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Breaking News: tests on landing gear nuts and bolts

The data source is.....

Dave,


The service history of the RV-8 landing gear includes several incidents in which the nuts securing the saddles at the outboard landing gear attachments failed in tension.

Thanks, Bob K.

Bob,
I'd like to run those failures to ground. Where did you find the data regarding the failures?
thanks,
Don
 
Bob,
I'd like to run those failures to ground. Where did you find the data regarding the failures?
thanks,
Don

Don, all of the failures I know of were reported here on VAF. You would have to search on a variety of keywords to find them all.

Here are a couple of leads to get you started:

http://www.vansairforce.com/community/showthread.php?p=163234

http://www.vansairforce.com/community/showthread.php?t=43599

http://www.vansairforce.com/community/showthread.php?t=84572

Thanks, Bob K.
 
Bolt length

My question is whether we can use the same bolt. I think the NAS nut is a taller nut. I'm thinking we won't get the full thread pas the nut and might need longer bolts. Not sure.
 
Here's what I got for my grove gear

I spoke with Tom Brink on what was best for my grove gear.

Here is what I got.

MS21250-06036
12 Point Bolt 180 KSI Minimum EA (1) 55.20
3/8 Diameter 12 Point Head
Condition : Factory New


MS21299-6
Cad II Plated High Strength 5 (5) 2.70
Flat Washer Good to 260 KSI
Condition : Factory New


MS21299C6
Cad II Plated High Strength 5 EA (5) 3.20
Center is Counter Bored
Washer Strength up to 260 Ksi
Condition : Factory New


NAS1804-6
12 Point Nut, 180Ksi.450 deg, pkg/5 (5) 27.50
3/8-24
Condition : Factory New

Genuine Aircraft Hardware Co
[email protected]

At the time, it was just under $90 for everything i needed.

No special tools needed.


Don
 
I test the entire landing gear quite often. So far I have not been able to destroy an

If I can't hurt it is adequate!
 
Please confirm I can just use a common 12 pt socket. I feared that I might need some special, hard to find, expensive socket.

Hi Kevin,

Yes, a standard 12-pt socket works. Im not positive, but pretty sure Kahuna is right, it is one size smaller than the original nuts, so I think 1/2" is right.

If you are worried about getting a thread engagement on the nut that includes a thread or two outside the nut, then I think you might need to order a slightly longer bolt. I don't remember for sure. Recall that the NAS close tolerance bolts are spec'ed by grip length, not overall length. So it may be that there is adequate thread for the stronger nuts. I'm sorry I just don't remember exactly.

For sure the Grove gear gets longer bolts, because the gear leg is thicker. I'm pretty sure Grove has worked this out and supplies the proper length, as well as the high-strength nuts.
 
Thanks for the info Steve.

Can anyone with the standard RV-8 landing gear and the NAS1804-6 nuts comment on whether the bolts delivered from Van's are long enough to put at least one thread extend past the end of the nuts, or whether I would need to go up one increment on the bolt length?
 
My question is whether we can use the same bolt. I think the NAS nut is a taller nut. I'm thinking we won't get the full thread pas the nut and might need longer bolts. Not sure.

Post #41 in this thread would suggest that a slightly longer bolt would be beneficial. Post #32 mentions using NAS 6606-27 rather than the standard NAS 6206-27. This means the grip length is the same, but the threaded portion is longer. As I try to recall what I did, this rings familiar. I think thats what I did.
 
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Kevin

in answer to your question, I tried to use the standard AN6-27 bolt with the stronger (longer) nuts, but they would not allow any of the threads to protrude past the nut. I ended up using the MS21250 bolts, I think they were -30. I did have to use a couple of extra washers, but the -30 was the only length I could find... and I had lots of the MS20002C chamfered washers after buying the minimum of 100...

Skygeek had the best buy on the bolts. Genuine Aircraft Hardware wanted $27 per each, while Skygeek provided the things for about $7, if memory serves.

By the way, do try to use those MS20002C washers, they have a slightly smaller OD and fit inside the weldment without having to modify the Van's provided AN washers.
 
My Bad

I mean NAS bolts, not AN bolts. I did use the high strength MS21250 in place of the NAS 6602-27, despite the longer exposed head that will require a bit of magic with the intersection fairing....
 
I just saw a post on the Van's builder's Facebook page complaining that the landing gear nuts ought to be castellated with cotter pins to keep them from loosening. Steve's analysis and our tests make it pretty clear that cotter pins would just shear as the nuts hopped the threads on the bolts.
 
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<xxxx> For new-comers that may not have seen our tests a few years ago, and unfortunately are still using the horrible stamped lightweight nuts that Vans supplies (or at least used to supply), PLEASE go back and review our results.

We watched with our own eyes as that horrible lightweight nut stretched circumferentially until it leapfrogged over the thread to the next one. And then again and again until the nut was loose.

People think, "gee the thread is not stripped, so the nut must have turned." But not so.

I installed the high-strength 12-point nuts 8 years ago, and I have not had them turn even a tiny bit on re-check of torque each year. I land on rough dirt fields full of squirrel holes. It is sad how many RV-8's have suffered damage because of loose gear bolts because of those stupid stamped steel nuts.
 
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Question?Is this only an issue on the -8, or do the other models use the same setup?

Steve, the -8 is the only model with a flat steel (or Grove aluminum) gear strut that is bolted to the fuselage with steel saddle clamps. All the other models have round steel gear that engage sockets in the engine mount.

So -- this issue is confined to the -8
 
The RV-12 also has this type of main gear attachment. It uses AN365 nuts.

But that's it - none of the others. So far.

Dave
 
The RV-12 also has this type of main gear attachment. It uses AN365 nuts...

Garden-variety AN hardware is probably adequate for the RV-12. It is a lighter airplane with shorter landing gear, so the moment applied to the gear leg attachments is substantially smaller than on the RV-8.

--Bob K.
 
<xxxx> For new-comers that may not have seen our tests a few years ago, and unfortunately are still using the horrible stamped lightweight nuts that Vans supplies (or at least used to supply), PLEASE go back and review our results.

We watched with our own eyes as that horrible lightweight nut stretched circumferentially until it leapfrogged over the thread to the next one. And then again and again until the nut was loose.

People think, "gee the thread is not stripped, so the nut must have turned." But not so.

I installed the high-strength 12-point nuts 8 years ago, and I have not had them turn even a tiny bit on re-check of torque each year. I land on rough dirt fields full of squirrel holes. It is sad how many RV-8's have suffered damage because of loose gear bolts because of those stupid stamped steel nuts.


Steve, can you give the part number for these nuts? Thanks
 
Steve, can you give the part number for these nuts? Thanks

As shown in the original post where we did the strength tests, the bad nuts are NAS679A6. The good nuts are NAS1804-6.

The origin and history of the NAS679 nuts I believes goes back to the development of rockets. They have ring flanges that hold things together that have many many bolts and nuts around the circumference of the rocket. There was a desire/need for extremely light-weight nuts to save weight because they had hundreds of them, so these stamp-formed nuts were developed. Considering how they are made and now little metal is in them, they are pretty strong. But they are NOT appropriate for high-load bolted joints such as our landing gear attachment.

The band of metal that surrounds the bolt threads, which has the nut threads on the inside, is so thin that when you pull, the band expands because of the outward pressure from the thread acting like a wedge. You can watch as it expands enough to climb over the thread, then shrink back down again, having climbed one thread up the bolt.
 
Torque limits

Does anyone have or can direct me to the source that can provide touque limits for the bolts and nuts in question?
NAS1804-6 nut and NAS6306-27
 
Torque Limits for Landing Gear Bolts

Does anyone have or can direct me to the source that can provide touque limits for the bolts and nuts in question?
NAS1804-6 nut and NAS6306-27

Van's recommendation (on the plans) is 240 in-lbs. You don't want to exceed this because additional torque will cause the outboard landing gear brackets to bend excessively.

Skylor
RV-8
 
Still tight!

...Last weekend Steve (scsmith) and I checked the torque on his RV-8 gear leg nuts. They hadn't budged any since we last checked them, and in fact hadn't budged significantly since the original installation ten or twelve years ago.

At this point, I think that it is completely settled by the preponderance of evidence that:

* If you find your RV-8 landing gear leg nuts loose, it is not because they've unscrewed themselves. Rather, it is because the nuts were overloaded in tension, and leapfrogged over the threads of the bolt.

* If you find a loose nut, you should definitely remove and inspect the nut and bolt for thread damage. Do not just torque it back up and call it good. It will take a lot less tension to make it slip the next time.

* The NAS679A6 nuts originally supplied in the kit have relatively little margin for loads beyond those applied in normal operation.

* Substituting NAS1804-6 nuts, and also NAS6606-27 or similar bolts, adds considerable margin to the landing gear attachment with little added cost and no weight penalty.

Thanks, Bob K.
 
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Easier to install too

At first I installed the stock Vans nuts and bolts, but after reading this thread, switched them out. I opted not to do the landing gear tower mod on mine, and another benefit of this style but is that it was far and away easier to install them than the stock Vans ones in the limited amount of space. On the Vans ones my socket kept slipping off of the nut. Have a lot more confidence the joint was torqued correctly.
 
Summit Racing 12 pt. nuts

Steve-- I commend you for taking the time to test these nuts. Just to muddy the waters, on my exhaust flanges I used these ARP 12-Point Nuts 301-8343 from Summit Racing. I did that for socket-wrench access; A Snap-On 12 pt. swivel socket will easily grip them. Summit advertises a Yield Strength of 180,000 psi. I don't think I would try them on my landing gear, though.
 
Steve-- I commend you for taking the time to test these nuts. Just to muddy the waters, on my exhaust flanges I used these ARP 12-Point Nuts 301-8343 from Summit Racing. I did that for socket-wrench access; A Snap-On 12 pt. swivel socket will easily grip them. Summit advertises a Yield Strength of 180,000 psi. I don't think I would try them on my landing gear, though.

Although those are not NAS hardware, they may be equivalent and perform well. Without testing, I would stick to the NAS 1804 for the gear- it's just too important.
 
Been reading this, and trying to decide if this is a project to move forward on.

Does this hardware change only pertain to the outboard bracket, U-803?

So, 4 of each and 240 ft-lbs or tq?

Thanks
 
Been reading this, and trying to decide if this is a project to move forward on.

Does this hardware change only pertain to the outboard bracket, U-803?

So, 4 of each and 240 ft-lbs or tq?

Thanks

Yes, just the four outboard gear bolts that go through the U803 saddles.

Not 240 ft-lbs of torque though! 8^O
 
Yes, just the four outboard gear bolts that go through the U803 saddles.

Not 240 ft-lbs of torque though! 8^O

Feet, Inches, Nanometers, they're all the same right? It's just the quantity that counts! :eek:

A quick review of the plans, it is 240 INCH-LBS.

I am assuming with this hardware it's the same. Anybody retrofitted from a completed airplane? How much "fun" was it?

Thanks!
 
FWIW, mine (replaced nuts) have not budged in years and I likely have the heaviest repeat load tests on the plane being a Super 8 with 84gal of fuel. There is no question that after the stock nuts, replaced a few times, kept loosening, this is fixed.
 
After reading all these posts, I ordered 4 NAS nuts from Aircraft Spruce. They are not cheap but insurance will cost some money. I haven't mounted the gear yet but I like the idea that I only have to torgue these nuts once and they should be tight for years.
 
I like the idea that I only have to torgue these nuts once and they should be tight for years.


Even if these nuts stay put, don't forget to (as per Van's instructions):
"Check these bolts and re-torqued after the first ten flying hours, then again
at 50 hours, and annually thereafter. Failure to do so could lead to premature wear."
 
I can?t remember the details but I replaced the bolts with the next longer to get the required thread protrusion.
 
Feet, Inches, Nanometers, they're all the same right? It's just the quantity that counts! :eek:

A quick review of the plans, it is 240 INCH-LBS.

I am assuming with this hardware it's the same. Anybody retrofitted from a completed airplane? How much "fun" was it?

Thanks!

Mine is not flying yet, but should be within the next 4 weeks (depending on the Virus-Thing development).
However, whilst fully assembled (and standing on the gear) i switched to longer bolts and the stronger nuts. That wasn´t a Problem at all as the gearlegs are hold in place by the single big bolt and the U-804 inboard main gear attach bracket. The aircrafts weight actually pushes the U-801-L/R gear leg firmly against the U-805-1 outb wear plate.
I removed one bolt at a time and replaced with the new Hardware thightened them and torqued them when both bolts&nuts where replaced on the same side.

No biggy, if you neglect that i do not have the tower mods done. You need two persons though.

Just make shure that the Aircraft is unable to move while you are on it.
I put mine in Level-flight attitude (put the tail on a sawhorse) to have the load of the gear coming in perpendicular onto the U-805-1 outb wear plate.

One might argue that the torque value is not correct because the whole assembly is pre-loaded……….i did it anyways and will re-check after taxi tasts have been completed, after 10 and 50 Hours and then annually.
 
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I can?t remember the details but I replaced the bolts with the next longer to get the required thread protrusion.

Can anyone point out the NAS part number that is longer than Vans stock bolt that will work with the NAS nut? I tried to fit the NAS nut on the stock close tolerance bolt but unfortunately the bolt is too short. I am used to the AN sizing but I am having trouble figuring out the NAS numbering

Thanks.
 
I ordered a different bolt with the size of NAS6206-31. It's about 1/8" longer but I think the thread length is on a short side, where as your NAS6606 bolt has the standard thread length for the NAS nut. I'll wait until I get the new bolts and compare. Thanks
 
New NAS Bolts

I just received the new NAS bolts that are long enough for the higher strength nut.

In the picture below, the NAS6206-27 bolt and the shallow nut are from Van's RV8 kit. This bolt it turns out has a shallow thread depth which is designed for the shallow nut. The NAS6606-27 on the right has the standard thread depth which allows extra threaded length for the NAS1804-6 nut or other standard sized nut. Both of these bolts have the same un-threaded shank size, and the same diameter.

49940576837_2ffc363a8c_b.jpg
 
I just received the new NAS bolts that are long enough for the higher strength nut.

In the picture below, the NAS6206-27 bolt and the shallow nut are from Van's RV8 kit. This bolt it turns out has a shallow thread depth which is designed for the shallow nut. The NAS6606-27 on the right has the standard thread depth which allows extra threaded length for the NAS1804-6 nut or other standard sized nut. Both of these bolts have the same un-threaded shank size, and the same diameter.

49940576837_2ffc363a8c_b.jpg

Awesome. I understand that these bolts are just the four outboard gear bolts that go through the U803 saddles and I need to torque them to 240 in/lbs but Aircraft Spruce doesn't have either one of them (unless the nut is NAS1804-6N and they add an N to the end, if it's the same one) and that's on backorder until next month. Where did you order them from?
 
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Genuine Aircraft Hardware Co

Awesome. I understand that these bolts are just the four outboard gear bolts that go through the U803 saddles and I need to torque them to 240 in/lbs but Aircraft Spruce doesn't have either one of them (unless the nut is NAS1804-6N and they add an N to the end, if it's the same one) and that's on backorder until next month. Where did you order them from?

Try Genuine Aircraft Hardware Co.

Skylor
 
I just received the new NAS bolts that are long enough for the higher strength nut.

In the picture below, the NAS6206-27 bolt and the shallow nut are from Van's RV8 kit. This bolt it turns out has a shallow thread depth which is designed for the shallow nut. The NAS6606-27 on the right has the standard thread depth which allows extra threaded length for the NAS1804-6 nut or other standard sized nut. Both of these bolts have the same un-threaded shank size, and the same diameter.

49940576837_2ffc363a8c_b.jpg

Thanks for posting this picture and description. It is a great addition to the thread (ooh! is that a good pun?) to help people get the right bolts.
 
I ordered them from https://military-fasteners.com. Aircraft Spruce doesn't carry this size and the order person there refused to make special order. Bummer.

Unfortunately, the military-fasterner only sells in a pack of 10 bolts. After I install 4 bolts, I have 6 left. Let me know if you want the rest or a partial. Send me a PM.

Thanks,

Phat Vu

Thank you very much for the generous offer, yes I'll take 4 sets.
 
Thanks for posting this picture and description. It is a great addition to the thread (ooh! is that a good pun?) to help people get the right bolts.
Is there any other difference between the NAS1804-6 and the NAS1804-6N that Aircraft Spruce sells? The only thing I found in the description on Military Fasteners is the N is "non dry film lube"
https://military-fasteners.com/nuts/self_locking+extended+washer+nuts/NAS1804-6N

while the one without the N says "dry film lube"
https://military-fasteners.com/nuts/self_locking+extended+washer+nuts/NAS1804-6

Everything mentioned on this thread is the part model without the N.
 
Is there any other difference between the NAS1804-6 and the NAS1804-6N that Aircraft Spruce sells? The only thing I found in the description on Military Fasteners is the N is "non dry film lube"
https://military-fasteners.com/nuts/self_locking+extended+washer+nuts/NAS1804-6N

while the one without the N says "dry film lube"
https://military-fasteners.com/nuts/self_locking+extended+washer+nuts/NAS1804-6

Everything mentioned on this thread is the part model without the N.

This is the one I ordered from ACSpruce

https://www.aircraftspruce.com/catalog/hapages/mas1804-6n04-03822.php
 
Any if you are using Grove gear, you need a NAS6206-36 bolt to work with the NAS1804-6 nut. I may have some extras if someone needs them.
 
Any if you are using Grove gear, you need a NAS6206-36 bolt to work with the NAS1804-6 nut. I may have some extras if someone needs them.

Please tell me the Grove gear was an option and not part of the kit back in 2007ish !

How do I know if I have a factory gear or a Grove? I just ordered the bolts and nuts everybody said here and now this wrench in the system. I checked the Grove webiste and they don;t show a landing gear for any Van's aircraft. Now I'm really confused. https://www.groveaircraft.com/aircraft.html
 
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