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Old 05-07-2018, 06:08 PM
tracy tracy is offline
Join Date: Dec 2012
Location: chattanooga,tn
Posts: 176

Originally Posted by scsmith View Post
<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
Tracy Willingham
Pitts S2B- sold
Chattanooga, Tn
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Old 05-07-2018, 06:56 PM
scsmith scsmith is offline
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,955

Originally Posted by tracy View Post
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.
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 525 in 9 years (would have flown more this year if not for fire smoke)
also LS-6-15/18 sailplane
VAF donation Jan 2019
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Old 05-25-2018, 11:11 PM
Dcohran Dcohran is offline
Join Date: May 2018
Location: Pineville, Louisiana
Posts: 1
Default 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
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Old 05-26-2018, 12:24 AM
skylor's Avatar
skylor skylor is online now
Join Date: Aug 2009
Location: Southern California
Posts: 650
Default Torque Limits for Landing Gear Bolts

Originally Posted by Dcohran View Post
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.

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