U Bolt replacement

I used bottle jacks on top of a stack of dunnage ... crossed 4x4s and plywood squares. The ACA jack adapters help a lot. I secured the tail and wings with takedowns and put the tailspring up on a jackstand. I'll post some pictures later.

Woke up this morning and the wind was honking. Plane is currently in a shade hangar so I freaked out a bit. Went to check and it was fine. Structure at the end shielded it. I tightened everything up good to make sure. Hopefully will have the gear back on by Tuesday, after I paint them, though I am still considering ordering reconditioned legs from rainbow Ron.

No problem getting anything out of the frame. The only sticking point was the thru bolt and the gear leg. I will be careful to use antiseize when I assemble. I think maybe paint in the holes might have caused it to freeze up, so I will clear that out before assembly..
 
Alignment is critical. As you tap the new bolt in place make sure that the gear leg is not at a different angle - it can become a Chinese finger trap.
 
Rainbow Ron sent me an email today saying he had a pair of reconditioned steel gear ready for shipment. I ordered them. At 800 bucks, it's a good stopgap until I decide to do the aluminum gear, which I will eventually. FWIW, the lead time from ACA for Aluminum gear is 6-8 months.

Should have the steel gear in a week. Will post before-and-after pics.

For reference, here is a side-by-side of my old gear legs. I did my best to align the upper ends. You can see the lower end on the right is extended about 1/2" further out.

I still would prefer the Aluminum gear, but we'll get to that later.

20210221_013521.webp
 
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The folks at Grove here in San Diego are busy. They make the aluminum gear legs for ACA.
 
Yep, Jerry Mehalf from ACA said on FB that they were backlogged 6-8 months on orders. I had a chance to order a pair in stock a few weeks ago, but dawdled too long.

What a mess aviation is, with all these single source parts.
 
A $100 Harbor Freight engine hoist might have helped. I always have a backup when under these things.
 
OK, got the reconditioned gear legs from Rainbow Ron. Set them side by side with my legs and TBH I cannot see any difference in dimensions, curvature, angles, etc. Perhaps they will flex less under load because they have been retempered?

They d0 look great. Resurfaced and primed nicely. I painted last night with enamel and hardener, and plan to install today if the paint is fully cured.

PXL_20210306_161930184 (1).webp
 
One huge issue with disassembly was clearance between the thru bolt and the hole on the gear leg. Very close tolerance, and stray paint fills the gap. It was seized up pretty good and very difficult to disassemble, because there was no good way to get opposing pressure on the gear leg and bolt. I am going to clear out the paint overspray from the hole and use antiseize to try to prevent a repeat. If anyone takes theirs apart, recommend trying to find an automotive ball joint separator or similar tool that fits the gap between the bolt head and the frame.
 
the steel legs from my 8kcab project are going out west to be reconditioned and then they'll end up on my Citabria. thanks for posting the info and pics from your swap, should help mine a lot when we get to it. :)
 
Bartman said:
the steel legs from my 8kcab project are going out west to be reconditioned and then they'll end up on my Citabria. thanks for posting the info and pics from your swap, should help mine a lot when we get to it. :)
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Roger, I'll try to remember to take some pics of the process as it comes back together.
 
Might want to check with Ron re: retempering. I think they are just cold-straightened.
 
Bob Turner said:
Might want to check with Ron re: retempering. I think they are just cold-straightened.
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they're definitely not cold-straightened. Jim is the guy that does the gear legs and he's a full blown repair shop with crack detection techniques, heat treating skills, and whatever else you'd expect for the job. If you call and talk to him he'll give you the full rundown on what he brings to the party to make sure the gear are first repairable and then what can be done depending on how badly each leg is out of spec.
 
Ok, got about 80% thru the install yesterday. Bird is off the jacks and back on gear. Hope to finish today.

One minor (hopefully) issue: the brake lines are pressing against the bolt heads. Going to grab a tubing bender and try to reroute slightly.

Initial impression: the new gear legs are a significant improvement. Aircraft sits level and both wheels have positive camber. Will post photos tonight.
 
Any idea how those torque nuts work? Do the threads deform? Or is the nut coated with some kind of locking compound? Asking because I'm second-guessing myself on one aspect of assembly, and trying to decide whether loosening and retorquing is an option.
 
If I remember right, those nuts are squeezed or tapered at the end of the nut. You will be fine to loosen and retorque
 
Here was my tool setup for loosening and tightening the inboard thru bolts. Torque wrench and hex bit socket on the bottom, 12 pt box wrench on top. It worked OK, but involved cutting a pair of 1" holes in the belly fabric. No big deal, but did drag out the repair time because of the patches in an awkward location. If I had to do it again, I would probably try to find a 12 pt box end torque extension for the top, and a low profile hex bit for the bottom, in order to avoid punching the fabric. I suppose an inspection ring would work too, but it might be tricky to get the ring directly under the bolt head. There is a metal lip running about 2 inches back from the belly fabric bracket, and the hole is only about 1/2" off the edge of that.

PXL_20210306_200807040.jpg

One disassembly tip for anyone who stumbles across this thread: the thru bolts were very difficult to remove. The bolts slide freely in the fuselage frame but are a very tight fit in the gear leg hole. In my case I think some stray paint caused them to freeze. It was hard to apply downward pressure on the bolt while simultaneously applying upward pressure on the gear legs. I did not anticipate this problem, and had to improvise. I used a chisel and stacked wrenches to gradually pry the bolt head downward from the gear leg. Took about 2 hours per bolt, and tore the holy hell out of the bolts. With hindsight, brains would have been better than brawn. I would suggest clamping the gear leg to the fuse frame member above it, using a pry bar to lever the top of the bolt head down flush with the fitting, then finishing the job with a tie rod pickle fork between the bolt head and gear leg.

On assembly, I cleared the holes of excess paint, and applied aluminum anti-seize to the portion of the bolt shaft in contact with the gear leg. Hopefully that plus improved removal technique will make the process go smoother when I upgrade to aluminum gear in a few years.
 
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