retain components. It's not intended for use where parts move relative to each other. You could spend bucks on some specialized compound that's not even designed for this application, or you could just use something like grease or fuelube -- that would take up the space in the same fashion but cost way less (since you already have it in your shop). Either way, it'll probably eventually work out of there. It's a stopgap, not a solution imho.
 
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What's the difference ?

Someone please explain why it's so important that the bolt not
turn on the bushing? (versus bushing turning on the housing)

I plan on brazing the bushing into the stick housing, then using
a close tolerance bolt. I'll set the tension with a castle nut
(to allow turning) and pin the nut. No slop there.
I'd rather do this than have to worry about elevator flutter.
 
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