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Rudder horn wear bushing

scard

Well Known Member
Advertiser
Today's little project was to deal with the progressing wear of the rudder cable attach hole in the rudder horn. This is after about 1400 hours.

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First up was to make a drill jig. The final hole in the rudder is going to have to be drilled by hand, and I'm going to "move" the hole in order to preserve what is left of edge distance. That calls for a big heavy piece of steel with a perfect hole. Yeah, we can do that. I can't imagine going back to the dark old days without a milling machine.

With the drill jig (big piece of steel with a perfect hole in it), I made up a little test piece to prove process and fit before taking the airplane out of service. Little details like, what is the actual final size of a 5/16 hole drilled by hand with THIS jig? That tells me how big to oversize the bushing for a nice low to medium force press fit.

Off to the trusty South Bend lathe with a piece of stock in the collet closer. In a jiffy I had one bushing for my test sample. Pressed in with the arbor press, yep, just the amount of force I was looking for. I cutoff six more bushings for production use. Their OD ended up within .0002 of my target. I continue to be amazed at the accuracy that I'm able to produce with this old school butt ugly machine. I intend to resolve the latter condition some day when there isn't an airplane project in the shop.

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It is finally time to head to the airport and take the airplane out of service. It might be for an hour or two, or I might be completely rebuilding the rudder... The rudder was off in moments and up on the bench in the A/C office. I clamped up the drill jig EXACTLY where I wanted the final hole to land. Perfect isn't fast and deciding exactly where to place this hole takes a little soul searching as there is no good location. I use extremely high clamping force here with the "jig".

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The holes are drilled with a freshly sharpened bit at too high of a speed with too light of pressure so as to keep from walking the jig toward the center of the hole. Slow and steady and you have moved the perfectly round hole. Albeit with a more dull drill bit.

The bushings pressed in exactly the same as the test coupon back in the shop. I touched up the bolt hole with a reamer. I'm very happy with the slight reduction in ID after pressing in. That tells me that I got my materials just as intended and that there is still good strength in the parent part.

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Like I said, this isn't ideal. I wish Vans wouldn't pre-drill these holes and give us much more material to work with. But, this is definitely better than just waiting for the failure. I'll keep an eye on it and if need be, I'll make another horn from scratch with more meat on it. I figure that this bushing is good for another 1000hrs and I already have the replacements made. The rudder is back on the airplane and back in service.
 
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Scott, good solution to the problem.

Nice to not only have the tools, but the skill to use them:D
 
The RV-3 plans call fopr a pushing right off the bat!

Good repair Scott - thanks for sharing.
 
My -8 project is getting bushings today. Tanya commented yesterday that we have always said that we are trying our best to wear it out. I guess we're meeting our goal.
 
Rudder Horn

Another way to "skin this cat", is to buy some steel flat stock 1/2in. wide X 1/8th thick from your local Ace or Lowes Depot. Cut it length-wise about 1.5 in. longer than the rudder horn. Determine correct hole sizes and drill 4 holes; two that fit the present holes in the rudder horn and one forward and one aft of the horn. Bolt the steel strip to the horn using the already present holes in the rudder horn. Attatch the rudder cable clevis to the forward hole and the rudder springs to the aft hole of the steel strip. Do this for both sides. Might have to adjust tail wheel springs a bit.

Hope this makes sense! Don't have any pics

The strip is sacraficial so if it ever wears out, replace it with another. No danger of ever ruining your aluminum rudder horn.:)
 
Another way to "skin this cat", is to buy some steel flat stock 1/2in. wide X 1/8th thick from your local Ace or Lowes Depot. Cut it length-wise about 1.5 in. longer than the rudder horn. Determine correct hole sizes and drill 4 holes; two that fit the present holes in the rudder horn and one forward and one aft of the horn. Bolt the steel strip to the horn using the already present holes in the rudder horn. Attatch the rudder cable clevis to the forward hole and the rudder springs to the aft hole of the steel strip. Do this for both sides. Might have to adjust tail wheel springs a bit.

Hope this makes sense! Don't have any pics

The strip is sacraficial so if it ever wears out, replace it with another. No danger of ever ruining your aluminum rudder horn.:)

I would be concerned having steel bolt wearing on a steel plate. The mild steel plate will certainly wear faster, but the bolts would see more wear than if a bronze busing was used. I would remove your bolts at every CI if I was to use this approach.
I remove my bolts every once in a while and have found no visible signs of wear from the stock aluminum. I am sure bushings are in my future, but with more than 600 hours, thus far, the wear is not discernible on the arm, or bolt.
 
Hey Scott can you cut two pieces for me? I am almost at 22C wear. I can even come to pick them up...


Added: .... And two for 215TK as well. :D
 
Hey Scott can you cut two pieces for me? I am almost at 22C wear. I can even come to pick them up...


Added: .... And two for 215TK as well. :D

Vlad and others, I only made the bushings myself because I could. It is a very standard part. Look on McMaster for a bushing with ID 3/16, OD 5/16 (or 1/4 if that is your preference). They'll probably be 1/4 long, so you'll have to cut them down. Mine were .0007 oversize of the final hole that they were pressed into.
 
Pre-flight

part of my pre-flight is to rotate the clevice bolts a quarter turn on each of the rudder attach points. This is supposed to help keep the bolts and the hole from eroding. Don't know if it does, as I only have 400 hrs on the ship.
Comments?
Jim Frisbie
Rv-9A
 
part of my pre-flight is to rotate the clevice bolts a quarter turn on each of the rudder attach points. This is supposed to help keep the bolts and the hole from eroding. Don't know if it does, as I only have 400 hrs on the ship.
Comments?
Jim Frisbie
Rv-9A

Can't hurt....
 
Here's another alternative, which also helps space the chains away from the rudder bottom a bit more:

tailwheel%202%20.jpg


You can get the eyebolt, clevis, etc. from ACS. Also, if you put a bit of heat shrink tubing around the chain before installation, it won't scuff your rudder paint as easily.

You'll notice that there aren't any of those teardrop shaped clips that come with the Van's setup either. Those things have a bad habit of disconnecting themselves.
 
Here's another alternative, which also helps space the chains away from the rudder bottom a bit more:

You can get the eyebolt, clevis, etc. from ACS. Also, if you put a bit of heat shrink tubing around the chain before installation, it won't scuff your rudder paint as easily.

You'll notice that there aren't any of those teardrop shaped clips that come with the Van's setup either. Those things have a bad habit of disconnecting themselves.

Different solution to a different problem. It is my opinion that the whole eye bolt thing isn't appropriate for the rudder cables, even though we've seen it done.
 
Here's another alternative, which also helps space the chains away from the rudder bottom a bit more:

tailwheel%202%20.jpg

I have a similar or same setup. Had the rudder off last week to inspect the holes. Still almost like new after 2,895+ flying hours.
 
I was at the hangar today doing some routine maintenance.
I noticed the rudder cables and thought of this thread. So I checked to see just how much play I had in the rudder horn bolt holes.

I couldn't detect any! And that's with a 1,015 hours.

This area stays wet with smoke oil residue:) That must help.

Mark
 
Excellent Mark! Keep 'em smokin' and all will be ok. Get that added to the Vans instructions will ya' :). OR, dude, hold position with wings level with lead, use rudder to adjust... You are clearly cheating :).
 
Scott,

What is wrong with using the eye bolts and clevises? They're certainly bulletproof on the installations I've seen, including my own. And it certainly reduced the chain rubbing on my rudder bottom.

If it's just cost and complexity, I'll take that over a rudder horn repair every time.

If it's the concern over a slight side load on the eye bolt, the heavier and faster Rockets using them successfully would seem to negate that concern.

And if Gary can run them for 2900 hours without appreciable wear, well, that trumps my 350 hours without wear (on turf).
 
Scott,

What is wrong with using the eye bolts and clevises? They're certainly bulletproof on the installations I've seen, including my own. And it certainly reduced the chain rubbing on my rudder bottom.

If it's just cost and complexity, I'll take that over a rudder horn repair every time.

If it's the concern over a slight side load on the eye bolt, the heavier and faster Rockets using them successfully would seem to negate that concern.

And if Gary can run them for 2900 hours without appreciable wear, well, that trumps my 350 hours without wear (on turf).

I see no problem for the tailwheel attachment you have pictured. I'm talking about the rudder cable attachment.
 
Scott,

Once again, please tell me what you see that is wrong. If it is indeed something that can be improved, I'd like to know.
 
While taking inventory of my new -14 kit yesterday I noticed that my rudder horn has small stainless bushings pressed in the cable attachment holes.
 
Here's another alternative, which also helps space the chains away from the rudder bottom a bit more:

You can get the eyebolt, clevis, etc. from ACS. Also, if you put a bit of heat shrink tubing around the chain before installation, it won't scuff your rudder paint as easily.

You'll notice that there aren't any of those teardrop shaped clips that come with the Van's setup either. Those things have a bad habit of disconnecting themselves.
I have the exact same setup but the issue is not with the tailwheel cables but rather where the ruder cables come out of the fuselage and attach to the rudder horns.

Thanks Scott! I need to check mine.
 
While taking inventory of my new -14 kit yesterday I noticed that my rudder horn has small stainless bushings pressed in the cable attachment holes.

If memory serves me right, I believe my rudder also has a small bushing. I have not taken the bolt off yet to confirm this.
 
I have the exact same setup but the issue is not with the tailwheel cables but rather where the ruder cables come out of the fuselage and attach to the rudder horns.

Thanks Scott! I need to check mine.

Thanks Bill, my words were failing somehow.

Started my condition inspection today. Removed the rudder cables and found this :eek:



Yep, Vlad, it might be time to act. I've been watching our progression here for about 18 months. You might be able to do a 1/32" wall bushing if things really got critical. The bushing replacement process will only work so many times with off-the-shelf bushings... Clearly a bushing is important here. The comment of a stainless bushing from Vans is surprising to me without whatever guidance came along with that. That indicates a clear life limit on the bolt to me?

Those that are building more "modern" RVs (mine is only 7yrs old), please post pictures of the more modern plans and parts! There are a lot of us that are interested in the factory changes that we aren't privy to as we do maintenance.
 
OK, thanks for pointing out exactly what you were talking about. It obviously wasn't clear to me that you were indicating a wear problem with the front hole on the rudder horn. (Because I had a serious brain spasm and didn't re-read the OP. Sorry)

I haven't seen this area become a problem on the several local RVs, but perhaps it's just hidden and we've not noticed it yet.

Or perhaps there has been a bit too much load on these particular holes? The hole in the photo shows a bit of evidence of deformation, as opposed to simple wear. The curled up edge of the hole is what I'm talking about.

Here's what I'm getting at, and I am guilty of this too. It is all too easy to push simultaneously on both rudder pedals in order to move your butt further back into the seat. IMHO, this is a bad thing to do because it puts all of your weight on the rudder horn and rod end bearings, and also the rudder pedals.

Or maybe it's just simple wear from environmental dust, dirt, etc.

Just my opinions..... YMMV!!

I suppose we can all agree... no matter what, these planes are never gonna be "maintenance free". That is the standing joke around here. All of us agree that when we build that next airplane, we're gonna make it "maintenance free". Stay tuned. I'll let you know if that ever happens! :rolleyes:
 
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Let me elaborate a bit more. My opinions, of course, YMMV.

If you're seeing this kind of wear on an "A" model RV, then I'd investigate "why". The load on the rudder, without a tailwheel attached, shouldn't be enough to cause significant wear on those forward holes. My opinion.

Is it a case of simply not having enough lubrication on the hole? Is it overstressing from aerobatics, heavy feet, or just from the rudder swinging in the wind?
 
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The Anti Splat guys have been looking for product ideas this may be a good match.

Allan, you out there?

Larosta
 
Bushings came from McMaster. I will cut them and install tomorrow morning. Still undecided which OD to use. Any suggestions?


 
Bushings came from McMaster. I will cut them and install tomorrow morning. Still undecided which OD to use. Any suggestions?

Sweet! I chose my size based on those that are available commercially because surely me or someone else won't feel like making them from scratch in the future. I was very interested in the press force so was very happy that I was able to produce a better expected tolerance than published in many of the available bushings. .0015 - .002" was much more press force than I wanted to apply to the aluminum meat that I had left. I expect them to wear just a little bit faster than the 2024 aluminum. Actually, yours will wear just a bit faster than mine will, based on the material. It is a big give and take in all directions. The big key for us is to "move" the hole. With the smaller OD, you don't have to move it as far, but also don't solve as much of the problem. Next time I might try an end mill in the drill jig instead of a twist drill. Keep us posted if it works out.
 
Like the childrens game, one of these things is not like the other. With over 600 hours my holes are still pristine. I measured the hole with a ball gage and mic'd them. No signs of wear. You can even still see the slight chamfer from the deburring and it is uniform all the way around the hole. Both sides, top and bottom. The bolt has some wear of the cad plating, but still measures within a few thousands of new, well within tolerance, so again, little to no wear. I chose the right side for obvious reasons.

Right or wrong, I do not tighten the bolt to the clevis. I tighten and then back off so the bolt will rotate freely in the hole and clevis. I lubricate with LPS 2, every 25 hours minimum.

Vlad, pictures can be deceiving, but it appears there is corrosion in the hole. If so, this would cause accelerated wear. Perhaps it is just dirt.

I do not have any wear at 600 hours and do not expect anything to change at 1200 or 2400.

Something else is going on here to see this kind of wear Scott and Vlad.
241jlf6.jpg
 
I should add that I do quite a bit of formation flying and aerobatics. Just another data point.
 
Like the childrens game, one of these things is not like the other. With over 600 hours my holes are still pristine. I measured the hole with a ball gage and mic'd them. No signs of wear. You can even still see the slight chamfer from the deburring and it is uniform all the way around the hole. Both sides, top and bottom. The bolt has some wear of the cad plating, but still measures within a few thousands of new, well within tolerance, so again, little to no wear. I chose the right side for obvious reasons.

Right or wrong, I do not tighten the bolt to the clevis. I tighten and then back off so the bolt will rotate freely in the hole and clevis. I lubricate with LPS 2, every 25 hours minimum.

Vlad, pictures can be deceiving, but it appears there is corrosion in the hole. If so, this would cause accelerated wear. Perhaps it is just dirt.

I do not have any wear at 600 hours and do not expect anything to change at 1200 or 2400.

Something else is going on here to see this kind of wear Scott and Vlad.

Wow, that is amazing. We do have this huge rudder compared to the -6. I'm pretty sure much of mine is contributed by tons of heavily pushing it around in formation. It has also never been lubricated.
 
. It has also never been lubricated.

I think you might have found the cause, or at least a contributor to it. These must be lubricated, and often, especially on tail daggers where there is more exposure to spray and dirt. Regardless, even in A models, steel on aluminum isn't going to wear well without lubrication.
Your bushing fix is well done. Lubricate it to extend the bushings life and you may never need another.
 
First size (1/4) bushings installed. Will report wear and tear in three hundred hours or in a year whichever comes first. All new hardware installed. I don't fly aerobatics or formation but I do use the rudder a lot :)





 
Looks great, Vlad. That should provide for many hundreds of hours of crazy slips on approach. :D

Could excessive/insufficient cable tension be a factor here?
 
Could excessive/insufficient cable tension be a factor here?[/QUOTE said:
I seriously doubt it. In both examples graciously shared here in pics, it appears to be galling due to inadequate lubrication. The evidence is in the splaying of material outside of the hole. This is indicative of a surface tear as the aluminum "gums up" on the steel bolt resulting in higher friction and displaced material.

Vlad - I would encourage you to radius the corners of your rudder horn. While extremely unlikely to be an issue in this thick of material, it is a point of stress that can easily be relieved. Since your part is not painted, a couple of minutes with a file and your done. It also get's you style points!
 
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