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My landing gear needs some suggestions, quick!

CAVU Mark

Well Known Member
A few weeks ago my left tire went flat on rollout. I bought new tires and tubes which I installed today. My gear has been shaky and I thought the new rubber may help. I previously reviewed the wheel/axel alignment and it looked ok.

Today after the tires were installed I started to check things and found I could move the left gear by hand back and forth a few degrees. I looked up and saw the gear/engine mount bolt moving. I removed the bolt and found this. (yes, JB Weld was involved)

https://flic.kr/p/232LTNM

Of course everyone at the EAA chapter had a suggestion but wanted to ask if anyone else has seen this and could suggest a solution without too much trouble involved. One suggest is to make a couple of saddle washers and weld them to the engine mount after alignment. I will also contact Van's after the first.

I decided to post this here first but realize it is a gear problem that could affect a number of models.
 
Yep, that's ugly.

If you're looking to do this without parts replacement, the saddle washer idea sounds like a reasonable option, though getting to the back side of the gear socket to weld will be tight with the mount installed.

Welding up the edges of oversize holes, then redrilling might be an option as well, maybe in conjunction with saddle washers for the belt and suspenders approach.

It might be possible to drill for a larger bolt? How large would the bolt have to be to get a clean hole through the socket and gear leg?

It will be interesting to hear what Van's suggests.

Rusty
 
Replacement bolt options

This year at condition inspection I discovered some slight movement in the gear axle. While investigating, I concluded access for the classic welded washer fix was VERY limited, probably requiring mount removal 😔 The next question was can you even get at the bolt hole with a drill or reamer while assembled and aligned ? I deferred action here in Indiana until warm weather because my problem is detectable but miniscuel. IF you can drill in assembly (properly aligned), I would be happy to make you a custom bolt to fit the next size reamer that will clean up the hole. I believe the next AN bolt is .375, and that might consume too much material for a long term fix. First priority is can you drill in assembly without removing the engine and or mount. If not, a substantial sleeve over the mount may be the best long term option. Just food fo r thought...Larry
 
Do you know what all the dings around the hole are?

It sounds like this was a purchased plane - how long have you owned it. Has someone given it a REAL good going-over to look for other workmanship issues? Putting the gear on comes late in the build. If JB weld was the solution for someone late in the build, I would worry about the issues from early in the build.
 
There are X and Y designation (rather expensive) over sized bolts available that are approved for use on RV gear legs but they are only .015 and .030" over sized. Based on your photo it looks like you will need a bit more than that to fix it.

All of the dents / punch marks look like someones (wishful) attempt at staking/peening the perimeter of the hole to reducing its I.D. That was never going to work in this instance since it usually only gets you a few thou reduction due to plastic deformation of the surrounding material.


My recommendation is that you contact Harmon Lange at Langair machining.

http://www.langair.com/

Langair has made the RV gear legs for decades and Harmon has helped many people resolve loose leg and alignment issues with some very creative fixes in the past.
 
I agree with von - get a taper reamer and taper pin. However, check the back side of the hole to make sure you can do this with the proper size taper pin and get a good clean surface on both holes in the engine mount. There are some older threads on here about taper pins for both nosegear and mains.
 
After having the experience of building and then having to sell due to moving around for jobs, I decided to buy and already built airplane. As an A&P/IA and previous builder I did my own rebuy and missed that the main gear of a -6A was mis-aligned. After going through tires quite quickly, I investigated and found the toe in/out off quite a bit. When I removed the gear leg bolts, I found egged out holes in the mounts and the gear legs. After consulting with Vans, I decided to do a weld repair by filling the existing mount holes with weld and relocating/reaming the holes. It required machining a tool with a 1/8 pilot which I kept open when welding the mount. I then aligned the gear leg clamping everything in place and counter bored out the mount undersized. Removed the gear leg changed the tool to one that picked up the counterbored hole one one side and had a pilot hole to counterbore from the 2nd side. After the basic alignment was established with the relocated holes in the gear mount, I then enlarged the attach bolt by one size (Vans approved) to remove the belmouth shape of the hole through the gear leg.
Worked like a charm. Much easier than any alternate, especially for the -6A that would otherwise have required replacing the mounts and picking up the spar bolts.

Sorry no pics on this but I could describe in more detail in a PM if you?d like.
 
Bolt

I built my first Wittman Tailwind to an old set of plans that did not specify the gear bolt size. I don't remember how I made the decision but I used an AN6 bolt. 1000 hours when I sold the airplane it now has at least 1700 hours.
The AN 6 is the simplest fix. A welded fix would be better but will require removing the engine and mount.
There is an example of a simple drill jig in either Kitplanes or Sport Aviation. Build the drill jig and get an assortment of hardened bushings starting 1/64 undersize, then .371, 372 and maybe .373 depending on the exact diameter of the bolts. What you are trying for is a moderate drive fit. You absolutely do not want the bolt to push in place easily or next time you will be starting with new gear legs.
Jig the gear securely in place with proper toe and start with the 1/64 undersize drill. The titanium bits may work or you could even use carbide tip drills. Slow r/m and moderate pressure, lots of lubricant and stop occasionally to keep everything cool, heat is your enemy. The reamers should be high speed steel, I prefer straight flute. A 1/2" capacity drill motor is optimal, it allows slower rotation speed with more power. PM me for some more info.
 
Might it be possible to drill another hole in the tube and gear leg at a different location, assuming there is a place on the tube to allow sufficient clearance?
 
Gear

That is not possible on the Wittman Gear. The upper portion of the gear leg where the bolt goes is only about 3/4" in length, the gear then steps down in diameter to 7/8* diameter on most RV's and I think 3/4" on some or all 3's. No place to drill an additional hole.
On an A model an artist/contortionist can weld up the holes without removing the gear support structure. I have never heard of anyone doing that successfully on a taildragger.
 
Thanks for all the suggestions. To add some detail, this is a 24 year old 3. Wings were built buy a factory person in OR and the owner did the rest. The wings are great, the rest of the plane is a 6. The wing spar mode has not been done nor do I plan on doing it since acrobatics are not on my list. I lost my 170 so this is the only plane I have to fly and that is what I want to do.

The gear already has a AN6 and the other gear (right) has a bolt and what appears to be an AN4 threaded into the side. That gear seems solid but so did the left side.

It sounds to me that the most correct solution would be to remove the gear and the engine mount and put some new collars on the top of the mount so I can drill new holes. But then I will need to match drill to the gear while being jigged correctly for alignment.

I bought the plane for a good price... moral, a deal is not always a deal.
Ohhhhh the pain.
 
Quite some years ago, I decided to bite the bullet and realign the landing gear on my RV-4 due to excessive tire wear. (The toe out was extreme, don't remember where is was measured from, but I do recall that it was almost 5/16" instead of 0.00 - 0.050")

Anyhow, I pulled the engine mount and had plugs welded into the gear legs and the motor mount holes were reduced in diameter, IIRC. Then everything was jigged up, the holes were drilled out in 1/64" increments on the drill press, and that got things in perfect alignment.

But the other thing I did was to have the motor mount magnafluxed to check for cracks. Sometimes poor workmanship goes along with poor flying skills, and who knows what might be lurking in your airplane. And who knows what the other gear leg looks like, even if it's not (yet) loose.

Yes, this suggestion is over-cautious... unless it turns out that it's not.
 
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If the bolt is a decent fit through the gear leg, how about spot facing the motor mount where it's peened, make a bushing out of 4130 and tack the bushing to the motor mount with the bolt in and tight. Remove the bolt and leg and finish the weld. The bolt would have more bearing surface than the original motor mount tube. The repair would be above the cluster. I don't see how this repair would compromise the mount??

Might leave the bolt in for the weld and replace when finished.

If the leg is oversize, a decent machinist should be able to ream out the leg and fabricate a press in bushing into the leg to get it back down to size. Could carefully be done on the average drill press if you are comfortable with it.
 
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Bushing vs flat doubler

I considered that but prefer the flat 4130 doubler shaped to match the socket. My reasoning is that welding a bushing in place produces a lot of scale on the inside which means the bushing must be reamed a second time. This is not the case with the flat doubler. A heavy wall bushing would help but considering the tight area the bushing is harder to weld.
 
Bushing vs. flat doubler

I am not a certified welder so I didn't see that coming. I get it. The problem I see with a plate is there will be a unsupported area between the plate and the gear leg the thickness of the tube. Might not be a big deal??
 
Bolt

I am not a certified welder so I didn't see that coming. I get it. The problem I see with a plate is there will be a unsupported area between the plate and the gear leg the thickness of the tube. Might not be a big deal??
Not a big deal. The shaped flat doubler is pretty much the standard repair. I think there are a lot more of these repairs than people realize, just not many talking about it. My proposed doubler would be oval on the outside and would be just large enough to extend outside of the peened area. Actually the optimum doubler would be a section of .120 wall tubing cut from a tube with od 1/4" larger than od of socket.
 
....It sounds to me that the most correct solution would be to remove the gear and the engine mount and put some new collars on the top of the mount so I can drill new holes....

I disagree. The next solution is what I think ought to be done:

....My recommendation is that you contact Harmon Lange at Langair machining.

http://www.langair.com/

Langair has made the RV gear legs for decades and Harmon has helped many people resolve loose leg and alignment issues with some very creative fixes in the past.....

My first mentor had a saying,

"If you want it done like downtown,
Take it downtown."

In this case, that means Langair.

Good luck!
Dave
 
Bolt

I am not a certified welder so I didn't see that coming. I get it. The problem I see with a plate is there will be a unsupported area between the plate and the gear leg the thickness of the tube. Might not be a big deal??
Not a big deal. The shaped flat doubler is pretty much the standard repair. I think there are a lot more of these repairs than people realize, just not many talking about it. My proposed doubler would be oval on the outside and would be just large enough to extend outside of the peened area. Actually the optimum doubler would be a section of .120 wall tubing cut from a tube with od 1/4" larger than od of socket.
 
Actually the optimum doubler would be a section of .120 wall tubing cut from a tube with od 1/4" larger than od of socket.[/QUOTE]

OK then. How about slipping a snug fitting .120 solid tube piece over the top. Leave the new piece about 3/16" above in the rear and slightly below the original tube in front for ease of access to weld. Should be able to weld that without removing the mount?

We can keep this going all night!
 
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Weld

There simply is not enough room to do any welding on the aft side of the gear socket. The mount must be removed form the airplane. As I posted before, a talented welder can close up the holes on the 6A main gear.
Who's on first What's on second and I don't know is on third. If you never heard the entire thing this would be an excellent time to look it up. Great stress reliever!!!
 
Who

Abbott and Costello "who's on first" dates to 1938. Audio, video and text available online. One of the all time classics in my opinion.
 
Abbott and Costello "who's on first" dates to 1938. Audio, video and text available online. One of the all time classics in my opinion.

OK then. How about... :eek: How many ways are there to plug a hole?

I've seen it. It's one of my favorites :D

Sorry CAVU
 
Not a big deal. The shaped flat doubler is pretty much the standard repair. I think there are a lot more of these repairs than people realize, just not many talking about it. My proposed doubler would be oval on the outside and would be just large enough to extend outside of the peened area. Actually the optimum doubler would be a section of .120 wall tubing cut from a tube with od 1/4" larger than od of socket.

It is a common repair method but this is a very oversized hole.
That would mean that instead of a single shear point on each end of the bolt it would be in double shear with a slight gap inducing a bending moment.
Less than desirable. I would be looking for a different fix it it were mine.
 
Nothing ever goes wrong....

The report is the gear doesn't align properly. I need to get down to the fabricator doing the work and size things up. The plan is to align the gear and place some fabricated spacers in the holes and weld them to the gear tubes. Perhaps the gear is bent from my learning to land on these springs.

P.S. I know people think highly of Van's but I did send a request to them for a repair suggestion and no reply. Thanks to VAF I have some input, making the VAF contribution worthwhile.
 
..........
P.S. I know people think highly of Van's but I did send a request to them for a repair suggestion and no reply. Thanks to VAF I have some input, making the VAF contribution worthwhile.

Just a thought. I always follow up a Van's email with a phone call.
Sometime the email gets lost in the shuffle between the three techs.
 
The report is the gear doesn't align properly. I need to get down to the fabricator doing the work and size things up. The plan is to align the gear and place some fabricated spacers in the holes and weld them to the gear tubes. Perhaps the gear is bent from my learning to land on these springs.

P.S. I know people think highly of Van's but I did send a request to them for a repair suggestion and no reply. Thanks to VAF I have some input, making the VAF contribution worthwhile.

Did you follow up after you got no reply?

It is fairly common for breakdowns to happen with e-mail (it is not 100% reliable).

One of the common causes of a failed connection with Van's tech. support is for the reply to go in the customers SPAM folder.
 
Repair started

I did not follow up with Van's. I suspect that Van's response would be covered by responses here so I forged ahead.

Today we aligned the gear on the mount which was bolted down to the welding table. A few spacers (3/8 bolt dia) are going to be welded to the mount. A calculated repair considering all the input and that of the fabricator.

I tried to talk him into making the Grove type gear but he wasn't interested. He'd rather build English race bikes.
 
What happened today

Repair consisted of welding steel bushings on the top of the gear tube after alignment. We welded the bushes on with the gear legs in place.

I installed the repaired gear, this would be the second time I had it welded, the first shot did not meet with my alignment specs. The second was closer but when taxied it shimmied worst than ever. Shook everything inside at a fast taxi. Finished the wood/glass mod today and at fast taxi no shimmy. Yeah! Now for a test flight.

Noteworthy points. I used wood on the front and back of the gear. I did not use "oak" as suggested by my fellow EAA members. I used finger jointed pine trim on the front and solid pine trim on the aft. Didn't think about the finger joints until my contractor friend piped up. Used a mill to bore the groove for the new brake lines.

I did contact Langford and they suggested swapping the gear legs and drilling new holes in the top and the subsequent axle holes. I didn't dig that suggestion and carried on with the weld repair.

My gut said I should not jig in the shop but align it on the plane and tack weld it. I think I will listen to my gut next time since I was expecting it not to shimmy without the wood/glass mod. I am a slightly better fiberglass person now.

New Michelin tires, tubes and balancing took place.

I suppose this gear works well if installed correctly from the start but it is not fun as a repair.
 
Gear shmmy

Mark
I had similar experience with my gear. The mount was broken when I bought it, and we replaced with the new motor mount and gear legs. I checked the alignment and it was spot-on, but still would get the shimmy unless my landing technique was PERFECT.
SO I put the wood stiffeners on, I did front and back with Maple, and I let in the round with a router, and even put a channel down the leading edge for my brake lines.
All was great after that, but I had a couple of hard landings in gusty conditions and ended up finding the wood had cracked. I ground the glass out and wrapped it again, but I think the wood being partially un-bonded is still causing a periodic shimmy, mostly as I slow (using brakes) after putting the tail down and approaching the runway turn out.
I need to pull the wheel pants and leg fairings off again and see if I can figure out what needs to be done, but that means jacking the plane up and all that fun stuff.
Feel your pain brother....The round gear legs are more susceptible to shimmy than other types, I wish I could say I nail my landing every time, but I don't. Just part of the RV game I guess.
Cheers
Dave Cronwall
N66GB
 
I am not familiar with the landing gear on a -3, but on the -4 the gear is sensitive to tire pressure. Too much or too little, and it will shimmy. I run 32 PSI. Smoky I think mentioned he uses 30 psi. Just a thought. The plans in the -4 manual spell out how to add the wood to the landing gear, but I never needed it.
 
Are there any other airports you can move to :p

I still haven't figured out how to consistently land this particular RV-3B. Of course it doesn't help that the runway isn't flat, so you kind of have to play the slope. I'm still waiting to find a hangar closer to home since my current hangar is a 3 hr round trip drive. I've joked that I'm staying here where no one knows me until I figure it out :D

Rusty
 
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