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-   -   Grove gear bolts bottomed out (https://vansairforce.net/community/showthread.php?t=30929)

Harold Lanfear 06-11-2008 06:00 AM

Grove gear bolts bottomed out
 
We just did the final assembly of my Grove airfoil gear and noticed that the NAS 6206-36 bolts (supplied by Grove) would turn in the holes after full torque was complete. When I measured the thread from the washer head under the nut to the end of the bolt, it was clear the bolts were a few thousandths too long. We'll have to add another washer.

By the way, these are the two outboard, hardened bolts on each gear - the ones that are hard to get at :( I've sent a note to Grove, but haven't heard back yet.

If you are installing or retorqueing (have no idea how to spell that) your bolts you may want to confirm the nuts have not bottomed. I'll update after I hear from Grove. I did confirm the thread and bolt length versus specs.

BuckWynd 08-24-2009 09:06 PM

I've had the opposite problem. After installing the Grove-supplied NAS 6206-36 bolts, it's become apparent that the bolts are about one step too short. I don't have the required minimum 1-1/2 bolt threads showing. Will be ordering longer bolts shortly, I guess -- but only after a call to Grove and/or Vans first.

Anyone else had this happen?

Doug Knab 08-24-2009 09:19 PM

Grove Gear Leg Bolts
 
I've had the same problem with the non airfoil Grove gear legs. I added an extra washer and the bolts torqued up fine.

DanH 08-24-2009 09:19 PM

Hmmm....mine were the correct length when used with the supplied nuts, but too short for the taller, stronger nuts. I too need longer bolts.

scsmith 08-27-2009 03:27 PM

Remember NAS gear bolts sized by grip length
 
Hey guys,
remember that NAS bolts are sized by grip length, not overall length.
The stock gear bolts are NAS6206-27. For those of you that would like to use higher strength nuts and find that your stock bolts are not long enough, GAHco has NAS6206-28 that should be enough longer. For anyone that finds that the nut bottoms out, They also have NAS6206-26.

For the folks with Grove gear, the gear leg is thicker, so the bolts are longer, but I do not believe they are NAS6206-36 - that would be 9/16" longer than stock! The grove gear are not that much thicker, are they? So, remember when determining what length you need that the size number is the grip length.

GAHco has lengths of 26,28,30,31,32,34,35,36 listed on the website.

This may seem a bit of a tangent, but for people wrestling with bolt length to fit with the taller nuts, here is a thought:

This may be controversial and is intended as much as a question as a statement: Normal practice for nylon lock nuts (AN365) is to have 1-1/2 threads extending beyond the nut, right? I can see that this is important for two reasons. One- if you can see the end of the bolt, it assures that it went all the way through, and Two - since the nylon locking feature is just at the very end, you would not get full locking effect if only the last thread ( which is a little undersized from the end bevel) was in the nylon. BUT with a metal locknut that is made by deforming the last several threads of the nut, it would seem accepable from a functional standpoint to have the end of the bolt just barely beyond the nut. You will get full locking effect because several threads are deformed, and you will get full strength as long as the bolt is all the way through the nut. Finally, the NAS bolts come with a fairly short threaded portion. This leaves very little lattitude in adjusting nut position on the bolt - there is very little length change between bottoming on the thread and having the end of the bolt not extend beyond the nut.

Thoughts?

Toobuilder 08-27-2009 05:29 PM

Due to weight concerns, the military aircraft program that I work on deviated from the "1 1/2 thread protrusion" standard 50+ years ago and allows "flush" ...but we don't use nylock nuts either.

BuckWynd 08-27-2009 07:07 PM

Quote:

Originally Posted by scsmith (Post 353746)
For the folks with Grove gear, the gear leg is thicker, so the bolts are longer, but I do not believe they are NAS6206-36 - that would be 9/16" longer than stock! The grove gear are not that much thicker, are they? So, remember when determining what length you need that the size number is the grip length.

After checking this evening, I can confirm that for the airfoiled Grove gear on an RV-8, the Grove-supplied bolts are NAS6206-36s, with a length of 2.704". The Grove gear legs themselves are not that much thicker than the stock gear, but the Grove saddles definitely are. They stick out significantly past the edge of the fuselage.

If you use the taller NAS1804-6 nuts (as discussed elsewhere in this forum), you will not have 1-1/2 threads showing when you're done torquing them. Whether this would be an issue with your DAR is unknown. I just know that I don't want to chance it. And I certainly don't want to re-do anything inside those bleeping gear towers any more than I have to.

I propose that an NAS6606-36 bolt would be suitable in this application, since it's 2.828" long (about 1/8" longer than the Grove-supplied bolt), but with the same grip length. As Steve pointed out, NAS bolts are sized by grip length, not overall length, so the "dash" number would be the same. The 66XX series has longer thread lengths, or "T" lengths.

I have not yet fully explored what installation consequences there might be with a longer bolt -- it doesn't look like there will be any in my airplane, but your situation might be different. And remember, I'm referring to:
1. An RV-8,
2. The airfoiled Grove gear,
3. The taller NAS1804-6 nuts,
...and nothing else.

More updates soon, when I figure out exactly what I'm going to do.

GAHco 08-27-2009 09:41 PM

Here, here !!
 
Quote:

I propose that an NAS6606-36 bolt would be suitable in this application, since it's 2.828" long (about 1/8" longer than the Grove-supplied bolt), but with the same grip length. As Steve pointed out, NAS bolts are sized by grip length, not overall length, so the "dash" number would be the same. The 66XX series has longer thread lengths, or "T" lengths.
I will second that suggestion from a technical standpoint.

It is the same fastener, except the thread length is slightly longer, and it has a 6606-?? instead of a 6206-??. The materials and strengths are identical.

I probably can get the 6606-36 in qty cheaper than the 6206-36, they are a little more common.

We already have the NAS1804 nuts.

I found my last response/post from before.

http://www.vansairforce.com/communit...9&postcount=21

I don't have an 8, I think the bolt is going to be in tension,but if its' simple shear the nas1804 is overkill, if it is in tension or a combination then you can't get a better nut for the money.

scsmith 08-28-2009 11:07 AM

Great Solution Buck!
 
Thanks for finding out about the NAS6606 - that is a great solution.

And Tom, thanks for adding the info to confirm.

Yes, the gear bolts see a combination of shear and significant tension when the wheel hits something like a pothole that can put an aft load on the wheel. This produces a torque in the gear leg that is reacted by tension in the forward gear bolt, and there have been a couple of instances where the NAS679 nuts have stripped.

BuckWynd 08-28-2009 05:33 PM

I must thank Tom at GAHCo for publishing what must be the best hardware reference guide ever. I don't know if I could even attempt to build an airplane if I didn't have that thing sitting on my workbench.

You guys all do have it, right? Right? ;)

Get it now if not.


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