ZEB locknut on high strength bolt

[Ed Haywood]

What is the locking mechanism on the nut at far left in the picture? Deformed thread, some kind of coating? Is it strictly single use, or can it be loosened and retorqued some number of times without losing its locking ability or mechanical strength?

 

[Bell206]

What is the locking mechanism on the nut at far left in the picture?

The crown (top) portion of the nut is crimped providing the self-locking.

Is it strictly single use, or can it be loosened and retorqued some number of times without losing its locking ability or mechanical strength?

Not familiar with ZEB as that could be a mfg name. But it looks like a BACN or NAS spec 12 pt flange nut. Whether single use is dependent on the installation instructions. Otherwise you usually check for a minimum tare torque on the nut and compare to spec before reusing it and usually can be reused until the tare torque drops below the minimum.

 

[Dan Thomas]

Ah. Citabria landing gear 500-hour bolt replacement. I always replaced those nuts, too. Cheap insurance. At less than $20 each, and there are six of them, it adds 23 cents to each operating hour's cost.

That's the price from Univair. I bet other places would have them cheaper. I used to buy from Aviall.

 

[Ed Haywood]

I always replaced those nuts, too. Cheap insurance.

I replaced with new, but am second-guessing myself on one aspect of the process. Wondering if loosening and retorquing would cause any problems.

I had the old style u-bolts. As far as I can tell, they were original from the factory 42 years and 2,000 hours ago. Really happy to upgrade to bar style. I ordered from ACA; I support them when I can.

That does not extend to paying $7,000 for aluminum Grove landing gear, at least not yet. I replaced my sagging gear legs with reconditioned steel gear from rainbow Ron. Appears to be a big improvement, at least based on how it sits. I am anxious to see how it handles.

 

[Dan Thomas]

I replaced with new, but am second-guessing myself on one aspect of the process. Wondering if loosening and retorquing would cause any problems.

I had the old style u-bolts. As far as I can tell, they were original from the factory 42 years and 2,000 hours ago. Really happy to upgrade to bar style. I ordered from ACA; I support them when I can.

That does not extend to paying $7,000 for aluminum Grove landing gear, at least not yet. I replaced my sagging gear legs with reconditioned steel gear from rainbow Ron. Appears to be a big improvement, at least based on how it sits. I am anxious to see how it handles.

We had one of those steel legs snap when a student groundlooped the airplane. I couldn't get another steel leg from anyone, so the airplane had to be converted to the aluminum gear. If the leg hadn't broken (just above the wheel) the wing wouldn't have gotten bent. The broken end sank into the turf and the wing hit the ground, bending the rear spar.

American Champion has had problems with those steel legs breaking, which is the chief reason they went to the aluminum. The conversion saves about 13 pounds.

 

[Ed Haywood]

Aluminum gear have several advantages; the biggest is the 1" of extra length gets a 150lb gross weight increase when paired with the metal wings (I still have wood). Very high on my list of wants, but the timing wasn't right to do the conversion right now. I'll get that done with the fuselage recover/restore, which I hope to do in the next 3-5 years.

From my research, I concluded the old U-bolts were a bigger concern than the gear, so I wanted to get those replaced with the new-style brackets as quickly as possible. The reconditioned steel legs were more of a spur-of-the-moment buy. They were available and only $800 for a pair, and an easy weekend install with no welding or fabric work needed.

Biggest problem with the aluminum gear is availability. ACA is backlogged 6 to 8 months on orders right now. I had a chance to order a pair in stock in January, but wasn't quite ready to pull the trigger on $7K. I probably have an engine rebuild on the horizon, so my discretionary $$ is set aside for that.